Patent Publication Number: US-9409417-B2

Title: Conveyor device and inkjet recording apparatus

Description:
INCORPORATION BY REFERENCE 
     The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2014-075588, filed Apr. 1, 2014. The contents of this application are incorporated herein by reference in their entirety. 
     BACKGROUND 
     The present disclosure relates to a conveyor device for installation in a recording apparatus and an inkjet recording apparatus including the conveyor device. 
     An inkjet recording apparatus is a commonly known type of recording apparatus. Inkjet recording apparatuses are widely used in machines such as printers, copiers, and multifunction peripherals due to their compactness, low cost, and low operating noise. Inkjet recording apparatuses are broadly classified as being either a line head or a serial head type. 
     A line head inkjet recording apparatus includes a conveyor device for conveying a recording medium. The conveyor device typically includes a conveyor belt. The conveyor device is located opposite to a recording head and holds a recording medium on the conveyor belt while conveying the recording medium. The recording medium is held on the conveyor belt by using static electricity to attract the recording medium or negative pressure to suck the recording medium. 
     A conveyor device that creates negative pressure includes a suction section that sucks on the recording medium through the conveyor belt. The conveyor belt has a plurality of suction holes perforated therein. The suction section includes a guide member that supports the recording medium through the conveyor belt. The guide member has through holes that run through the guide member in a thickness direction thereof. The suction section creates negative pressure and thereby sucks air through the suction holes in the conveyor belt and through the through holes in the guide member. Through the above, the recording medium is sucked onto the conveyor belt. Unfortunately, a conveyor device having the configuration described above suffers from the following problem. 
     Namely, when a recording medium having paper dust attached thereto is conveyed to a position opposite to the recording head, the paper dust may be stirred up by suction air flow (air current) and may become attached to the nozzle orifice. As a consequence, the nozzle orifice may unfortunately become clogged by the attached paper dust. The suction air flow is created by the negative pressure that is used to suck the recording medium onto the conveyor belt. Clogging of the nozzle orifice makes it difficult for the nozzle orifice to eject ink droplets and may result in formation of an image that has white lines along a conveyance direction of the recording medium. 
     Attachment of paper dust to the nozzle orifice can be prevented by making suction air flow that is created below the recording head smaller. In one example of a serial head inkjet recording apparatus, the guide member does not have through holes at either end in a main scanning direction of a region in which ink droplets are ejected. 
     The main scanning direction is perpendicular to a recording medium conveyance direction. The above configuration enables suction air flow that is created in the region in which ink droplets are ejected to be made smaller. 
     SUMMARY 
     A conveyor device according to an aspect of the present disclosure is for installation opposite to a recording head in a recording apparatus. The conveyor device includes a conveyor belt and a suction section. The conveyor belt conveys a recording medium. The suction section includes a guide member having a plurality of through holes therein. The guide member is located opposite to the recording head with the conveyor belt therebetween. The suction section sucks on the recording medium through the conveyor belt and the guide member. The guide member has a surface with a plurality of grooves therein that faces toward the recording head with the conveyor belt therebetween. The through holes are each located inside of a corresponding one of the grooves. The through holes include a first through hole within a first region of the guide member and a second through hole within a second region of the guide member. The first region is located opposite to an ejection region of the recording head. The second region is located opposite to a non-ejection region of the recording head. The grooves include a first groove and a second groove. The first through hole is located inside of the first groove. The second through hole is located inside of the second groove. The second groove is longer than the first groove. 
     A conveyor device according to another aspect of the present disclosure is for installation opposite to a recording head in a recording apparatus. The conveyor device includes a conveyor belt and a suction section. The conveyor belt conveys a recording medium. The suction section includes a guide member having a plurality of through holes therein. The guide member is located opposite to the recording head with the conveyor belt therebetween. The suction section sucks on the recording medium through the conveyor belt and the guide member. The guide member has a surface with a plurality of grooves therein that faces toward the recording head with the conveyor belt therebetween. The through holes are each located inside of a corresponding one of the grooves and outside of a first region of the guide member. The first region is located opposite to an ejection region of the recording head. The through holes include a first through hole and a second through hole. The first through hole is located outside of a head facing region of the guide member and the second through hole is located within a second region of the guide member. The second region is located opposite to a non-ejection region of the recording head. The grooves include a first groove and a second groove. The first through hole is located inside of the first groove. The second through hole is located inside of the second groove. The first groove includes a section located outside of the head facing region and a section located within the first region. 
     A conveyor device according to another aspect of the present disclosure is for installation opposite to a recording head in a recording apparatus. The conveyor device includes a conveyor belt and a suction section. The conveyor belt conveys a recording medium. The suction section includes a guide member having a plurality of through holes therein. The guide member is located opposite to the recording head with the conveyor belt therebetween. The suction section sucks on the recording medium through the conveyor belt and the guide member. The through holes include a first through hole within a first region of the guide member and a second through hole within a second region of the guide member. The first region is located opposite to an ejection region of the recording head. The second region is located opposite to a non-ejection region of the recording head. The guide member has a surface that faces toward the recording head with the conveyor belt therebetween and that has a groove therein. The second through hole is located inside of the groove and the first through hole is located outside of the groove. 
     An inkjet recording apparatus according to another aspect of the present disclosure includes a recording head and any one of the conveyor devices described above. The recording head ejects ink droplets. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates configuration of an inkjet recording apparatus including a conveyor device according to a first embodiment of the present disclosure. 
         FIG. 2  is a plan view illustrating a guide member according to the first embodiment of the present disclosure. 
         FIG. 3  is a cross-sectional view illustrating a groove and a through hole of the guide member according to the first embodiment of the present disclosure. 
         FIG. 4  is a plan view illustrating a conveyor belt according to the first embodiment of the present disclosure. 
         FIG. 5  is a plan view illustrating section A of  FIG. 2 . 
         FIG. 6  is a plan view illustrating the guide member according to the first embodiment of the present disclosure. 
         FIG. 7  is a plan view illustrating section B of  FIG. 6 . 
         FIGS. 8A, 8B, and 8C  are cross-sectional views illustrating the flow rate of suction air flow created under a recording head. 
         FIG. 9A  is a plan view illustrating a first groove according to the first embodiment of the present disclosure and  FIG. 9B  is a plan view illustrating a second groove according to the first embodiment of the present disclosure. 
         FIG. 10  is a cross-sectional view illustrating the flow rate of suction air flow created under a recording head. 
         FIG. 11A  is a plan view illustrating a first alternative example of the first groove according to the first embodiment of the present disclosure and  FIG. 11B  is a plan view illustrating a first alternative example of the second groove according to the first embodiment of the present disclosure. 
         FIG. 12A  is a cross-sectional view illustrating a second alternative example of the first groove according to the first embodiment of the present disclosure and  FIG. 12B  is a cross-sectional view illustrating a second alternative example of the second groove according to the first embodiment of the present disclosure. 
         FIG. 13A  is a plan view illustrating a first alternative example of a first through hole according to the first embodiment of the present disclosure and  FIG. 13B  is a plan view illustrating a first alternative example of a second through hole according to the first embodiment of the present disclosure. 
         FIG. 14A  is a cross-sectional view illustrating a second alternative example of the first through hole according to the first embodiment of the present disclosure and  FIG. 14B  is a cross-sectional view illustrating a second alternative example of the second through hole according to the first embodiment of the present disclosure. 
