Abstract:
An image reading device comprising: a document placing portion; a conveyor; a reading unit configured to read an image of the document, wherein the reading unit includes: an image sensor; a support which supports the image sensor, wherein in the case of reading the image of the document conveyed by the conveyor, the support is to be stopped at a predetermined reading position; a guide; and a driving unit, wherein the reading unit further includes: a release unit configured to release the contact with the guide by separating the support from the guide when the support is moved toward the predetermined reading position; and a contact portion configured to contact with the support separated from the guide by the release unit when the support is moved toward the predetermined reading position.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority from Japanese Patent Application No. 2012-190059 filed on Aug. 30, 2012, the entire subject matter of which is incorporated herein by reference. 
       TECHNICAL FIELD 
       [0002]    This disclosure relates to an image reading device. 
       BACKGROUND 
       [0003]    There is an image reading device called a flatbed type. In general, such an image reading device includes an image sensor having reading elements arranged in a main scanning direction and a carriage moving the image sensor in a sub-scanning direction. The carriage has a structure capable of moving along a guide shaft. As such a guide shaft, a round bar shaped metal shaft is used (e.g., see JP-A-H11-266347). 
       SUMMARY 
       [0004]    Meanwhile, in the above-described flatbed type image reading device, one image reading device is additionally provided with an automatic document feeder (hereinafter referred to as an “ADF”). In the case of using the ADF, the above-described carriage and image sensor are stopped at a predetermined reading position. If a document is conveyed by the ADF, the document passes through a point which faces the image sensor at the reading position during conveyance, and at that time, the image sensor reads an image of the document. 
         [0005]    In such an image reading device, many parts may not be interposed between the image sensor and the guide shaft. Accordingly, even in consideration of tolerance of their part dimensions or tolerance of the positioning precision between the parts, the image sensor and the guide shaft are in a state where their positions can be determined with relatively good precision, and the reading quality of the image is stabilized in the reading using the flatbed. 
         [0006]    However, between the image sensor and the ADF, the parts interposed between the image sensor and the guide shaft are increased and many parts are additionally interposed between the guide shaft and the ADF. Accordingly, in consideration of the tolerance of their part dimensions or the tolerance of the positioning precision between the parts with respect to all the parts, it is correspondingly difficult to position the image sensor and the ADF with good precision. 
         [0007]    If the positioning precision of the image sensor and the ADF is low, the arrangement direction of the reading elements of the image sensor (main scanning direction) and the conveyance direction of the document by the ADF (sub-scanning direction) may be slightly inclined and may not be at right angles. Since the degrees of inclination are different from each device, the inclination becomes the cause where unevenness occurs in the reading quality of the image using the ADF. 
         [0008]    Accordingly, this disclosure provides at least an image reading device, which is configured to determine relative positional relations between an image sensor and an ADF with better precision than that in the related art. 
         [0009]    Hereinafter, the configuration adopted in this disclosure will be described. An image reading device of this disclosure includes: a document placing portion on which a document is placed; a conveyor configured to convey a document along a predetermined conveyance path; and a reading unit configured to read an image of the document. The reading unit includes: an image sensor having a plurality of reading elements arranged in a main scanning direction; a support which supports the image sensor and is movable together with the image sensor in a sub-scanning direction that is orthogonal to the main scanning direction; a guide, which guides the support in the sub-scanning direction through coming in contact with the support when the support is moved in the sub-scanning direction; and a driving unit configured to move the support in the sub-scanning direction. In the case of reading the image of the document placed on the document placing portion, the support is moved in the sub-scanning direction within a predetermined reading range, and in the case of reading the image of the document conveyed by the conveyor, the support is to be stopped at a predetermined reading position. In the case of moving in the sub-scanning direction within the predetermined reading range, the support is moved while keeping in contact with the guide. The reading unit further includes: a release unit configured to release the contact with the guide by separating the support and the guide when the support is moved toward the predetermined reading position; and a contact portion configured to contact with the support separated from the guide by the release unit when the support is moved toward the predetermined reading position. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The foregoing and additional features and characteristics of this disclosure will become more apparent from the following detailed descriptions considered with the reference to the accompanying drawings, wherein: 
           [0011]      FIG. 1  is a perspective view illustrating an external appearance of the whole multifunction peripheral; 
           [0012]      FIG. 2  is a block diagram illustrating the internal configuration of the multifunction peripheral; 
           [0013]      FIG. 3  is a perspective view illustrating an external appearance of a scanner unit and an ADF unit; 
           [0014]      FIG. 4  is a perspective view illustrating a structure in the vicinity of a hinge portion; 
           [0015]      FIG. 5  is a plan view illustrating a scanner unit; 
           [0016]      FIG. 6  is a longitudinal cross-sectional view illustrating a schematic structure of a scanner unit and an ADF unit; 
           [0017]      FIG. 7  is a perspective view illustrating a guide unit and a release unit. 
