JP4056427B2 - Automatic document feeder and image forming apparatus using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an automatic document feeder having a sheet-through type image reading unit and an image forming apparatus using the automatic document feeder.
[0002]
[Prior art]
A sheet-through type automatic document feeder (hereinafter referred to as ADF) scans an image as it passes over a reading glass while conveying the document at a constant speed to a reading means fixed to the image forming apparatus main body. However, if the transport path changes suddenly immediately downstream of the scanning position, a shock occurs at the moment when the leading edge of the document that has passed through the scanning position contacts the guide that forms the transport path. Or even after contact, it may be strongly pressed against the guide and receive a large conveyance resistance, which causes fluctuations in the document conveyance speed. At this time, if the fluctuation of the document conveying speed is transmitted to the reading position, the read image may be misaligned in the case of a jitter or color machine, resulting in an image defect. Therefore, the conveyance path after the reading position needs to have a gentle conveyance path shape so that the conveyance resistance of the document is small and the fluctuation amount of the conveyance resistance is small. Ideally, the conveyance path shape is the reading glass. It is desirable to be constant on the extended line of the shape.
[0003]
On the other hand, the sheet-through ADF includes a paper discharge tray for discharging and stacking read originals downstream of the reading unit. In general, a pressure plate type reading unit that reads a document in a stationary state is provided separately from the sheet-through type reading unit. In this case, a pressure plate for holding the document is provided below the discharge tray. There are many things to prepare for. Here, it is possible to reduce the overall size of the image forming apparatus by placing the ADF and the body size of the image forming apparatus main body within a certain space, or reversing for reading the back side of the document. In order to make the read document stack or to stack the read document on the discharge tray, it is necessary to scoop up the leading edge of the document that has passed through the reading position, change the conveyance direction, and guide the document upward. For this reason, as a general configuration, a scooping guide having an inclined portion for scooping up the front end of the original is provided at a position close to the end on the downstream side of the reading glass, and is integrated with a scale serving as a reference for original for reading the pressure plate. I have to. Here, the scooping guide and scale should have a steep angle and a small width in terms of component placement, space saving, etc., but with regard to the reading quality, as described above, the document conveyance resistance is small and the conveyance resistance fluctuates. It is advantageous to make the angle low and wide so that the amount is small.
[0004]
FIG. 7 is a cross-sectional view showing a configuration of a reading unit in a conventional example of an automatic document feeder having a sheet-through type image reading unit. In the figure, 51 is a white background plate, 54 is a reading glass, 55 is a reading glass bracket, 56 is a reading position, 57 is a document, 58 is a pressure plate reading glass, 59 is a scooping guide, and 59a is a starting point of the inclined portion.
[0005]
The reading glass 54 and the scooping guide 59 are separate parts, and the joint is supported by the reading glass bracket 55. Since the reading glass bracket 55 made of sheet metal has a certain width in terms of strength, the inclined portion starting point 59a of the scooping guide 59 and the reading position 56 are separated to some extent according to the width of the reading glass bracket 55.
[0006]
The leading edge of the document 57 being read passes through the reading position 56 and then reaches the scooping guide 59 and enters the conveyance path formed by the white background plate 51 and the scooping guide 59 while climbing the scooping guide 59. Go. At this time, the conveyance resistance is received by sliding contact with the members constituting the conveyance path, the document conveyance speed fluctuates at the reading position 56, and the read image has a defect such as jitter or color misregistration in the case of a color scanner. May end up. In the case of the illustrated example, the point at which jitter and color misregistration occur is relatively in the middle of the image depending on the distance between the inclined portion start point 59 a of the scooping guide 59 and the reading position 56.
[0007]
As a conventionally known technique, the reading glass is tilted so as to be close to the tilt angle of the scale so as to reduce the shock when the front end of the document enters the scale (see Patent Document 1), or the attachment position of the conveyance guide There is a technique that makes it possible to optimally adjust the transport gap in the vicinity of the reading unit by making the variable, and prevents a decrease in reading accuracy due to variations in the transport gap in the vicinity of the reading unit (see Patent Document 2).
