Patent Publication Number: US-2022224800-A1

Title: Image reading apparatus and image forming apparatus

Description:
FIELD OF THE INVENTION AND RELATED ART 
     The present invention relates to an image reading apparatus for reading an image of an original and an image forming apparatus for forming the image on a recording material. 
     The image reading apparatus for use with a document scanner or a copying machine irradiates the original with light and forms an image of reflected light on an image pick-up device (light receiving element). The image pick-up device converts the formed image into an electric signal and outputs the electric signal. The reflected light from the original is reflected by a reflection member and is guided to the image pick-up device. 
     In a constitution of Japanese Laid-Open Patent Application (JP-A) 2017-163604, a projection opposing a reflecting surface of a mirror is provided on a housing in which the mirror which is the reflection member is accommodated. In this constitution, the projection and the reflecting surface of the mirror are bonded to each other, so that the mirror is fixed. 
     In the constitution of JP-A 2017-163604, onto the reflecting surface of the mirror, an adhesive is applied, and therefore, there was a liability that a droplet and a spray of the adhesive are deposited on an effective reflect region of the reflecting surface and has an influence on a reading image. 
     SUMMARY OF THE INVENTION 
     A principal object of the present invention is to provide an image reading apparatus and an image forming apparatus which are capable of reducing a possibility that deposition (adhesion) of an adhesive has an influence on a reading image. 
     According to an aspect of the present invention, there is provided an image reading apparatus for reading an image of an original, comprising: an illumination portion configured to illuminate the original with light; a reflection member including a reflecting surface for reflecting the light from the original; a converting portion configured to photoelectrically convert the light reflected by the reflection member; and a casing configured to accommodate the reflection member, wherein the casing is provided with an opening which is open to an outside of the casing, and wherein a surface of the reflecting member opposite from the reflecting surface and a portion defining the opening are bonded to each other with an adhesive. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a printer according to an embodiment of the present invention. 
         FIG. 2  is a schematic view showing a main body of a scanner of an image reading apparatus. 
         FIG. 3  is a schematic view showing a cross-sectional structure of a scanner unit. 
       Parts (a) of  FIG. 4  is a schematic view for illustrating a connection structure between a mirror and a box frame, and parts (b) and (c) of  FIG. 4  are enlarged views each showing a part of the connection structure. 
         FIG. 5  is a schematic view of a scanner unit as seen from one side with respect to a sub-scan direction. 
         FIG. 6  is a schematic view of the scanner unit as seen from the other side with respect to the sub-scan direction. 
         FIG. 7  is a schematic view of the scanner unit as seen in a height direction. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     In the following, an exemplary embodiment for carrying out the present invention will be described with reference to the drawings. 
     First, a general structure of a printer  101  which is an image forming apparatus of this embodiment will be described with reference to  FIG. 1 . The printer  101  includes a printer main assembly  101 A and an image reading apparatus  103  as shown in  FIG. 1 . The image reading apparatus  103  provided on the printer main assembly  101 A includes a main body unit  30  and an ADF (automatic document feeder)  1  as described specifically later and reads image information by optically scanning an original D. The original D is a sheet including paper such as a sheet or an envelope, a plastic film such as a sheet for an overhead projector (OHP), a cloth, or the like. The image information converted into an electrical signal by the image reading apparatus  103  is transferred to a controller  132  provided in the printer main assembly  101 A. 
     The printer main assembly  101 A includes an image forming portion  133  for forming an image on a sheet P which is a recording material (medium) and a sheet feeding portion  134  for feeding the sheet P to the image forming portion  133 . The sheet feeding portion  134  includes sheet accommodating portions  137   a ,  137   b ,  137   c  and  137   d  capable of accommodating sheets different in size from each other. The sheets accommodated in each of the sheet accommodating portions are fed by a pick-up roller  112  and separated one by one by a feed roller  113   a  and a retard roller  113   b , and then is delivered to a corresponding feeding roller pair  131 . Then, the sheet P is successively delivered to a plurality of feeding roller pairs  131  provided along a sheet feeding path, and then is fed toward a registration roller pair  136 . 
     Incidentally, the sheet P placed on a manual feeding tray  137   e  by the user is fed to an inside of the printer main assembly  101 A by a feeding roller  138  and then is fed toward the registration roller pair  136 . The registration roller pair  136  not only corrects oblique movement of the sheet P by stopping a leading end of the sheet P but also resumes feeding of the sheet P in synchronism with progress of an image forming operation which is a toner image forming process by the image forming portion  133 . 
