JP5746958B2 - Image reading apparatus and image forming apparatus having the same - Google Patents

Description

  The present invention relates to an image reading apparatus that reads a document image and an image forming apparatus including the image reading apparatus.

  As a reading method of the image reading apparatus, two methods, a document fixed reading method and a document conveyance reading method, are known. The original fixed reading method is a method in which an original is placed on a contact glass, the original is pressed against the contact glass by a platen mat, an original conveying device, or the like, and an original image is read by scanning the reading unit. . On the other hand, the document conveyance reading method is a method in which a reading unit is fixed at a predetermined position, and a document image is read while the document is conveyed on the reading unit.

  Conventionally, an image reading apparatus as described in Patent Document 1 is known as a fixed document reading method. In the image reading apparatus, a contact image sensor extended in the main scanning direction is arranged as a reading unit below the contact glass. Then, the image sensor is moved in the sub-scanning direction, whereby the document on the contact glass is scanned two-dimensionally. In the image sensor, the outer frame is made of a resin material, and the central portion of the outer frame in the main scanning direction may warp upward after resin molding. For this reason, in the technique described in Patent Document 1, the inner surface of the contact glass is previously curved in an arc shape so that the image sensor and the contact glass are in close contact with each other.

JP 2000-138803 A

  When the contact image sensor is moved in the sub-scanning direction in the image reading apparatus as in the technique described in Patent Document 1, the image sensor is guided in the sub-scanning direction while supporting the image sensor. Guide means is disposed at the bottom of the main body frame of the image reading apparatus. However, since the main body frame is also often molded from a resin material, warping is likely to occur. As described above, when the main body frame is warped, the vertical position of the image sensor supported by the guide means on the main body frame varies. For this reason, the distance between the contact glass and the image sensor varies. As a result, the distance between the image sensor and the document placed on the contact glass varies, and the read image is distorted.

  The present invention has been made in view of the above-described problem, and an image in which the distance between the contact glass and the reading unit does not fluctuate even when the main body frame that movably supports the reading unit is warped. It is an object of the present invention to provide a reading device and an image forming apparatus including the reading device.

An image reading apparatus according to an aspect of the present invention includes an original plate on which an original is placed, a bottom made of a resin material , a case that supports the original plate, and a main scanning direction in the case. Are arranged in the main scanning direction and are arranged at both ends of the reading unit in the main scanning direction. said bottom contact with, without restricting the main scanning direction of the position of said reading means, a first positioning means for regulating the position in the vertical direction with respect to the original plate of the reading means, the main scanning of the reading unit An engaging portion disposed on a surface of the reading unit facing the bottom portion, and projecting upward from the bottom portion of the housing, facing the engaging portion, By engaging with the engaging portion, the reading means Without restricting the vertical position relative to the serial original plate, and having a second positioning means for regulating the position of the main scanning direction of said reading means.

According to this configuration, the document plate on which the document is placed on the upper surface is supported by the housing. Further, a reading unit is arranged in the casing so as to extend in the main scanning direction, move in the casing in the sub-scanning direction, and read an image of the document. At both ends of the reading means in the main scanning direction, first positioning means that abuts against the bottom of the housing is disposed. Even when the case is warped and the central portion of the bottom of the case is displaced up and down, the first positioning means is located at both ends in the main scanning direction of the reading means with respect to the original plate of the reading means. Determine the vertical position. For this reason, the displacement of the bottom of the housing hardly affects the vertical position of the reading means, and the position of the reading means is stably maintained. As a result, the vertical distance between the reading means and the original plate is unlikely to fluctuate, and the original image can be read with high accuracy. Further, according to this configuration, the engaging portion is disposed on the surface facing the bottom portion of the reading unit at the center in the main scanning direction of the reading unit. The second positioning means protrudes upward from the bottom of the housing so as to face the engaging portion. Then, the position of the reading unit in the main scanning direction is regulated by the engaging portion and the second positioning unit engaging each other. For this reason, the positioning in the vertical direction of the reading unit and the positioning in the main scanning direction are set in different regions in the main scanning direction of the reading unit. Therefore, even when a part of the bottom of the casing is deformed, the position of the reading unit is prevented from greatly fluctuating.

  In the above-described configuration, it is preferable that the first positioning unit is a first projection that projects downward from the reading unit and contacts the bottom of the housing.

  According to this configuration, the first protrusions projecting downward from the both ends in the main scanning direction of the reading unit abut on the bottom of the housing as the first positioning unit. Therefore, the vertical position of the reading unit is stably maintained by the simple configuration of the reading unit and the bottom of the housing.

  In the above configuration, an original plate supporting member that protrudes from the bottom portion and supports the original plate outside the main scanning direction from the portion of the bottom portion of the housing that contacts the first positioning means. It is preferable to further provide.

