Patent Publication Number: US-8113645-B2

Title: Recording apparatus

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to a recording apparatus having a loading section in which a recording medium is set, a feed roller feeding the recording medium, an urging mechanism urging one of the loading section and the feed roller to decrease a distance between the set recording medium and the feed roller, and an edge guide being movable in a width direction of the recording medium to align lateral edges of the recording medium set in the loading section. 
     In the invention, examples of the recording apparatus include an ink jet printer, a wire dot printer, a laser printer, a line printer, a copier, and a facsimile. 
     2. Related Art 
     In the past, as described in JP-A-2002-128286, a recording apparatus included a feed roller feeding a sheet and a hopper which is movable close to and apart from the feed roller and in which sheets are placed. A pair of edge guides guiding the width direction of the sheets was disposed in the hopper to be slidable in the width direction. Accordingly, when a user sets sheets, the user should broaden the edge guides in the width direction and then place the sheets on the hopper. Then, the user should allow the edge guides to slide toward each other, thereby aligning both lateral edges of the sheets. As a result, the sheets could be fed in a state where the posture of the sheets is stabilized. 
     However, the user should manually allow the edge guides to slide to a predetermined position. Accordingly, the posture of the sheets in feed might be inclined without the user&#39;s manual operation. Both lateral edges of the sheets stacked on the hopper might not be aligned. In this case, the positions of the sheets in the width direction might not be matched with each other, thereby causing a mismatch in recording positions of the sheets. As a result, the recording operation might not be performed well. 
     SUMMARY 
     An advantage of some aspects of the invention is that it provides a recording apparatus that can satisfactorily align both lateral edges of recording mediums and stabilize postures of the recording mediums. 
     According to an aspect of the invention, there is provided a recording apparatus including: a loading section into which a recording medium is set; a feed roller feeding the recording medium set in the loading section; a first urging mechanism urging one of the loading section and the feed roller to decrease a distance between the set recording medium and the feed roller; an edge guide being movable in a width direction of the recording medium to align lateral edges of the recording medium set in the loading section; a DC motor allowing the edge guide to move; and a determination unit determining whether a current value at the time of driving the DC motor reaches a predetermined threshold value. Here, the driving of the DC motor is stopped when it is determined by the determination unit that the current value reaches the predetermined threshold value. 
     Here, the “DC motor” means a so-called “brush-attached DC motor” or “brushless motor” using a DC power source and does not include a “stepping motor” driven in proportion to the number of input pulses. 
     According to the above-mentioned configuration, the recording apparatus includes the edge guide, the DC motor, and the determination unit determining whether the current value at the time of driving the DC motor reaches the predetermined threshold value, and stops the driving of the DC motor when the determination unit determines that the current value reaches the predetermined threshold value. 
     Here, the “predetermined threshold value” is a value greater than the current value when the recording medium with the lateral edge not aligned is pressed in an alignment direction in the course of movement of the edge guide and smaller than the current value when the edge guide comes in contact with the lateral edge of the recording medium with the lateral edge aligned. 
     Therefore, by allowing the edge guide to move by the use of the DC motor and determining whether the current value reaches the predetermined threshold value, it can be determined whether the edge guide has aligned the lateral edge of the recording medium. 
     Specifically, when the current value does not reach the predetermined threshold value, it can be determined that both lateral edges of the recording mediums are not aligned. Then, the DC motor can be further driven to press the edge guide against the lateral edges of the recording mediums. 
     On the other hand, when the current value reaches the predetermined threshold value, it can be determined that the edge guide comes in contact with the lateral edges of the recording mediums with the lateral edges aligned. Then, the DC motor can be stopped. 
     As a result, it is possible to stabilize the postures of the recording mediums. When plural recording mediums are set, it is possible to align both lateral edges of the recording mediums. 
     The recording apparatus may further include a recording medium size detector including a linear scale disposed in one of the loading section and the edge guide and a sensor disposed in the other to detect the linear scale. 
     According to this configuration, in addition to the above-mentioned operational advantage, the recording apparatus further includes a sheet size detector including a linear scale disposed in one of the loading section and the edge guide and a sensor disposed in the other to detect the linear scale. Accordingly, the recording medium size detector can detect the position of the edge guide when the DC motor is stopped. As a result, the recording medium size detector can detect the size of the recording medium set in the loading section with high precision. 
     The recording apparatus may further include a vibration generating mechanism causing the loading section to vibrate when the edge guide moves. 
     According to this configuration, the recording apparatus further includes a vibration generating mechanism causing the loading section to vibrate when the edge guide moves. Accordingly, it is possible to generate a gap between a recording medium and a recording medium being set in the loading section and overlapping with each other. That is, the gap can be generated when the recording mediums are closely attached, thereby easily aligning the lateral edges of the recording mediums. As a result, it is possible to align the lateral edges of the recording mediums with high precision. 
     It is possible to detect the recording medium size with high precision by the use of the sheet size detector. 
     For example, cutting surfaces of the recording mediums which are ends of the recording mediums may be closely attached to each other when a bundle of new recording mediums is set in the loading section. In this case, the gap can be generated to facilitate the alignment and the bundle of recording mediums can be undone to facilitate the separation at the time of feeding the recording mediums. Specifically, only the uppermost recording medium relative to the feed roller can be easily separated from the remaining recording mediums and can be fed. Accordingly, when a user sets a bundle of recording mediums, the user need not undo the bundle of recording mediums in advance. 
     In the recording apparatus, the vibration generating mechanism may generate a vibration in a stacking direction of the recording medium. 
     According to this configuration, in addition to the above-mentioned operational advantage, the vibration generating mechanism generates a vibration in a stacking direction of the recording medium. 
     When the vibration generating mechanism generates the vibration in the width direction, the recording mediums overlapping with each other tend to move together. That is, the recording mediums may not move relative to each other. Accordingly, no gap may be generated between the recording mediums overlapping with each other. 
     Therefore, by generating the vibration in the stacking direction intersecting the width direction and the feed direction, the recording mediums overlapping with each other can be made to easily move relative to each other. Accordingly, compared with the case where the vibration in the width direction is generated, it is possible to satisfactorily generate a gap between the recording mediums overlapping with each other. 
     The above description is specifically explained as follows. 
