JP2009130762A - Image reader and image forming apparatus including the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reader and image forming apparatus including the same, which accurately reads a document image in simple configuration even when there is a foreign substance exists on a contact glass. <P>SOLUTION: An image reader includes: a document feeding section 30 for feeding a document toward a guide member 53 that is rotatable on the contact glass 63; and a document reading section 60 for reading the image of the document moving between the guide member 53 and the contact glass 63 under the contact glass 63. The guide member 53 is constituted of a prism-shaped roller. When feeding the document, the side surface portion 53a of a prism body faces the contact glass 63 with a predetermined gap therebetween. When no document is fed, the guide member 53 is rotated to detect the foreign substance at a position where the document reading section 60 reads the document image. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus used for a copying machine, a printer, a scanner device, and the like, and an image forming apparatus including the image reading apparatus. The present invention relates to an image forming apparatus including the same.

  Conventionally, in an image reading apparatus, a document placed on a document tray is transported and guided so as to pass over a contact glass by a feed roller, a transport guide, or the like, where a document image is read and read by an optical scanning system. The document is discharged to the discharge tray. When foreign material such as eraser debris, paper dust, or toner adheres to the scanned surface of the document set up on the document tray, when the scanned surface of the document conveyed by the feed roller or the like faces down, The foreign matter falls and scatters on the contact glass, and is further pressed against the original, whereby the foreign matter adheres to the contact glass. When the foreign matter adhering to the contact glass stays at the image reading position by the optical scanning system, the illumination light is blocked by the foreign matter, and defects such as black streaks or white spots occur in the scanned image by the optical scanning system. Resulting in.

  Therefore, in Patent Document 1, the document table provided with the contact glass has an inclined surface arranged in a state of facing the document to be conveyed, and the horizontal in which the upstream side in the document conveyance direction is arranged higher than the downstream side. It is inclined at a predetermined angle, for example, 30 degrees from the state. Therefore, even if a foreign object attached to the surface to be read of the original document falls on the contact glass when the original document is conveyed on the contact glass, the foreign substance slides down along the inclined surface. As a result, foreign matter does not stagnate at the image reading position by the optical scanning system on the contact glass, so that defects such as black lines and white spots are prevented from occurring in the read image.

  However, in the above-described prior art, even if the foreign matter falling or scattering on the contact glass from the reading surface of the document is removed from the image reading position, the foreign matter directly scattered on the contact glass is caused to be charged on the contact glass by electrostatic charging. In addition, there is a possibility that foreign matter may adhere to the contact glass by being pressed together with the original. Also, in order to make the image quality of the scanned image uniform when placing the document on the platen and reading it, and when feeding and reading the document by the automatic document feeder, the glass plate is tilted on the platen. When placed, it is necessary to correct the optical axis of the optical scanning system at a right angle with respect to the surface to be read of the document so that the thickness of the glass plate continuously decreases from the high side to the low side of the inclined surface. become. Such a glass plate becomes a special glass having a wedge-shaped cross section, and there is a disadvantage in that the cost increases due to complicated assembly operations such as parts processing of the glass plate and optical axis correction.

  Further, in Patent Document 2, the automatic document feeder includes a feed roller and a guide member, and the guide member includes a brush roller whose entire circumference is covered with hair, and the brush roller is always on the glass directly above the contact image sensor. Yes, the bristles of the brush roller are in contact with the glass in a slightly bent state. When the feed roller rotates, the brush roller starts rotating at the same time, and the glass is cleaned and foreign matter on the glass is removed before the original reaches the position of the brush roller.

However, in the above-described prior art, when reading a document image, the document is guided by the feed roller so as to pass through the brush roller on the glass, and at the image reading position, the document is held on the glass by the brush roller. become. Since the document at this document reading position is only in contact with the bristles of the brush roller being bent, the holding state on the glass becomes unstable in the direction (main scanning direction) perpendicular to the transport direction, May float partially from the top of the glass. When the document is lifted from the glass in this way, there is a possibility that the scanning optical system is out of focus or magnification, and there is a problem that the document image cannot be read accurately.
JP 2001-274950 A (paragraphs [0024]-[0028], FIG. 2) JP 2004-112121 A (paragraphs [0015]-[0018], FIG. 3)

  The present invention has been made to solve the above-described problems. An image reading apparatus capable of accurately reading a document image with a simple configuration even if there is a foreign object on the contact glass, and an image including the image reading apparatus. An object is to provide a forming apparatus.