         FIGS. 15A and 15B  are cross-sectional views illustrating a variation of the guide member according to the first embodiment of the present disclosure. 
         FIG. 16  is a plan view illustrating a guide member according to a second embodiment of the present disclosure. 
         FIG. 17  is a plan view illustrating section C of  FIG. 16 . 
         FIG. 18  is a cross-sectional view illustrating the flow rate of suction air flow created under a recording head according to the second embodiment of the present disclosure. 
         FIG. 19  is a plan view illustrating a guide member according to a third embodiment of the present disclosure. 
         FIG. 20  is a plan view illustrating section D of  FIG. 19 . 
         FIG. 21  is a plan view illustrating a guide member according to another embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The following explains embodiments of the present disclosure with reference to the drawings. Elements that are the same or equivalent are indicated by the same reference signs in the drawings and explanation thereof is not repeated. The drawings are schematic illustrations that emphasize elements of configuration in order to facilitate understanding thereof. Therefore, in order that the elements can be easily illustrated in the drawings, properties of each of the elements, such as thickness, length, and number thereof, may differ from actual properties of the element. Also note that material properties, shapes, dimensions, and the like, described for each of the elements of configuration in the following embodiments, are only examples and are not intended to impose any particular limitations on the elements. 
     First Embodiment 
     [Basic Configuration of Inkjet Recording Apparatus  1 ] 
       FIG. 1  illustrates configuration of an inkjet recording apparatus  1  including a conveyor device  310  according to a first embodiment of the present disclosure. 
     The inkjet recording apparatus  1  (an example of a recording apparatus) includes a housing  100 , a sheet feed section  200 , an image forming section  300  that uses an inkjet recording method, a sheet conveying section  400 , and a sheet ejecting section  500 . The sheet feed section  200  is located in a lower section of the housing  100 . The image forming section  300  is located above the sheet feed section  200 . The sheet conveying section  400  is located at one side of the image forming section  300 . The sheet ejecting section  500  is located at the other side of the image forming section  300 . 
     The sheet feed section  200  includes a sheet feed cassette  201  that is freely detachable from the housing  100 . The sheet feed section  200  also includes a sheet feed roller  202  and guide plates  203 . The sheet feed roller  202  is located above the sheet feed cassette  201  at one end thereof. The guide plates  203  are located between the sheet feed roller  202  and the sheet conveying section  400 . 
     The sheet feed cassette  201  contains a plurality of sheets of paper P (an example of a recording medium) in a stacked state. In the following explanation, a sheet of paper is simply referred to as a sheet. The sheet feed roller  202  (pick-up roller) is a feed member that feeds a sheet P in a conveyance direction thereof. The sheet feed roller  202  picks up sheets P, one at a time, from the sheet feed cassette  201 . The guide plates  203  guide a sheet P that has been picked up by the sheet feed roller  202  to the sheet conveying section  400 . 
     The sheet conveying section  400  includes a sheet conveyance path  401  that is roughly C-shaped, a first pair of conveyance rollers  402  (primary sheet feed roller pair), a second pair of conveyance rollers  403  (secondary sheet feed roller pair), and a pair of registration rollers  404 . The first pair of conveyance rollers  402  is located at an input end of the sheet conveyance path  401 . The second pair of conveyance rollers  403  is located partway along the sheet conveyance path  401 . The pair of registration rollers  404  is located at an output end of the sheet conveyance path  401 . The sheet conveyance path  401  forms one section of a conveyance path of the sheet P (an example of a recording medium conveyance path). 
     The first pair of conveyance rollers  402  is a feed member that feeds the sheet P in the conveyance direction thereof. The first pair of conveyance rollers  402  sandwiches the sheet P fed from the sheet feed section  200  therebetween and feeds the sheet P into the sheet conveyance path  401 . The second pair of conveyance rollers  403  is also a feed member. The second pair of conveyance rollers  403  sandwiches the sheet P fed from the first pair of conveyance rollers  402  therebetween and feeds the sheet P in the sheet conveyance direction. 
     The pair of registration rollers  404  performs skew correction on the sheet P fed from the second pair of conveyance rollers  403 . The pair of registration rollers  404  temporarily holds the sheet P stationary in order to synchronize conveyance of the sheet P with a timing at which image formation is to be performed on the sheet P. The pair of registration rollers  404  subsequently feeds the sheet P to the image forming section  300  in accordance with the timing of image formation on the sheet P. 
     The image forming section  300  includes the conveyor device  310 , four types of line head  340   a ,  340   b ,  340   c , and  340   d , and a conveyance guide  350 . The four types of line head  340   a ,  340   b ,  340   c , and  340   d  are located above the conveyor device  310 . The conveyance guide  350  is located downstream of the conveyor device  310  in terms of the conveyance direction of the sheet P. Although not illustrated in the drawings, the four types of line head  340   a ,  340   b ,  340   c , and  340   d  each include a plurality of nozzles. The nozzles eject ink droplets in order to form an image, such as a diagram or text, on the sheet P. The image forming section  300  may also include a drying device. The drying device dries ink droplets that have landed onto the sheet P. 
     The conveyor device  310  includes a belt speed detecting roller  311 , a sheet holding roller  312 , a drive roller  313 , a tension roller  314 , a pair of guide rollers  315 , an endless conveyor belt  320 , and a suction section  330 . The conveyor device  310  is located opposite to the four types of line head  340   a ,  340   b ,  340   c , and  340   d  in the housing  100 . The conveyor belt  320  is wound around the belt speed detecting roller  311 , the drive roller  313 , the tension roller  314 , and the pair of guide rollers  315 . The conveyor belt  320  is driven in the conveyance direction of the sheet P and thus conveys the sheet P in the aforementioned direction. 
     The conveyor belt  320  is for example made from a material such as polyimide (PI), polyamide-imide (PAI), polyvinylidene fluoride (PVDF), or polycarbonate (PC). Use of polyimide or polyamide-imide is preferable in terms of reducing unevenness in thickness of the conveyor belt  320 . Also, a layer made of a rubber material such as ethylene propylene diene monomer (EPDM) rubber may be layered on a rear surface of the conveyor belt  320  (i.e., a surface facing the suction section  330 ). The conveyor belt has a thickness of, for example, 100 μm. 
     The tension roller  314  ensures that the conveyor belt  320  does not sag by applying tensile force to the conveyor belt  320 . The conveyor device  310  may include a mechanism that when meandering of the conveyor belt  320  occurs, changes the orientation of the axial center of the tension roller  314  in accordance with the meandering. Such a mechanism corrects the meandering of the conveyor belt  320 . 
     The belt speed detecting roller  311  is located upstream relative to the suction section  330  in terms of the conveyance direction of the sheet P. The belt speed detecting roller  311  rotates due to friction generated between the belt speed detecting roller  311  and the conveyor belt  320 . The belt speed detecting roller  311  includes a pulse plate (not illustrated) that rotates integrally with the belt speed detecting roller  311 . The circulation speed of the conveyor belt  320  is detected by measuring the rotation speed of the pulse plate. Therefore, when unevenness in circulation speed of the conveyor belt  320  occurs, the unevenness can be corrected by controlling the rotation speed of the drive roller  313 . 