     When the vibration in the stacking direction is generated, the recording mediums overlapping with each other can be bumped against each other to generate a slight gap between the recording mediums overlapping with each other. That is, the lower recording medium in the stacking direction acts to slightly tip up the upper recording medium, thereby generating a slight gap between the recording mediums. Accordingly, it is possible to satisfactorily release the state where the recording mediums are closely attached to each other. 
     When the vibration in the stacking direction is being generated, the upper recording medium and the lower recording medium are repeatedly bumped against each other, thereby continuously generating the slight gap. The frictional resistance between the recording mediums overlapping with each other can be reduced by the slight gap. As a result, it is possible to easily align the lateral edges of the recording mediums. 
     On the other hand, when the vibration in the width direction is generated, the lower recording medium does not act to tip up the upper recording medium. Accordingly, a gap is hardly generated between the recording mediums. 
     When the recording mediums overlapping with each other have a flexible sheet shape, the recording mediums are easily bent in the stacking direction, but are hardly bent in the width direction. Accordingly, when the vibration in the stacking direction is generated, the recording mediums can be slightly bent, thereby generating the slight gap between the recording mediums overlapping with each other. 
     On the other hand, when the vibration in the width direction is generated, the recording mediums are hardly bent and thus a gap is hardly generated between the recording mediums overlapping with each other. 
     In the recording medium, the vibration generating mechanism may include: a first uneven portion disposed in one of the loading section and the edge guide to have an uneven shape in the width direction; and a first convex portion disposed in the other to come in contact with the first uneven portion. 
     According to this configuration, in addition to the above-mentioned operational advantages, the vibration generating mechanism includes a first uneven portion disposed in one of the loading section and the edge guide to have an uneven shape in the width direction, and a first convex portion disposed in the other to come in contact with the first uneven portion. Accordingly, when the edge guide moves, the first convex portion goes over the first uneven portion while vibrating. 
     In the recording apparatus, the vibration generating mechanism may be an ink suction device cleaning a recording head disposed in the recording section by suction. 
     According to this configuration, in addition to the above-mentioned operational advantages, the vibration generating mechanism is an ink suction device cleaning a recording head disposed in the recording section by suction. 
     Here, the ink suction device generally includes a pump generating a negative pressure. The pump includes a rotating member. By making the rotating member eccentric, it is possible to easily generate a relative great vibration. 
     Accordingly, by operating the ink suction device, it is possible to gives the vibration to the recording mediums set in the loading section. That is, it is possible to generate a vibration without newly providing a convex portion and an uneven portion. 
     The recording apparatus may further include a hopper lever urging the loading section to the feed roller and a cam portion allowing the hopper lever to fluctuate and the vibration generating mechanism may include a second uneven portion disposed in the hopper lever and the cam portion to have an uneven shape in a rotation direction of the cam portion and a second convex portion disposed in the other to come in contact with the second uneven portion. Here, the second uneven portion and the second convex portion may be brought into contact with each other in a state where the set recording medium and the feed roller are separated from each other. 
     According to this configuration, the recording apparatus includes the second uneven portion and the second convex portion and brings the second uneven portion into contact with the second convex portion in the state where the recording mediums are separated apart from the feed roller. Accordingly, in the state where the recording mediums are separated apart from the feed roller, the second convex portion goes over the second uneven portion while vibrating. As a result, it is possible to give the vibration to the recording mediums set in the loading section. That is, in a state before the loading section approaches the feed roller, that is, in a hopper down state before hopper up, it is possible to align the lateral edges of the recording mediums. 
     In the recording medium, the loading section may be made to move further apart from the feed roller when the edge guide moves in a state where the set recording medium and the feed roller are separated from each other. 
     According to this configuration, in addition to the above-mentioned operational advantages, the loading section is made to move further apart from the feed roller when the edge guide moves in a state where the set recording medium and the feed roller are separated from each other. Accordingly, at the time of allowing the edge guide to move, it is possible to generate a gap between the recording mediums set in the loading section and overlapping with each other. As a result, it is possible to align the lateral edges of the recording mediums with high precision. 
     The recording apparatus may be configured to drive the DC motor so as to allow the edge guide to move close to the lateral edge of the recording medium, to stop the driving of the DC motor when the current value reaches the predetermined threshold value, and to repeat backward and forward rotations of the DC motor to bump the edge guide against the lateral edge of the recording medium several times. 
     According to this configuration, in addition to the above-mentioned operational advantages, the backward and forward rotations of the DC motor are repeated to bump the edge guide against the lateral edge of the recording medium several times. Accordingly, it is possible to align the lateral edges of the recording mediums with higher precision. That is, since the once contact and press of the edge guide with the lateral edges of the recording mediums may not be sufficient, the precision can be enhanced by several contacts. This is particularly effective when it is difficult to align the lateral edges of the recording mediums due to materials of the recording mediums. 
     In the recording apparatus, the edge guide may include: an arm portion being movable in a stacking direction of the set recording medium; a spherical portion rotatably disposed at an end of the arm portion; and a second urging mechanism urging the arm portion to the recording medium. 
     According to this configuration, in addition to the above-mentioned advantages, the edge guide includes an arm portion being movable in a stacking direction of the set recording medium, a spherical portion rotatably disposed at an end of the arm portion, and a second urging mechanism urging the arm portion to the recording medium. Accordingly, it is possible to allow the edge guide to move while pressing the recording mediums set in the loading section. That is, when a relatively small number of recording mediums is set and the edge guide presses the lateral edges of the recording mediums, it is possible to prevent a so-called lifting deformation that a center portion in the width direction of the recording medium is lifted. As a result, even when the small number of recording mediums is set, it is possible to align the lateral edges of the recording mediums, like a large number of recording mediums. 
     Even when the small number of recording mediums is set, it is possible to detect the sheet size with high precision like a large number of recording mediums. 
     The spherical portion supported to be rotatable comes in contact with the recording medium. Accordingly, even when the spherical portion presses the recording medium, it does not prevent the recording medium from being fed. 
    
    
     
       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 perspective view schematically illustrating the entire configuration of a recording apparatus according to an embodiment of the invention. 
         FIG. 2  is a side view schematically illustrating a feeding section according to the embodiment of the invention. 
         FIG. 3  is a perspective view schematically illustrating a loading section according to the embodiment of the invention. 
         FIG. 4  is a bottom view schematically illustrating the loading section according to the embodiment of the invention. 