  According to this configuration, the original plate support member protrudes from the bottom portion on the outer side in the main scanning direction with respect to the portion where the first positioning means contacts the bottom portion of the housing. The original plate is supported by the original plate support member. Therefore, the document plate and the reading unit are positioned with reference to the bottom of the housing. For this reason, it is possible to reduce the number of members that affect the distance between the original plate and the reading unit as much as possible.

  In the above configuration, it is preferable that the second positioning unit is a ridge extending in the sub-scanning direction, and guides the reading unit along the sub-scanning direction.

  According to this configuration, the second positioning unit is a ridge extending in the sub-scanning direction, and has a function of regulating the position of the reading unit in the main scanning direction and guiding the reading unit in the sub-scanning direction.

In the above-described configuration, the engaging portion has a pair of standing walls standing downward from the reading unit so as to face each other in the main scanning direction, and a ceiling portion that connects the pair of standing walls upward. The second positioning means includes a pair of outer walls inserted between the pair of standing walls of the engaging portion, and the pair of outer walls connected in the upward direction , and the ceiling in the vertical direction. It is preferable to provide a tip portion that is spaced apart from the portion.

  According to this configuration, the position of the reading unit in the main scanning direction is regulated by inserting the pair of outer walls of the second positioning unit between the pair of standing walls of the engaging portion. Furthermore, the front-end | tip part of a 2nd positioning means is arrange | positioned at intervals with respect to the ceiling part of an engaging part. Therefore, even when the bottom of the housing is warped upward, the warping of the housing is absorbed, and the central portion of the reading unit in the main scanning direction is prevented from being displaced upward.

  In the above configuration, it is preferable that the reading unit includes a contact image sensor arranged to face the original plate.

  According to this configuration, even when the reading unit includes a contact image sensor (CIS sensor) having a smaller depth of field than the CCD sensor, the vertical distance between the contact image sensor and the original plate. Is difficult to fluctuate, and the image of the original can be read with high accuracy.

  In the above-described configuration, the reading unit is opposed to the original plate and includes a reading unit that accommodates the contact image sensor, and protrudes from both ends of the reading unit in the main scanning direction toward the original plate. A second protrusion that abuts on the original plate, a reading unit support member that supports the reading unit and in which the first positioning means is disposed, and between the reading unit and the reading unit support member And an elastic member that presses the reading unit toward the original plate.

  According to this configuration, the reading unit includes the reading unit that houses the contact image sensor. The reading unit includes second protrusions that protrude from both ends of the reading unit in the main scanning direction toward the original plate and come into contact with the original plate. The reading unit is supported on the reading support member via an elastic member, and is pressed toward the original plate by the elastic member. Therefore, the distance between the reading unit and the original plate is maintained by the protrusion amount of the second protrusion. In addition, the displacement caused to the support member is absorbed by the elastic member, and the position of the reading unit is stably maintained.

  An image forming apparatus according to another aspect of the present invention is an image forming apparatus that forms an image on a sheet based on any of the image reading apparatuses described above and an image of the original read by the reading unit. And a section.

  According to this configuration, the displacement of the bottom of the housing hardly affects the vertical position of the reading unit, and the position of the reading unit is stably maintained. For this reason, the vertical distance between the reading means and the original plate is unlikely to fluctuate, and the original image can be read with high accuracy. As a result, image quality defects such as distortion are prevented from occurring in the image formed on the sheet.

  According to the present invention, even when the main body frame that movably supports the reading unit is warped, the image reading apparatus in which the distance between the contact glass and the reading unit does not fluctuate, and the image formation provided with the image reading unit. An apparatus is provided. In particular, even if warpage occurs in the direction away from the contact glass in the center portion of the main frame in the sub-scanning direction, the distance between the center portion of the reading means and the contact glass does not vary, A good read image can be obtained.

1 is a perspective view of an image forming apparatus according to an embodiment of the present invention. 1 is a cross-sectional view showing an internal structure of an image forming apparatus according to an embodiment of the present invention. 1 is a perspective view of an image reading apparatus according to an embodiment of the present invention. 1 is a cross-sectional view of a main part of an image reading apparatus according to an embodiment of the present invention. 1 is an enlarged cross-sectional view of a main part of an image reading apparatus according to an embodiment of the present invention. It is a perspective view of the conventional image reading apparatus. It is an expanded sectional view of the principal part of the conventional image reading apparatus.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of an image forming apparatus according to an embodiment of the present invention. FIG. 2 schematically shows an internal structure of the image forming apparatus shown in FIG. The image forming apparatus shown in FIGS. 1 and 2 is a so-called in-body discharge type copying machine, but in other embodiments, a printer, a facsimile machine, a multifunction machine having these functions, or a toner image on a sheet. Other devices for forming may be used.

  The image forming apparatus 1 includes a main housing 2 having a substantially rectangular parallelepiped shape. The main housing 2 connects a substantially rectangular parallelepiped lower housing 21, a substantially rectangular parallelepiped upper housing 22 disposed above the lower housing 21, and the lower housing 21 and the upper housing 22. And a connecting housing 23. The connection housing 23 extends along the right edge and the back edge of the main housing 2. The sheet subjected to the printing process is discharged into a discharge space 24 surrounded by the lower casing 21, the upper casing 22, and the connecting casing 23.