     The drive roller  313  is located downstream relative to the suction section  330  in terms of the conveyance direction of the sheet P. Preferably the drive roller  313  is located such as to function in combination with the belt speed detecting roller  311  to maintain flatness of the conveyor belt  320 . Such a configuration also maintains flatness of the conveyor belt  320  when meandering correction is performed on the conveyor belt  320 . 
     The drive roller  313  is driven by a motor (not illustrated). In other words, the motor causes the drive roller  313  to rotate. When the drive roller  313  rotates, friction generated between the drive roller  313  and the conveyor belt  320  causes the conveyor belt  320  to circulate in a direction corresponding to counter clockwise in  FIG. 1 . The drive roller  313  has a diameter of, for example, 30.0 mm. 
     In a configuration in which correction of unevenness of speed of the conveyor belt  320  is performed by correcting rotation speed of the drive roller  313 , the drive roller  313  preferably has a small moment of inertia. In other words, the drive roller  313  is preferably light. In consideration of the above, in the first embodiment the drive roller  313  is preferably a hollow pipe such as an aluminum pipe or a pipe having a three-spoke cross-section. In a configuration in which unevenness of speed of the conveyor belt  320  is not corrected, the drive roller  313  preferably has a large moment of inertia in order to stabilize rotation of the drive roller  313  through a flywheel effect. In other words, the drive roller  313  is preferably heavy. Therefore, in such a configuration the drive roller  313  is preferably made of a material such as solid metal. 
     In a configuration in which the conveyor belt  320  is made from a resinous material such as polyimide, a surface layer of the drive roller  313  is preferably made from a rubber material such as EPDM rubber, urethane rubber, or nitrile rubber. In a configuration in which the image forming section  300  forms an image on the sheet P using an aqueous ink, EPDM rubber is preferably used as a material of the surface layer of the drive roller  313  in order to prevent swelling of the rubber material. The surface layer formed from the rubber material has a thickness of, for example, 1.0 mm. In a configuration in which a layer of a rubber material such as EPDM rubber is disposed over the rear surface of the conveyor belt  320 , the surface layer of the drive roller  313  may be made from metal. In a configuration in which the surface layer of the drive roller  313  is made from aluminum, the surface of the drive roller  313  may be anodized in order to prevent abrasion. 
     The pair of guide rollers  315  is located lower than suction section  330 . By positioning the pair of guide rollers  315  as described above, a space is formed under the suction section  330  and thus a section of the conveyor belt  320  that is located under the suction section  330  is prevented from coming into contact with the suction section  330 . Also, a guide roller  315  among the pair of guide rollers  315  that is closer to the drive roller  313  maintains a degree to which the conveyor belt  320  is wound around the drive roller  313 . A guide roller  315  among the pair of guide rollers  315  that is closer to the tension roller  314  maintains a degree to which the conveyor belt  320  is wound around the tension roller  314 , thereby ensuring that meandering correction can be reliably performed. 
     The four types of line head  340   a ,  340   b ,  340   c , and  340   d  are located in respective order from upstream to downstream in terms of the conveyance direction of the sheet P. The line heads  340   a ,  340   b ,  340   c , and  340   d  each include a plurality of nozzles (not illustrated) that are arranged in a width direction of the conveyor belt  320  (i.e., a direction perpendicular to the conveyance direction of the sheet P). In other words, the inkjet recording apparatus  1  is a line head inkjet recording apparatus. 
     The following explains a generic line head inkjet recording apparatus. In order to eject ink droplets of a single color toward a recording medium, the line head inkjet recording apparatus includes a single recording head having a greater width than the recording medium. Alternatively, the line head inkjet recording apparatus may include a plurality of recording heads that are arranged in a direction perpendicular to the conveyance direction of the recording medium (i.e., arranged in a width direction of the recording medium). In a configuration in which the inkjet recording apparatus ejects ink droplets of a plurality of different colors, the inkjet recording apparatus includes either a single recording head or a group of recording heads for each of the colors, and the recording heads for the respective colors are arranged in the conveyance direction of the recording medium. The recording heads are fixed in place and the recording medium is conveyed under the recording heads. The recording heads form an image on the recording medium by ejecting ink droplets onto the recording medium while the recording medium is being conveyed. Note that in a serial head inkjet recording apparatus, a recording medium is held stationary partway along a recording medium conveyance path and recording heads eject ink droplets onto the stationary recording medium while moving. 
     The following resumes explanation of the inkjet recording apparatus  1  according to the first embodiment. The line head  340   a  includes a plurality of nozzles that are each in communication with a pressure chamber (not illustrated) located within a recording head. The pressure chamber is in communication with an ink chamber (not illustrated) located within the recording head. The ink chamber is in communication with a black (Bk) ink tank (not illustrated) via an ink supply tube (not illustrated). In other words, the ink chamber is connected to the black ink tank. 
     The line head  340   b  includes a plurality of nozzles that are each in communication with a pressure chamber (not illustrated) located within a recording head. The pressure chamber is in communication with an ink chamber (not illustrated) located within the recording head. The ink chamber is in communication with a cyan (C) ink tank (not illustrated) via an ink supply tube (not illustrated). In other words, the ink chamber is connected to the cyan ink tank. 
     The line head  340   c  includes a plurality of nozzles that are each in communication with a pressure chamber (not illustrated) located within a recording head. The pressure chamber is in communication with an ink chamber (not illustrated) located within the recording head. The ink chamber is in communication with a magenta (M) ink tank (not illustrated) via an ink supply tube (not illustrated). In other words, the ink chamber is connected to the magenta ink tank. 
     The line head  340   d  includes a plurality of nozzles that are each in communication with a pressure chamber (not illustrated) located within a recording head. The pressure chamber is in communication with an ink chamber (not illustrated) located within the recording head. The ink chamber is in communication with a yellow (Y) ink tank (not illustrated) via an ink supply tube (not illustrated). In other words, the ink chamber is connected to the yellow ink tank. 
     The suction section  330  faces the rear surface of the conveyor belt  320  such as to be located opposite to the four types of line head  340   a ,  340   b ,  340   c , and  340   d  with the conveyor belt  320  therebetween. The suction section  330  includes an air flow chamber  331  (an example of a gas flow chamber), a guide member  332  that covers an upper surface aperture of the air flow chamber  331 , and a suction device  336 . The guide member  332  supports the sheet P through the conveyor belt  320 . 
     The sheet holding roller  312  is a driven roller. The sheet holding roller  312  is located opposite to the guide member  332  with the conveyor belt  320  therebetween. The sheet holding roller  312  guides a sheet P that has been fed from the pair of registration rollers  404  onto the conveyor belt  320  and causes the sheet P to be sucked onto the conveyor belt  320 . 
     The sheet holding roller  312  preferably has a small moment of inertia in order to soften impact vibration generated by the sheet P impacting with the sheet holding roller  312 . In other words, the sheet holding roller  312  is preferably light. The sheet holding roller  312  is for example preferably a hollow pipe such as an aluminum pipe or a pipe having a three-spoke cross-section. In a configuration in which the sheet holding roller  312  is made from aluminum, the surface of the sheet holding roller  312  may be anodized in order to prevent abrasion. 
     In the first embodiment, pressing force that presses the sheet holding roller  312  toward the conveyor belt  320  (i.e., toward the guide member  332 ) is applied to the sheet holding roller  312 . Through the above configuration, even when there is a disparity between the conveyance speed of the sheet P by the pair of registration rollers  404  and the circulation speed of the conveyor belt  320 , a position at which close contact between the sheet P and the conveyor belt  320  begins can be made to correspond to a position at which the sheet holding roller  312  is located. 