     The image forming portion  133  for forming the image on the sheet P is an image forming unit of an electrophotographic type in which a photosensitive drum  121  which is a photosensitive member. The photosensitive drum  121  is rotatable along a feeding direction of the sheet P, and at a periphery of the photosensitive drum  121 , a charger  118 , an exposure device  123 , a developing device  124 , a transfer charger  125 , a separation charger  126  and a cleaner  127  are provided. The charger  118  electrically charges a surface of the photosensitive drum  121 , and the exposure device  123  exposes the photosensitive drum  121  to light on the basis of the image information inputted from the image reading apparatus  103  or the like, so that an electrostatic latent image is formed on the photosensitive drum  121 . 
     The developing device  124  accommodates a developer containing toner and develops the electrostatic latent image into a toner image by supplying charged toner to the photosensitive drum  121 . The toner image carried on the photosensitive drum  121  is transferred onto the sheet P fed from the registration roller pair  136 , by a bias electric field formed by the transfer charger  125 . The sheet P on which the toner image is transferred is spaced from the photosensitive drum  121  by a bias electric field formed by the separation charger  126  and then is fed toward a fixing portion  129  by a pre-fixing feeding portion  128 . Incidentally, a deposited matter such as a transfer residual toner or the like remaining on the photosensitive drum  121  without being transferred onto the photosensitive drum  121  is removed by the cleaner  127 , and the photosensitive drum  121  prepares for a subsequent image forming operation. 
     The sheet P fed to the fixing portion  129  is subjected to a fixing process including pressing and heating while being nipped and pressed by a roller pair. As a result, an image is fixed on the sheet P by melting and then fixing of the toner on the sheet P. In the case where image output is completed, the sheet P on which a fixed image is obtained is discharged through a discharging roller pair  116  onto a discharge tray  130  projecting toward an outside of the printer main assembly  101 A. In the case where the image is formed on a back surface of the sheet P in double-side printing, the sheet P passed through the fixing portion  129  is turned upside down by a reversing portion  139 , and is fed toward the registration roller pair  136  through a feeding path  140  for the double-side printing. Then, the sheet P on which the image is formed again by the image forming portion  133  is discharged onto the discharge tray  130 . 
     The image forming portion  133  is an example of an image forming means, and for example, an image forming unit of an ink jet type or a printing mechanism of an offset printing type may also be used as the image forming means. 
     (Image Reading Apparatus) 
     Next, with reference to  FIGS. 1 to 3 , a structure of the image reading apparatus  103  will be described. As shown in  FIG. 1 , the ADF  1  feeds the original D, placed on an original feeding tray  2 , toward an original discharge tray  3 . The ADF  1  is openable relative to the main body unit  30 , and the main body unit  30  is fixed to the printer main assembly  101 A. 
     The main body unit  30  includes, as shown in  FIG. 2 , a frame  30   a  also functioning as an outer casing member, and at an upper surface of the frame  30   a , an original supporting platen glass  31  as an image reading portion and a platen glass  31   a  are provided. The original supporting platen glass  31  is stacking table in this embodiment. Inside the frame  30   a , a scanner unit  50  is held. The scanner unit  50  is supported by a frame  30   a  so as to be movable in parallel to the original supporting platen glass  31  by an unshown wire or belt driven by a motor. 
     The scanner unit  50  is an image reading unit of a CCD (Charge Coupled Device) type as shown in  FIG. 3 . The scanner unit  50  includes a box frame  51 , an illumination unit  52  as an illumination portion, a first mirror  53 , a second mirror  54 , a third mirror  55 , a fourth mirror  56 , a fifth mirror  57 , a lens unit  58  and a CCD substrate  59 . The first mirror  53  and the fourth mirror  56  are accommodated in the box frame  51 . On the CCD substrate  59 , a CCD  59   a  which is an example of an imaging (image pick-up) device is arranged along a main scan direction. As a converting portion for photoelectrically converting light from the original, the CCD  59   a  was used as an example of the imaging device, but it is also possible to use a CMOS (complementary metal oxide semiconductor) as the converting portion. 
     The illumination unit  52  is mounted above the box frame  51  constituting a casing of the scanner unit  50 . The illumination unit  52  includes unshown light emitting elements (for example, light emitting diodes), and two light guide units  60 L and  60 R. An original D as an object subjected to reading of image information is irradiated with light L 1  and light L 2  which are emitted by the light emitting elements in a state in which they are uniformly diffused in the main scan direction by the light guide units  60 L and  60 R. 
