JP2006115030A - Document feeder, image reader, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a document feeder capable of sufficiently removing dust and foreign matter by a level difference even at the front end part of a low-rigidity document such as thin paper. <P>SOLUTION: The document feeder is provided with a 1st support means (22) of supporting the reverse flank of the document P nearby an image read position 8, a level difference forming means (24) of forming the level difference (24C) crossing the moving document surface upstream from the image read position 8, and a 2nd support means (25) of supporting the reverse flank of the document P upstream from the level difference (24C), and the document surface whose reverse surface is supported by the 1st support means (22) and the 2nd support means (25) comes into slide contact with the top surface of the level difference (24C). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a document feeding device that transports a document to a predetermined image reading position, an image reading device equipped with the document feeding device, and an image forming apparatus equipped with the image reading device.

  Color copiers, monochrome copiers, scanners, facsimiles, multifunction printers, character recognition devices (OCR), image data storage devices, and the like equipped with document feeders have been put into practical use. This document feeding device conveys a document to a predetermined image reading position of the image reading device. The image reading device recognizes an image on the document surface in a linear form by a light receiving element array such as laser beam scanning or CCD, The image is read by a so-called flow reading method.

  In such an image reading apparatus, if dust or foreign matter exists at the image reading position, a linear image in the transport direction is superimposed on the read image. In other words, a line image obtained by pulling the shadow of a foreign object for the staying time is erroneously read as an image on the document surface.

  Therefore, the document feeder disclosed in Patent Document 1 includes a conveyance path that guides the document to a predetermined image reading position, and a driving unit that drives the document to move to the image reading position along the conveyance path. The feeding device includes a first rotation support member that supports the back side of the document immediately above the image reading position, and a step forming unit that forms a step across the moving document surface upstream from the image reading position. The document surface supported by the first support means and the elasticity of the document slides into contact with the surface of the step, so that dust and foreign matter adhering to the document surface are removed immediately before the document is transported to the image reading position. To do. Further, by transporting the original in a state of being separated from the platen glass, it is possible to prevent the dirt on the original from adhering to the glass surface.

JP 2002-314753 A

  In the document feeder disclosed in Patent Document 1, when a low-rigidity (so-called weak) original such as thin paper is conveyed, there is a possibility that dust and foreign matter on the surface of the original cannot be sufficiently removed by steps. is there. Further, since sufficient elasticity is not generated on the document until the document reaches the first rotation support member and is bent, the document surface cannot sufficiently contact the surface of the step at the leading part of the document, and therefore the leading part of the document. There is a possibility that dust or foreign matter adhering to the document falls to the document reading position. Further, since the document is conveyed in a state of being separated from the platen glass, the document cannot be read stably, and blurring may occur.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a document feeding device that can sufficiently remove dust and foreign matter by a step even at a leading portion of a document having low rigidity such as thin paper. It is another object of the present invention to provide a reading system using a contact image sensor with a shallow depth of focus and a reading system for a document feeding apparatus that requires high image quality by conveying the document in contact with a platen glass.

  An original feeding apparatus according to the present invention includes a conveyance path that guides an original to a predetermined image reading position, and a driving unit that drives the original and moves the original along the conveyance path to the image reading position. In the apparatus, a first support means for supporting the back side of the original surface of the original document in the vicinity of the image reading position and a step formation for forming a step across the moving original surface upstream from the image reading position. And a second support means for supporting the back side surface upstream of the formed step, whereby the first support means and the second support means are supported from the back side surface. The document surface is in sliding contact with the surface of the step.

  In the document feeder of the present invention, the back side of the document is supported by the first support means and the second support means, and the document surface is slidably brought into contact with the step at an intermediate position between them. Movement (floating, rampage, flapping) is suppressed, and a stable sliding contact state is maintained even with light contact pressure.

  In addition, the arrangement of the second support means reduces the length of the document that bears the pressing force on the step as compared with the case of only the first supporting means, and accordingly, the ratio of the pressing force on the step depending on the rigidity of the document decreases. Therefore, the pressing force to the step can be sufficiently ensured even in the low-rigidity document or the leading end portion of the document, in which the pressing force to the step cannot be sufficiently secured only by the first support means. Then, the gap between the platen glass surface arranged at the image reading position and the first support means is set narrower than shown in Patent Document 1, and the original is run with the original surface and the platen glass kept almost in contact with each other. In other words, even with a contact image sensor or the like having a shallow depth of focus, it is possible to achieve high-quality reading at the in-focus position while suppressing document violence.