     The suction device  336  is for example a fan. However, the suction device  336  is not limited to being a fan and may for example be a vacuum pump instead. While the suction device  336  is being operated, the suction section  330  sucks on the sheet P through the conveyor belt  320 . 
     The conveyance guide  350  guides the sheet P to the sheet ejecting section  500  upon the sheet P being ejected from the conveyor belt  320 . The sheet ejecting section  500  includes a pair of ejection rollers  501  and an exit tray  502 . The exit tray  502  is fixed to the housing  100  such as to project outward from an exit port  101  formed in the housing  100 . 
     Once the sheet P has passed through the conveyance guide  350 , the sheet P is fed toward the exit port  101  by the pair of ejection rollers  501  and is guided onto the exit tray  502 . As a result, the sheet P is ejected externally from the housing  100  through the exit port  101 . 
     The air flow chamber  331  is formed by a box-shaped member having a covered bottom end and an open top end. The suction device  336  is located under the air flow chamber  331 . A bottom wall of the box-shaped member forming the air flow chamber  331  has a gas outlet (not illustrated) corresponding to the suction device  336 . The suction device  336  is connected to a power source (not illustrated). Operation of the suction device  336  creates negative pressure in the air flow chamber  331 . The negative pressure causes suction on the sheet P through the conveyor belt  320 . 
       FIG. 2  is a plan view of the guide member  332 .  FIG. 2  illustrates positional relationship of the guide member  332  and the four types of line head  340   a ,  340   b ,  340   c , and  340   d . Note that the conveyor belt  320  is not illustrated in  FIG. 2  in order to facilitate understanding. 
     As illustrated in  FIG. 2 , the line head  340   a  for black (Bk) includes three recording heads  341 . The three recording heads  341  are arranged in the width direction of the guide member  332  (i.e., the direction perpendicular to the sheet conveyance direction) in a staggered formation. 
     The line head  340   b  for cyan (C) includes three recording heads  342 . The three recording heads  342  are arranged in the width direction of the guide member  332  in a staggered formation. 
     The line head  340   c  for magenta (M) includes three recording heads  343 . The three recording heads  343  are arranged in the width direction of the guide member  332  in a staggered formation. 
     The line head  340   d  for yellow (Y) includes three recording heads  344 . The three recording heads  344  are arranged in the width direction of the guide member  332  in a staggered formation. 
     The guide member  332  has a plurality of grooves  334  into a surface  333  thereof on a side closest to the line heads  340   a - 340   d  (recording heads  341 - 344 ). The surface  333  faces toward the line heads  340   a - 340   d  (recording heads  341 - 344 ). The grooves  334  each have a rod-like shape with rounded ends that extends in the sheet conveyance direction.  FIG. 3  is a cross-sectional view illustrating a groove  334  and a through hole  335  in the guide member  332 . As illustrated in  FIGS. 2 and 3 , for each of the plurality of grooves  334 , the guide member  332  has a corresponding through hole  335  that runs through the guide member  332  in a thickness direction thereof. 
       FIG. 4  is a plan view illustrating the conveyor belt  320 . As illustrated in  FIG. 4 , the conveyor belt  320  has a plurality of suction holes  321  that are perforated through the conveyor belt  320 . The suction holes  321  each have a diameter of, for example, 2 mm. The spacing between adjacent suction holes  321  is, for example, 8 mm. 
     A plurality of columns that each include a plurality of the suction holes  321  arranged in the sheet conveyance direction are arranged in the width direction of the conveyor belt  320  (i.e., the direction perpendicular to the sheet conveyance direction) such that the suction holes  321  are arranged in a staggered formation. On the other hand, in the guide member  332  a plurality of columns that each include a plurality of the grooves  334  arranged in the sheet conveyance direction are arranged in the width direction of the guide member  332  (i.e., the direction perpendicular to the sheet conveyance direction) as illustrated in  FIG. 2 . The columns of the suction holes  321  in the conveyor belt  320  are arranged such as to correspond to the columns of the grooves  334  in the guide member  332 . 
     Each of the grooves  334  is located such as to be opposite to at least two of the suction holes  321 . The suction holes  321  that are opposite to the groove  334  change one-by-one as the conveyor belt  320  circulates. 
     The air flow chamber  331  (refer to  FIG. 1 ) is in communication with the suction holes  321  (refer to  FIG. 4 ) in the conveyor belt  320  through the through holes  335  (refer to  FIG. 2 ) and the grooves  334  (refer to  FIG. 2 ) in the guide member  332 . 
     [Operation of Inkjet Recording Apparatus  1 ] 
     The following explains operation of the inkjet recording apparatus  1  with reference to  FIG. 1 . A sheet P is picked up from the sheet feed cassette  201  by the sheet feed roller  202 . The picked-up sheet P is guided to the first pair of conveyance rollers  402  by the guide plates  203 . In a situation in which a plurality of sheets P are stacked in the sheet feed cassette  201 , an uppermost sheet P in the stack is picked up from the sheet feed cassette  201  by the sheet feed roller  202 . 
     The sheet P is fed into the sheet conveyance path  401  by the first pair of conveyance rollers  402  and is then conveyed in the sheet conveyance direction by the second pair of conveyance rollers  403 . The sheet P stops upon coming into contact with the pair of registration rollers  404 . Through the above, skew correction is performed on the sheet P. The sheet P is subsequently fed to the image forming section  300  in synchronization with timing of image formation. 
     The sheet P is guided and caused to be sucked onto the conveyor belt  320  by the sheet holding roller  312 . Preferably the sheet P is guided onto the conveyor belt  320  such that the center of the sheet P in terms of the width direction thereof coincides with the center of the conveyor belt  320  in terms of the width direction thereof. The sheet P covers a portion of the suction holes  321  in the conveyor belt  320 . The suction section  330  sucks air (an example of a gas) through the through holes  335  and the grooves  334  in the guide member  332  and the suction holes  321  in the conveyor belt  320 . In other words, the suction section  330  creates negative pressure in the air flow chamber  331 . The negative pressure acts on the sheet P, thereby sucking the sheet P onto the conveyor belt  320 . The sheet P is conveyed in the sheet conveyance direction as the conveyor belt  320  circulates. 
     The conveyor belt  320  conveys each portion of the sheet P, in turn, to positions opposite to the four types of line head  340   a ,  340   b ,  340   c , and  340   d  (recording heads  341 - 344 ). During the aforementioned conveyance, each of the four types of line head  340   a ,  340   b ,  340   c , and  340   d  (recording heads  341 - 344 ) ejects ink droplets of the corresponding color toward the sheet P. Through the above process, an image is formed on the sheet P. 
     The sheet P is conveyed from the conveyor belt  320  to the conveyance guide  350 . Once the sheet P has passed through the conveyance guide  350 , the sheet P is fed toward the exit port  101  by the pair of ejection rollers  501  and is guided onto the exit tray  502 . As a result, the sheet P is ejected externally from the housing  100  through the exit port  101 . 