         FIG. 5  is a side perspective view schematically illustrating the loading section according to the embodiment of the invention. 
         FIG. 6  is a rear perspective view schematically illustrating the loading section according to the embodiment of the invention. 
         FIG. 7  is an enlarged perspective view illustrating a part of a pressing mechanism according to the embodiment of the invention. 
         FIG. 8  is a perspective view illustrating a hopper according to the embodiment of the invention. 
         FIG. 9  is a rear enlarged perspective view illustrating an edge guide according to the embodiment of the invention. 
         FIGS. 10A and 10B  are diagrams illustrating a flow of operations of the edge guide according to the embodiment of the invention. 
         FIG. 11  is a side view illustrating a loading section according to another embodiment of the invention. 
         FIGS. 12A to 12D  are side views schematically illustrating operations of a vibration generating mechanism. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Hereinafter, exemplary embodiments of the invention will be described with reference to the accompanying drawings. 
       FIG. 1  is a perspective view schematically illustrating the entire configuration of a recording apparatus as an example of a liquid ejecting apparatus according to an embodiment of the invention. 
     Here, examples of the liquid ejecting apparatus include an ink jet recording apparatus, a copier, and a facsimile performing a recording operation on a recording medium such as a sheet by ejecting ink to the recording medium from a recording head as a liquid ejecting head and apparatuses ejecting a liquid for particular use instead of the ink to an ejecting medium corresponding to the recording medium from a liquid ejecting head corresponding to the recording head and attaching the liquid to the ejecting medium in addition. 
     Examples of the liquid ejecting head include a coloring material ejecting head used to manufacture a color filter of a liquid crystal display and the like, an electrode material (conductive paste) ejecting head used to form an electrode of an organic EL display or a field emission display (FED), a biological organics ejecting head used to manufacturing a bio chip, and a sample ejecting head ejecting a sample as a precise pipette, in addition to the above-mentioned recording head. 
     A hopper  101  as a loading section  145  on which sheets P as the recording mediums are set and stacked is disposed on the rear side of the body of a recording apparatus  100  so as to be movable close to and apart from a feed roller  190  of a feeding section  144  described later. Specifically, the hopper is rotatable about a pair of hopper shafts  304  and  304  (see  FIGS. 3 to 5 ) disposed above the hopper  101 . The sheet P set at the uppermost position in the hopper  101  is fed toward a recording section which is downstream in a feeding direction by the feeding section  144 . 
     Specifically, the set sheet P is fed to a transport roller pair  220  (see  FIG. 2 ) downstream in the feeding direction by a feed roller  190  driven by a feeding motor  104  while being guided by right and left edge guides  103  and  103 . The sheet P fed to the transport roller pair  220  is transported again to a recording section  143  located downstream in the transport direction by a transport driving roller  221  (see  FIG. 2 ) of the transport roller pair  220  driving by a transport motor (not shown). 
     The recording section  143  includes a platen  105  supporting the sheet P from the downside and a carriage  107  disposed opposed to the platen  105  from the upside. The carriage  107  is guided by a carriage guide shaft (not shown) extending in a main scanning direction which is the width direction X of the transported sheet P and is driven by a carriage motor  102 . A recording head  106  ejecting ink to the sheet P is disposed at the bottom of the carriage  107 . The sheet P having been subjected to a recording operation by the recording section  143  is transported downstream and is discharged from the front surface of the recording apparatus  100  by a discharge roller (not shown). 
     An ink cartridge (not shown) is mounted into the lower portion of the recording apparatus  100  and ink is supplied to an ink supply path (not shown) through an ink supply needle (not shown). The ink is supplied to the recording head  106  of the carriage  107  through an ink supply tube  110 . At the time of flushing and cleaning the recording head  106 , the operation of ejecting and sucking the ink is performed in an ink suction device  200  as an ejection characteristic maintenance section disposed in one digit place to maintain an ejection characteristic of the recording section  143 . The ink suction device  200  includes a cap portion  204  and is configured to move up and down the cap portion  204  to seal the recording head  106 . 
       FIG. 2  is a side sectional view schematically illustrating a feeding section according to the embodiment of the invention. 
     As shown in  FIG. 2 , the feeding section  144  of the recording apparatus  100  includes a base portion  210 , a fee roller  190 , a hopper  101 , and a hopper lever  280 . The feed roller  190  is formed in a D shape as viewed from a feed roller shaft  231  and includes an arc portion  190   a  and a chord portion  190   b . The hopper lever  280  is formed monolithic with a cam follower  282  to be rotatable about a lever shaft  281 . A cam shaft  261  is provided with a hopper cam  260  and an urging force adjusting cam  270 . The hopper cam  260  can engage with the cam follower  282 . On the other hand, the urging force adjusting cam  270  is formed in a linear shape and includes a cam arc portion  271 , a cam first linear portion  272 , and a cam second linear portion  273 . 
     A first arm portion  291  of a torsion coil spring  290  as an example of the urging mechanism engages with the hopper lever  280  and a second arm portion  292  comes in contact with the urging force adjusting cam  270 . 
     The base portion  210  is provided with a clearance regulating portion  211  preliminarily separating a sheet P to be fed, a bank separation portion  212  as an example of the separation mechanism, and a guide surface portion  213  guiding the sheet P to the transport roller pair  220 . 
     The bank separation portion  212  is a pad formed of a material having a high friction coefficient. The transport roller pair  220  includes a transport diving roller  221  driven with the power of the transport motor and a transport driven roller  222  rotating with the rotation of the transport driving roller  221 . 
     The feeding section  144  includes a pair of return levers  250  and  250  returning the second uppermost and lower sheets P to the hopper  101  when the feed is finished, in the width direction X of the sheet P. The return levers  250  and  250  are configured to perform a returning operation with the power of the feeding motor  104 . 
     When the hopper cam  260  rotates counterclockwise in  FIG. 2  and engages with the cam follower  282 , the hopper cam  260  rotates the hopper lever  280  clockwise against the urging force of the torsion coil spring  290 . Accordingly, the hopper  101  moves apart from the feed roller  190 , which is called hopper-down state. 
     When the hopper cam  260  rotates counterclockwise again and disengages from the cam follower  282 , the hopper lever  280  rotates counterclockwise with the urging force of the torsion coil spring  290 . Accordingly, the hopper  101  moves close to the feed roller  190 , which is called hopper-up state. 