           [0018]      FIG. 8A  is a longitudinal cross-sectional view illustrating a state where a slider portion and a guide unit are at a contact position as seen from the front side of the device, and  FIG. 8B  is a longitudinal cross-sectional view illustrating a range taken along line A-A in  FIG. 8A . 
           [0019]      FIG. 9A  is a longitudinal cross-sectional view illustrating a state where a slider portion and a guide unit are at separate positions as seen from the front side of the device, and  FIG. 9B  is a longitudinal cross-sectional view illustrating a range taken along line B-B in  FIG. 9A . 
           [0020]      FIGS. 10A and 10B  are explanatory views illustrating the state of positioning of a support and a contact portion. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    Hereinafter, embodiments of this disclosure will be described. In this embodiment, an exemplified image reading device is configured as a multifunction peripheral having other functions (e.g., print function, copy function, facsimile transmission/reception function, and the like) in addition to the function (scan function) as the image reading device. In the following description, for simple explanation of relative positional relations between respective portions of the multifunction peripheral, respective directions, that is, upper, lower, left, right, front, and rear directions, as described in the drawings will be used. 
         [0022]    [Structure of a Multifunction Peripheral] 
         [0023]    As illustrated in  FIG. 1 , a multifunction peripheral  1  includes a main body unit  2 , a scanner unit  3  mounted on an upper side of the main body unit  2 , and an ADF unit  4  mounted on an upper side of the scanner unit  3 . On an upper portion of the front side of the main body unit  2 , an operation panel  6  that is operated by a user is provided. On a lower portion of the main body unit  2 , a feeder cassettes  8 A and  8 B, in which recorded medium before printing is accommodated, are mounted. 
         [0024]    In the main body unit  2 , as illustrated in  FIG. 2 , a controller  11 , an image forming unit  12 , a LAN communication unit  13 , and a PSTN communication unit  14  are provided in addition to the operation panel  6 . 
         [0025]    The controller  11  includes a known CPU  11 A, a ROM  11 B, a RAM  11 C, an NVRAM  11 D, and an interface unit  11 E. The CPU  11 A executes a predetermined process according to a control program stored in the ROM  11 B or the RAM  11 C, and thus the control of respective units of the multifunction peripheral  1  is executed. 
         [0026]    The image forming unit  12  is provided with an electrographic or ink jet print mechanism. The LAN communication unit  13  includes a communication interface device supporting wireless LAN, and a communication interface device supporting wire LAN. The PSTN communication unit  14  includes various kinds of devices that are necessary to connect to the public switched telephone network (PSTN). 
         [0027]    In the operation panel  6 , input devices (e.g., a touch panel, various kinds of buttons, and switches), which is operated when a user provides various kinds of commands to the multifunction peripheral, and an output device (e.g., liquid crystal display device) for notifying a user of the operating state of the multifunction peripheral  1 . 
         [0028]    The scanner unit  3  includes a line type image sensor  21  having a plurality of reading elements, and a support  23  supporting the image sensor  21 . Further, the scanner unit  3  includes a motor  25 , a gear mechanism  27  that is driven by the motor  25 , and a timing belt  29  that is driven by the gear mechanism  27 , and the above-described support  23  is connected to the timing belt  29 . The motor  25  receives a driving signal from a motor driving unit  11 F provided in an interface unit  11 E of the controller  11  to operate. The power that is generated by the motor  25  is transmitted to the support  23  through the gear mechanism  27  and the timing belt  29 , and as a result, the support  23  is moved in the left/right direction together with the image sensor  21 . 