  The operation unit 221 protruding in the front direction of the upper housing 22 includes, for example, an LCD touch panel 222. The operation unit 221 is formed so as to be able to input information related to the image forming process. For example, the user can input the number of sheets to be printed, the print density, and the like through the LCD touch panel 222.

  An image reading unit 3 (image reading device) is disposed in the upper housing 22. The image reading unit 3 includes a contact glass 225, a CIS unit 80, and an image processing unit 224. The contact glass 225 faces a fixed document placed on the upper surface with the document surface facing down, and serves as a reading surface when an image of the fixed document is read.

  The CIS unit 80 optically reads the document information on the document sheet. A CIS reading unit 800 is mounted on the CIS unit 80. The CIS reading unit 800 includes an LED light source (not shown), a GRIN (Graded-Index) lens, and a CIS (Contact Image Sensor). Reflected light from the original illuminated by the LED light source is incident on the light receiving surface of the CIS in which the image pickup elements are arranged in a line through a GRIN lens arranged in an array. The CIS photoelectrically converts the reflected light to read an image of the document. The analog image data of the original image photoelectrically converted by the CIS is digitally converted and sent to the image processing unit 224. The image processing unit 224 performs various types of image processing on the image data according to the document image reading conditions, and then sends the processed image data to the exposure unit 904.

  A document cover 223 disposed on the upper housing 22 is used to hold the document. The document cover 223 is attached to the upper housing 22 so as to be rotatable up and down. The user rotates the document cover 223 upward with the rear end of the document cover 223 as a fulcrum, and places the document on the upper housing 22. Thereafter, the user can operate the operation unit 221 to cause the image reading unit 3 disposed in the upper housing 22 to read the image of the document.

  The lower casing 21 is provided with a sheet tray 250 on which a plurality of sheets are stacked. The sheet tray 250 can be pulled out from the lower housing 21 in the front direction. The sheet P stored in the sheet tray 250 is sent upward in the lower housing 21 and is subjected to image formation processing in the lower housing 21 based on an instruction input by the user through the operation unit 221. It is discharged into the discharge space 24.

  A tray 212 is rotatably attached to the right surface of the lower housing 21. As shown in FIG. 1, when the tray 212 is in a position protruding to the right of the lower housing 21, the user can place a sheet on the tray 212. The sheet on the tray 212 is drawn into the lower housing 21 based on an instruction input by the user through the operation unit 221, is subjected to image forming processing, and is discharged into the discharge space 24. When the tray 212 is rotated upward, the tray 212 is accommodated in the accommodation space 203 that is recessed in the right surface of the lower casing 21, and the supply port for drawing the sheet into the lower casing 21 is closed.

  The lower housing 21 accommodates various devices for forming an image on a sheet. Further, the connection housing 23 accommodates various devices for discharging the sheet subjected to the image forming process to the discharge space 24.

  The lower casing 21 accommodates toner containers 900Y, 900M, 900C, 900Bk, an intermediate transfer unit 902, an image forming unit 903, an exposure unit 904, a fixing unit 97, and a paper discharge unit 96.

  The image forming unit 903 includes a yellow toner container 900Y, a magenta toner container 900M, a cyan toner container 900C, and a black toner container 900Bk. Below these containers, developing devices 10Y, 10M, 10C, and 10Bk corresponding to the respective colors of YMCBk are arranged.

  The image forming unit 903 includes a photosensitive drum 17 that carries toner images of respective colors. As the photosensitive drum 17, a photosensitive drum using an amorphous silicon (a-Si) material can be used. The photosensitive drums 17 are supplied with yellow, magenta, cyan, and black toner from the toner containers 900Y, 900M, 900C, and 900Bk, respectively.

  Around the photosensitive drum 17, a charger 16, a developing device 10 (10Y, 10M, 10C, 10Bk), a transfer device 19 and a cleaning device 18 are arranged. The charger 16 uniformly charges the surface of the photosensitive drum 17. The charged surface of the photosensitive drum 17 is exposed by the exposure unit 904, and an electrostatic latent image is formed. The exposure unit 904 irradiates laser light based on the digital signal generated by the scanning mechanism 224 described above. The developing devices 10Y, 10M, 10C, and 10Bk develop the electrostatic latent images formed on the respective photosensitive drums 17 using the toners of the respective colors supplied from the toner containers 900Y, 900M, 900C, and 900Bk, respectively ( Visualization). The transfer roller 19 forms a nip portion with the photosensitive drum 17 across the intermediate transfer belt 921, and primarily transfers the toner image on the photosensitive drum 17 onto the intermediate transfer belt 921. The cleaning device 18 cleans the peripheral surface of the photosensitive drum 17 after the toner image is transferred.