[0008]
[Patent Document 1]
JP 2000-351482 A
[Patent Document 2]
JP 2000-292991 A
[0009]
[Problems to be solved by the invention]
By the way, in the general sheet-through ADF scooping guide having the above-described configuration, the scooping guide and scale shape, size, and layout are determined depending on the arrangement of other parts, the reversal of the original, the paper discharge, the size of the machine body, and the like. Although there are considerable restrictions on the position, the shape, size, and position of the scooping guide and scale must be set appropriately so that the desired reading quality can be achieved.
[0010]
In the sheet-through type automatic document feeder and an image reading apparatus using the same, the present invention reduces the speed fluctuation at the reading position that occurs when the document tip enters from the moment when it touches the scooping guide, An object of the present invention is to provide an automatic document feeder capable of suppressing the occurrence of jitter and color misregistration and an image forming apparatus using the automatic document feeder.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, an automatic document feeder according to claim 1 of the present invention is an automatic document feeder comprising a sheet-through type image reading unit, wherein the image reading unit includes a transparent reading member, A guide plate facing the member, and a scooping guide having an inclined portion for scooping up the leading end of the document on the downstream side in the document transport direction of the reading member, image Of reading section Original feed direction The horizontal distance from the downstream end portion to the inclined portion of the scooping guide is 3 mm or more, and an extending portion is provided on the reading portion side of the scooping guide so as to form a surface connected to the upper surface of the reading member. The installation portion is provided at a position between the downstream end of the reading portion of the guide plate and the inclined portion of the scooping guide in the document transport direction.
[0012]
Here, the scooping guide may be of any shape and material, and the surface of the part closer to the reading member than the inclined part for scooping up the front end of the document, that is, the part having a horizontal distance of 3 mm or more is the surface. Either an inclined surface or a non-inclined surface may be used, but this portion has a function of guiding the document but does not have a function of scooping the leading edge of the document. Further, it may be a space or a gap where no member is present in the portion having a horizontal distance of 3 mm or more.
[0013]
In order to achieve the above object, Claim 1 In automatic document feeder ,Up In the scooping guide, at least the vicinity of the leading edge of the document has an inclination angle of 45 ° or less obliquely upward from the incident direction of the document.
[0014]
Here, the scooping guide may be of any shape and material, and the portion having an inclination angle of 45 ° or less obliquely upward may be at least near the front of the original, or the entire inclined portion is inclined. It may be an angle.
[0015]
According to claim 3 Image forming apparatus In order to achieve the above purpose, Claim 1 or 2 Automatic document feeder With It is characterized by that.
[0017]
In order to achieve the above object, an image forming apparatus according to claim 4 includes the automatic document feeder according to any one of claims 1 to 3. The image forming apparatus mentioned here includes a copying machine, a scanner, a multi-function machine having these functions, and the like, and also includes devices similar to these.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. In the following description, common parts are denoted by common reference numerals.
[0019]
The automatic document feeder and the image forming apparatus using the automatic document feeder according to the present embodiment are devices that convey a document to be read to a fixed reading device unit, perform image reading and image formation while conveying the document at a predetermined speed. FIG. 1 is a conceptual cross-sectional view showing an image forming apparatus according to an embodiment of the image forming apparatus according to the present invention. The image forming apparatus according to the present embodiment mainly stacks a reading unit 121 that reads a document, an image forming unit 122 that forms an image, an automatic document feeder (hereinafter also referred to as ADF) 123, and documents sent from the ADF 123. The document stacker 90, a paper feed unit 129 having paper feed cassettes 125 to 128, and a paper discharge tray 130 for stacking recording papers. In the image forming unit 122, a plurality of image forming units 132 are arranged in parallel on a belt-like intermediate transfer belt 131. In each image forming unit 132, a photoconductor 133 is arranged around a drum-shaped photoconductor 133. A charging device that charges the surface of the photosensitive member 133, an exposure device that irradiates the surface of the photosensitive member 133 with laser light, a developing device that visualizes the electrostatic latent image formed by exposing the surface of the photosensitive member 133, and a photosensitive member A cleaning device that removes and collects toner remaining on the body 133 is disposed.