  In order to achieve the above object, the present invention provides a document transport unit that transports a document toward a guide member that can rotate on the contact glass, and an image of the document that moves between the guide member and the contact glass. And a guide reading portion formed by a prism-shaped roller, and when the document is conveyed, a side portion of the prismatic body has a predetermined distance from the contact glass. The guide member rotates when the document is not conveyed, and the document reading unit detects a foreign substance at a position where the document image is read.

  According to this configuration, the document is transported by the document transport unit, reaches the contact glass, and passes through the contact glass while being guided by the guide member. Since the side surface portion of the guide member faces the contact glass surface during the passage, the document is maintained so as to uniformly face the contact glass in the entire region where the document image is read. Further, when the foreign material is detected by detecting the foreign material at the position where the document reading unit reads the document image by rotating the guide member when the document is not transported, it corresponds to the position where the foreign material is attached. Processing will be performed.

  Further, according to this configuration, the guide member is composed of a prismatic roller, so that the configuration of the apparatus is simple and no special member is required.

  The invention described in claim 2 is characterized in that a foreign matter removing mechanism for removing foreign matter adhering to the guide member is provided. According to this configuration, the foreign matter removing mechanism removes the foreign matter attached to the guide member.

  According to a third aspect of the present invention, the foreign matter removing mechanism includes a cleaning roller and an elastic member that always brings the cleaning roller into contact with the side surface portion. According to this configuration, when the guide member rotates, the foreign matter adhering to the side surface portion is removed by the cleaning roller in contact therewith.

  According to a fourth aspect of the present invention, when the document reading unit detects a foreign matter adhering to the guide member at the reading position, the guide member rotates and the side surface portion elastically contacts the cleaning roller. It is characterized by touching. According to this configuration, when the document is not conveyed, such as before the document is read, the foreign matter attached to the side surface is removed by the cleaning roller that is in contact with the document.

  According to a fifth aspect of the present invention, there is provided an image forming apparatus equipped with the image reading apparatus having the above configuration.

  According to the first aspect of the present invention, the document is transported by the document transport unit, reaches the contact glass, and passes through the contact glass while being guided by the guide member. Since the side surface portion of the guide member faces the contact glass surface when passing, the document is maintained so as to uniformly face the contact glass in the entire region where the document image is read. There is no risk of lifting from above. Therefore, the original image is accurately read without shifting the focus or magnification with respect to the optical system of the original reading unit. When the document is not conveyed, the guide member rotates, and the document reading unit detects the foreign material at the position where the document image is read. Since the processing can be performed, it is possible to prevent a defect such as a black line or white spot from occurring in the read image. Further, since the guide member is composed of a prismatic roller, the configuration of the apparatus is simple, and no special member is required, so that an increase in cost can be suppressed.

  According to the second aspect of the present invention, the foreign matter removing mechanism can easily remove the foreign matter attached to the guide member.

  According to the third aspect of the present invention, when the guide member rotates, the foreign matter adhering to the side surface portion can be easily removed by the cleaning roller in contact therewith.

  According to the fourth aspect of the present invention, the foreign matter adhering to the side surface can be easily removed by the abutting cleaning roller when the original is not being conveyed, such as before reading the original.

  According to the fifth aspect of the present invention, it is possible to provide an image forming apparatus including an image reading apparatus that can accurately read a document image with a simple configuration even if there is a foreign matter on the contact glass.

  Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these embodiments. The embodiment of the present invention shows the most preferable form of the invention, and the use of the invention and the terms shown here are not limited thereto.

(First embodiment)
FIG. 1 is a schematic sectional view showing an image forming apparatus according to an embodiment of the present invention. Note that solid arrows in the figure indicate the transport path and transport direction of the paper or document.

  As shown in FIG. 1, a cassette type paper feeding unit 20 is disposed at the lower part of the main body 2 of the image forming apparatus 1. The cassette type paper supply unit 20 includes a general general-purpose paper cassette 21 and a large capacity paper cassette 22. Two large-capacity paper cassettes 22 having the same capacity are arranged in the horizontal direction at the same height, a large-capacity paper cassette 22A is disposed on the upstream side, and a large-capacity paper cassette 22B is disposed on the downstream side. In these paper cassettes, paper P such as cut paper before printing is stacked and stored, and the paper P is separated and sent out one by one.