  Each of the developing devices 10Y, 10M, 10C, and 10Bk includes a developing case 20. A two-component developer having a magnetic carrier and toner is accommodated in the developing case 20. In the developing case 20, two stirring rollers 11 and 12 are rotatably arranged in parallel near the bottom of the developing case 20 with the longitudinal direction as the axial direction.

  A developer circulation path is set on the inner bottom surface of the developing case 20, and the stirring rollers 11 and 12 are disposed in the circulation path. A partition wall 201 erected from the bottom of the developing case 20 is provided in the axial direction between the stirring rollers 11 and 12. The partition wall 201 divides the circulation path. A circulation path is formed so as to circulate around the partition wall 201. The two-component developer is charged while being stirred and conveyed on the circulation path by the stirring rollers 11 and 12.

  The two-component developer circulates in the developing housing 20 while being stirred by the stirring rollers 11 and 12, and the toner is charged. The two-component developer on the stirring roller 11 is attracted and conveyed by the magnetic roller 14 located on the upper side. The sucked two-component developer forms a magnetic brush (not shown) on the magnetic roller 14. The layer thickness of the magnetic brush is regulated by the doctor blade 13, and the toner is supplied to the upper developing roller 15. The toner layer on the developing roller 15 is formed by a potential difference between the magnetic roller 14 and the developing roller 15. The electrostatic latent image on the photosensitive drum 17 is developed by the toner layer.

  The exposure unit 904 includes various optical system devices such as a light source, a polygon mirror, a reflection mirror, and a deflection mirror, and light based on image data is provided on the peripheral surface of the photosensitive drum 17 provided in each of the image forming units 903. To form an electrostatic latent image.

  The intermediate transfer unit 902 includes an intermediate transfer belt 921, a driving roller 922, and a driven roller 923. On the intermediate transfer belt 921, toner images are overcoated from a plurality of photosensitive drums 17 (primary transfer). The overcoated toner image is secondarily transferred by the secondary transfer unit 98 to a sheet supplied from the sheet tray 250 or the tray 212 (see FIG. 1). A driving roller 922 and a driven roller 923 that rotate the intermediate transfer belt 921 are rotatably supported by the lower casing 21.

  The fixing unit 97 performs a fixing process on the toner image on the sheet secondarily transferred from the intermediate transfer unit 902. The sheet with the color image that has been subjected to the fixing process is discharged toward a paper discharge unit 96 formed in the upper part of the fixing unit 97 (in the connection housing 23).

  The paper discharge unit 96 discharges the sheet conveyed from the fixing unit 97 onto the upper surface 213 of the lower housing 21 used as a paper discharge tray.

<Basic Configuration of Image Reading Unit 3>
Next, details of the image reading unit 3 according to the present embodiment will be described. FIG. 3 is a perspective view of the image reading apparatus 3 according to the present embodiment. FIG. 3 shows a state in which the contact glass 225 and the cover frame that holds the upper side of the contact glass 225 are removed. 4 is a cross-sectional view when the CIS unit 80 is moved to the position of the XY line in FIG.

  The image reading unit 3 includes a housing 500 that is a part of the upper housing 22. Further, the image reading unit 3 includes a winding unit 600 and a wire 601.

  The housing 500 includes a front wall 501, a rear wall 502, a left wall 503, a right wall 504, and a bottom plate 505. The front wall 501 and the rear wall 502 are a pair of wall portions that face each other in the main scanning direction (front-rear direction) of the image reading unit 3. Also. The left wall 503 and the right wall 504 are a pair of wall portions that face each other in the sub-scanning direction (left-right direction) of the image reading unit 3. The bottom plate 505 is a bottom portion of the image reading unit 3 and connects the above four wall portions downward. In the present embodiment, the housing 500 is made of a resin material and is formed by integral molding. The housing 500 accommodates the CIS unit 80 and the like inside, and supports the contact glass 225 disposed on the upper surface from below.

  The housing 500 further includes an eleventh support portion 506A, a twelfth support portion 506B, a first side support portion 507, a front support portion 508, a rear support portion 509, and a second side support disposed on the bottom plate 505. A portion 510, a front guide surface 512, a rear guide surface 513, and a guide portion 70.

  The eleventh support portion 506A and the twelfth support portion 506B are a pair of standing walls that are erected from the front and rear end portions of the bottom plate 505 at the left end portion of the image reading unit 3, respectively. Further, the first side support portion 507 is erected from the bottom plate 505 in parallel with the left wall 503 at two locations near the inside of the left wall 503 between the eleventh support portion 506A and the twelfth support portion 506B. It is a standing wall. The left end portion of the contact glass 225 installed on the top of the housing 500 is supported by the eleventh support portion 506A, the twelfth support portion 506B, and the first side support portion 507.

  The front support portion 508 (document plate support member) is a standing wall erected from the bottom plate 505 at four locations inside the front wall 501. Similarly, the rear support portion 509 (document plate support member) is a standing wall that is erected from the bottom plate 505 at three locations inside the rear wall 502. The center portion of the contact glass 225 is supported by the front support portion 508 and the rear support portion 509.