         [0029]    The ADF unit  4  includes conveyance rollers  31  to  39  conveying the document along a predetermined conveyance path. Further, in the ADF unit  4 , a motor  41  and a gear mechanism  43  that is driven by the motor  41  are provided. The motor  41  receives a driving signal from a motor driving unit  11 G provided in the interface unit  11 E of the controller  11  to operate. The power that is generated by the motor  41  is transmitted to the conveyance rollers  31  to  39  through the gear mechanism  43 . On the other hand, some of the conveyance rollers  31  to  39  is driving rollers directly driven by the gear mechanism  43 , and other rollers are driven rollers rotated to follow the driving rollers or the document. 
         [0030]    [Attachment Structure of the ADF Unit for the Scanner Unit] 
         [0031]    As illustrated in  FIG. 1 , on an upper portion of the scanner unit  3 , a cover member  51  is provided, and a platen glass  53  is attached to the cover member  51 . The cover member  51  includes a frame portion  51 A surrounding four sides of the platen glass  53 , and a partition portion  51 B dividing an upper surface of the platen glass  53  into a first area  53 A and a second area  53 B. In this embodiment, one sheet of platen glass  53  is divided into the first area  53 A and the second area  53 B. However, the first area  53 A and the second area  53 B may be provided by different platen glasses  53 . 
         [0032]    As illustrated in  FIG. 3 , the ADF unit  4  is attached to the scanner unit  3  to be opened and closed by a pair of hinge portions  55  provided at positions that are spaced apart from each other in the left/right direction. On an upper end side of the hinge portion, as illustrated in  FIG. 4 , a bearing portion  55 A is provided, and a rotating shaft  4 A is provided on the side of the ADF unit  4 . The rotating shaft  4 A is rotatably supported by the bearing portion  55 A. 
         [0033]    If the ADF unit  4  is opened, as illustrated in  FIG. 1 , the upper surface of the platen glass  53  is exposed to an outside. On the other hand, if the ADF unit  4  is closed, the ADF unit  4  functions as a cover that covers the upper surface of the platen glass  53 . 
         [0034]    As illustrated in  FIGS. 3 and 4 , the hinge portion  55  is fixed to the scanner unit  3  by a screw  57 . In the cover member  51  provided in the scanner unit  3 , as illustrated in  FIG. 3 , two positioning projections  59  are provided to be corresponded to one hinge portion  55 . 
         [0035]    In the case of fixing the hinge portion  55  to the scanner unit  3 , the positioning projection  59  is inserted into a positioning hole  55 B formed on the side of the hinge portion  55 , so that the hinge portion  55  is fixed to the scanner unit  3  in a state where it is positioned with relatively good precision with respect to the cover member  51 . In this embodiment, the hinge portions  55  are provided at two points on the rear end side of the device main body. However, the number of hinge portions  55  is not limited to 2, and the attachment method is not limited to the above-described fixing method in so far as the hinge portion  55  is fixed to the scanner unit  3 . 
         [0036]    [Details of the Scanner Unit] 
         [0037]    In the scanner unit  3 , as illustrated in  FIGS. 3 and 5 , the above-described image sensor  21 , the support  23 , and the timing belt  29  are provided. On the other hand,  FIG. 5  illustrates both a state, where the image sensor  21  has moved to a position P 1  together with the support  23 , and a state, where the image sensor  21  has moved to a position P 2 . 
         [0038]    In this embodiment, the image sensor  21  is composed of a CIS (Contact Image Sensor). A plurality of reading elements provided in the image sensor  21  are arranged in the front/rear direction in the multifunction peripheral  1 . Hereinafter, the front/rear direction that is the arrangement direction of the reading elements is called a main scanning direction. 
         [0039]    As illustrated in  FIG. 5 , the support  23  has a carriage unit  23 A, and a slider portion  23 B that is attached to a bottom portion of the carriage unit  23 A. The slider portion  23 B is provided in the vicinity of the center in the main scanning direction of the carriage unit  23 A, and it is made of a material having higher slidability than that of the carriage unit  23 A. Specifically, in this embodiment, the carriage unit  23 A is formed of ABS resin, and the slider portion  23 B is formed of polyacetal resin (POM). 