  A manual paper feed unit 3 is disposed on the upper right side of the cassette type paper feed unit 20. The manual paper feed unit 3 feeds sheets and OHP sheets that are not in the cassette type paper feed unit 20 one by one.

  A vertical conveyance path 4 is disposed on the right side of the cassette type paper feeding unit 20. The vertical conveyance path 4 conveys the paper P sent out from the cassette type paper feeding unit 20 vertically upward along the right side surface of the main body 2 and the paper P sent out from the manual paper feeding unit 3 horizontally leftward. . Of the two large-capacity paper cassettes 22, the paper P sent out from the large-capacity paper cassette 22A is fed right above the large-capacity paper cassette 22B horizontally and then along the right side of the main body 2. And is conveyed vertically upward.

  A registration roller 5 is disposed between the downstream end of the vertical conveyance path 4 in the sheet conveyance direction and the transfer unit 8. The registration roller 5 corrects the oblique feeding of the paper P and sends the paper P toward the transfer unit 8 in synchronization with the timing at which the image forming unit 7 forms a toner image.

  On the other hand, on the upper surface of the main body 2 of the image forming apparatus 1, a document conveying unit 30 exposed to the outside is disposed, and a document reading unit 60 is disposed below the document conveying unit 30 and inside the main body 2. . In addition, an operation panel 6 on which the user confirms the display and performs button operations is arranged on the front surface of the main body 2.

  The document transport unit 30 automatically transports the documents placed on the document placing tray 31 one by one in response to an input instruction to start copying (copying), and the document that the document reading unit 60 passes through. When the image data is read and the image data is read, a so-called sheet-through type document reading is performed in which the document is discharged onto the document discharge tray 32. When the user performs copying for each original document, the original transport unit 30 is opened upward, the original document is placed on the original reading unit 60, and a print start operation is performed. The document 60 is exposed and scanned by the unit 60, and the image data is read.

  The document reading unit 60 irradiates the document transported by the document transport unit 30 or the document placed on the contact glass, reads the document image from the reflected light, and converts the read image into an electrical signal. As a result, image data corresponding to the document image is generated. The document conveying unit 30 and the document reading unit 60 will be described in detail later.

  The image forming unit 7 forms an electrostatic latent image on the surface of the photosensitive drum by irradiating the photosensitive drum with laser light based on the image data of the original read by the original reading unit 60. The electrostatic latent image is developed with toner to form a toner image on the surface of the photosensitive drum. The transfer unit 8 transfers the toner image on the surface of the photosensitive drum to the paper P sent from the vertical conveyance path 4.

  The fixing unit 9 presses and heats the paper P on which the toner image is transferred by the transfer unit 8 between the heating roller and the pressure roller, and fixes the toner image on the paper P.

  A branching portion 10 is disposed in the vicinity of the left side surface of the main body 2 on the downstream side of the fixing portion 9. The branching unit 10 branches and conveys the paper discharged outside the apparatus and the paper for duplex printing. When performing double-sided printing, the paper P discharged from the fixing unit 9 is sent again from the branching unit 10 to the transfer unit 8 through the double-sided printing conveyance path 12 and the vertical conveyance path 4 in order, and the toner image is transferred to the sheet. Transfer to the back of P. When duplex printing is not performed, the paper is discharged from the branching unit 10 to the paper receiving tray 11 outside the apparatus.

  Next, a detailed configuration of the document conveying unit 30 of the image forming apparatus 1 will be described with reference to FIG. 2 in addition to FIG. FIG. 2 is a schematic cross-sectional view showing a main part of the document conveying unit 30. A solid arrow shown in FIG. 2 indicates the document conveyance direction.

  As shown in FIG. 1, the document transport unit 30 includes a document placement tray 31, a document supply unit 40, and a document discharge tray 32. The documents loaded on the document placement tray 31 are sent into the document supply unit 40, and after the image is read by the document reading unit 60, the document is discharged to the document discharge tray 32.

  The document supply unit 40 has a document insertion port 41 provided at the downstream end of the document loading tray 31 in the document conveyance direction, and extends substantially horizontally from the document insertion port 41, and has a U-shaped path toward the document discharge tray 32. A first document conveyance path 43 is provided.

  As shown in FIG. 2, on the first document conveyance path 43, a first conveyance roller pair 44, a second conveyance roller pair 48, and a first conveyance roller 43 that are in pressure contact with each other in the order in which the document is conveyed. A pair of three transport rollers 49 is provided. The document that has passed through the third conveyance roller pair 49 is sent to the document guide unit 50.