[0020]
The illustrated example is a color image forming apparatus in which the image forming unit 132 is for yellow (Y), magenta (M), cyan (C), and black (BK), for example. While rotating, toners of yellow (Y) to black (BK) are sequentially developed and transferred to the intermediate transfer belt 131, and the four color toner images developed on the intermediate transfer belt 131 are transferred onto a sheet by a transfer device. However, the present invention is not limited to the image forming apparatus of this example, and can be applied to various types.
[0021]
FIG. 2 is an enlarged sectional view of the ADF 123, and FIG. 3 is a control block diagram thereof. Based on these drawings, the processing operation for a bundle of documents of the same size will be described first.
[0022]
The ADF 123 includes a document setting unit 1 for setting a read document bundle 13, a separation feeding unit 2 for separating and feeding documents one by one from the set document bundle 13, and primary feeding and alignment of the fed documents. In addition, the registration unit 3 that pulls out and conveys the aligned document, the turn unit 4 that turns the conveyed document and conveys the document surface toward the reading side (downward), and reads the surface image of the document from below the reading glass 54. A first reading / conveying unit 5 for reading, a second reading / conveying unit 6 for reading the back side image of the original after reading, a paper discharging unit 7 for feeding the original whose front and back sides have been read to the outside of the machine or a reversing unit, for re-reading The reversing unit 8 for reversing the document, the stack unit 9 for stacking and holding the original after reading, the driving units 101 to 104 for driving these conveying operations, and controlling a series of operations. It is constituted from that controller 100 Prefecture.
[0023]
In this apparatus, the document bundle 13 to be read is set on the document setting table 10 with the leading end of the document bundle 13 abutting the broken line position of the document stopper 25, and the width direction of the document bundle 13 is set in the side guide 11 (not shown). Positioning in the direction perpendicular to the conveying direction. In this state, the document set detection filler 21 is displaced from the broken line position to the solid line position. Accordingly, the shielding of the document set detection sensor 28 is released, and when the document set is detected, the document set detection sensor 21 is detected via the I / F unit 107. A document set signal is transmitted to the main body control unit 111. Further, the document length detection sensors 12 and 14 provided on the document table surface (use a reflection type sensor or an actuator type sensor capable of detecting even one document) are used to determine the approximate length of the document in the conveyance direction. In this example, at least a sensor arrangement that can determine whether the document size is vertical or horizontal is necessary.
[0024]
Thereafter, a document feeding operation is executed by a document feeding signal (a signal input from an operation unit (not shown) and instructed from the main body control unit to the controller unit 100 via the I / F unit 107). That is, the document stopper 25 rotates to retract to the solid line position by rotating the calling motor 101 as a driving source in the counterclockwise direction (referred to as rotation in the drawing, the same applies hereinafter) to open the document leading end. To do. Thereafter, the pick-up roller 20 is rotated and moved by driving the calling motor 101 from the broken line position to the upper surface of the document indicated by the solid line position, and is pressed against the upper surface of the document with a predetermined force. The home position sensor 19 is a sensor for detecting the states of the pickup roller 20 and the document stopper 25. A stepping motor may be used as the calling motor 101, but the same function can be realized by a solenoid.
[0025]
When the number of originals is small during the pressure contact operation of the pickup roller 20, the drop height of the pickup roller 20 is large and the cushioning action of the original between the original setting table 10 and the pickup roller 20 is small, so that the pickup roller 20 Since the drop impact sound becomes louder, in the illustrated example, a concave roller relief is formed at the contact point of the document setting table 10 with the pickup roller 20, and the pickup roller 20 does not directly hit the document setting table 10. It is like that.