  The second side support portions 510 are standing walls that are erected from the bottom plate 505 in parallel with the right wall 504 at two locations near the inside of the right wall 504. The right side end portion of the contact glass 225 is supported by the second side support portion 510.

  As described above, in the present embodiment, the contact glass 225 is supported from below by the plurality of standing walls standing from the bottom plate 505 of the housing 500. For this reason, the height dimensions of the plurality of standing walls are set with high accuracy.

  A part of the bottom plate 505 is a raised flat portion, and the front guide surface 512 is disposed on the inner side (rear side) of the front support portion 508 (FIG. 4). Similarly, a part of the bottom plate 505 is also a raised flat part, and the rear guide surface 513 is disposed on the inner side (front side) of the rear support part 509. In other words, the front support portion 508 is erected upward from the front guide surface 512, and the rear support portion 509 is erected upward from the rear guide surface 513.

  The guide portion 70 (second positioning means) is provided so as to project upward from the bottom plate 505 from the inside of the left wall 503 to the inside of the right wall 504 at a substantially central portion of the bottom plate 505 in the main scanning direction. The guide part 70 is a convex line extending in the left-right direction at the bottom part 505. The guide unit 70 has a function of guiding the movement of the CIS unit 80.

  The winding unit 600 is a rotational drive unit that is disposed at the inner side of the left wall 503 at the substantially central portion of the bottom plate 505 in the main scanning direction. The wire 601 is wound around the winding portion 600 and a pulley (not shown) disposed inside the right wall 504. A part of the wire 601 is fixed to the CIS unit 80. When the winding unit 600 rotates in the forward and reverse directions and winds up the wire 601, the CIS unit 80 can be moved in the sub-scanning direction (left-right direction).

  The CIS unit 80 (reading means) is disposed in the internal space of the housing 500 so as to extend in the main scanning direction. That is, the CIS unit 80 has a casing shape that is long in the CIS arrangement direction, and is disposed in the housing 500 so that the longitudinal direction thereof matches the main scanning direction. Referring to FIG. 4, CIS unit 80 includes a CIS reading unit 800, a support plate 801, and a spring 802.

  The CIS reading unit 800 (reading unit) is mounted with a CIS (contact image sensor) as described above. The CIS reading unit 800 includes contact protrusions 803 that protrude toward the contact glass 225 at both ends in the main scanning direction. The contact protrusion 803 has a hemispherical shape at the tip. The contact protrusion 803 has a function of keeping the distance between the CIS reading unit 800 and the contact glass 225 constant.

  The support plate 801 (reading unit support member) is a box-shaped member that supports the CIS reading unit 800 along the main scanning direction. The support plate 801 includes a pair of support protrusions 804 and an engagement portion 805.

  A pair of support protrusions 804 (first protrusions) are provided so as to protrude downward from the lower surface 801A of the support plate 801 facing the bottom plate 505 of the support plate 801 at both ends in the main scanning direction. The support protrusion 804 has a hemispherical shape at the tip. The pair of support protrusions 804 abut against the front guide surface 512 and the rear guide surface 513 of the housing 500, respectively. Thereby, the lower part of the CIS unit 80 is supported by the housing 500, and the vertical position of the CIS unit 80 is regulated.

  The engaging portion 805 is disposed on the lower surface 801A of the support plate 801 at the center of the support plate 801 in the main scanning direction. In the present embodiment, the engaging portion 805 protrudes downward from the lower surface 801A. The engaging portion 805 has a substantially U-shape when viewed in cross section along the line XY in FIG. The engaging portion 805 has a function of regulating the position of the CIS unit 80 in the main scanning direction.

  The spring 802 (elastic member) is disposed between the CIS reading unit 800 and the support plate 801. A pair of springs 802 are arranged at both ends of the CIS reading unit 800 in the main scanning direction. The lower end of the spring 802 is fixed to the support plate 801, and the upper end of the spring 802 is fixed to the CIS reading unit 800. The spring 802 has a function of pressing the CIS reading unit 800 upward at both ends of the CIS reading unit 800 in the main scanning direction.

<CIS unit issues>
Next, a problem caused by the supporting structure of the CIS unit 80Z referred to the CIS unit 80 according to the present embodiment will be described. FIG. 6 is a perspective view showing a configuration in which the CIS unit 80Z is supported so as to be movable in the sub-scanning direction (left-right direction) in the housing 500Z. FIG. 7 is a cross-sectional view of the central portion of the CIS unit 80Z in the main scanning direction. 7 corresponds to a cross-sectional view taken along line AB in FIG.

  A CIS unit 80Z provided with a CIS (contact image sensor) is supported by a support plate on the lower side, and reads a document image on a contact glass (not shown) disposed on the upper side.