         [0040]    On an upper surface side of a base portion  3 A that is provided in the scanner unit  3 , a guide unit  61  that extends in the left/right direction is provided. The base portion  3 A and the guide unit  61  are integrally formed of a resin material. If the timing belt is driven, the support  23  slides on the guide unit  61 . Hereinafter, the left/right direction that is the moving direction of the image sensor  21  and the support is called a sub-scanning direction. 
         [0041]    In the vicinity of both ends in the front/rear direction of the image sensor  21 , as illustrated in  FIGS. 5 and 6 , a spacer  63  that is interposed between the image sensor  21  and the platen glass  53  is attached. Further, a compression spring  65  is interposed between the support  23  and the image sensor  21 . 
         [0042]    The image sensor  21  and the spacer  63  are always in a compressed state toward the side of the platen glass  53 . Accordingly, when the support  23  is moved, even if the support  23  slightly moves upward and downward, the spacer  63  keeps the contact state with the lower surface of the platen glass  53 , and the image sensor  21  is maintained in parallel to the lower surface of the platen glass  53 . 
         [0043]    On the lower surface of the partition portion  51 B that the cover member  51  has, a reference member  67  is incorporated. The reference member  67  is a member formed to have white portions and black portions for a predetermined pattern. When reading the image, in order to perform original point position correction and shading correction of the image sensor  21 , the reference member  67  is read by the image sensor  21 . 
         [0044]    [Details of the ADF Unit] 
         [0045]    In the ADF unit  4 , as illustrated in  FIG. 6 , the plurality of conveyance rollers  31  to  39  as described above are provided. If the conveyance rollers  31  to  39  are driven, the document can be conveyed along a predetermined conveyance path (a path indicated by a dashed line). 
         [0046]    In the case where the multifunction peripheral  1  is used as an ADF type image scanner, the image sensor  21  in the scanner unit  3  moves to the position P 1  as shown in  FIG. 5 , and then it is stopped (hereinafter, the position P 1  is also called a reading position P 1 ). Further, the conveyance rollers  31  to  39  in the ADF unit  4  convey the document along the above-described conveyance path. 
         [0047]    The conveyed document passes through a position where the document comes in contact with the second area  53 B of the platen glass  53  in the left/right direction in the middle of the conveyance path. At this position, a document pressing portion  71  is provided. When the conveyed document passes through the position where the document pressing portion  71  is positioned, the document pressing portion  71  presses the document toward the second area  53 B, and the document comes in close contact with the second area  53 B of the platen glass  53 . The image sensor  21  that is at the reading position P 1  faces the second area  53 B and the document pressing portion  71 . In this state, the image sensor  21  can read the image of the document that passes through the reading position P 1  by the reading elements arranged in the main scanning direction. 
         [0048]    As illustrated in  FIG. 6 , on the lower surface of the ADF unit  4 , an elastic member  73  is provided at a position that comes in contact with the first area  53 A of the platen glass  53  when the ADF unit  4  is closed. The elastic member  73  is a laminated body including a foaming resin layer as its upper layer and a resin film layer as its lower layer. 
         [0049]    In the case where the multifunction peripheral  1  is used as an image scanner, a document is placed on the first area  53 A of the platen glass  53 . If needed, the ADF unit  4  is closed. At this time, the elastic member  73  presses the document placed on the first area  53 A from the upper side, and the document comes in close contact with the first area  53 A of the platen glass  53 . In this state, the image sensor  21  moves in the sub-scanning direction together with the support  23 . 
         [0050]    In this embodiment, during the forward movement to the left, the image sensor  21  is within a predetermined reading range A 1 , and the image of the document placed on the first area  53 A of the platen glass  53  is read by the reading elements that are arranged in the main scanning direction. Thereafter, if the image reading is terminated, the image sensor  21  returns to the initial position through the return movement in the left direction. 