     A position at which the light emitted from the light guide units  60 L and  60 R is concentrated on a reading surface is referred to as an “original irradiation (illumination) position F”. A sub-scan direction is a direction perpendicular to the main scan direction and is a movement direction of the scanner unit  50  in this embodiment when the scanner unit  50  moves below the original supporting platen glass  31 . Further, the reading surface refers to a phantom (virtual) flat surface extending at a predetermined height (an object point position of an optical system) where the scanner unit  50  is capable of performing reading of image information with high accuracy with respect to a height direction (direction of depth of field) perpendicular to the main scan direction and the sub-scan direction. The reading surface in this embodiment corresponds to, for example, a lower surface of the original D in a state in which the original D is left at rest on the original supporting platen glass  31 . 
     The five (first to fifth) mirrors  53  to  57  and the lens unit  58  form an optical path for guiding the reflected light from the original D to the CCD substrate  59 . As the respective mirrors  53  to  57  which are examples of a reflection member, for example, mirrors each provided with a reflecting surface prepared by forming an aluminum deposition film on a supporting member such as glass are used. The reflected light (light beam L 3 ) reflected by the original D at the original irradiation position F travels through the first mirror  53 , the second mirror  54 , the third mirror  55 , the fourth mirror  56 , the fifth mirror  57  and the lens unit  58  and is focused as an image on the CCD  59   a.    
     The CCD  59   a  receives the light beam L 3  and photoelectrically converts the light beam L 3  into an electric signal representing an image of the original D. Image information read by the CCD  59   a  is transmitted to a controller  132  of the printer main assembly  101 A and is used for image formation by the image forming portion  133 . 
     In the following, a path of the light, of scattered light reflected by the original D, travelling through the first mirror  53 , the second mirror  54 , the third mirror  55 , the fourth mirror  56 , the fifth mirror  57  and the lens unit  58  and reaching the CCD  59   a  is referred to as an optical path of the scanner unit  50 . The light beam L 3  shown in  FIG. 3  is a light beam which represents a pencil of light (ray bundle) delivered from the original irradiation position F and reaching the CCD  59   a  through the optical path of the scanner unit  50 . An optical system constituted by the first to fifth mirrors  53  to  57  is supported by the box frame  51 . The box frame  51  further supports the lens unit  58  and the CCD  59   a.    
     A space inside the box frame  51  is covered at an upper portion thereof with the illumination frame  52   a  of the illumination unit  52  and is covered at a lower portion thereof with a lower cover  63  which is a cover in this embodiment. Further, as seen in the main scan direction, the CCD  59   a  is disposed in a space defined by a CCD accommodating portion  51   a  provided on the box frame  51  and a substrate main body  59   b  of the CCD substrate  59 . 
     Further, the box frame  51  is reflection region with a first side wall opening  51   b  and a second side wall opening  51   c  which are closed by the second mirror  54  and the third mirror  55 , respectively. Accordingly, the second mirror  54  and the third mirror  55  in this embodiment constitute a part of the outer casing partitioning the inside and the outside of the scanner unit  50  in cooperation with the box frame  51 , the frame  52   a  of the illumination unit  52 , the lower cover  63  and the substrate main body  59   b . The inside of the scanner unit  50  is a space in which the normal optical path and the reading portion and accommodated. Here, a constitution in which the casing (optical box) accommodating the first mirror  53  and the fourth mirror  56  is constituted by the box frame  51  and the frame  52   a  was described, but this is merely an example, and a shape and an arrangement of the casing can be appropriately changed. 
     The thus-constituted image reading apparatus  103  reads image information from a sheet as the original D in a skimming (through) mode in which an original image is scanned while feeding the original D by the ADF  1  and in a fixedly reading mode in which the original placed on the original supporting platen glass  31  is scanned. 
     The skimming mode is selected in the case where the image reading apparatus detects the original D placed on the original feeding tray  2  or in the case where the user explicitly provides an instruction through the operating panel or the like of the printer main assembly  101 A. In this case, in a state in which the scanner unit  50  is positioned below the platen glass  31   a , the ADF  1  feeds the original D, placed on the original feeding tray  2 , one by one, and then, the scanner unit  50  reads the image information from the fed original D. That is, in the skimming mode, the original D is scanned by being fed in the sub-scan direction relative to the scanner unit  50  of which position is fixed. 
     On the other hand, the fixedly reading mode is selected in the case where the image reading apparatus detects the original D placed on the original supporting platen glass  31  or in the case where the user explicitly provides an instruction through the operating panel or the like of the printer main assembly  101 A. In the case of the fixedly reading mode, first, the user opens the ADF  1  and places the original on the original supporting platen glass  31  and closes the ADF  1 , so that the original is positioned relative to the original supporting platen glass  31 . Then, the scanner unit  50  reads the image information from the original D placed on the original supporting platen glass  31  while moving along the original supporting platen glass  31 . That is, in the fixedly reading mode, the scanner unit  50  scans the original D while moving in the sub-scan direction relative to the original D which is positionally fixed. 