     In case of hopper up, the uppermost sheet P of the sheets P set in the hopper  101  is fed by the feed roller  190 . Specifically, the uppermost sheet P is preliminarily separated from the second uppermost and lower sheets P by the clearance regulating portion  211  disposed in the base portion  210 . When the feed roller  190  rotates again clockwise in  FIG. 2 , the leading end of the sheet P enters the bank separation portion  212  as the separation mechanism. In this embodiment, the bank separation portion  212  is a pad formed of an elastic material having a high friction coefficient as described above. Only the uppermost sheet P can go over the bank separation portion  212 . 
     When the feed roller  190  rotates again, the leading end of the uppermost sheet P is guided by the guide surface portion  213  formed in the base portion  210  and reaches the transport roller pair  220 . When the leading end of the sheet P reaches the transport roller pair  220 , skew of the sheet P is removed by the transport roller pair  220  and the feed roller  190 . The removal of skew may employ a “contact system” or a “biting and discharging system.” 
     Here, the “contact system” means a system in which the leading end of the sheet P comes in contact with the stationary transport roller pair  220 , the sheet P is bent between the feed roller  190  and the transport roller pair  220 , and the posture of the leading end of the sheet P is made to comply with a nip line of the transport roller pair  220 . 
     On the other hand, the “biting and discharging system” means a system in which the leading end of the sheet P is nipped by a predetermined amount by the transport roller pair  220  rotating forward, the transport roller pair  220  is made to rotate backward to bend the sheet P between the feed roller  190  and the transport roller pair  220 , and the posture of the leading end of the sheet P is made to comply with the nip line of the transport roller pair  220 . 
     After removing the skew, the sheet P is transported to the recording section  143  by the transport roller pair  220 . At this time, the posture of the feed roller  190  is at a reset position. 
     Here, the “reset position” means a posture taken when the feeding is finished and means a phase where the chord portion  190   b  of the feed roller  190  is opposed to the clearance regulating portion  211  and the hopper  101 . 
     A cork member as an example of the high frictional member is disposed at a position in the hopper  101  opposed to the feed roller  190  in the hopper-up state. Accordingly, a so-called avalanche phenomenon that the second uppermost and lower sheets P avalanches to the clearance regulating portion  211  can be reduced. 
       FIG. 3  is a perspective view illustrating a loading section according to the embodiment of the invention. 
     As shown in  FIG. 3 , the hopper  101  is provided with the edge guides  103  and  103  slidable in the width direction X of the sheet P. Specifically, the hopper  101  is provided with a first guide rail portion  305  and a second guide rail portion  306  guiding the edge guides  103  and  103  in the width direction X of the sheet P. The edge guides  103  and  103  engage with the first guide rail portion  305  and are guided to be slidable in the width direction X. 
     The edge guides  103  and  103  include a right guide  307  and a left guide  308 . The right guide  307  is disposed to guide the right end of the sheet P set in the hopper  101 . On the other hand, the left guide  308  is disposed to guide the left end of the sheet P set in the hopper  101 . 
     The right guide  307  and the left guide  308  slide to be symmetric about the center in the width direction X by a rack and pinion mechanism to be described later. The bottom of the hopper  101  is provided with a DC motor  302 . The right guide  307  and the left guide  308  slide with the power of the DC motor  302 . The recording apparatus  100  includes a determination unit  300  determining whether the current value at the time of driving the DC motor  302  reaches a predetermined threshold value. Specifically, a control unit  301  controlling the driving of the DC motor  302  serves as the determination unit  300 . The “predetermined threshold value” is described later. 
     Pressing mechanisms  340  and  340  are disposed in the right guide  307  and the left guide  308 , respectively. Although the detailed structure is described later, the pressing mechanisms  340  and  340  are configured to press the sheets P set in the hopper  101  from the upside to the downside in the stacking direction. Accordingly, the pressing mechanisms  340  and  340  can prevent the sheets P set in the hopper  101  from floating in the stacking direction Z. 
       FIG. 4  is a bottom view illustrating the loading section according to the embodiment of the invention.  FIG. 5  is a side perspective view illustrating the loading section according to the embodiment of the invention.  FIG. 6  is a rear perspective view of  FIG. 5 . 
     In  FIG. 6 , the DC motor is not shown for the purpose of easy understanding. 
     As shown in  FIGS. 4 to 6 , a link mechanism  360  as the rack and pinion mechanism making the movement of the right guide  307  and the movement of the left guide  308  symmetric is disposed in the bottom of the hopper  101 . The link mechanism  360  includes a first rail engaging portion  310 , a second rail engaging portion  320 , and a complex pinion gear  323 . The first rail engaging portion  310  engages with the right guide  307  to be movable in the Y axis direction as the feeding direction. The first rail engaging portion  310  comes in slidable contact with the second guide rail portion  306 . 
     More specifically, one end of the first engagement spring  312  is locked to the right guide  307  and the other end is locked to the first rail engaging portion  310 . Accordingly, the right guide  307  comes in slidable contact with the first guide rail portion  305  and the first rail engaging portion  310  comes in slidable contact with the second guide rail portion  306 . Therefore, the position of the right guide  307  can be stabilized in the Y axis direction perpendicular to the X axis direction. The posture of the right guide  307  relative to the Y axis can be stabilized. 
     Similarly, the second rail engaging portion  320  engages with the left guide  308  to be movable in the Y axis direction. The second rail engaging portion  320  comes in slidable contact with the second guide rail portion  306 . 
     More specifically, one end of the second engagement spring  322  is locked to the left guide  308  and the other end is locked to the second rail engaging portion  320 . Accordingly, the left guide  308  comes in slidable contact with the first guide rail portion  305  and the second rail engaging portion  320  comes in slidable contact with the second guide rail portion  306 . Therefore, the position of the left guide  308  can be stabilized in the Y axis direction perpendicular to the X axis direction. The posture of the left guide  308  relative to the Y axis can be stabilized. 
     The first rail engaging portion  310  includes a first rack portion  311  engaging with the complex pinion gear  323 . Similarly, the second rail engaging portion  320  includes a second rack portion  321  engaging with the complex pinion gear  323 . Accordingly, the movement of the right guide  307  and the movement of the left guide  308  can be made to be symmetric. 