  FIG. 1 is a diagram illustrating the configuration of an image forming apparatus according to an embodiment of the present invention, FIG. 2 is a diagram illustrating the configuration of an image reading unit according to the embodiment of the present invention, and FIG. FIG. 4 is an explanatory diagram of a drive transmission system of a conveyance motor in the document feeder, FIG. 5 is a partial enlarged view of an image reading unit and the like, and FIG. 6 is a further partial enlarged view of an image reading unit and the like. FIGS. 7A and 7B are explanatory diagrams of a document conveying state, and FIG. 8 is a flowchart of control of the document feeder.

  As shown in FIG. 7, the document feeder 2 which is one embodiment of the present invention includes, for example, a reading roller 22 as a first support means, a dirt scraping sheet 24 as a step forming means, and a second. For example, a reading roller 25 which is a supporting unit is provided, and the document surface of the document P supported by the reading roller 22 and the reading roller 25 is in sliding contact with the surface of the dirt scraping sheet 24. Further, for example, the reading roller 25 as the second supporting means is smaller in diameter than the reading roller 22 as the first supporting means. Further, for example, the reading roller 22 which is the first support means is arranged on the downstream side of the image reading position 8 which is the image reading position, for example the reading roller 22 which is the first supporting means and the second supporting means such as the reading. A step 24 </ b> C formed by a dirt scraping sheet 24, which is one form of the step forming means, is disposed at an intermediate position with respect to the roller 25.

  As shown in FIG. 1, the image forming apparatus 1 is configured by attaching a document feeder 2 to the upper surface of an apparatus body 1A. The apparatus main body 1A includes an image reading unit 1B provided on the upper portion thereof, and an image forming unit 1C provided below the image reading unit 1B.

  Here, the document feeder 2 transports the document P placed on the paper feed tray 3 to a predetermined image reading position set on the upper surface of the apparatus body 1A, and transports the document P after scanning to the discharge tray 12. To discharge.

  As shown in FIG. 2, when reading a document image, first, the document P placed on the sheet feed tray 3 is read by the feeding unit 4 (FIG. 1) including the pickup roller 4b and the sheet feed roller 4a. The sheets are sequentially separated and conveyed to the stopped registration roller pair 5. Then, the original P is brought into contact with the resist roller pair 5 in the stopped state to form a loop, thereby correcting the skew of the original P.

  Next, after correcting the skew as described above, the registration roller pair 5 is rotated to cause the document P to enter the introduction path 7. Thereafter, the document P is introduced by the introduction conveyance roller pair 6 provided in the introduction path 7. To drive the image reading position 8 on the platen glass 21. When the document P passes the reading position 8, the image on the surface of the document P is read by the image reading unit 1B.

  The document P that has passed the image reading position 8 passes through a discharge path 9 and is discharged onto a discharge tray 12 by a reverse roller pair 11 including a discharge conveyance drive roller pair 10, a reverse driven roller 11b, and a reverse drive roller 11a. Is done.

  When reading both the front and back sides of the document P, the document P that has passed the image reading position 8 is again transferred to the registration roller pair 5 by the reversal drive roller 11a of the reversal roller pair 11 that is reversed at a predetermined timing. In the same manner as the front side reading, after the skew is corrected by the registration roller pair 5, the image formed on the front side (in this case, the back side) is read at the image reading position 8 through the introduction path 7. ing.

  On the other hand, the image reading unit 1B irradiates light on the surface of the document P passing through the image reading position 8 by the illumination system 14 in the contact image sensor 13 and forms an image of reflected light obtained there by the optical element 15. Thus, the original image is read.

  As shown in FIG. 1, the image forming unit 1C forms a toner image corresponding to the read original image, and a latent image is formed on the surface by exposure corresponding to the original image by an exposure unit (not shown). The photosensitive drum 16 is provided. The latent image is developed with toner supplied from a toner supply device (not shown) so that a toner image is formed on the photosensitive drum.