     Incidentally, the scanner unit  50  may also be mounted in an image reading apparatus capable of executing an operation in only one of the skimming mode and the fixedly reading mode. Further, by additionally providing the scanner unit  50  inside the ADF  1 , and the image information may also be read by the two scanner units from both sides (surfaces) of the original D fed by the ADF  1 . 
     (Connection Structure Between Mirror and Box Frame) 
     A structure connecting the mirrors disposed in the scanner unit  50  and the box frame  51  will be described. 
     Part (a) of  FIG. 4  is a sectional view of the scanner unit  50  in a position of a line  4 A- 4 A in each of  FIGS. 5 to 7  as seen in a main scan direction, and parts (b) and (c) of  FIG. 4  are enlarged views each showing a part of the scanner unit  50 .  FIG. 5  is a side view of the scanner unit  50  as seen from one side (left-hand side of part (a) of  FIG. 4 ) with respect to the sub-scan direction.  FIG. 6  is a side view of the scanner unit  50  as seen from the other side (right-hand side of part (a) of  FIG. 4 ) with respect to the sub-scan direction.  FIG. 7  is a side view of the scanner unit  50  as seen in a height direction perpendicular to the main scan direction and the sub-scan direction (from a side below the scanner unit  50  of part (a) of  FIG. 4 ). 
     Incidentally, part (a) of  FIG. 4  and  FIGS. 5 to 7  show a state in which an adhesive  61  is not applied yet, and parts (b) and (c) of  FIG. 4  shows a state after an adhesive  61  is applied. Further, in  FIGS. 4 to 7 , the sub-scan direction is represented by an arrow “X”, the main scan direction is represented by an arrow “Y”, and a height direction perpendicular to the main scan direction and the sub-scan direction is represented by an arrow “Z”. 
     (1) Second Mirror Connection Structure 
     First, the second mirror  54  which is an example of the reflection member will be described. As shown in part (a) of  FIG. 4  and  FIG. 5 , the box frame  51  includes a side wall portion  51   d  provided with a recessed portion  51   e  on one side with respect to the sub scan direction X. The recessed portion  51   e  is a semicylindrical recessed portion (groove shape) extending from the outside toward the inside of the scanner unit  50  along the sub scan direction X. In other words, the recessed portion  51   e  has a semi circular opening shape as seen in the sub scan direction X as shown in  FIG. 5 . As shown in part (b) of  FIG. 4 , by applying an adhesive  61  onto the recessed portion  51   e , so that the second mirror  54  and the box frame  51  are connected to each other. 
     Specifically, the second mirror  54  is mounted so that a window portion w 1  provided on the side wall portion  51   d  is covered from the outside of the box frame  51 . The side wall portion  51   d  is provided with a second mirror mounting portion  240  as a recessed portion recessed from the outside toward the inside of the box frame  51  (i.e., from a left hand side toward a right hand side of part (a) of  FIG. 4 ). The window portion w 1  is an opening formed at a bottom (portion)  241  of the second mirror mounting portion  240 , and an effective reflect region of a reflecting surface  54   a  of the second mirror  54  is exposed toward the inside of the box frame  51  through the window portion w 1 . The second mirror  54  is disposed in the second mirror mounting portion  240  as a mounting portion ( FIG. 5 ), an outer peripheral portion of the second mirror  54  as seen in the sub scan direction X opposes an inner wall (inner surface)  242  of the second mirror mounting portion  240 . 
     The groove portion (recessed portion)  51   e  where the adhesive  61  is applied is provided on the inner window  242 . The groove portion  51   e  is provided in a position opposing the end surface  54   c , with respect to the height direction Z, of the second mirror  54  engaged in the second mirror position  240  (part (b) of  FIG. 4  and  FIG. 5 ). Accordingly, when the adhesive  61  is applied (injected) into the groove portion  51   e  as shown in part (b) of  FIG. 4  and then is cured, the inner peripheral surface of the groove portion  51   e  and the side surface (end surface)  54   c  of the second mirror  54  with respect to the height direction Z are bonded to each other through the adhesive  61 . In other words, the end surface  54   c  of the second mirror  54 , which is an example of the reflection member, with respect to a direction along the reflecting surface  54   a  and the inner wall  242  defining the second mirror mounting portion  240  are bonded to each other by the adhesive  61 . 