  The document guide 50 is provided immediately downstream of the third conveyance roller pair 49. The document fed into the document guide unit 50 is captured by the optical system 61 of the document reading unit 60 provided therebelow while moving further downstream on the first document transport path 43. . Further, when the document is not being conveyed, an image of a portion of the document guide unit 50 and the document reading unit 60 through which the document passes is captured by the optical system 61, and dust and paper dust adhered to the document guide unit 50 and the document reading unit 60. The presence or absence of foreign matter such as toner is detected. The foreign object detection will be described in detail later.

  A downstream side of the document guide unit 50 is provided with a fourth conveying roller pair 51 composed of rollers and rollers that come into pressure contact with each other, and further on the downstream side, a document discharge roller pair 56 is provided. The document that has passed through is discharged from the document discharge port 55 to the document discharge tray 32 by the document discharge roller pair 56.

  In the document supply unit 40, switching guides 46 and 53 are provided on the first document transport path 43 so as to be swingable, thereby switching the document transport direction. When performing double-sided reading of a document, the document whose surface image has been read by the document guide unit 50 is guided to the second transport path 54 by the switching guide 53 and further guided to the third transport path 47 by the switching guide 46. When transported, the document is placed on the document tray 31 (see FIG. 1) with the back side up, so that the back side of the document can be read.

FIG. 3 is a schematic cross-sectional view showing a document reading unit of the image forming apparatus. The document reading unit 60 includes contact glasses 63 and 64 on which a document is placed, a scanner unit 70 that reads a document image, and generates image data from the read document image. The contact glass 63 passes the original when reading a sheet-through type original, and the contact glass 64 is placed when the original is read by exposure scanning.

  The scanner unit 70 includes an optical system (first carriage) 61 disposed below the contact glasses 63 and 64, a second carriage 72 disposed on the left side of the first carriage 61, and the scanner unit 70. The image pickup unit 80 is disposed at an appropriate position below.

  The first carriage 61 and the second carriage 72 are connected to the scanning mechanism section, and the scanning mechanism section moves on the contact glass 64 by moving in the arrow direction (left-right direction) shown in FIG. 3 at a predetermined speed. The entire surface of the placed document can be scanned and the image on the entire surface of the document can be read.

  The first carriage 61 includes a frame 75 connected to the scanning mechanism unit, a light source 76 such as an exposure lamp that irradiates light on a document placed on the contact glass 64, and second light from the contact glass 64. And a mirror 78 that reflects toward the carriage 72.

  The second carriage 72 is provided with a pair of mirrors 72a and 72b disposed so as to face each other in the vertical direction. Light from the mirror 78 of the first carriage 61 is sequentially reflected by the mirrors 72a and 72b, and the imaging unit 80. Lead to.

  The imaging unit 80 includes an imaging lens 73 and an image sensor 74 disposed on the right side of the imaging lens 73. The imaging lens 73 has a plurality of lenses for imaging reflected light from the original that has entered through the mirror 72 b of the second carriage 72, and is fixed at a predetermined position of the imaging unit 80. . The image sensor 74 has an imaging element such as a CCD arranged on the optical axis Z of the imaging lens 73 in a direction perpendicular to the document conveyance direction (main scanning direction, depth direction in FIG. 3). 73 converts the optical image of the original image formed on the image sensor into an electrical signal.

  In the document reading unit 60 configured as described above, light is irradiated onto the contact glass 64 by the light source 76, and reflected light from the document on the contact glass 64 is reflected by the mirror 78 of the first carriage 61, and the reflected light. Are sequentially reflected by the mirrors 72 a and 72 b of the second carriage 72, and an optical image of the document is formed on the image sensor 74 via the imaging lens 73. Thereby, a part of the document image is read. Then, the scanning mechanism section moves the first carriage 61 and the second carriage 72 at a predetermined speed, thereby scanning the entire surface of the document image, reading the entire surface of the document image, and forming a read image.

  Next, reading of a document image by the sheet through type will be described with reference to FIG. FIG. 4 is a schematic cross-sectional view showing the document reading unit and the document guide unit. The broken line arrows indicate the document conveyance direction.

  As shown in FIG. 4, the sheet-through type document reading unit 60 includes a contact glass 63, a first carriage 61, and a second carriage 72. The document guide unit 50 includes a guide member 53, a cleaning roller 57, and an elastic member 58. Is provided.