  The cassette 17 accommodates a recording medium such as paper or plastic film. A recording medium (not shown) stored in the cassette 17 is fed by a pickup roller 17a or the like in accordance with a recording signal from the CPU 29, and then supplied to a position facing the photosensitive drum 16 at a predetermined timing. The toner image formed on the body drum 16 is transferred to a recording medium by the transfer device 18.

  The recording medium onto which the toner image has been transferred in this manner is sent to the fixing device 19, where the toner image is fixed, and then discharged onto the paper discharge tray 19a. When images are formed on both sides of the recording medium, after the toner image is fixed by the fixing device 19, the recording medium passes through the double-sided path 20 provided on the downstream side of the fixing device 19 and is again a photosensitive drum. 16, the toner image is transferred between the transfer device 18 and the back surface.

  As shown in FIG. 3, the document feeder 2 includes a feed motor M1 that can freely rotate forward and backward to drive the feed roller 4a and the like. The forward drive of the feed motor M1 is moved from the pulley P1 to the pulley P2. Driven by the timing belt T1, the drive of the pulley P2 is transmitted in the order of the gear Z1, the gear Z2 and the gear Z3 attached to the drive shaft 34 of the paper feed roller 4a, whereby the paper feed roller 4a feeds the document. Rotate in the direction of paper.

  Further, the drive shaft 34 of the paper feed roller 4a is provided with a pulley P3. The pulley P3 provided on the shaft 35 of the pickup roller 4b is connected to the pickup roller 4b via a timing belt T2. The drive is also transmitted.

  Note that one end side of a lifting arm 4c that supports the pickup roller 4b is attached to the drive shaft 34 of the paper feed roller 4a. As a result, the elevating arm 4c is rotated downward, and the pickup roller 4b is lowered.

  After that, when the pickup roller 4b comes into contact with the original P, the drive shaft 34 of the paper feed roller 4a is idled with respect to the lifting arm 4c by the action of the spring clutch X and the spring clutch Y.

  At this time, the registration drive roller 5a constituting the registration roller pair 5 is connected by a timing belt T3 stretched around a pulley P5 provided on the drive shaft 36 and a pulley P6 provided coaxially with the pulley P2. However, the one-way clutch OW1 provided in the pulley P5 does not rotate.

  On the other hand, when the paper feed motor M1 is driven in reverse, the reverse drive is sequentially transmitted from the pulley P1 to the pulley P2, the pulley P6, and the pulley P5, whereby the registration drive roller 5a rotates in the paper feed direction. At this time, the reverse drive of the paper feed motor M1 is also transmitted to the drive shaft 34 of the paper feed roller 4a, whereby the elevating arm 4c rotates upward and the pickup roller 4b rises. However, the paper feed roller 4a does not rotate by the action of the one-way clutch OW2 provided therein. After that, when the lift arm 4c rotated upward comes into contact with a regulating member (not shown), the drive shaft 34 of the paper feed roller 4a rotates idly with respect to the lift arm 4c by the action of the spring clutch Z.

  As shown in FIG. 4, the document feeder 2 includes a transport motor M <b> 2 that can freely rotate forward and backward to drive the reverse drive roller 11 and the like. The drive of the conveyance motor M2 is transmitted from the pulley P7 provided on the drive shaft 37 to the pulley P8 via the timing belt T4, and further discharged from the pulley P9 provided coaxially with the pulley P8 via the timing belt T6. It is transmitted to the pulley P10 attached to the shaft 38 of the discharge conveyance drive roller 10a constituting the conveyance drive roller pair 10. Thereby, the discharge conveyance drive roller 10a rotates forward or backward.

  Further, the drive transmitted to the pulley P10 is transmitted to the pulley P11 attached to the shaft 39 of the introduction conveyance drive roller 6a via the timing belt T7, whereby the introduction conveyance drive roller 6a rotates forward or backward. .

  The drive transmitted to the pulley P11 is transmitted from the pulley P14 attached to the shaft 39 of the drive roller 6a to the pulley P15 attached to the shaft 43 of the reading roller 22 described later via the timing belt T8. As a result, the reading roller 22 rotates forward or backward.

  Further, the drive of the conveyance motor M2 transmitted to the pulley P8 via the timing belt T4 is driven by a pulley attached to the shaft 40 of the reverse drive roller 11a via the timing belt T5 from the pulley P12 provided coaxially with the pulley P8. As a result, the reverse driving roller 11a rotates forward or backward.