     Here, in order to suppress that the adhesive  61  applied into the groove portion  51   e  passes through a minute gap and wraps around the reflecting surface  54   a  of the second mirror  54 , as the adhesive  61 , an adhesive having proper viscosity may desirably be selected. Further, the bottom  51   f  of the groove portion  51   e  is disposed toward the outside of the box frame  51  than the reflecting surface  54   a  of the second mirror  54  is, and thus a stagnation shape of the adhesive  61  may preferably be formed. That is, the bottom  51   f  of the groove portion  51   e  with respect to the sub-scan direction X may preferably be disposed toward the outside (left-hand side of parts (a) and (b) of  FIG. 4 ) with respect to the sub-scan direction X than a bottom  241  of the second mirror mounting portion  240  opposing the reflecting surface  54   a  of the second mirror at a periphery of the window portion w 1  is. By this, when the adhesive  61  is applied (injected) into the groove portion  51   e  from the left-hand side of part (b) of  FIG. 4 , flow of the adhesive  61  is received by the bottom  51   f  of the groove portion  51   e , and therefore, it is possible to effectively suppress that a part of the adhesive  61  wraps around the reflecting surface  54   a . In a cross-section of part (a) of  FIG. 4 , of the inner wall  242 , a surface opposing the end surface  54   c  of the second mirror  54  includes a first portion  91  and a second portion  92  which is the inner peripheral surface of the groove portion  51   e . Here, the second portion  92  where the adhesive is applied is more distant from the reflecting surface  54   a  with respect to the direction perpendicular to the reflecting surface  54   a  of the second mirror  54  than the first portion  91  is and is more distant from the end surface  54   c  of the second mirror  54  with respect to the direction along the reflecting surface  54   a  than the first portion  91  is. By this positional relationship between the first portion  91  and the second portion  92  (groove portion  51   e ), it is possible to suppress that a part of the adhesive  61  wraps around the reflecting surface  54   a.    
     Further, as the adhesive  61 , it is preferable that an adhesive (for example, an adhesive for which Young&#39;s modulus after curing is smaller than Young&#39;s modulus of a constituent material of the box frame  51 ) which has elasticity and which is relatively soft. By this, even in the case where the scanner unit  50  is moved in the sub-scan direction or even in the case where vibration occurs due to external impact or the like, by the elasticity of the adhesive  61 , it is possible to suppress the vibration transmitted to the second mirror  54 . This contributes to stable image reading with accuracy. 
     In the case where the adhesive having the elasticity is used, it is desirable that a fixing means between the mirrors and the box frame  51  is separately prepared. In this embodiment, the second mirror  54  is fixed to the box frame  51  at opposite end portions with respect to the main scan direction by fixing members  62  and  62  which are leaf springs made of metal as shown in  FIG. 5 . 
     Further, the box frame  51  in this embodiment is provided with another groove portion  51   g  different in position from the groove portion  51   e  with respect to the main scan direction Y as shown in  FIG. 5 . The second mirror  54  is bonded to the box frame  51  by the adhesive  61  applied into the groove portion  51   g , in addition to the adhesive  61  into the groove portion (recessed portion)  51   e . Thus, in the case where a plurality of groove portions  51   e  and  51   g  for permitting bonding of the mirror onto the box frame  51  with the adhesive are provided, as shown in  FIG. 5 , these groove portions may preferably be symmetrically disposed on the basis of center position Yc with respect to the main scan direction Y of the scanner unit  50 . In an example shown in  FIG. 5 , the two groove portions  51   e  and  51   g  are provided, and therefore, with respect to the main scan direction Y, distances H 1  and H 2  from the center position Yc to positions (opening groove portions) of the groove portions  51   e  and  51   g , respectively, are equal to each other (H 1 =H 2 ). 
     Incidentally, the number of the groove portions used for applying the adhesive to the second mirror  54  may also be one or three or more, and a constitution in which the fixing members  62  and  62  are omitted and in which the second mirror  54  is bonded to the box frame  51  only with the adhesive  61  may also be employed. 
     (2) Fourth Mirror Connection Structure 
     First, the fourth mirror  56  which is another example of the reflection member will be described. As shown in part (a) of  FIG. 4  and  FIG. 5 , the box frame  51  includes a side wall portion  51   d  provided with a hole  51   h  on one side with respect to the sub-scan direction X. The hole  51   h  which is another example of the opening is a through hole penetrating from the outside toward the inside of the scanner unit  50 . The hole  51   h  establishes communication between an outside space of the box frame  51  and a back surface  56   b  of the fourth mirror  56 . Here, the back surface  56   b  is a surface of the opposite from a reflecting surface  56   a  of the fourth mirror  56 . As shown in part (b) of  FIG. 4 , by applying an adhesive  61  into the hole  51   h , so that the fourth mirror  56  and the box frame  51  are connected to each other. 