  The CIS unit 80Z includes an engaging portion 805Z that protrudes downward from the support plate 801Z at the center in the main scanning direction. The housing 500Z includes a guide portion 70Z that extends in the sub-scanning direction at the center in the main scanning direction. The guide part 70Z protrudes upward from the bottom plate 505Z. The engagement portion 805Z is engaged with the guide portion 70Z, whereby the position of the CIS unit 80Z is determined. In FIG. 7, the guide portion 70Z includes a front surface portion 70H, a rear surface portion 70I, and a front end portion 70J. Each of the front surface portion 70H and the rear surface portion 70I is a wall portion extending vertically upward from the bottom plate 505Z, and the front end portion 70J connects the front surface portion 70H and the rear surface portion 70I upward. The distal end portion 70J has a semicircular shape in a cross-sectional view in the main scanning direction.

  The engaging portion 805Z includes a first wall portion 805H, a second wall portion 805I, a first slope 805J, an upper wall 805K, and a second slope 805L. The first wall portion 805H and the second wall portion 805I are a pair of wall portions that define the front-rear direction of the engaging portion 805Z. The first inclined surface 805J and the second inclined surface 805L are disposed above the first wall portion 805H and the second wall portion 805I and inside the engaging portion 805Z, respectively. The first slope 805J and the second slope 805L are arranged to face each other at an angle of about 45 degrees with respect to the horizontal direction. The upper wall 805K connects the first inclined surface 805J and the second inclined surface 805L on the upper end side.

  In the above configuration, the position of the CIS unit 80Z provided with the CIS is determined in the front-rear direction and the vertical direction by the engagement of the engaging portion 805Z and the guide portion 70Z. That is, the CIS unit 80Z is disposed on the bottom plate 505Z so that the engaging portion 805Z engages with the guide portion 70Z. Then, the first inclined surface 805J and the second inclined surface 805L abut on the peripheral surface of the distal end portion 70J of the guide portion 70Z. Since the first inclined surface 805J and the second inclined surface 805L are disposed with an inclination of about 45 degrees so as to face each other, the position of the guide portion 70Z in the front-rear direction and the vertical direction is determined.

  In such a configuration, the housing 500 </ b> Z formed by resin molding may be deformed by a stress stage after molding or after molding. In particular, the center portion Z of the bottom plate 505Z as shown in FIG. 6 often projects downward so that the bottom plate 505Z is curved. The housing 500Z is set to have a longer length in the left-right direction than a length in the front-rear direction in order to read a document of a predetermined size. For this reason, the bottom plate 505Z is often deformed in a region extending in the left-right direction at the center portion, and is hardly deformed at both end portions in the front-rear direction.

  When the deformation of the bottom plate 505Z as described above occurs, the bottom plate 505Z is displaced downward in FIG. Along with this, the guide portion 70Z disposed on the bottom plate 505Z moves downward. For this reason, the CIS unit 80Z whose position in the vertical direction is determined by the distal end portion 70J similarly moves downward. As a result, in the central portion of the CIS unit 80Z in the main scanning direction, the CIS unit 80Z moves away from the contact glass 225 disposed above. In this case, the reading distance of the document placed on the contact glass 225 changes, and the read image is distorted. In particular, when a CIS sensor having a depth of field smaller than that of a CCD sensor is used as a reading unit, the above-described fluctuation in the reading distance has a great influence on a read image. As described above, in the CIS unit 80Z supported in such a manner that it is placed from above on the housing 500Z molded from a resin material, the distance between the CIS unit 80Z and the contact glass 225 is caused by deformation (warping) of the housing 500Z. Has the problem of fluctuating. And in order to solve such a subject, in this embodiment, the support structure of the CIS unit 80 which is hard to receive the influence of a deformation | transformation of the housing 500Z is employ | adopted.

<Support structure of CIS unit 80>
Next, the support structure of the CIS unit 80 according to the present embodiment will be described in detail. FIG. 5 is an enlarged cross-sectional view of the engaging portion 805 of the CIS unit 80 in the present embodiment. FIG. 5 corresponds to an enlarged view of the central portion of FIG.

  The guide part 70 protruding from the bottom plate 505 includes a front part 70A, a rear part 70B, and a tip part 70C. The front surface portion 70A and the rear surface portion 70B are wall portions extending vertically upward from the bottom plate 505, respectively. The rear surface portion 70B is a wall portion on the opposite side of the front surface portion 70A. The front end portion 70C connects the front surface portion 70A and the rear surface portion 70B upward. The distal end portion 70C has an inverted U shape so as to protrude upward in a cross-sectional view in the main scanning direction.

  The engaging portion 805 of the support plate 801 includes a first inner wall 805A, a second inner wall 805B, and a third inner wall 805C. The first inner wall 805A and the second inner wall 805B are wall portions protruding vertically downward from the support plate 801 so as to face each other. The third inner wall 805C is horizontally disposed between the first inner wall 805A and the second inner wall 805B. The third inner wall 805C connects the first inner wall 805A and the second inner wall 805B on the base end side. The interval between the first inner wall 805A and the second inner wall 805B is set to be slightly larger than the interval between the front surface portion 70A and the rear surface portion 70B of the guide portion 70. For example, the distance between the first inner wall 805A and the second inner wall 805B is set larger by about 0.05 mm to 0.10 mm than the distance between the front surface portion 70A and the rear surface portion 70B of the guide portion 70.