  As shown in FIG. 1, the reverse driven roller 11 b urged by the pressure contact solenoid 30 is in contact with the reverse drive roller 11 a, and can be brought into contact with and separated from the reverse drive roller 11 a according to ON / OFF of the pressure contact solenoid 30. Yes. That is, when the pressure contact solenoid 30 is excited (ON), the reverse driven roller 11b moves to a position where it is pressed against the reverse drive roller 11a. However, when the pressure contact solenoid 30 is deenergized (OFF), the reverse driven roller 11b is moved. The reverse driven roller 11b moves to a position away from the reverse drive roller 11a by the action of a biasing spring that biases the reverse drive roller 11a away from the reverse drive roller 11a.

  As shown in FIG. 2, document size detection sensors S1, S2, and S3 for detecting a plurality of document sizes are provided on the paper feed tray 3. Depending on the ON / OFF states of the sensors S1, S2, and S3, The length of the document P placed on the sheet feed tray 3 is detected. Further, in the transport path for guiding the document P, an empty sensor S4 for detecting that the document P is placed on the sheet feed tray 3, and a document transported between the feeding unit 4 and the registration roller pair 5. A registration sensor S5 that detects the edge of the P, a lead sensor S6 that is provided in front of the image reading position 8 and detects the edge of the document P, and a discharge that detects the edge of the document P discharged from the image reading position 8. A sensor S7 is provided.

  And these sensors (S1-S7) are connected to CPU29 which controls the drive of the whole apparatus, CPU29 is based on the detection signal from each sensor (S1-S7), each motor M1, which was mentioned above, A predetermined document feed operation is executed by controlling the drive of M2 and exciting and releasing the excitation solenoid 30.

  Now, as shown in an enlarged view in FIG. 5, a main portion in which one embodiment of the present invention is embodied includes a reading roller 22, a dirt scraping sheet 24, and a reading roller 25.

  The reading roller 25 is a cylindrical rotating member that is rotatably supported, and is rotated in contact with the back surface of the document P. The reading roller 25 is a document regulating member provided upstream of the image reading position 8 and urges the document on the platen glass 21 at a position sufficiently upstream from the reading position to suppress fluttering of the document.

  The reading roller 22 is driven by the drive system shown in FIG. 4 to drive the document P together with the introduction conveyance roller pair 6 and the discharge conveyance drive roller pair 10. The reading roller 22 is disposed above the image reading position 8 of the platen glass 21, and stabilizes the document so that the document P urged on the platen glass 21 by the reading roller 25 does not float from the platen glass 21. Can be transported.

  Further, as further enlarged and shown in FIG. 6, the reading roller 22 is arranged with a gap A for one document so that the document P does not flutter. That is, in the document feeder 2, the gap A between the reading roller 22 and the platen glass 21 is narrower than that shown in Patent Document 1, and the document P is intended to run while the document surface and the platen glass 21 are kept almost in contact with each other. Has been. In other words, it is considered that the original P is brought into contact with the platen glass 21 and is read in conformity with the contact image sensor 13 (optical element 15) having a shallow depth of focus and high image quality reading that does not disturb the original.

According to the experiment, the gap A is a thickness of a general plain paper in consideration of the depth of focus of the contact image sensor 13 (optical element 15) and the conveyance load by the reading roller 22. Assuming a thickness of 0.15 mm to 0.15 mm of thick paper (basis weight 128 g / m ² ), it is desirable to set it to about 0.15 mm.

  By the way, there are cases where paste such as post-it or correction liquid adheres to the original P, and such an adhesive is carried along with the original P to the platen glass 21 and adheres or stays at the image reading position 8. In such a case, a line enters the read image, and a phenomenon called black streaks occurs on the image copied by the image forming apparatus 1.

  Therefore, in the document feeder 2, as shown in FIG. 6, a low friction resin such as a Mylar film is placed on the platen glass 21 on the upstream side of the image reading position 8 and along the direction orthogonal to the conveying direction of the document P. A dirt scraping sheet 24 that is a sheet of material is disposed, and a step 24C that is higher than the image reading position 8 of the platen glass 21 by a thickness D is formed. The thickness D is larger than the gap A and is 0.4 mm.