  In the sheet-through type document reading unit 60, the first and second carriages 61 and 72 shown in FIG. 3 move leftward in the scanner unit 70, and the optical axis Z incident on the mirror 78 of the first carriage 61 is changed. It is fixed and held at a position facing the contact glass 63. The optical axis Z is orthogonal to the surface of the contact glass 63, and the region of the light flux centering on the position where the surface of the contact glass 63 and the optical axis Z intersect is the reading position R of the document.

  When the document image is captured by the first carriage 61, the guide member 53 stops and maintains the conveyed document so as to face the contact glass 63 at the reading position R, and rotates when the document is not conveyed. Thus, it is used for detecting foreign matter adhering to the contact glass 63 and the guide member 53. Accordingly, the guide member 53 is formed of, for example, an octagonal prism body, and each side surface portion 53a extends in the main scanning direction and is rotatably held in the direction of the solid line arrow in FIG. When each side surface portion 53a is at a position facing the contact glass 63, the side surface portion 53a and the surface of the contact glass 63 are parallel to each other and are arranged at a predetermined interval through which the document passes.

  Each side portion 53a has a color equivalent to that of plain paper, for example, the lightness N of the Munsell color system is set to 9 or more so that there is no color fog when reading a document, and the surface roughness of the side portion 53a is reduced. is doing.

  The cleaning roller 57 constitutes a foreign matter removing mechanism together with the elastic member 58, and removes the foreign matter attached to the side surface portion 53a of the guide member 53. When removing the foreign matter adhering to the side surface portion 53a, the cleaning roller 57 is formed of an elastic material so as to always come into contact with the side surface portion 53a with a constant force even when the guide member 53 rotates, and the urging force Is pressed against the side surface portion 53a by an elastic member 58 having Therefore, when the guide member 53 rotates, the cleaning roller 57 is pressed against each side portion 53a with a uniform force, and the foreign matter is removed regardless of where the foreign matter adheres to each side portion 53a. In place of the roller, a blade or a brush may be pressed against the side surface portion 53a.

  Further, instead of the cleaning roller 57, when the side surface portion 53a is contaminated with foreign matter, the foreign matter may be wiped off with water or alcohol. In this case, the guide member 53 may be formed of a synthetic resin having solvent resistance. The guide member 53 is formed by adding an antistatic agent to rubber such as EPDM (ethylene propylene diene rubber) instead of synthetic resin, or when the antistatic coating process is performed, the side surface portion 53a is not easily stained. Durability is improved.

  The distance between the side surface portion 53a and the surface of the contact glass 63 is at least large enough to allow the document to pass through. That is, when the guide member 53 is formed of an elastic member such as the rubber described above or a synthetic resin having an elastic shape, and the guide member 53 rotates, an edge portion where the adjacent side surface portions 53a intersect is the surface of the contact glass 63. The foreign matter on the contact glass 63 may be peeled off. Further, the edge portion may be rounded so as not to contact the surface of the contact glass 63, or the interval may be increased so that the edge portion does not contact the surface of the contact glass 63. .

  The document reading operation will be described. Documents on the document placement tray 31 shown in FIG. 1 are separated one by one and fed to the document insertion port 41, and the first, second, and third conveyance roller pairs 44, 48, 49 (see FIG. 2), reaches the contact glass 63, and passes through the contact glass 63 while being guided by the guide member 53 shown in FIG. When this document passes over the contact glass 63, the guide member 53 is stopped with the side surface 53a being parallel to the surface of the contact glass 63, and the contact glass 63 is located in the entire region of the reading position R. So as to face evenly. This original image is read by the image sensor 74 (see FIG. 3) via the first and second carriages 61 and 72 and the imaging lens 73 (see FIG. 3). Thereafter, as shown in FIG. 2, the document is transported by the fourth transport roller pair 51 and discharged from the document discharge port 55 to the document discharge tray 32 by the document discharge roller pair 56.

  Next, the foreign object detection operation will be described with reference to FIGS. FIG. 5 is a diagram showing a main part of the document reading unit to which foreign matter is attached, and FIG. 6 is a diagram schematically showing image data obtained by reading the foreign matter shown in FIG. 5 with an image sensor. The arrow X indicates the main scanning direction, and the arrow Y indicates the sub scanning direction.