     As described above, the postures of the first rail engaging portion  310  and the second rail engaging portion  320  can be stabilized by the first engagement spring  312  and the second engagement spring  322 . The first rack portion  311  is formed monolithic with the first rail engaging portion  310 . Similarly, the second rack portion  321  is formed monolithic with the second rail engaging portion  320 . Accordingly, the postures of the first rack portion  311  and the second rack portion  321  can be stabilized. That is, the movement of the right guide  307  and the movement of the left guide  308  can be made to be symmetric with high precision. 
     The DC motor  302  is provided with a motor pinion  303 . The motor pinion  303  is disposed to engage with the complex pinion gear  323 . Accordingly, the right guide  307  and the left guide  308  can be made to move with the power of the DC motor  302 . 
     The recording apparatus  100  further includes a sheet size detector  330  detecting the size of the sheets P. The sheet size detector  330  includes an encoder sensor  332 , a linear scale  331 , and a control unit  301 . 
     The encoder sensor  332  is disposed monolithic with the second rail engaging portion  320 . The linear scale  331  is disposed monolithic with the hopper  101 . Accordingly, it is possible to detect the position of the left guide  308 . 
     Here, the right guide  307  is located at a symmetric position of the left guide  308  by the link mechanism  360 . Accordingly, the control unit  301  can necessarily recognize the position of the right guide  307 . 
     The recording apparatus  100  is turned on, the sheets P is set in the hopper  101 , the sheet size is detected in accordance with a recording command, and then the recording operation is performed. In detecting the sheet size, the right guide  307  and the left guide  308  widened in the width direction X are first made to move to the center by driving the DC motor  302 . Accordingly, the right guide  307  and the left guide  308  come in contact with the right ends and the left ends of the sheets P, respectively. 
     When the current value of the DC motor  302  is less than a predetermined threshold value, the control unit  301  continues to drive the DC motor  302 . When the current value of the DC motor  302  reaches the predetermined threshold value, the control unit  301  stops the driving of the DC motor  302 . That is, when the current value is less than the threshold value, both lateral edges of the sheets P are not aligned and it is thus determined that the load is small and the current value is small. On the other hand, when the current value reaches the threshold value, both lateral edges of the sheets P are aligned and it is thus determined that the right guide  307  and the left guide  308  cannot move to the center any more. 
     Then, the position of the left guide  308  when the current value reaches the threshold value is detected by the encoder sensor  332  and the linear scale  331 . Here, the position of the right guide  307  is a symmetric position of the left guide  308  as described above. Accordingly, the sheet size set in the hopper  101  can be detected. 
       FIG. 7  is an enlarged perspective view illustrating a part of the pressing mechanism according to the embodiment of the invention. 
     As shown in  FIG. 7 , the pressing mechanism  340  includes an arm portion  341 , a ball portion  344 , and a pressing spring  345 . The arm portion  341  has an arm shaft  342  at one end and a ball holding portion  343  at the other end. The arm shaft  342  is rotatably held by the right guide  307 . The ball holding portion  343  is disposed to rotatably hold the ball portion  344 . The arm portion  341  rotates so that the ball portion  344  moves in the stacking direction Z of the sheets P about the arm shaft  342 . 
     The pressing spring  345  urges the arm portion  341  so that the ball portion  344  moves down in the stacking direction. 
     Accordingly, the pressing mechanism  340  can prevent the stacked sheets P from floating up in the stacking direction. The ball portion  344  held by the ball holding portion  343  is rotatable in any direction. Accordingly, when the right guide  307  is moving in the width direction, the ball portion does not prevent the movement of the right guide  307 . That is, it is possible to minimize the increase in load of the DC motor  302 . 
     When the current value reaches the threshold value, that is, when the right guide  307  and the left guide  308  come in pressing contact with the sheets P having both lateral edges aligned, the central portion of the sheets P may be bent to be lifted up in the stacking direction, which is called lifting deformation. In this case, the sheet size may not be detected with high precision. 
     In this case, the pressing mechanism  340  can prevent the central portion of the sheet P from being bent upward in the stacking direction. That is, it is possible to prevent the lifting deformation of the sheet P. 
     As a result, it is possible to detect the sheet size with high precision. This configuration is effective particularly when the number of stacked sheets P is relatively small or when the flexibility of the sheets P is small. Even when only one sheet of normal paper is set in the hopper  101 , it is possible to detect the sheet size with high precision. 
     As described above, the ball holding portion  343  is disposed to rotatably hold the ball portion  344 . Accordingly, at the time of feeding the sheets P, it is possible to minimize the resistance generated between the sheet P and the pressing mechanism  340 . 
     Although the right guide is described, the same is true in the left guide and thus description thereof is omitted. 
       FIG. 8  is a perspective view illustrating the hopper according to the embodiment of the invention.  FIG. 9  is a rear enlarged perspective view illustrating the edge guide according to the embodiment of the invention. 
     As shown in  FIGS. 8 and 9 , the loading section  145  is provided with a vibration generating mechanism  350 . The vibration generating mechanism  350  includes an uneven portion  351  disposed on the front surface of the hopper  101  and protruding portions  352  and  352  disposed on the bottom surface of the edge guides  103  and  103 . The protruding portions  352  and  352  come in contact with the uneven portion  351 . The vibration generating mechanism  350  generates a vibration by allowing the protruding portions  352  and  352  to move while coming in contact with the uneven portion  351 . 
     Accordingly, when the right guide  307  and the left guide  308  move to the center to align both lateral edges of the sheets P, it is possible to allow the sheets P to vibrate by the use of the hopper  101 . 
     Here, it may be difficult to align both lateral edges due to the close attachment of the sheet P and the sheet stacked in the hopper. 
     Therefore, it is possible to give a vibration to the sheets P by the use of the vibration generating mechanism  350 . At this time, the vibration direction is a direction intersecting the surface of the sheet P. Accordingly, it is possible to generate a gap between the sheet P and the sheet P. That is, it is possible to align both lateral edges while undoing a bundle of sheets P. Accordingly, it is possible to easily align both lateral edges of the sheets P. As a result, it is possible to precisely detect the sheet size. 
     The above description will be described again in detail as follows. 