     The fourth mirror  56  is provided inside the box frame  51  and is disposed so that the back surface  56   b  of the fourth mirror  56  overlaps with the hole  51   h  as seen from the outside (left-hand side of  FIG. 4 ) of the scanner unit  50  (part (b) of  FIG. 4  and  FIG. 5 ). 
     As shown in part (b) of  FIG. 4 , when the adhesive  61  is applied (injected) into the hole  51   h  and cured in a state in which the fourth mirror  56  is set at a position where the fourth mirror  56  is opposed to the hole  51   h  at the back surface  56   b  thereof, an inner wall of the hole  51   h  and the back surface  56   b  of the fourth mirror  56  are bonded to each other through the adhesive  61 . In other words, the fourth mirror  56  which is an example of the reflection member is bonded to the box frame  51  by the adhesive  61  at a side surface different from the reflecting surface  56   a.    
     Similarly as in the case of the above-described second mirror  54 , in order reduce a degree such that the adhesive  61  wraps around the reflecting surface  56   a , as the adhesive  61 , it is desirable that an adhesive with proper viscosity is selected. Further, by disposing the hole  51   h  so as to oppose the back surface  56   b  of the fourth mirror  56 , an application region is positioned away from the reflecting surface  56   a , and therefore, it is possible to further effectively suppress that the adhesive  61  wraps around the reflecting surface  56   a . Further, similarly as in the case of the second mirror  54 , it is suitable that an adhesive (agent) which has elasticity and which is relatively soft is used as the adhesive. 
     Further, the box frame  51  in this embodiment is provided with another hole  51   i  different in position from the hole  51   h  with respect to the main scan direction Y as shown in  FIG. 5 . The second mirror  54  is bonded to the box frame  51  by the adhesive  61  applied into the hole  51   i , in addition to the adhesive  61  into the hole  51   h . Thus, in the case where a plurality of holes  51   h  and  51   i  for permitting bonding of the mirror to the box frame  51  with the adhesive are provided, as shown in  FIG. 5 , these groove portions may preferably be symmetrically disposed on the basis of center position Yc with respect to the main scan direction Y of the scanner unit  50 . In an example shown in  FIG. 5 , the two holes  51   h  and  51   i  are provided, and therefore, with respect to the main scan direction Y, distances H 1  and H 2  from the center position Yc to positions (opening groove portions) of the holes  51   h  and  51   i , respectively, are equal to each other (H 1 =H 2 ). 
     Incidentally, the number of the openings (holes) used for applying the adhesive to the fourth mirror  56  may also be one or three or more. 
     Here, as shown in  FIG. 5 , the recessed portion  51   e  used for connection between the second mirror  54  and the box frame  51  and the hole  51   h  used for connection between the fourth mirror  56  and the box frame  51  are distant from the center position Yc by the same distance with respect to the main scan direction (H 1 =H 1 ). That is, the recessed portion  51   e  and the hole  51   h  are positioned in the same position and are disposed on the same phantom (virtual) plane G 1  perpendicular to the main scan direction Y 1 . Incidentally, in  FIG. 5 , the phantom plane G 1  is represented by a phantom line extending in the height direction Z, and the recessed portion  51   e  and the hole  51   h  are arranged on the phantom line. When the second mirror  54  is a first reflection member in this embodiment and the recessed portion  51   e  is a first opening in this embodiment, the fourth mirror  56  is an example of a second reflection member and the hole  51   h  is an example of a second opening. 
     When the position of the recessed portion  51   e  with respect to the main scan direction Y and the position of the hole  51   h  with respect to the main scan direction Y are disposed so as to at least partially overlap with each other, the following advantage is achieved. In the case where the connection of the second mirror  54  to the box frame  51  and the connection of the fourth mirror  56  to the box frame  51  are successively performed, there is no need to operate an application means such as a needle or the like, and therefore, an applying step can be simplified. Particularly, in the case where an automatic application device is used, simplification of a device structure, simplification of control and reduction in application time become possible, and therefore, a large advantage is achieved. 