  A case where foreign matter is not attached to the reading position R on the contact glass 63 and the side surface portions 53a will be described. As indicated by the arrows in FIG. 5, the guide member 53 rotates to detect the presence or absence of foreign matter before the document is conveyed, and the contact glass 63 and each side surface portion 53 a are placed on the scanner portion 70 at the reading position R. Read by line sensor 74. When there is no foreign matter at the reading position R and each side part 53a, the image read by the line sensor 74 is a continuous image of each side part 53a. Since the side surface portion 53a is white having a Munsell color system lightness of N9 or more, the image data is image data of the entire surface and white level.

  On the other hand, when foreign matters are attached to the reading position R on the contact glass 63 and the side portions 53a, for example, the foreign matter S shown in FIG. 5 is attached to the surface of the contact glass 63, and the foreign matter T is one of the side portions 53a. Suppose that it adheres to the surface. In the same manner as described above, the guide member 53 rotates to detect the presence or absence of a foreign substance before reading the document, and the line sensor 74 reads the contact glass 63 and each side surface portion 53a at the reading position R.

  As shown in FIG. 6, in the read image data, black line S ′ and black line T ′ data are generated in a white level image data area corresponding to each side surface portion 53a. The black line S ′ is line segment data extending to both ends of the sub-scanning direction Y at the position where the foreign substance S in the main scanning direction X exists, and the black line T ′ is the position where the foreign substance T in the main scanning direction X exists. This is line segment data corresponding to the length in the sub-scanning direction Y attached to the side surface portion 53a. In addition, the dashed-dotted line of FIG. 6 has shown the intersection line of the adjacent side part 53a.

  Each of the white level, black line S ′, and black line T ′ image data is obtained by using the density of the white image data of the side surface portion 53a read in advance by a control means such as a CPU as reference image data. Compared with data. When the density of the image data of the black line S ′ and the black line T ′ exceeds the density of the reference image data, the foreign matters S and T are determined as foreign matters.

  Of the image data of the black line S ′ and the black line T ′ determined to be foreign matter, the data that extends without interruption to both ends in the sub-scanning direction Y as in the image data of the black line S ′ is on the contact glass 63. It is determined as a foreign object. As shown in the image data of the black line T ′, what continuously extends only in the region surrounded by the alternate long and short dash line shown in FIG. 6 is determined as a foreign matter attached to the side surface portion 53a. Even the image data of the black line T ′ that extends continuously beyond the area surrounded by the alternate long and short dash line and does not extend to both ends in the sub-scanning direction Y is not determined as a foreign object and is processed as an error. .

  When a foreign object is detected in this way, processing corresponding to the position where the foreign object is attached is performed. When foreign matter adheres on the contact glass 63, the first and second carriages 61 and 72 are operated so that the document reading position R shown in FIG. 4 is moved to a position where no foreign matter is attached. Thereafter, the document is conveyed from the document placing tray 31, and the image is read by the document reading unit 60. When foreign matter is attached to the side surface portion 53a, the foreign material attached to the side surface portion 53a is removed by the cleaning roller 57 by rotating the guide member 53 while contacting the cleaning roller 57 before reading the document. .

  According to the first embodiment, the image reading apparatus is configured to convey the document toward the guide member 53 that can rotate on the contact glass 63, and between the guide member 53 and the contact glass 63. And a document reading unit 60 that reads an image of the document that is moving below the contact glass 63. The document reading unit 60 includes first and second carriages 61 and 72, an imaging lens 73, an image sensor 74, and the like. The guide member 53 is composed of a prismatic roller, and when the document is transported, the side surface portion 53a of the prism body is opposed to the contact glass 63 with a predetermined interval so that the guide is not transported when the document is not transported. The member 53 rotates and the document reading unit 60 detects foreign matter at a position where the document image is read.

  According to this configuration, the document is transported by the document transport unit 30, reaches the contact glass 63, and passes through the contact glass 63 while being guided by the guide member 53. Since the side surface portion 53a of the guide member 53 faces the surface of the contact glass 63 during this passage, the document is maintained so as to uniformly face the contact glass 63 in the entire region where the document image is read. There is no possibility that the document floats from the contact glass 63. Therefore, the original image is accurately read without shifting the focus or magnification with respect to the optical system of the original reading unit 60. When the document is not conveyed, the guide member 53 rotates and the document reading unit 60 detects the foreign material at the position where the document image is read. Therefore, it is possible to prevent defects such as black lines and white spots from occurring in the read image.