     When the vibration in the direction intersecting the surface of the sheet P is generated, it is possible to generate a slight gap between the sheet P and the sheet P by bumping the sheet P and the sheet P overlapping with each other. That is, the lower sheet P in the stacking direction acts to slightly tip up the upper sheet P, thereby generating a slight gap between the sheet P and the sheet P. Accordingly, the sheet P and the sheet P closely attached to each other can be satisfactorily detached. 
     When the vibration in the direction intersecting the surface of the sheet P is being generated, the upper sheet P and the lower sheet P are repeatedly slightly bumped against each other, thereby continuously generating the slight gap. Due to the slight gap, it is possible to reduce the frictional resistance between the sheet P and the sheet P overlapping with each other. As a result, it is possible to easily align the lateral edges of the sheets P. 
     Since the sheets P overlapping with each other have a flexible sheet shape, the sheets can be easily bent in the stacking direction Z and can be hardly bent in the width direction X. Accordingly, when the vibration in the stacking direction Z is generated, the sheets P are slightly bent, thereby generating a slight gap between the sheet P and the sheet P overlapping with each other. 
     Here, when a bundle of new sheets P is set in the hopper  101 , the sheet P and the sheet P may be closely attached in the cutting surface of the sheets P. In this case, the bundle of sheets P can be undone by generating the vibration. Accordingly, it is possible to easily pick up the sheets P with the feed roller  190  at the time of feeding the sheets. The bank separation portion  212  and the feed roller  190  can cooperate to easily separate only the uppermost sheet from the second uppermost and lower sheets. That is, it is possible to reduce the possibility that two or more sheets P are feed at a time. 
     The number of protruding portions  352  is not limited. Although the vibration generating mechanism  350  is disposed in the right guide, it may be disposed in the left guide. 
     Operations of detecting the sheet size will be described now. 
       FIGS. 10A and 10B  are diagrams illustrating a flow of operations of the edge guides according to the embodiment of the invention. 
     As shown in  FIGS. 10A and 10B , in step  11  (hereinafter, simply referred to as S 11 ), a user turns on the recording apparatus  100 . Then, the process of S 12  is performed. 
     In S 12 , a home position (HP) seeking operation is performed. Specifically, the control unit  301  allows the right guide  307  and the left guide  308  to move to the home position (position shown in  FIGS. 5 and 6 ) which is the outermost position in the movable range in the width direction X. Then, the process of S 13  is performed. 
     In S 13 , a so-called measurement process of measuring a load is performed. Specifically, the control unit  301  measures the current value of the DC motor  302  as a load when the right guide  307  and the left guide  308  move. At this time, the right guide  307  and the left guide  308  move to the innermost position in the movable range from the home position and then move to the home position. 
     Here, by the measurement, the “predetermined threshold value” to be described later can be changed. 
     Then, the process of S 14  is performed. 
     In S 14 , it is determined whether a sheet P remains in the hopper. This is to confirm whether the measurement of load performed in S 13  is normally finished. Specifically, in the measurement of load performed in S 13 , it is determined whether the moving distance of the right guide  307  and the left guide  308  is less than 20 mm. 
     Here, the distance of “20 mm” is a distance slightly greater than the distance from the home position to a position to which the minimum size of predetermined sheet sizes is guided. Accordingly, when the moving distance is less than 20 mm, it means that a sheet P of any size remains in the hopper. On the other hand, when the moving distance is 20 mm or more, it means that a sheet P does not remain in the hopper. 
     When the moving distance is less than 20 mm, the process of S 15  is performed. On the other hand, when the moving distance is 20 mm or more, the process of S 30  is performed. 
     In S 15 , the load value normally measured in the measurement of load in S 13  is written to an EEPROM of the control unit  301 . Then, the process of S 16  is performed. 
     In S 16 , a user sets sheets P in the hopper. Then, the process of S 17  is performed. 
     In S 17 , a recording start button is pressed. That is, a command for starting a recording operation is given to the recording apparatus  100 . Here, the command for starting the recording operation is not limited to the actual operation of button. Then, the process of S 18  is performed. 
     In S 18 , the edge guides  103  and  103  are driven. Specifically, the control unit  301  drives the DC motor  302  and allow the right guide  307  and the left guide  308  to move to the center from the home position. At this time, as described above, it is possible to align both lateral edges of the sheets P while undoing the bundle of sheets P by the use of the vibration generating mechanism  350 . 
     Then, the process of S 19  is performed. 
     In S 19 , the determination unit  300  of the control unit  301  determines whether the current value of the DC motor  302  reaches a predetermined threshold value. 
     Here, the “predetermined threshold value” is a value greater than the current value resulting from the load when the right guide  307  and the left guide  308  come in contact with one lateral edge of the sheets P. The predetermined threshold value is also a value smaller than the current value resulting from the load when the right guide  307  and the left guide  308  come in contact with both lateral edges of the sheets P of which both lateral edges are aligned. 
     Accordingly, when the current value reaches the predetermined threshold value, this state can be determined as a state where both lateral edges of the sheets P are aligned. On the other hand, when the current value does not reach the predetermined threshold value, this state can be determined as a state before the right guide  307  and the left guide  308  come in contact with both lateral edges of the sheets P or a state where both lateral edges of the stacked sheets P are not aligned. 
     When the current value reaches the predetermined threshold value, the process of S 20  is performed. On the other hand, when the current value does not reach the predetermined threshold value, the DC motor  302  is continuously driven in S 18 . 
     In S 20 , the edge guides  103  and  103  are stopped. Specifically, the control unit  301  stops the driving of the DC motor  302  to stop the movement of the right guide  307  and the left guide  308 . Then, the process of S 21  is performed. 
     In S 21 , it is determined whether the number of times when the current value reaches the threshold value is three or more. When the number of times is three or more, the process of S 22  is performed. When the number of times is less than three, the process of S 32  is performed. 
     In S 22 , the DC motor  302  is held. Specifically, the motor pinion  303  is made not to rotate by supplying small current to the DC motor  302 . 
     Here, when no current is supplied, the motor pinion  303  may rotate with an external force receiving through the edge guides  103  and  103  and the link mechanism  360 . That is, the positions of the right guide  307  and the left guide  308  may move. In this case, the posture of the sheets P of which both lateral edges are aligned may be unstable. The lateral edges of the sheets P may not be uniform. 
     Therefore, by holding the DC motor  302 , the posture of the sheets P and the state where both lateral edges of the sheets P are aligned can be maintained. Then, the process of S 23  is performed. 