  Here, by providing the dirt scraping sheet 24, the document surface of the document P introduced into the image reading position 8 is conveyed while being rubbed against the surface 24F and the corners (24C) of the dirt scraping sheet 24. As a result, the dirt that has been carried to the image reading position 8 and has been adhered or staying in the past is removed before reaching the image reading position 8.

  At this time, since the gap A between the reading roller 22 and the platen glass 21 is set to a size corresponding to the above-described one original, the step 24C due to the dirt scraping sheet 24 is as shown in FIG. The position has reached a position sufficiently higher than the original surface, whereby the original P can be rubbed against the step 24C while the original is being conveyed, and the dirt cleaning effect can be maintained.

  According to the experiment, the distance C between the tip corner (24C) of the dirt scraping sheet 24 and the image reading position 8 is desirably 4 mm upstream. However, the scraping effect increases as the step 24C is arranged on the downstream side. However, the dirt scraped off by the dirt scraping sheet 24 is scattered, and the harmful effect becomes larger. It is also possible to arrange the step 24C further upstream by making the height different.

  As described above, the step 24C of the dirt scraping sheet 24 is disposed upstream of the image reading position 8 of the platen glass 21, and the surface 24F and the corners are passed when the reading surface of the document P passes the dirt scraping sheet 24. (24C), the dirt on the original P is removed immediately before reaching the image reading position 8 to reduce the dirt on the image reading position 8, so that the appearance of lines on the image read by the image reading unit 1B is reduced. A good image can be formed on the copy screen by the image forming apparatus 1.

  The document feeder 2 configured as described above is controlled according to the flowchart shown in FIG. As shown in FIG. 8, in step 111, the outputs of the document size detection sensors S <b> 1 to S <b> 3 and the empty sensor S <b> 4 on the paper feed tray 3 are referred to, and one of them is ON (the document is placed on the paper feed tray 15. If a document is detected on the paper feed tray 15, the routine proceeds to step 112, where the paper feed motor M1 is driven reversely for a predetermined time, whereby the pickup roller 4b and the paper feed motor are fed. Regardless of the position of the paper roller 4a, the paper roller 4a rises to the highest position and retreats from the paper feed port. At this time, the regulating force increases as the regulating member of the stopper member moves to an appropriate position.

  Thereafter, in step 113, it is determined whether or not there is a start signal from the apparatus main body 1A of the image forming apparatus 1. When the start signal is detected, the process proceeds to step 114 where the paper feed motor M1 is driven to rotate forward, and the pickup roller 4b. The paper feed roller 4a is lowered while rotating to feed the original P. At this time, the pickup roller 4b and the paper feed roller 4a rotate in the document feeding direction, but the registration roller pair 5 does not rotate by the action of the one-way clutch WO2.

  Thereafter, in step 115, it is determined whether or not the registration sensor S5 has been turned on. When the leading edge of the document fed by being turned on is detected, the process proceeds to step 116, and whether a predetermined time t1 has passed since the detection. It is determined whether or not. When the predetermined time t1 elapses, the routine proceeds to step 117, where the paper feed motor M1 is temporarily stopped. When the paper feed motor M1 is stopped, the leading edge of the original P is applied to the nip portion of the registration roller pair 5 and is bent. Then, the leading edge of the original is aligned and the skew is removed.

  Thereafter, in step 118, it is determined whether or not a predetermined time t2 has elapsed since the paper feed motor M1 was stopped. When the predetermined time t2 has elapsed, the routine proceeds to step 119, where the paper feed motor M1 is driven in reverse and the transport motor M2 is driven forward. At this time, the pickup roller 4b rises to a position away from the document, the drive of the paper feed roller 4a is cut off by the action of the one-way clutch WO1, and the registration drive roller 5a of the registration roller pair 5 is rotated in the document feed direction. .

  Thereafter, in step 120, it is determined whether or not the lead sensor S6 is turned on. When the motors M1 and M2 are rotationally driven, the document P is transported from the paper feed tray 3 to the transport path 7, and when the lead sensor S6 detects the passage of the leading edge of the document P, the process proceeds to step 121 and a reading operation is started. That is, sub-scanning using the contact image sensor 13 (optical element 15) is started at a timing when the leading end of the document P reaches the image reading position 8 after a predetermined time has elapsed after the read sensor S6 is turned on.