[0026]
Thereafter, after a predetermined time, a paper feed motor 102 as a drive source for driving the separation feeding unit 2 and the registration unit 3 rotates the pickup roller 20 to feed the uppermost sheet of the original bundle 13 toward the separation unit 2. The paper feed belt 23 is wound around the belt pulleys 22 and 24 with a predetermined tension, and is pressed against the separation roller 26 provided oppositely. The separation roller 26 is friction-driven through a torque limiter (not shown) having a predetermined magnitude of torque, and is in a state of being engaged with the paper feed belt 23 or in a state of being engaged through one original. When the paper feed belt 23 rotates counterclockwise and two or more originals enter between the paper feed belt 23 and the separation roller 26, the follow-up force becomes lower than the torque limiter torque. Therefore, the separation roller 26 rotates in the clockwise direction, which is the original driving direction, and pushes back an excess document to prevent double feeding.
[0027]
The original document separated into one sheet by the action of the paper feed belt 23 and the separation roller 26 is further fed by the paper feed belt 23 and advances through the paper feed path 27. In this process, the abutting sensor 29 detects the tip. The document further advances and strikes the pull-out roller 31 that is stopped. Thereafter, the document is fed by a predetermined distance from the detection of the abutting sensor 29. As a result, the paper feed belt 23 is driven by the paper feed motor 102 while being pressed against the pull-out roller 31 with a predetermined amount of warpage. Stop. At this time, the calling motor 101 is rotated to rotate the pickup roller 20 in the clockwise direction, retract from the upper surface of the original, and send the original only by the conveying force of the paper feeding belt 23, thereby pulling the front end of the original with the pull-out roller 31. The driven roller 30 is made to enter the nip of the upper and lower roller pairs, and the tip is aligned (skew correction).
[0028]
Thereafter, the pull-out roller 31 is driven by the paper feed motor 102 to convey the document in the direction of the turn part 4. Here, when feeding the first sheet of the original bundle 13 to the registration stop position, the conveying speed of the pull-out roller 31 is set to be higher than the reading speed, and the reading conveying roller 43 is also driven by the reading motor 103 which is a driving source. Drive at the same speed. In the case of the second and subsequent sheets, it takes the form of first advance of the next document. Since the reading conveyance roller 43 during reading of the original image is driven by the reading motor 103 at a speed corresponding to the reading magnification instructed from the main body control unit 111, the conveyance speed of the next original is read at the same speed as the reading conveyance roller 43. It must be fed into the nip between the conveying roller 43 and the pressure roller 35. Therefore, when the trailing edge of the document being read passes through the abutting sensor 29, a pulse count for controlling the space between the documents is started, and the advance of the next document is conveyed while monitoring the progress of the trailing edge of the document being read. Start.
[0029]
That is, the pick-up roller 20 is first brought into pressure contact with the upper surface of the next original by the calling motor 101, and then the original is conveyed until it contacts the pull-out roller 31 that is stopped by driving the paper feed motor 102. Here, the position of the trailing edge of the document being read is calculated from the above-described inter-sheet pulse count value, and when the paper advances from the pull-out roller 31 by a predetermined inter-sheet interval, the paper feed motor 102 is rotated in reverse and the pull-out roller 31 is moved to one sheet. Like the eye, it is rotated at a high speed, sent to the leading edge detection sensor 34 at this speed, and decelerated to the reading speed (speed of the reading conveyance roller 43) by the detection of the leading edge detection sensor 34. By performing this operation between successive original sheets, the time stopped by the original abutting operation is recovered and a predetermined original interval is maintained.