     In S 32 , the position information on the edge guides  103  and  103  is acquired by the encoder sensor  332 . Specifically, the control unit  301  acquires the position information on the left guide  308  by the use of the encoder sensor  332  and the linear scale  331 . At this time, as described above, the position of the right guide  307  becomes a symmetric position of the left guide  308  by the link mechanism  360 . That is, when the position information on the left guide  308  is acquired, the position of the right guide  307  can be acquired. Accordingly, the control unit  301  can detect which sheet size of the sheets P set in the hopper is out of predetermined sheet sizes with high precision. Here, when the sheet size acquired from the position information on the edge guides  103  and  103  is greatly different from the predetermined sheet size, an error or an alarm can be displayed. When the difference in sheet size is small, the size of the sheets P set in the hopper can be estimated as the predetermined sheet size. Then, the process of S 24  is performed. 
     In S 24 , a sheet image is developed to be matched with the sheet width. Specifically, the control unit  301  adjusts the size reflecting the recording range in recording data on the basis of the acquired information on the sheet size. 
     Here, the size reflecting the range may be adjusted on the basis of the estimated sheet size. 
     Then, the process of S 25  is performed. 
     In S 25 , a sheet is fed by the use of an automatic sheet feeder (ASF) as the feeding section  144 . Specifically, as described above, the hopper moves up and the rotation of the feed roller  190  is started. The uppermost sheet P of the sheets P set in the hopper  101  is sent downstream in the feeding direction. Then, the process of S 26  is performed. 
     In S 26 , the edge guides  103  and  103  are made to move outward in the width direction X by 0.5 mm to start the recording operation. Specifically, after the leading end of the fed sheet P is nipped by the transport roller pair  220 , the control unit  301  drives the DC motor  302  to allow the right guide  307  and the left guide  308  to move outward by 0.5 mm. Accordingly, a slight gap is generated between both lateral edges of the sheet P and the right guide  307  and the left guide  308 . That is, frictional resistance is not generated between the right guide  307  and the left guide  308  and both lateral edges of the sheet P. The fed sheet p is satisfactorily nipped by the transport roller pair  220 . Accordingly, even when the right guide  307  and the left guide  308  are apart from the lateral edges of the sheet P, the posture of the fed sheet P is not unstable. 
     Thereafter, the recording operation using the recording head  106  is started while transporting the sheet P by the use of the transport roller pair  220 . Accordingly, it is possible to minimize the back tension in the course of performing the recording operation. Then, the process of S 27  is performed. 
     In S 27 , the recording operation is ended and the sheet P is discharged. Then, the process of S 28  is performed. 
     In S 28 , it is determined whether a next job remains. Specifically, the control unit  301  determines whether a recording command as the next job is given. When the next job does not remain, the process of S 29  is performed. On the other hand, when the next job remains, the process of S 33  is performed. 
     In S 29 , the edge guides  103  and  103  are made to move to the home position. Specifically, the control unit  301  drives the DC motor  302  to allow the right guide  307  and the left guide  308  to move to the home position. Accordingly, sheets P having a different size may be reset in the hopper to change the size of the sheets P as needed. At this time, the right guide  307  and the left guide  308  are located at the outermost within the movable range in the width direction X. Accordingly, a sheet P having any settable sheet size can be set. 
     In S 30 , the previous load value is adopted. Specifically, since any sheet P remains in the hopper, the present measurement of load is not performed normally. Accordingly, the previous load value is used instead. Then, the process of S 16  is performed. 
     In S 31 , the edge guides  103  and  103  are made to move outward by 1 mm. Specifically, the control unit  301  drives the DC motor  302  to allow the right guide  307  and the left guide  308  to move outward in the width direction by 1 mm. That is, the right guide  307  and the left guide  308  are apart from both lateral edges of the sheets P. Then, the process of S 18  is performed. 
     In S 32 , N=N+1 is set. Specifically, the number of times when the current value reaches the threshold value is increased. Then, the process of S 31  is performed. 
     By performing the loop of S 18  to S 21 , S 32 , and S 31  three times, the edge guides  103  and  103  can be bumped against both lateral edges of the sheets P three times at the time of aligning both lateral edges of the sheets P. Accordingly, compared with the case where the number of bumping times is only one, it is possible to align both lateral edges of the sheets P with higher precision. 
     That is, only once bumping may not be sufficient and thus it is possible to satisfactorily align both lateral edges of the sheets P by the plural times of bumping. This is effective particularly when a frictional coefficient between the sheet P and the sheet P overlapping with each other is relatively high and it is difficult to align both lateral edges of the sheets P. 
     By the plural times of bumping, it is possible to generate a gap between the sheet P and the sheet P. Accordingly, it is possible to align both lateral edges while undoing the bundle of stacked sheets P. That is, it is possible to undo the sheet P and the sheet P closely attached to each other and to align both lateral edges of the sheets with high precision. 
     In S 21 , the number of times can be set to a natural number other than 3. Specifically, the number of times can be set to a natural number of 2 or 4 or more. 
     In this embodiment, the edge guides  103  and  103  are of a center alignment type where the right guide  307  and the left guide  308  move symmetrically, but are not limited to the center alignment type. That is, the edge guides  103  and  103  may be of a one-sided type where one is fixed and the other is movable. 
     The recording apparatus  100  according to this embodiment includes the hopper  101  as the loading section  145  in which sheets P as an example of the recording mediums are set; the feed roller  190  feeding the sheets set in the hopper  101 ; the hopper lever  280  and the torsion coil spring  290  as the first urging mechanism urging one of the hopper  101  and the feed roller  190  to decrease a distance between the set sheets P and the feed roller  190 ; the right guide  307  and the left guide  308  as the edge guides being movable in the width direction X of the sheets P to align the lateral edges of the sheets P set in the hopper  101 ; the DC motor  302  allowing the right guide  307  and the left guide  308  to move; the determination unit  300  determining whether the current value at the time of driving the DC motor  302  reaches a predetermined threshold value; and the recording section  143  performing a recording operation on the fed sheet P by the use of the recording head  106 , and stops the driving of the DC motor  302  when it is determined by the determination unit  300  that the current value reaches the predetermined threshold value. 
     The recording apparatus  100  according to this embodiment further includes the sheet size detector  330  as the medium size detector including: the linear scale  331  disposed in one of the hopper  101  and the edge guides  103  and  103 ; and the sensor  332  disposed in the other thereof to detect the linear scale  331 . 