  In FIG. 4, the CIS unit 80 is placed on the bottom plate 505 while the engaging portion 805 of the CIS unit 80 is engaged with the guide portion 70 protruding from the bottom plate 505. Then, the pair of support protrusions 804 of the CIS unit 80 abuts on the front guide surface 512 and the rear guide surface 513 of the housing 500. At this time, as shown in FIG. 5, the distal end portion 70 </ b> C of the guide portion 70 is disposed so as to be separated from the third inner wall 805 </ b> C of the CIS unit 80 with a predetermined interval.

  According to the above configuration, even if the central portion (see FIG. 6) of the bottom plate 505 of the housing 500 is deformed so as to curve downward after resin molding, the CIS reading unit 800 and the contact are formed. The distance from the glass 225 is stably maintained. That is, in FIG. 5, the engaging portion 805 is inserted into the guide portion 70 while the first inner wall 805A and the second inner wall 805B face the front surface portion 70A and the rear surface portion 70B. However, as described above, the distal end portion 70C is not in contact with the third inner wall 805C. Accordingly, in the CIS unit 80, only the position in the main scanning direction is restricted at the center portion in the front-rear direction of the housing 500, and the position in the vertical direction is not restricted.

  On the other hand, as shown in FIG. 4, the pair of support protrusions 804 of the support plate 801 abut on the front guide surface 512 and the rear guide surface 513 of the housing 500, thereby restricting the vertical position of the CIS unit 80. The That is, in this embodiment, the CIS unit 80 is positioned in the vertical direction at both ends in the main scanning direction, and is positioned in the main scanning (front-rear) direction at the center in the main scanning direction. For this reason, even if the housing 500 is curved so that the central portion of the bottom plate 505 is displaced downward, the central portion in the main scanning direction of the CIS unit 80 is not displaced downward. Accordingly, it is possible to prevent the CIS reading unit 800 from moving away from the contact glass 225 in the central portion in the main scanning direction and the reading distance of the document placed on the contact glass 225 from fluctuating. As a result, a document image can be read with high accuracy even with a reading unit including a CIS sensor having a small depth of field.

  Further, as shown in FIG. 5, a predetermined interval is provided between the distal end portion 70 </ b> C of the guide portion 70 and the third inner wall 805 </ b> C of the support plate 801. For this reason, even if the housing 500 is curved so that the center portion of the bottom plate 505 is displaced upward, the distance can absorb the deformation amount of the bottom plate 505. Therefore, the central portion of the CIS unit 80 in the main scanning direction is not displaced upward. As a result, it is possible to prevent the CIS reading unit 800 from approaching the contact glass 225 in the central portion in the main scanning direction and changing the reading distance of the document placed on the contact glass 225.

  Further, in the present embodiment, as shown in FIGS. 3 and 4, a front support portion 508 and a rear support portion 509 that support the contact glass 225 protrude upward from the front guide surface 512 and the rear guide surface 513, respectively. The Therefore, the CIS unit 80 and the contact glass 225 are supported on the basis of the same seat surface (the front guide surface 512 and the rear guide surface 513), respectively, and a support structure that does not intervene with other support members as much as possible. Adopted. For this reason, the positional relationship between the contact glass 225 and the CIS unit 80 in the vertical direction is stably maintained without being influenced by other members.

  Furthermore, in the present embodiment, the CIS reading unit 800 includes contact protrusions 803 that protrude from both ends of the CIS reading unit 800 in the main scanning direction toward the contact glass 225 and contact the contact glass 225. The CIS reading unit 800 is supported on the support plate 801 via a spring 802 and is pressed toward the contact glass 225 by the spring 802. Thus, since the spring 802 presses the CIS reading unit 800 upward, the distance between the CIS reading unit 800 and the contact glass 225 is stably maintained by the protruding amount of the contact protrusion 803. Further, even if a slight displacement occurs in the support plate 801, the spring 802 absorbs the displacement, and thus the displacement is not easily transmitted to the CIS reading unit 800. As a result, the position of the CIS reading unit 800 is stably maintained.

  The image reading apparatus 3 and the image forming apparatus 1 including the image reading apparatus 3 according to the present embodiment have been described above. However, the present invention is not limited to these embodiments, and for example, the following modified embodiments are provided. Can be taken.

  (1) In the above embodiment, the front support portion 508 and the rear support portion 509 have been described as being protruded from the bottom plate 505 by integral molding of the housing 500. However, the present invention is not limited to this. Standing walls that support the front support portion 508, the rear support portion 509, and other contact glasses 225 may be fixed to the housing 500 as a separate member from the housing 500.