         [0051]    [Positioning Mechanism of the Support at the Reading Position P 1 ] 
         [0052]    In the vicinity of the left end side of the guide unit  61 , as illustrated in FIG.  7 , a first projection portion  81  and a second projection portion  82  are formed. The first projection portion  81  and the second projection portion  82  are formed at positions that are separated from each other in the left/right direction, and are at the positions where they are seen to overlap each other as seen from the sub-scanning direction. 
         [0053]    Further, both the first projection portion  81  and the second projection portion  82  project upward from the upper end of the guide unit  61 , but the upper end of the second projection portion is at a higher position (upper side) than the upper end of the first projection portion  81 . On the right end side of the first projection portion  81 , an inclination portion  81 A having an upward slop from the right side to the left side is formed. Even on the right end side of the second projection portion  82 , an inclination portion  81 A having an upward slop from the right side to the left side is formed. The upper ends of the first projection portion  81  and the second projection portion that continue on the upper end sides of the inclination portions  81 A and  82 A are flat planes. 
         [0054]    On the other hand, on the slider portion  23 B, as illustrated in  FIGS. 8A ,  8 B,  9 A, and  9 B, a first convex portion  83  and a second convex portion that project downward are formed. The first convex portion  83  is formed at a position where the support  23  comes in contact with the first projection portion  81  when the support  23  is moved to the reading position P 1 , and the second convex portion  84  is formed at a position where the support  23  comes in contact with the second projection portion  82  when the support  23  is moved to the reading position P 1  (see  FIG. 8A ). 
         [0055]    When the slider portion  23 B moves to the position where the slider portion  23 B is separated from the first projection portion  81  and the second projection portion  82 , the slider portion  23 B moves in the left/right direction while keeping a state where the upper surface portion of the slider portion  23 B is at a drop position H 1 . At this time, a groove portion that is formed on the lower side of the slider portion  23 B comes in contact with the guide unit  61  at both sides of the guide unit  61  in the front/rear direction in the vicinity of the upper end of the guide unit  61 . (See  FIG. 8B ). 
         [0056]    In such a contact state, the slider portion  23 B is unable to be displaced in the rotating direction along the surface perpendicular to the upper/lower direction (i.e. surface parallel to the front/rear direction or the left/right direction). Accordingly, the support  23  is positioned at a position where the length direction of the support  23  and the length direction of the guide unit  61  are orthogonal to each other on the basis of the guide unit  61 . 
         [0057]    On the other hand, if the support  23  is moved in the left direction and is reached the reading position P 1 , as illustrated in  FIGS. 9A and 9B , the slider portion  23 B runs onto the first projection portion  81  and the second projection portion  82 . At this time, since the inclination portions  81 A and  82 A are provided on the first projection portion  81  and the second projection portion  82 , respectively, the slider portion  23 B can be smoothly guided to the upper side of the first projection portion  81  and the second projection portion  82  as the support  23  move in the left direction. 
         [0058]    Further, the upper ends of the first projection portion  81  and the second projection portion  82  have different positions (heights), and thus the positions (heights) of the upper ends of the first projection portion  81  and the second projection portion  82  are changed. Through this, when the support  23  reaches the reading position P 1 , the lower end of the second convex portion  84  passes in the left direction along the upper side of the first projection portion  81  and runs onto the second projection portion  82  without coming in contact with the upper end of the first projection portion  81 . 
         [0059]    If the slider portion  23 B runs onto the first projection portion  81  and the second projection portion  82 , the support  23  is moved slightly upward without changing the inclination for the left/right direction and the front/rear direction, and the upper surface portion of the slider portion  23 B is displaced to a rise position H 2 . Further, since the upper ends of the first projection portion  81  and the second projection portion  82  are flat surface and come in surface contact with the first projection portion  83  and the second projection portion  84 , it becomes possible to support the rising slider portion  23 B in a stable state with respect to the guide unit  61 . 
         [0060]    Further, in this state, the groove portion  85  that is formed on the lower side of the slider portion  23 B is separated from the upper end of the guide  61  (see  FIG. 9B ). In this state, the slider portion  23 B is supported by the upper ends of the first projection portion  81  and the second projection portion  82  and the timing belt  29 , and it is in a condition to be able to be displaced in the rotating direction along the surface perpendicular to the upper/lower direction (i.e. surface in parallel to the front/rear direction and the left/right direction). That is, the first projection portion  81  and the second projection portion  82  function as release units to release the contact with the guide unit  61  when the support  23  is moved toward the reading position P 1 . 