     The recording apparatus  100  according to this embodiment further includes the vibration generating mechanism  350  generating a vibration in the hopper  101  when the right guide  307  and the left guide  308  as the edge guides  103  and  103  move. 
     In this embodiment, the vibration generating mechanism  350  generates a vibration in the stacking direction Z of the sheets P intersecting the width direction X and the feeding direction Y. 
     In this embodiment, the vibration generating mechanism  350  includes the uneven portion  351  as the first uneven portion disposed in one of the hopper  101  and the edge guides  103  and  103  to have an uneven shape in the width direction X and the protruding portions  352  and  352  as the first convex portion disposed in the other thereof to come in contact with the uneven portion  351 . 
     In this embodiment, the DC motor  302  is driven to allow the edge guides  103  and  103  to move close to the lateral edges of the sheets P (S 18 ), the driving of the DC motor  302  is stopped (S 20 ) when the current value reaches the predetermined threshold value (S 19 ), and the backward (S 31 ) and forward (S 18 ) rotations of the DC motor  302  are repeated to bump the edge guides  103  and  103  against the lateral edges of the sheets P several times (S 18  to S 21 , S 32 , and S 31 ). 
     In the recording apparatus  100  according to this embodiment, the right guide  307  and the left guide  308  as the edge guides  103  and  103  include: the arm portion  341  being movable in the stacking direction or thickness direction Z of the set sheets P; the ball portion  344  as the spherical portion rotatably disposed at an end of the arm portion  341 ; and the pressing spring  345  as the second urging mechanism urging the arm portion  341  to the sheets. 
     Other Embodiments 
       FIG. 11  is a side view illustrating a loading section according to another embodiment of the invention. 
     As shown in  FIG. 11 , a cam portion  401  is disposed to be rotatable about a camp shaft  402 . A hopper lever  404  is disposed to be rotatable about a lever shaft  405 . The hopper lever  404  is urged counterclockwise in the drawing by a hopper spring  408 . The hopper lever  404  is provided with a cam follower  406  engaging with the cam portion  401 . 
     Similarly to the above-mentioned embodiment, by allowing the cam portion  401  to rotate, it is possible to allow the hopper lever  404  to fluctuate. Specifically, by allowing the cam portion  401  to engage with the cam follower  406 , the hopper-down state can be obtained. When the cam portion  401  is disengaged from the cam follower  406 , the hopper-up state can be obtained with the urging force of the hopper spring  408 . 
     The loading section  145  according to another embodiment includes a vibration generating mechanism  400 . The vibration generating mechanism  400  includes an uneven portion  403  and an angled portion  407 . The uneven portion  403  is formed in the cam portion  401 . The angled portion  407  is formed in the cam follower  406 . 
     Since the other members are similar to those of the above-mentioned embodiment, the same reference numerals and signs are used and thus description thereof is omitted. 
     Operations of the vibration generating mechanism  400  will be described now. 
       FIGS. 12A to 12B  are side views schematically illustrating operations of the vibration generating mechanism.  FIGS. 12A to 12C  show the hopper-down state just before the hopper-up state.  FIG. 12D  shows the hopper-up state. 
     As shown in  FIG. 12A , the hopper  101  before the feeding is in the hopper-down state. At the time of S 18  in the above-mentioned embodiment, the cam portion  401  is made to rotate counterclockwise. Accordingly, the angled portion  407  engages with the uneven portion  403  to generate a vibration. At this time, it is possible to transmit the vibration to the hopper  101  through the hopper lever  404 . 
     As shown in  FIGS. 12B and 12C , when the cam portion  401  rotates counterclockwise again from the state shown in  FIG. 12A , the vibration can be continuously generated. Accordingly, when the loop of S 18  to S 21 , S 32 , and S 31  in the above-mentioned embodiment is being repeated, the vibration can be continuously generated. As a result, similarly to the above-mentioned embodiment, a gap is generated between the sheet P and the sheet P, thereby undoing the bundle of stacked sheets P. It is possible to align both lateral edges of the sheets P with high precision, thereby detecting the sheet size with high precision. 
     As shown in  FIG. 12D , when the cam portion  401  rotates counterclockwise again from the state shown in  FIG. 12C , the engagement of the cam portion  401  and the cam follower  406  is released to obtain the hopper-up state. 
     Here, the hopper-up time is the time of S 25  in the above-mentioned embodiment. 
     The rotating member (not shown) of a suction pump of the ink suction device  200  (see  FIG. 1 ) as the vibration generating mechanism may be made to be eccentric to generate the vibration. 
     When the loop of S 18  to S 21 , S 32 , and S 31  in the above-mentioned embodiment is being repeated, the hopper  101  may be made to move from the hopper-down state in the direction in which it is apart from the feed roller  190 . That is, a new hopper-down operation can be embodied. In this case, similarly to the above-mentioned vibration generating mechanism, a gap is generated between the sheet P and the sheet P, thereby undoing the bundle of sheets P. 
     In another embodiment, the recording apparatus  100  includes the hopper lever  404  urging the hopper  101  as the loading section  145  in the direction in which it is close to the feed roller  190  and a cam portion  401  allowing the hopper lever  404  to fluctuate. 
     The vibration generating mechanism  400  includes the uneven portion  403  as the second uneven portion disposed in one of the hopper lever  404  and the cam portion  401  to have an uneven shape in a rotation direction of the cam portion  401  and the angled portion  407  as the second convex portion disposed in the other thereof to come in contact with the uneven portion  403 , and brings the uneven portion  403  and the angled portion  407  into contact with each other in a state where the set sheets P and the feed roller  190  are separated from each other. 
     In another embodiment, the vibration generating mechanism is an ink suction device  200  (see  FIG. 1 ) cleaning the recording head  106  disposed in the recording section  143  by suction. 
     In the recording apparatus  100  according to another embodiment, the hopper  101  is made to move further apart from the feed roller  190  when the right guide  307  and the left guide  308  as the edge guides  103  and  103  move in a state where the set sheets P and the feed roller  190  are separated from each other. 
     The invention is not limited to the above-mentioned embodiments, but may be modified in various forms without departing from the scope of the invention described in the appended claims. Of course, the modifications are included in the scope of the invention.