     In the line head inkjet recording apparatus  1  explained above, the line heads  340   a ,  340   b ,  340   c , and  340   d  (recording heads  341 - 344 ) are fixed in place. The sheet P is conveyed under the line heads  340   a ,  340   b ,  340   c , and  340   d  (recording heads  341 - 344 ). Therefore, the recording rate of the inkjet recording apparatus  1  can be increased by increasing the conveyance speed of the sheet P. For example, the conveyance speed of the sheet P in the inkjet recording apparatus  1  can be set at 900 mm/s. Also, in a situation in which A4 size paper P is conveyed with a long edge thereof orientated perpendicularly to the conveyance direction, the inkjet recording apparatus  1  can for example have a printing rate of 150 sheets per minute. 
     [Configuration of Guide Member  332 ] 
       FIG. 5  is a plan view illustrating section A of  FIG. 2 . In other words,  FIG. 5  is an enlarged view of one section of the guide member  332 . Note that the conveyor belt  320  is not illustrated in  FIG. 5  in order to facilitate understanding. 
     As illustrated in  FIGS. 2 and 5 , a head surface of each of the recording heads  341 ,  342 ,  343 , and  344  has ejection regions  345   a  and a non-ejection region  345   b . The head surface is a belt facing surface that faces toward the conveyor belt  320 . Nozzle orifices are present in the ejection regions  345   a . The non-ejection region  345   b  is a region of the head surface that is exclusive of the ejection regions  345   a . In other words, the non-ejection region  345   b  is a region of the head surface that is outside of the ejection regions  345   a.    
       FIG. 6  is a plan view illustrating the guide member  332 .  FIG. 7  is a plan view illustrating section B of  FIG. 6 . In other words,  FIG. 7  is an enlarged view of one section of the guide member  332 . As illustrated in  FIGS. 6 and 7 , the through holes  335  include first through holes  335   a  and second through holes  335   b . The first through holes  335   a  are within first regions  51  of the guide member  332 . The second through holes  335   b  are within second regions  52  of the guide member  332 . The first regions  51  are located opposite to the ejection regions  345   a  explained with reference to  FIGS. 2 and 5 . The second regions  52  are located opposite to the non-ejection regions  345   b  explained with reference to  FIGS. 2 and 5 . The first regions  51  and the second regions  52  form head facing regions  50  that are located opposite to the recording heads  341 ,  342 ,  343 , and  344  explained with reference to  FIG. 2 . 
     The grooves  334  into the surface  333  of the guide member  332  include first grooves  334   a  and second grooves  334   b . The first through holes  335   a  are located inside of the first grooves  334   a . The second through holes  335   b  are located inside of the second grooves  334   b.    
     Therefore, according to the first embodiment, the first through holes  335   a  are located below the ejection regions  345   a  of the head surfaces (i.e., within the first regions  51 ) and the second through holes  335   b  are located below the non-ejection regions  345   b  of the head surfaces (i.e., within the second regions  52 ). The above configuration ensures that suction force acting on the sheet P below each of the recording heads  341 ,  342 ,  343 , and  344  is not insufficient. Therefore, the above configuration restricts the sheet P from rising up off the conveyor belt  320 . In a situation in which the sheet P rises up off the conveyor belt  320  under the recording heads  341 ,  342 ,  343 , and  344 , a distorted image may be formed on the sheet P. Also, a paper jam may occur under the recording heads  341 ,  342 ,  343 , and  344 . The first embodiment enables restriction of rising up of the sheet P and thus enables restriction of distortion of the image formed on the sheet P. Also, the first embodiment enables reduced probability of a paper jam occurring under the recording heads  341 ,  342 ,  343 , and  344 . 
     Furthermore, as illustrated in  FIGS. 2 and 5-7 , the first grooves  334   a  are shorter than the second grooves  334   b  in the first embodiment. As a result, regions below the ejection regions  345   a  of the recording heads  341 - 344  (i.e., the first regions  51 ) have greater pressure loss than regions below the non-ejection regions  345   b  of the recording heads  341 - 344  (i.e., the second regions  52 ). 
     Therefore, the first embodiment enables suction air flow created below the ejection regions  345   a  of the head surfaces to be made smaller than suction air flow created below the non-ejection regions  345   b  of the head surfaces. The aforementioned suction air flow is created by air being sucked toward the air flow chamber  331  through the grooves  334  and the through holes  335  in the guide member  332  and the suction holes  321  in the conveyor belt  320 . The following explains the relationship between pressure loss and suction air flow using an example of suction air flow created under a recording head  341 . 
       FIGS. 8A, 8B, and 8C  are cross-sectional views illustrating the flow rate of suction air flow  337  created under the recording head  341 . Specifically,  FIG. 8A  illustrates suction air flow  337  created in a configuration in which a through hole  335  is not located inside of a groove  334 .  FIG. 8B  illustrates suction air flow  337  created in a configuration in which a groove  334  is located entirely within a region (head facing region  50 ) that is a projection of a head surface  345  (surface facing toward the guide member  332 ) of the recording head  341 .  FIG. 8C  illustrates suction air flow  337  created in a configuration in which both ends of a groove  334  protrude outside of the region (head facing region  50 ) that is a projection of the head surface  345 . Note that the conveyor belt  320  is not illustrated in  FIGS. 8A, 8B, and 8C  in order to facilitate understanding. 
     The thickness of arrows indicating suction air flow  337  in  FIGS. 8A, 8B, and 8C  represents the flow rate of suction air flow  337 . In general, the head surface  345  and the guide member  332  are separated by approximately 0.5 mm to 3.0 mm and thus the gap between the head surface  345  and the guide member  332  is extremely narrow. As a consequence, the flow rate of suction air flow  337  is small due to extremely high pressure loss directly under the head surface  345 . However, as illustrated in  FIGS. 8B and 8C , pressure loss directly under the head surface  345  can be made smaller and the flow rate of suction air flow  337  can be made larger by providing a groove  334  directly under the head surface  345 . Therefore, the flow rate of suction air flow  337  is smallest in a configuration in which no groove  334  is present ( FIG. 8A ). The area of an aperture of the groove  334  is made larger and pressure loss directly under the head surface  345  is made smaller by making the length of the groove  334  longer. Therefore, the flow rate of suction air flow  337  is greater in a configuration in which the groove  334  is longer ( FIGS. 8B and 8C ). 
     When a sheet P having paper dust attached thereto is conveyed to a position where the guide member  332  and the recording head  341  are directly opposite to one another, suction air flow  337  (air current) may cause the paper dust to be stirred up from the sheet P and become attached to a nozzle orifice (not illustrated) in the head surface  345 . As a consequence, the nozzle orifice may unfortunately become clogged by the attached paper dust. 
     In the first embodiment, the first through holes  335   a  are located opposite to the ejection regions  345   a  of the head surfaces and the second through holes  335   b  are located opposite to the non-ejection regions  345   b  of the head surfaces, as illustrated in  FIGS. 2 and 5 . Also, the first through holes  335   a  are located inside of the first grooves  334   a  and the second through holes  335   b  are located inside of the second grooves  334   b . The first grooves  334   a  are shorter than the second grooves  334   b.    