     Similarly, as regards the recessed portion  51   g  and the hole  51   i  positioned on the side opposite from the recessed portion  51   e  and the hole  51   h  on the basis of the center position Yc with respect to the main scan direction Y, the position of the recessed portion  51   g  with respect to the main scan direction Y and the position of the hole  51   i  with respect to the main scan direction Y are disposed so as to at least partially overlap with each other (particularly, at the same position with respect to the main scan direction Y). That is, the recessed portion  51   g  and the hole  51   i  are disposed on the same phantom plane G 2  perpendicular to the main scan direction Y and are arranged on the same phantom plane G 2  extending in the height direction Z in  FIG. 5 . By this, the application step of the adhesive  61  in the case where the connection of the second mirror  54  to the box frame  51  and the connection of the fourth mirror  56  to the box frame  51  are successively carried out can be simplified. 
     (3) Third Mirror Connection Structure 
     A connection structure of a third mirror  55  which is another example of the reflection member is similar to the connection structure of the second mirror  54  described above. 
     As shown in parts (a) and (c) of  FIG. 4  and  FIG. 6 , the box frame  51  includes a side wall portion  51   j  provided with a recessed portion  51   k  on the other side with respect to the sub-scan direction X. The recessed portion  51   k  which has a recessed shape recessed from the outside toward the inside of the scanner unit  50  and has a semicylindrical shape (a semi-circular opening shape as seen in the sub-scan direction X as shown in  FIG. 6  extending along the sub-scan direction X). As shown in part (c) of  FIG. 4 , by applying an adhesive  61  into the recessed portion  51   k , so that the third mirror  55  and the box frame  51  are connected to each other. As shown in  FIG. 6 , at a position symmetrical with the recessed portion  51   k  of the scanner unit  50  on the basis of the center position Yc with respect to the main scan direction Y, another recessed portion  51   l  is provided, and the third mirror  55  is adhesively bonded to the box frame  51  also by the adhesive  61  applied into the recessed portion  51   l.    
     Specifically, the third mirror  55  is mounted so that a window portion w 2  provided on the side wall portion  51   j  is covered from the outside of the box frame  51 . The side wall portion  51   d  is provided with a third mirror mounting portion  250  recessed from the outside toward the inside of the box frame  51  (i.e., from a right-hand side toward a left-hand side of part (a) of  FIG. 4 ). The window portion w 2  is a through hole formed at a bottom (portion)  251  of the third mirror mounting portion  250 . The third mirror  55  is engaged in the third mirror mounting portion  250  which is another example of an accommodating portion ( FIG. 6 ), an outer peripheral portion of the third mirror  55  as seen in the sub-scan direction X opposes an inner wall (inner surface)  252  of the third mirror position  250 . 
     The recessed portions  51   k  and  51   l  where the adhesive  61  is applied communicate with the third mirror mounting portion  250  and opposes the side surface  55   c , with respect to the height direction Z, of the third mirror  55  engaged in the third mirror position  250  (part (a) of  FIG. 4  and  FIG. 6 ). Accordingly, when the adhesive  61  is applied into the recessed portion  51   k  as shown in part (c) of  FIG. 4  and then is cured, the inner peripheral surface of the recessed portion  51   k  and the side surface  55   c  of the third mirror  55  with respect to the height direction Z are bonded to each other through the adhesive  61 . In other words, the side surface  55   c  of the third mirror  55 , which is different from the reflecting surface  55   a  is adhesively bonded to the box frame  51  by the adhesive  61 . 
     Further, the third mirror  55  is fixed to the box frame  51  at opposite end portions with respect to the main scan direction by fixing members  62  and  62  which are leaf springs made of metal as shown in  FIG. 6 . 
     (4) First Mirror Connection Structure 
     A connection structure of a first mirror  53  which is another example of the reflection member is similar to the connection structure of the fourth mirror  56  described above. As shown in parts (a) of  FIG. 4  and  FIG. 7 , the box frame  51  includes a side wall portion (lower surface portion)  51   m  provided with a hole  51   n  with respect to the height direction Z. The hole  51   n  is a through hole penetrating from the outside toward the inside of the scanner unit  50 . As shown in part (c) of  FIG. 4  by applying an adhesive  61  into the hole  51   n , so that the first mirror  53  and the box frame  51  are connected to each other. 
     As shown in  FIG. 7 , at a position symmetrical with the hole  51   n  of the scanner unit  50  on the basis of the center position Yc with respect to the main scan direction Y, another hole  51   o  is provided, and the first mirror  53  is adhesively bonded to the box frame  51  also by the adhesive  61  applied into the hole  51   o.    
     The first mirror  53  is provided inside the box frame  51  and is disposed so that the back surface  53   b  of the first mirror  53  overlaps with the hole  51   n  as seen from the outside (lower side of  FIG. 4 ) of the scanner unit  50  (part (c) of  FIG. 4  and  FIG. 7 ). However, the back surface  53   b  refers to a side surface of the first mirror  53  opposite from the reflecting surface  53   a  of the first mirror  53 . A space defined by the back surface  53   b  of the first mirror  53  and an inner surface of the hole  51   n  is a space roughly sealed closely except for the opening toward the outside of the scanner unit  50 . 