  Further, according to this configuration, the guide member 53 is composed of a prismatic roller, so that the configuration of the apparatus is simple and no special member is required, so that an increase in cost can be suppressed.

  Further, according to the first embodiment, the foreign matter removing mechanism includes the cleaning roller 57 and the elastic member 58 that always brings the cleaning roller 57 into contact with the side surface portion 53a. Foreign matter adhering to the side surface portion 53a is easily removed by the roller 57.

  Further, according to the first embodiment, when the document reading unit 60 detects a foreign matter adhering to the guide member 53 at the reading position R, the guide member 53 rotates and the side surface portion 53a elastically contacts the cleaning roller 57. By contacting, the foreign matter adhering to the side surface portion 53a can be easily removed by the cleaning roller 57 before reading the document.

(Second Embodiment)
FIG. 7 is a schematic cross-sectional view showing a sheet-through type document reading unit of the image forming apparatus according to the second embodiment of the present invention. The document guide unit 30 that is different from the first embodiment will be described.

  As shown in FIG. 7, the guide member 53 has a configuration in which a guide belt 53c is stretched by a driving roller 53d and a driven roller 53e. The guide belt 53c is parallel to the surface of the contact glass 63 and is disposed with a predetermined interval for allowing the document to pass therethrough. Above the guide belt 53c, a cleaning roller 57 that is always in contact with the guide belt 53c is provided to remove foreign matter adhering to the guide belt 53c.

  According to the second embodiment, the document is conveyed toward the guide belt 53 c that can rotate on the contact glass 63, and the image of the document that moves between the guide belt 53 c and the contact glass 63 is the contact glass 63. Are read by the first and second carriages 61 and 72, the image forming lens 73, the image sensor 74, and the like. When the document is not conveyed, the guide belt 53c rotates and the document reading unit 60 detects a foreign substance at a position where the document image is read. When foreign matter adhering to the guide belt 53c is detected, the foreign matter adhering to the guide belt 53c can be easily removed by the cleaning roller 57 by rotating the guide belt 53c.

  The present invention can be used for an image reading apparatus used in a copying machine, a printer, a scanner device, and the like and an image forming apparatus including the image reading apparatus.

1 is a schematic sectional view showing an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing a main part of a document conveying portion of the image forming apparatus according to the first embodiment of the present invention. FIG. 2 is a schematic cross-sectional view illustrating a document reading unit of the image forming apparatus according to the first embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing a sheet-through type document reading unit and document guide unit of the image forming apparatus according to the first embodiment of the present invention. FIG. 3 is a diagram illustrating a main part of a sheet-through type document reading unit of the image forming apparatus according to the first embodiment of the present invention. FIG. 3 is a diagram schematically illustrating image data read by a scanner unit of the image forming apparatus according to the first embodiment of the present invention. These are schematic sectional views showing a sheet-through type document reading section of an image forming apparatus according to a second embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 30 Original conveyance part 31 Original loading tray 32 Original discharge tray 40 Original supply part 43 First conveyance path 50 Original guide part 53 Guide member 53a Side surface part 53c Guide belt 53d Drive roller 53e Follower roller 57 Cleaning roller (foreign matter) Removal mechanism)
58 Elastic member (foreign matter removal mechanism)
60 Document Reading Unit 61 First Carriage (Optical System)
63, 64 Contact glass 70 Scanner unit 72 Second carriage 73 Imaging lens 74 Image sensor 80 Imaging unit

Claims (5)

An original conveying section that conveys an original toward a guide member that can rotate on the contact glass, and an original reading section that reads an image of the original moving between the guide member and the contact glass under the contact glass And
The guide member is composed of a prismatic roller, and when the document is transported, the side surface of the prism body is opposed to the contact glass with a predetermined interval, and when the document is not transported, An image reading apparatus, wherein a guide member rotates to detect foreign matter at a position where the original reading unit reads an original image.   The image reading apparatus according to claim 1, further comprising a foreign matter removing mechanism that removes foreign matter adhering to the guide member.   The image reading apparatus according to claim 2, wherein the foreign matter removing mechanism includes a cleaning roller and an elastic member that always brings the cleaning roller into contact with the side surface portion.   The said guide member rotates when the said document reading part detects the foreign material adhering to the said guide position in the said reading position, The said side part contacts the cleaning roller elastically. Image reading apparatus.   An image forming apparatus on which the image reading apparatus according to claim 1 is mounted.

Images