       FIG. 9A  is a plan view illustrating one of the first grooves  334   a  and  FIG. 9B  is a plan view illustrating one of the second grooves  334   b . As illustrated in  FIGS. 9A and 9B , the length L 1  of the first grooves  334   a  is shorter than the length L 2  of the second grooves  334   b  in the first embodiment. On the other hand, the width w 1  of the first grooves  334   a  is the same as the width w 2  of the second grooves  334   b . Consequently, the first grooves  334   a  have a smaller aperture area than the second grooves  334   b . Although not illustrated in  FIGS. 9A and 9B , the first grooves  334   a  have the same depth as the second grooves  334   b . The first through holes  335   a  and the second through holes  335   b  each have a circular cross-section and the diameter d 1  of the first through holes  335   a  is the same as the diameter d 2  of the second through holes  335   b . Although not illustrated in  FIGS. 9A and 9B , the first through holes  335   a  have the same depth as the second through holes  335   b.    
     Therefore, as explained with reference to  FIGS. 8B and 8C , regions below the ejection regions  345   a  of the head surfaces (i.e., the first regions  51 ) have a greater pressure loss than regions below the non-ejection regions  345   b  of the head surfaces (i.e., the second regions  52 ). Through the above, suction air flow created under the ejection regions  345   a  can be made smaller than suction air flow created under the non-ejection regions  345   b.    
     As a result, even when a sheet P having paper dust attached thereto is conveyed by the conveyor device  310 , stirring up of the paper dust can be restricted under the ejection regions  345   a  of the head surfaces and thus attachment of the paper dust to the nozzle orifices can be restricted. By restricting attachment of paper dust to the nozzle orifices, the probability of nozzle clogging occurring can be reduced. In particular, in the first embodiment the length in the sheet conveyance direction of each of the first grooves  334   a  is shorter than the length (width) in the sheet conveyance direction of the head surface of a corresponding one of the recording heads  341 ,  342 ,  343 , or  344  opposite thereto as illustrated in  FIGS. 2 and 5 . As explained with reference to  FIGS. 8B and 8C , the configuration described above effectively restricts the flow rate of suction air flow. 
     As a result of the second grooves  334   b  being longer than the first grooves  334   a , the flow rate of suction air flow created under the non-ejection regions  345   b  of the head surfaces is larger than the flow rate of suction air flow created under the ejection regions  345   a  of the head surfaces. Therefore, suction force acting on the sheet P under the non-ejection regions  345   b  of the head surfaces is larger than suction force acting on the sheet P under the ejection regions  345   a  of the head surfaces. The configuration described above effectively restricts attachment of paper dust to the nozzle orifices while also effectively restricting rising up of the sheet P. In particular note that in the first embodiment, the length in the sheet conveyance direction of each of the second grooves  334   b  is longer than the length (width) in the sheet conveyance direction of the head surface of the corresponding one of the recording heads  341 ,  342 ,  343 , or  344  opposite thereto. As explained with reference to  FIGS. 8B and 8C , the configuration described above makes the flow rate of suction air flow larger and thus effectively restricts rising up of the sheet P. 
     In the first embodiment, the second grooves  334   b  have a greater density than the first grooves  334   a  as illustrated in  FIGS. 2 and 6 . As a result of the above configuration, the flow rate of suction air flow created under the non-ejection regions  345   b  of the head surfaces is larger than the flow rate of suction air flow created under the ejection regions  345   a  of the head surfaces. Therefore, the above configuration effectively restricts rising up of the sheet P. On the other hand, as a result of suction air flow created under the ejection regions  345   a  of the head surfaces being smaller than suction air flow created under the non-ejection regions  345   b  of the head surfaces, the above configuration can also restrict attachment of paper dust to the nozzle orifices. 
     The second through holes  335   b  have a greater density than the first through holes  335   a  in the first embodiment. As a result of the above configuration, the flow rate of suction air flow created under the non-ejection regions  345   b  of the head surfaces is larger than the flow rate of suction air flow created under the ejection regions  345   a  of the head surfaces. Therefore, the above configuration effectively restricts rising up of the sheet P. On the other hand, as a result of suction air flow created under the ejection regions  345   a  of the head surfaces being smaller than suction air flow created under the non-ejection regions  345   b  of the head surfaces, the above configuration can also restrict attachment of paper dust to the nozzle orifices. 
     In the first embodiment, the second through holes  335   b  are located centrally in the second grooves  334   b  in terms of the sheet conveyance direction.  FIG. 10  is a cross-sectional view illustrating the flow rate of suction air flow  337  created under a recording head  341 . More specifically,  FIG. 10  illustrates suction air flow  337  that is created in a configuration in which the position of a through hole  335  is shifted downstream in the sheet conveyance direction relative to the center of a head surface  345 . Note that the conveyor belt  320  is not illustrated in  FIG. 10  in order to facilitate understanding. 
     The thickness of arrows indicating suction air flow  337  in  FIG. 10  represents the flow rate of suction air flow  337 . As illustrated in  FIG. 10 , in a configuration in which the position of the through hole  335  is shifted downstream in the sheet conveyance direction relative to the center of the head surface  345 , suction air flow  337  under the head surface  345  from a downstream side of the head surface  345  in terms of the sheet conveyance direction is large. On the other hand, suction air flow  337  under the head surface  345  from an upstream side of the head surface  345  in terms of the sheet conveyance direction is small. As a result, suction force acting on the sheet P has an uneven distribution. In consideration of the above, in the first embodiment the second through holes  335   b  are located centrally in the second grooves  334   b  in terms of the sheet conveyance direction. Therefore, unevenness in the distribution of suction force can be restricted, thereby effectively restricting rising up of the sheet P. 
     The cross-sectional area of the grooves  334  also influences pressure loss. For example, in a configuration in which the second grooves  334   b  are wider than the first grooves  334   a , regions opposite to the non-ejection regions  345   b  of the head surfaces (i.e., the second regions  52 ) have a smaller pressure loss than regions opposite to the ejection regions  345   a  of the head surfaces (i.e., the first regions  51 ). As a result, suction air flow created in the second regions  52  is larger than suction air flow created in the first regions  51 . Therefore, such a configuration effectively restricts rising up of the sheet P. The second regions  52  also have a smaller pressure loss than the first regions  51  in a configuration in which the second grooves  334   b  are deeper than the first grooves  334   a . Therefore, such a configuration effectively restricts rising up of the sheet P. 
       FIG. 11A  is a plan view illustrating a first alternative example of the first grooves  334   a  and  FIG. 11B  is a plan view illustrating a first alternative example of the second grooves  334   b . As illustrated in  FIGS. 11A and 11B , the length L 2  of the second grooves  334   b  is the same as the length L 1  of the first grooves  334   a . On the other hand, the width w 2  of the second grooves  334   b  is greater than the width w 1  of the first grooves  334   a . Although not illustrated in  FIGS. 11A and 11B , the second grooves  334   b  have the same depth as the first grooves  334   a . Therefore, the second grooves  334   b  have a larger cross-sectional area than the first grooves  334   a . The first through holes  335   a  and the second through holes  335   b  each have a circular cross-section and the diameter d 1  of the first through holes  335   a  is the same as the diameter d 2  of the second through holes  335   b . Although not illustrated in  FIGS. 11A and 11B , the first through holes  335   a  have the same depth as the second through holes  335   b.    
     Through the above configuration, regions opposite to the non-ejection regions  345   b  of the head surfaces (i.e., the second regions  52 ) have a smaller pressure loss than regions opposite to the ejection regions  345   a  of the head surfaces (i.e., the first regions  51 ). As a result, suction air flow created in the second regions  52  is larger than suction air flow created in the first regions  51 . Therefore, the above configuration effectively restricts rising up of the sheet P. Also, as a result of suction air flow created under the ejection regions  345   a  of the head surfaces being smaller than suction air flow created under the non-ejection regions  345   b  of the head surfaces, the above configuration also restricts attachment of paper dust to the nozzle orifices. 