     As shown in part (c) of  FIG. 4 , when the adhesive  61  is applied (injected) into the hole  51   n  and cured in a state in which the fourth mirror  56  is set at a position where the first mirror  53  is opposed to the hole  51   n  at the back surface  53   b  thereof, an inner wall of the hole  51   n  and the back surface  53   b  of the first mirror  53  are bonded to each other through the adhesive  61 . In other words, the first mirror  53  which is an example of the reflection member is bonded to the box frame  51  by the adhesive  61  at a side surface different from the reflecting surface  53   a.    
     Further, as shown in  FIGS. 5 to 7 , the recessed portions  51   e  and  51   k  and the holes  51   k  and  51   n , which are used for adhesive bonding of the first to fourth mirrors  53  to  56  are positioned in the same position and are disposed on the same phantom plane G 1  perpendicular to the main scan direction Y 1 . This is also true for the recessed portions  51   g  and  51   l  and the holes  51   i  and  51   o  which are disposed symmetrically with the recessed portions  51   e  and  51   k  and the holes  51   h  and  51   n , respectively, on the basis of the center position Yc with respect to the main scan direction Y. By this, in the case where the connection of each of the first to fourth mirrors  53  to  56  to the box frame  51  are successively performed, there is no need to operate an application means such as a needle or the like, and therefore, an applying step can be simplified. 
     However, in this embodiment, the second and fourth mirrors  54  and  56  and the first and third mirrors  53  and  55  are position on different side surfaces of the box frame  51 , and application directions of the adhesive  61  are different from each other. For that reason, in the case where connection of each of the first to fourth mirrors  53  to  56  to the box frame  51  is successively performed, there is a need to rotate the scanner unit  50  or the application means around an axis with respect to the main scan direction. 
     SUMMARY OF THIS EMBODIMENT 
     As described above, in this embodiment, when the reflection member is connected to the casing of the image reading unit, a constitution in which a surface of the reflection member different from the reflecting surface of the reflection member is connected to the casing with the adhesive is employed. By this, a possibility that the reading image is influenced by adhesion of the adhesive can be reduced. Incidentally, in this embodiment, a constitution in which each of all the four mirrors  53  to  56  which are examples of the reflection member is connected to the casing with the adhesive at the surface different from the reflecting surface is employed, but a similar effect can be obtained when the above constitution is employed for at least one of the reflection members. 
     Further, in this embodiment, a constitution in which as the opening which opens toward the outside of the casing, the recessed portion or the hole is provided and an adhesive application operation is enabled through the opening from the outside of the image reading unit is employed. By this, the adhesive application operation for the image connection (adhesive bonding) is simplified, so that an application error is reduced. 
     Incidentally, the present invention is not limited to the above-described embodiment, but can be variously modified and changed within a range which is not out of the scope of the appended claims. 
     For example, in order to properly support the reflection members by the casing, the shape and the number of the recessed portions and the holes which are examples of the openings may also be changed depending on a specific situation such as the weight of the reflection member, a length of the reflection member with respect to the main scan direction and the like. Further, in the above-described embodiment, connection of the second mirror  54  and the third mirror  55  is performed by using the recessed portions  51   e  and  51   k , but the connection of these mirrors may also be carried out through the through holes. Further, in the above-described embodiment, the connection of the first mirror  53  and the fourth mirror  56  is performed by using the holes  51   n  and  51   h  which are the through holes, but the connection of these mirrors may also be carried out by using the recessed portions (recessed-shape portions each having the bottom). Further, as regards the connection of the single mirror, the recessed portion and the through hole may also be used in combination. 
     Further, in the above-described embodiment, the image reading apparatus  103  assembled with the image forming apparatus was described, but the present invention is also applicable to the image reading apparatus capable of being used singly. Further, the image reading unit explained in the above-described embodiment is not limited to the image reading unit for reading the image information from the sheet as the original, but may also be applicable as an apparatus for reading the image information for another purpose. For example, the image reading unit can be used an apparatus for reading an image, formed on the recording material, in order to adjust image density and to adjust a position and distortion of the image. Further, the image reading unit is also applicable to apparatuses, reading and using the image information, such as an authenticity discrimination apparatus of paper money and an apparatus for automatically sorting baggage in a distribution warehouse. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Applications No. 2019-216149 filed on Nov. 29, 2019, which are hereby incorporated by reference herein in their entirety.