  The document P that has passed through the image reading position 8 is bent upward by a jump table 23 through a gap between the reading roller 22 and the platen glass 21, and reaches a pressurized interval between the discharge conveyance driving roller 10a and the discharge conveyance driven roller 10b. Led. The original P conveyed by the discharge conveyance drive roller 10a and the discharge conveyance driven roller 10b is discharged to the paper discharge tray 12 and stacked by the reverse drive roller 11a and the reverse driven roller 11b shown in FIG.

  The document feeder 2 according to the embodiment of the present invention described above includes the reading roller 22 that supports the back side of the document P in the vicinity of the image reading position, and the step 24C that crosses the moving document surface at the image reading position 8. A dirt scraping sheet 24 formed on the upstream side and a reading roller 25 supporting the back side surface of the document P on the upstream side of the step 24C are provided, and are supported from the back side by the reading roller 22 and the reading roller 25. Further, since the original surface of the original P is slidably contacted with the surface 24F and the corners (24C) of the step 24C, the vertical movement (floating, rampage, flapping) of the original P at the step 24C is suppressed and light. A stable sliding contact state is maintained even with contact pressure. Further, the arrangement of the reading roller 25 reduces the length of the document that bears the pressing force on the step 24C as compared with the case of using only the reading roller 22, and accordingly, the ratio of the pressing force on the step 24C depending on the rigidity of the document P is increased. Therefore, the reading roller 22 can sufficiently secure the pressing force to the step 24 </ b> C even in the low-rigidity original P or the leading end portion of the original P, which cannot sufficiently ensure the pressing force to the step.

  Further, since the reading roller 25 is a rotating member that rotates in contact with the back side of the document P, the document roller 25 rotates smoothly regardless of the coefficient of friction with the document P and does not restrain the document P. There is no fear of generating dust due to frictional contact with P, or causing unnecessary tension or tension fluctuation on the document P due to frictional force.

  Further, since the diameter of the reading roller 25 is smaller than the diameter of the reading roller 22, the reading roller 22 and the reading roller can be stored compactly in a limited space near the image reading position 8, and the reading roller having a relatively large diameter. 22 is employed, and the vertical movement of the document P at the image reading position 8 can be suppressed more effectively than when the diameter is small. Further, the support point interval of the original P becomes shorter than when both the diameters of the reading roller 25 and the reading roller 22 are increased, and accordingly, the ratio of the pressing force to the step 24C depending on the rigidity of the original P is reduced. In addition, it is possible to secure a sufficient pressing force to the step 24C even with a document having a lower rigidity.

  Further, as shown in FIG. 6, the reading roller 22 is arranged downstream of the image reading position 8 by a distance B (2 mm), and the image reading position 8 is set between the step 24 </ b> C and the reading roller 25. The reading roller 25 can be arranged with a margin as compared with the case where it is arranged immediately above the image reading position 8, and a reading roller 22 having a large diameter can be employed.

  In addition, since the vertical movement of the document at the image reading position 8 is suppressed in this way and a document feeding device that effectively removes dust and foreign matter on the document surface is employed, the image reading unit 1B has a high focus. Accurate image reading can be performed, and the frequency of erroneous reading of an image due to dust and foreign matter staying at the image reading position 8 is reduced. Then, the distance A between the reading roller 22 and the platen glass 21 is set as described above, and the original P is brought into contact with the platen glass 21 to be conveyed. It can be read with a stable focal length. Therefore, a contact image sensor with a shallow depth of focus can read a clear image at the focal point, and a high quality image of the read image has also been realized.

  Further, since the image reading unit 1B that can perform high-accuracy image reading and reduces the frequency of erroneous reading of images due to dust and foreign matters is mounted, the image forming apparatus 1 has high-quality dust. High-quality copying that is unaffected by or foreign objects can be executed.

  In other words, the vertical movement (floating, rampage, flapping) of the document is suppressed, and fine image reading with a stable focal length is realized, and at the same time, dust and dirt on the document surface are more reliably produced than when only the reading roller 22 is used. Since the possibility of erroneously reading a linear image extending in the transport direction is reduced by removing foreign substances, the image quality is improved by fine image reading, and at the same time, the linear image extended in the transport direction is erroneously corrected. Since the possibility of reading is reduced, the possibility of black streaks occurring in the image recorded on the recording medium is reduced.