       FIG. 12A  is a cross-sectional view illustrating a second alternative example of the first grooves  334   a . More specifically,  FIG. 12A  illustrates the second alternative example of the first grooves  334   a  as viewed in the sheet conveyance direction.  FIG. 12B  is a cross-sectional view illustrating a second alternative example of the second grooves  334   b . More specifically,  FIG. 12B  illustrates the second alternative example of the second grooves  334   b  as viewed in the sheet conveyance direction. As illustrated in  FIGS. 12A and 12B , the height (depth) h 2  of the second grooves  334   b  is greater (deeper) than the height (depth) h 1  of the first grooves  334   a . On the other hand, the width w 2  of the second grooves  334   b  is the same as the width w 1  of the first grooves  334   a . Therefore, the second grooves  334   b  have a greater cross-sectional area than the first grooves  334   a . Although not illustrated in  FIGS. 12A and 12B , the second grooves  334   b  have the same length as the first grooves  334   a . Also, although not illustrated in  FIGS. 12A and 12B , the first through holes  335   a  and the second through holes  335   b  each have a circular cross-section and the first through holes  335   a  have the same depth and diameter as the second through holes  335   b.    
     Through the above configuration, the regions opposite to the non-ejection regions  345   b  of the head surfaces (i.e., the second regions  52 ) have a smaller pressure loss than the regions opposite to the ejection regions  345   a  of the head surfaces (i.e., the first regions  51 ). As a result, suction air flow created in the second regions  52  is larger than suction air flow created in the first regions  51 . Therefore, the above configuration restricts rising up of the paper P. Also, as a result of suction air flow created under the ejection regions  345   a  of the head surfaces being smaller than suction air flow created under the non-ejection regions  345   b  of the head surfaces, the above configuration also restricts attachment of paper dust to the nozzle orifices. 
     Pressure loss is influenced not only by the grooves  334 , but also by the cross-sectional area and the depth of the through holes  335 .  FIG. 13A  is a plan view illustrating a first alternative example of the first through holes  335   a  and  FIG. 13B  is a plan view illustrating a first alternative example of the second through holes  335   b . As illustrated in  FIGS. 13A and 13B , the first through holes  335   a  and the second through holes  335   b  each have a circular cross-section and the diameter d 2  of the second through holes  335   b  is greater than the diameter d 1  of the first through holes  335   a . Therefore, the second through holes  335   b  have a greater cross-sectional area than the first through holes  335   a . On the other hand, although not illustrated in  FIGS. 13A and 13B , the second through holes  335   b  have the same depth as the first through holes  335   a . Also, the width w 1  and the length L 1  of the first grooves  334   a  are the same as the width w 2  and the length L 2  of the second grooves  334   b . Although not illustrated in  FIGS. 13A and 13B , the first grooves  334   a  have the same depth as the second grooves  334   b.    
     Through the above configuration, the regions opposite to the non-ejection regions  345   b  of the head surfaces (i.e., the second regions  52 ) have a smaller pressure loss than the regions opposite to the ejection regions  345   a  of the head surfaces (i.e., the first regions  51 ). As a result, suction air flow created in the second regions  52  is larger than suction air flow created in the first regions  51 . Therefore, the above configuration restricts rising up of the paper P. Also, as a result of suction air flow created under the ejection regions  345   a  of the head surfaces being smaller than suction air flow created under the non-ejection regions  345   b  of the head surfaces, the above configuration also restricts attachment of paper dust to the nozzle orifices. 
       FIG. 14A  is a cross-sectional view illustrating a second alternative example of the first through holes  335   a  and  FIG. 14B  is a cross-sectional view illustrating a second alternative example of the second through holes  335   b . The first through holes  335   a  and the second through holes  335   b  each have a circular cross-section. As illustrated in  FIGS. 14A and 14B , the depth de 2  of the second through holes  335   b  is smaller than the depth de 1  of the first through holes  335   a . On the other hand, the diameter d 2  of the second through holes  335   b  is the same as the diameter d 1  of the first through holes  335   a . Also, the height h 1  and the length L 1  of the first grooves  334   a  are the same as the height h 2  and the length L 2  of the second grooves  334   b . Although not illustrated in  FIGS. 14A and 14B , the first grooves  334   a  have the same width as the second grooves  334   b.    
     Through the above configuration, the regions opposite to the non-ejection regions  345   b  of the head surfaces (i.e., the second regions  52 ) have a smaller pressure loss than the regions opposite to the ejection regions  345   a  of the head surfaces (i.e., the first regions  51 ). As a result, suction air flow created in the second regions  52  is larger than suction air flow created in the first regions  51 . Therefore, the above configuration restricts rising up of the paper P. Also, as a result of suction air flow created under the ejection regions  345   a  of the head surfaces being smaller than suction air flow created under the non-ejection regions  345   b  of the head surfaces, the above configuration also restricts attachment of paper dust to the nozzle orifices. 
     As illustrated in  FIGS. 14A and 14B , the second alternative example of the first through holes  335   a  and the second alternative example of the second through holes  335   b  may be implemented by providing recesses  332   a  on the rear surface of the guide member  332 , which is on an opposite side of the guide member  332  to the surface  333 , at locations corresponding to the second through holes  335   b . In other words, the second alternative example of the first through holes  335   a  and the second alternative example of the second through holes  335   b  can be implemented by making the guide member  332  narrower at the locations corresponding to the second through holes  335   b  than the guide member  332  at locations corresponding to the first through holes  335   a . Further alternatively, protrusions  332   b  may be provided on the rear surface of the guide member  332  at the locations corresponding to the first through holes  335   a  as illustrated in  FIGS. 15A and 15B . In other words, the guide member  332  may be made thicker at the locations corresponding to the first through holes  335   a  than the guide member  332  at the locations corresponding to the second through holes  335   b.    
     Second Embodiment 
     The following explains a second embodiment of the present disclosure.  FIG. 16  is a plan view illustrating a guide member  332  according to the second embodiment of the present disclosure.  FIG. 17  is a plan view illustrating section C of  FIG. 16 . In other words,  FIG. 17  is an enlarged view of one section of the guide member  332  according to the second embodiment. The second embodiment only differs from the first embodiment in terms of configuration of the guide member  332 . The following explains the second embodiment based on differences compared to the first embodiment and omits explanation of matter that is the same as for the first embodiment. 
     In the second embodiment, the first through holes  335   a  are located outside of the head facing regions  50  (i.e., outside of regions located opposite to the head surfaces of the recording heads  341 ,  342 ,  343 , and  344 ). Therefore, all through holes  335  are located outside of the first regions  51  (i.e., outside of regions under the ejection regions  345   a  of the head surfaces of the recording heads  341 ,  342 ,  343 , and  344 ). Also, in the second embodiment, each of the first grooves  334   a  includes a section outside of the head facing regions  50  and a section within one of the first regions  51  (i.e., within a region under an ejection region  345   a  of the corresponding head surface).  FIG. 18  is a cross-sectional view illustrating the flow rate of suction air flow  337  created under a recording head  341 . More specifically,  FIG. 18  illustrates suction air flow  337  in a configuration in which a first through hole  335   a  is located upstream in terms of the sheet conveyance direction of a head facing region  50  opposite to a head surface  345 . In other words, the first through hole  335   a  is located outside of the head facing region  50 . Note that the conveyor belt  320  is not illustrated in  FIG. 18  in order to facilitate understanding. 