         [0061]    Further, as illustrated in  FIGS. 5 and 9A , a pair of contacted portions  87  are formed at positions separated from each other in the front/rear direction. When the support  23  is moved toward the reading position P 1 , the contact portion  51   c  that is integrally formed on the cover member  51  comes in contact with the contacted portion  87  (see  FIG. 9A ). 
         [0062]    Accordingly, as illustrated in  FIG. 10A , if the contact portion  51 C comes in contact with one of the contacted portions  87 , even though the support  23  is slightly inclined against the contact portion  51 , the support  23  is rotated in the direction in which the other of the contacted portions  87  approaches the contact portion  51 C as illustrated in  FIG. 10B . As a result, the support  23  is positioned on the basis of the cover member  51 . 
         [0063]    The support  23  is positioned on the basis of the cover member  51  at the reading position P 1 , and it is positioned on the basis of the guide unit  61  when it moves in the reading range A 1 . As described above, the ADF unit  4  is supported by the hinge portion  55 , and the cover member  51  of the hinge portion  55  is positioned with good precision. However, another component is interposed between the hinge portion  55  and the guide unit  61 , and thus the hinge portion  55  and the guide unit  61  are not in direct positioning relations. 
         [0064]    Accordingly, the tolerance of the relative position for the ADF unit  4  becomes smaller than that of the guide unit  61 . Accordingly, if the support  23  is moved toward the reading position P 1 , the positioning on the basis of the guide member  61  is released, and it is changed to the positioning based on the cover member  51 . Accordingly, the positioning accuracy between the support  23  and the ADF unit  4  can be further improved. 
         [0065]    [Effects] 
         [0066]    As described above, according to the above-described multifunction peripheral  1 , in the case of reading the image of the document conveyed in the ADF unit  4 , the support  23  comes in contact with the contact portion  51 C, and thus is positioned at a portion where the tolerance of the relative position for the ADF unit  4  is smaller than that for the guide unit  61 . 
         [0067]    Accordingly, as compared with the case where the support  23  is positioned against the guide unit  61 , the tolerance accumulated between the support  23  and the ADF unit  4  can be reduced, and thus the quality deterioration of the read image can be suppressed due to the tolerance accumulated between the support  23  and the ADF unit  4 . 
         [0068]    According to the above-described multifunction peripheral  1 , since the release unit is constructed by the first projection portion  81  and the second projection portion  82  formed to project from the guide unit  61 , the release unit has a simple structure, and thus can be easily prepared as compared with a case where the release unit having a complicated structure is prepared. 
         [0069]    According to the above-described multifunction peripheral  1 , when the support  23  is moved toward the reading position P 1 , the support  23  runs onto the first projection portion  81  and the second projection portion  82  at the same time, and then it is separated from the guide unit  61  while performing parallel movement. Accordingly, when the support  23  runs onto the projection portions, the inclination of the support  23  is changed, and thus the behavior of the support  23  becomes stabilized. Further, even after the support  23  runs onto the first projection portion  81  and the second projection portion  82 , the support  23  can be supported on the first projection portion  81  and the second projection portion  82  in more stable state. 
         [0070]    According to the above-described multifunction peripheral  1 , since the first projection portion  81  and the second projection portion  82  are in positions where they are seen to overlap each other as seen from the sub-scanning direction, a region required for arrangement of the projection portions becomes compact as compared with a case where the plurality of projection portions are in the position to not overlap each other as seen from the sub-scanning direction. Further, According to the above-described multifunction peripheral  1 , in the moving direction where the support  23  is moved toward the reading position P 1 , the projection height of the first projection portion  81  positioned in the more upstream side is set low, and the projection height of the second projection portion  82  positioned in the downstream side is set high. In other words, the highest portion of the first projection portion  81  positioned in the upstream side is lower than the highest portion of the second projection portion  82  positioned in the downstream side. Accordingly, although the first projection portion  81  and the second projection portion  82  are in positions where they are seen to overlap each other as seen from the sub-scanning direction, the second convex portion  84  can pass through the first projection portion  81  without running onto the first projection portion  81  in the upstream side when the support  23  is moved to the reading position P 1 . Accordingly, unlike a case where the projection height of the first projection portion  81  in the upstream side is higher than that of the second projection portion  82  in the downstream side or a case where the projection heights of the first projection portion  81  and the second projection portion  82  are equal to each other, the support  23  can appropriately run onto the second projection portion  82  in the downstream side. 