  (2) In the above embodiment, the configuration in which the engaging portion 805 is disposed on the support plate 801 of the CIS unit 80 and the guide portion 70 is disposed on the bottom plate 505 has been described, but the present invention is not limited thereto. For example, a plate-shaped guide portion 70 may be disposed on the support plate 801 side, and a U-shaped engagement portion 805 may be disposed on the bottom plate 505 side. Further, the engaging portion 805 disposed on the support plate 801 is not limited to the configuration protruding from the lower surface 801A of the support plate 801. That is, the concave portion may be formed directly on the lower surface 801 </ b> A, and the concave portion may be the engaging portion 805 that engages with the guide portion 70. Furthermore, a mode in which the position of the CIS unit 80 in the main scanning direction is regulated by other shapes may be employed.

  (3) In the above-described embodiment, the CIS unit 80 has been described as being provided with the contact protrusion 803 and the spring 802. However, the present invention is not limited to this. The CIS unit 80 may be provided with the contact protrusion 803 and the spring 802 alone, and does not include either the spring 802 or the contact protrusion 803, and only the support protrusion 804 is used in the vertical direction. A configuration in which the position is regulated may be used. Even in this case, the displacement generated in the center portion of the bottom plate 505 in the main scanning direction is prevented from affecting the vertical position of the CIS unit 80, and the distance between the CIS unit 80 and the contact glass 225 is stabilized. Maintained.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 3 Image reading unit (image reading apparatus)
22 Upper housing 223 Document cover 225 Contact glass (document plate)
224 Image processing unit 500 housing (housing)
501 front wall 502 rear wall 503 left wall 504 right wall 505 bottom plate 506 first support portion 506A eleventh support portion 506B twelfth support portion 507 first side support portion 508 front support portion (document plate support member)
509 Rear support part (original plate support member)
510 2nd side support part 512 Front guide surface 513 Back guide surface 600 Winding part 601 Wire 70 Guide part (2nd positioning means)
70A Front side (outer wall)
70B Rear surface (outer wall)
70C tip 80 CIS unit (reading means)
800 CIS reader (reader)
801 Support plate (reader support member)
802 Spring (elastic member)
803 Contact protrusion (second protrusion)
804 Support protrusion (first protrusion)
805 engagement portion 805A first inner wall (standing wall)
805B Second inner wall (standing wall)
805C 3rd inner wall (ceiling part)

Claims (8)

An original plate on which an original is placed;
A housing having a bottom made of a resin material and supporting the original plate;
A reading unit that is arranged extending in the main scanning direction in the housing, is movable in the sub-scanning direction in the housing, and reads an image of the document;
The reading means is disposed at both ends in the main scanning direction, abuts against the bottom of the housing, and restricts the position of the reading means in the main scanning direction with respect to the original plate. First positioning means for regulating the position in the vertical direction;
An engaging portion disposed on a surface of the reading unit facing the bottom of the reading unit at a central portion in the main scanning direction;
Opposite the engaging portion, it protrudes upward from the bottom portion of the housing, and engages with the engaging portion to restrict the vertical position of the reading unit with respect to the original plate. Without the second positioning means for restricting the position of the reading means in the main scanning direction,
An image reading apparatus comprising:   2. The image reading apparatus according to claim 1, wherein the first positioning unit is a first protrusion that protrudes downward from the reading unit and contacts the bottom of the housing.   The apparatus further comprises a document plate support member that protrudes from the bottom portion and supports the document plate outside the portion in the main scanning direction from the portion of the bottom portion of the housing where the first positioning means abuts. The image reading apparatus according to claim 1 or 2. Said second positioning means is a convex extending in the sub-scanning direction, according to the reading unit to any one of claims 1 to 3, wherein the guiding along the sub-scanning direction Image reading device. The engaging portion is
A pair of upright walls erected downward from the reading means so as to face each other in the main scanning direction;
A ceiling part that connects the pair of standing walls upward, and
The second positioning means includes
A pair of outer walls inserted between the pair of standing walls of the engaging portion;
The pair of outer walls are connected to each other on the upper side, and a front end portion that is spaced apart from the ceiling portion in the vertical direction is provided . the image reading apparatus according to any one. It said reading means includes an image reading apparatus according to any one of claims 1 to 5, characterized in that it comprises a contact image sensor arranged opposite to the document plate. The reading means includes
A reading unit facing the original plate and containing the contact image sensor;
A second projecting portion projecting from both ends of the reading unit in the main scanning direction toward the document plate and contacting the document plate;
A reading unit support member that supports the reading unit and in which the first positioning means is disposed;
The image reading apparatus according to claim 6 , further comprising an elastic member that is disposed between the reading unit and the reading unit support member and presses the reading unit toward the original plate. An image reading apparatus according to any one of claims 1 to 7 ,
An image forming unit that forms an image on a sheet based on an image of the document read by the reading unit;
An image forming apparatus comprising:

Images