     The thickness of arrows indicating suction air flow  337  in  FIG. 18  represents the flow rate of suction air flow  337 . In the configuration illustrated in  FIG. 18 , the first through hole  335   a  is located outside of the head facing region  50  opposite to the head surface  345 , and a first groove  334   a  includes a section that is located outside of the head facing region  50  and a section that is located below the head surface  345  (i.e., within the head facing region  50 ). Such a configuration makes suction air flow  337  under the head surface  345  smaller. Therefore, the second embodiment restricts the flow rate of suction air flow (i.e., makes suction air flow smaller) that is created in the first regions  51  (i.e., under the ejection regions  345   a  of the head surfaces). 
     As a result, even when a sheet P having paper dust attached thereto is conveyed by the conveyor device  310 , stirring up of the paper dust can be restricted in the first regions  51  (i.e., under the ejection regions  345   a  of the head surfaces) and thus attachment of the paper dust to nozzle orifices can be restricted. By restricting attachment of paper dust to the nozzle orifices, the probability of nozzle clogging occurring can be reduced. Note that attachment of paper dust to the nozzle orifices can be restricted in the same way in a configuration in which each of the first through holes  335   a  is located downstream in terms of the sheet conveyance direction relative to the head facing region  50  (i.e., the region located opposite to the corresponding head surface), and thus is located outside of the head facing region  50 . 
     As illustrated in  FIGS. 16 and 17 , in the second embodiment the first grooves  334   a  are present in the first regions  51  (i.e., under the ejection regions  345   a  of the head surfaces) and the second through holes  335   b  and the second grooves  334   b  are present in the second regions  52  (i.e., under the non-ejection regions  345   b  of the head surfaces). The above configuration ensures that suction force acting on the sheet P below each of the recording heads  341 ,  342 ,  343 , and  344  is not insufficient. 
     Note that in the same way as explained for the first embodiment, the second through holes  335   b  may have a greater density than the first through holes  335   a . Also, the second through holes  335   b  may have a greater cross-sectional area than the first through holes  335   a . Also, the second through holes  335   b  may be shallower than the first through holes  335   a . Furthermore, the first through holes  335   a  and the second through holes  335   b  may exhibit any combination of the aforementioned features. 
     Also, as explained for the first embodiment, the length of the second grooves  334   b  in the sheet conveyance direction may be greater than the length (width) of the head facing regions  50  (head surfaces) in the sheet conveyance direction. Also, the second grooves  334   b  may have a greater cross-sectional area than the first grooves  334   a . Also, the second grooves  334   b  may have a greater aperture area than the first grooves  334   a . Also, the second grooves  334   b  may have a greater density than the first grooves  334   a . Furthermore, the first grooves  334   a  and the second grooves  334   b  may exhibit any combination of the aforementioned features. 
     Third Embodiment 
     The following explains a third embodiment of the present disclosure.  FIG. 19  is a plan view illustrating a guide member  332  according to the third embodiment of the present disclosure.  FIG. 20  is a plan view illustrating section D of  FIG. 19 . In other words,  FIG. 20  is an enlarged view of one section of the guide member  332  according to the third embodiment. The third embodiment only differs from the first embodiment in terms of configuration of the guide member  332 . The following explains the third embodiment based on differences compared to the first embodiment. Explanation is omitted for matter that is the same as for the first and second embodiments. 
     In the third embodiment, the first through holes  335   a  are not located inside of grooves  334  and are hence located outside of the grooves  334 . As explained with reference to  FIGS. 8A, 8B, and 8C , the flow rate of suction air flow  337  is smallest in a configuration in which no groove  334  is present. 
     Therefore, the third embodiment restricts the flow rate of suction air flow (i.e., makes suction air flow smaller) that is created in the first regions  51  (i.e., under the ejection regions  345   a  of the head surfaces). As a result, even when a sheet P having paper dust attached thereto is conveyed by the conveyor device  310 , stiffing up of the paper dust can be restricted and thus attachment of the paper dust to nozzle orifices can be restricted. By restricting attachment of paper dust to the nozzle orifices, the probability of nozzle clogging occurring can be reduced. 
     As illustrated in  FIGS. 19 and 20 , in the third embodiment the first through holes  335   a  are located in the first regions  51  (i.e., below the ejection regions  345   a  of the head surfaces) and the second through holes  335   b  are located in the second regions  52  (i.e., below the non-ejection regions  345   b  of the head surfaces). The above configuration ensures that suction force acting on the sheet P below each of the recording heads  341 ,  342 ,  343 , and  344  is not insufficient. 
     Note that in the same way as explained for the first embodiment, the second through holes  335   b  may have a greater density than the first through holes  335   a . Also, the second through holes  335   b  may have a greater cross-sectional area than the first through holes  335   a . Also, the second through holes  335   b  may be shallower than the first through holes  335   a . Furthermore, the first through holes  335   a  and the second through holes  335   b  may exhibit any combination of the aforementioned features. 
     Matter explained in the first, second, and third embodiments may be combined as appropriate. For example, first through holes  335   a  located outside of grooves  334  and first through holes  335   a  located inside of first grooves  334   a  may both be present as illustrated in  FIG. 21 . 
     Specific embodiments of the present disclosure are explained above, but the present disclosure is of course not limited to the above embodiments and various alterations can be made to the embodiments. 
     For example, although the first through holes  335   a  and the second through holes  335   b  each have a circular cross-section in the embodiments, the cross-sectional shape of the first through holes  335   a  and the second through holes  335   b  is not limited to being circular. For example, the first through holes  335   a  and the second through holes  335   b  may each have a rectangular cross-section. 
     The embodiments are explained for a situation in which the present disclosure is applied to a line head inkjet recording apparatus, but the present disclosure can also be applied to a serial head inkjet recording apparatus. 
     In the embodiments, three recording heads are arranged for each color in a staggered formation along the direction perpendicular to the sheet conveyance direction, but there is no particular limitation on the number of recording heads for each of the colors. For example, a single recording head may be provided for each of the colors. Also, in a configuration in which a plurality of recording heads are provided for each of the colors, the plurality of recording heads for each of the colors are not limited to being arranged in a staggered formation and may instead be arranged in a single line along the direction perpendicular to the sheet conveyance direction. 
     The embodiments are explained for a situation in which the present disclosure is applied to an inkjet recording apparatus that is capable of forming a full-color image, but the present disclosure can also be applied to an inkjet recording apparatus that forms a monochrome image. 
     Although the embodiments are explained for a situation in which the present disclosure is applied to an inkjet recording apparatus, the present disclosure can also be applied to other image forming apparatuses (for example, an electrophotographic image forming apparatus). 
     Furthermore, although the embodiments are explained for a situation in which the recording medium is a sheet of paper, the recording medium may be a medium other than a sheet of paper (for example, a resin sheet or cloth). 
     In addition to the alterations explained above, a wide range of other alterations can be made to the embodiments so long as such alterations do not deviate from the intended scope of the present disclosure.