         [0071]    According to the above-described multifunction peripheral  1 , since the first convex portion  83  and the second convex portion  84  are provided on the side of the support  23 , the frictional force that acts between the support  23  and the guide unit  61  is reduced as compared with a case where the support  23  comes in contact with the first projection portion  81  and the second projection portion  82  at a surface that is larger than the front end of the first convex portion  83  and the second convex portion  84 , and thus the state where the support  23  is positioned at the position based on the guide unit  61  can be released more smoothly. 
         [0072]    According to the above-described multifunction peripheral  1 , when the support  23  runs onto the first projection portion  81  and the second projection portion  82 , the support  23  comes in contact with the inclination portions  81 A and  82 A and then runs onto the first projection portion  81  and the second projection portion  82  along the inclination portions  81 A and  82 A. Accordingly, the support  23  can smoothly run onto the first projection portion  81  and the second projection portion  82  as compared with a case where the inclination portions  81 A and  82 A are not provided. 
         [0073]    According to the above-described multifunction peripheral  1 , the reference member  67  can be appropriately read at a position that is not affected by the first projection portion  81  and the second projection portion  82 . 
         [0074]    Further, According to the above-described multifunction peripheral  1 , the tolerance that can be accumulated between the ADF unit  4  and the contact portion  51 C becomes the tolerance between the cover member  51  and the hinge portion  55  and the tolerance between the hinge portion  55  and the ADF unit  4 . Accordingly, the tolerance accumulated between the ADF unit  4  and the support  23  can be reduced in the case where the support  23  is positioned on the basis of the contact portion  51 C that is integrally formed with the cover member  51 , rather than in the case where the support  23  is positioned on the basis of the guide unit  61  separated from the cover member  51 , and thus the reading precision of the document can be heightened. 
         [0075]    According to the above-described multifunction peripheral  1 , since the guide unit  61  is made of a resin material, unlike the metal guide unit, the projection portions can be easily provided by a technique of integrally forming the guide unit  61  and the projection portions (e.g., first projection portion  81  and the second projection portion  82 ). 
         [0076]    According to the above-described multifunction peripheral  1 , the material that forms the slider portion  23 B has higher slidability than the material that forms the carriage unit  23 A, and thus the respective performances of the carriage unit  23 A and the slider portion  23 B can be optimized as compared with a case where the whole support  23  is integrally formed with the same material. 
       Other Embodiments 
       [0077]    Although the embodiment of this disclosure have been described, this disclosure is not limited to the above-described detailed embodiments, and may be embodied in various forms. 
         [0078]    For example, in the above-described embodiment, the first projection portion  81  and the second projection portion  82  are exemplified as a specific example of the release unit. However, the number of projection portions are optional, and one projection portion or three or more projection portions may be configured. However, if one projection portion is provided, the inclination is easy to occur on the support when the support runs onto the projection portion, and thus it is preferable that a plurality of projection portions are provided as in the above-described embodiment so that the support runs onto the plurality of projections at the same time. 
         [0079]    Further, if it is configured that the contact portion  51 C of the cover member  51  and the support  23  are directly positioned, as the above-described embodiment, such a configuration is not limited to the configuration that the projection-shaped contacted portions  87  are provided in the support  23 , but may have other shapes. 
         [0080]    In the above-described embodiment, it is exemplified that the guide unit  61  is formed of a resin material. However, the configuration of this disclosure can also be adopted even in the case where the metal guide shaft is adopted as the guide unit. 
         [0081]    Further, in the above-described embodiment, the image reading device according to this disclosure is configured as the multifunction peripheral. However, this is optional, and the configuration of this disclosure may be adopted in an image reading device, a copy machine, or a facsimile, which has a single function.