  In the embodiment described here, the step 24C is formed by sticking the dirt scraping sheet 24 to the surface of the platen glass 21, but the step is formed by various methods as disclosed in Patent Document 1. May be.

  For example, a step can be formed on the platen glass itself, or the dirt scraping sheet 24 can be fixed to the document feeder 2 side so that it can be rotated backward together with the document feeder 2. Further, the step may be formed by one or a plurality of ribs fixed to the platen glass and aligned in the direction crossing the document surface, or the step may be formed by a rotating body embedded in the platen glass.

  The reading roller 25 is a rotatable rotating member whose axial position is fixed. However, the reading roller 25 may be replaced with a blade member made of a material with less friction, and the axial position is moved up and down with the height shown in FIG. 6 as a lower limit. As a configuration that can be moved to a position, it may be biased downward by a spring.

  The document feeder according to the present invention is equipped not only in an image reading apparatus equipped or integrated with an image forming apparatus but also in an independent image reading apparatus such as a facsimile, a scanner, a character recognition device (OCR), an image data capturing device, etc. The document feeder is not limited to an automatic document feeder that automatically and continuously supplies a plurality of documents to the image reading position, but may be a document feeder that feeds documents one by one manually by the user. Further, the image forming apparatus is not limited to the copying machine described in the embodiments, and may be a multi-function machine with a printer, a facsimile, or the like, or a color image forming apparatus having a plurality of photosensitive drums.

1 is an explanatory diagram of a configuration of an image forming apparatus according to an embodiment of the present invention. It is explanatory drawing of a structure of the image reading apparatus in embodiment of this invention. FIG. 3 is an explanatory diagram of a drive transmission system of a paper feed motor in a document feeder. FIG. 4 is an explanatory diagram of a drive transmission system of a conveyance motor in the document feeder. It is a partial enlarged view of an image reading unit or the like. It is a partial enlarged view of an image reading unit and the like. FIG. 6 is an explanatory diagram of a document conveyance state. 6 is a flowchart of control of the document feeder.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 1A Apparatus main body 1B Image reading part 1C Image forming part 2 Document feeder 3 Paper feed tray 4 Feed part 4a Paper feed roller 4b Pickup roller 4c Lifting arm 5 Registration roller pair 5a Registration drive roller 6 Introduction conveyance roller pair (Driving means)
6a Introduction conveyance drive roller 7 Introduction path (conveyance path)
8 Image reading position 9 Discharge path 10 Discharge transport drive roller pair 12 Discharge tray 13 Contact image sensor 14 Light source 15 Optical element 16 Photosensitive drum 18 Transfer device 19 Fixing device 19a Discharge tray 20 Double-sided path 21 Platen glass 22 Reading roller (first roller Support means, first rotating member)
24 Dirt scraping sheet (level difference forming means)
24C Step 24F Surface 25 Reading roller (second support means, second rotating member)
29 CPU
30 Pressure contact solenoid P Document X, Y, Z Spring clutch M1 Paper feed motor M2 Conveyance motor

Claims (6)

In a document feeder comprising: a conveyance path that guides a document to a predetermined image reading position; and a driving unit that drives the document and moves the document to the image reading position along the conveyance path;
First support means for supporting a back side surface of the document surface in the vicinity of the image reading position;
A step forming means for forming a step across the moving document surface upstream of the image reading position;
Providing second support means for supporting the back side surface upstream of the formed step,
The document feeding device, wherein the document surface supported from the back side surface by the first support means and the second support means is in sliding contact with the surface of the step.   2. The document feeder according to claim 1, wherein the second support means is a second rotating member that rotates in contact with the back side surface.   The first support member is a first rotating member that rotates in contact with the back side surface, and the diameter of the second rotating member is smaller than the diameter of the first rotating member. The document feeder according to claim 1 or 2.   4. The image reading position according to claim 1, wherein the first support means is disposed downstream of the image reading position, and the image reading position is set between the step and the first support means. The document feeder described.   5. An image reading apparatus comprising a document feeding device according to claim 1, further comprising a reading unit configured to read an image on the document surface that moves at the image reading position. An image forming means for forming a toner image on an image carrier based on image information obtained by reading an image on the original surface moving at the image reading position, and a transfer image formed on the image carrier is transferred to a recording medium. An image forming apparatus comprising the image reading apparatus according to claim 5.

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