[0030]
Further, the size of the leading end of the document that has passed the position of the pull-out roller 31 is detected by the size detection sensor 32 in the direction perpendicular to the conveyance direction. When an accurate document size is determined by a combination of the width signal and the length signals obtained by the document length detection sensors 12 and 14, the controller unit 100 sends the document size signal to the I / F unit from the controller unit 100. 107 to transmit. Thereafter, the document is sent to the nip between the reading conveyance roller 43 and the pressure roller 35, stopped at a position conveyed by a predetermined pulse from the detection of the registration sensor 40, and a registration stop signal is transmitted to the main body control unit 111. It waits for an input of a reading start signal from the control unit 111 (a signal transmitted when synchronization with transfer paper or preparation for storage in the image memory is completed).
[0031]
Next, an original reading operation is executed by inputting a reading start signal. The document whose registration is stopped is sent to the first reading / conveying unit 5 by the reading / conveying roller 43 and the pressure roller 41 which are rotated by the normal rotation driving of the reading motor 103 which is a driving source. The driving speed of the reading motor 103 at this time is determined based on information transmitted from the main body control unit 111 to the controller unit 100 according to a reading magnification input from a main body operation unit (not shown).
[0032]
The first reading / conveying unit 5 conveys the document between the reading glass 54 and the white background plate 51 arranged at a predetermined interval with respect to the upper surface thereof. During this time, the image of the original is read by a reading system (not shown), converted into an electrical signal via a CCD (not shown), and also stored in a memory device (not shown). This reading / conveying unit takes a conveying gap as narrow as possible and takes measures to minimize the degree of freedom of the document. As such a method, it is effective to project a flexible guide member from the inner surface of the reading entrance guide 42 toward the white background plate 51 to fill the gap. Further, the white background plate 51 is pressed on the reading glass 54 with a gap of, for example, about 0.5 mm ± 0.2 mm and with a predetermined elasticity, thereby suppressing errors in the reading depth direction.
[0033]
The surface of the reading glass 54 is subjected to a surface-active agent (silicon-based activator) treatment or the like so that ink or the like does not easily adhere or adhere to the surface. Further, the above-described flexible guide is extended to the vicinity of the reading point, and the document surface does not positively contact the reading glass 54 at the reading position, and the leading edge of the document is wiped near the reading point of the reading glass 54 (the leading edge). The action of scraping off foreign matter on the glass surface) is taken.
[0034]
The timing at which the leading edge of the document reaches the above-described reading unit is controlled by the pulse count of the reading motor 103, and a surface DF gate signal indicating a surface image effective reading area in the sub-scanning direction is transmitted at this timing. Thereafter, the document is advanced while being read, and sent to the intermediate conveyance pressure roller 53 through the pickup guide 52. The pressure roller 41 and the intermediate conveyance pressure roller 53 are commonly driven by the reading conveyance roller 43. Therefore, the feeding speed and the drawing speed are the same, and the occurrence of a delivery shock can be reduced.
[0035]
An original image fed from the first reading conveyance unit 5 by the intermediate conveyance pressure roller 53 is sent to the second reading conveyance unit 6, and the contact image sensor 61 arranged with the reading unit facing downward from the upper surface, and the contact image sensor 61 from below. Between the pressing members 62 arranged on the reading surface with a predetermined pressure and a predetermined interval. In the double-side mode, the timing at which the leading edge of the document reaches the contact image sensor unit is controlled by the conveyance pulse count from the detection of the leading edge of the registration sensor, and at this timing, the effective reading area of the back image is transmitted to the contact sensor unit. Based on this signal, an image of the surface corresponding to the back side of the document is read, converted into an electrical signal in the same manner as the front side, temporarily stored in a frame memory unit (not shown), and then transferred to the main body control unit.
[0036]
The pressing member 62 serves as a reference for shading and also functions as a white background plate. The pressing member 62 can be formed of a rotating body in addition to the plate-shaped guide member shown in FIG.
[0037]
The timing for ending the reading area on the front and back sides of the document is controlled by the pulse count from the time when the trailing edge of the document is detected by the registration sensor. Thereafter, the original is discharged to the stack unit 9 by a pair of discharge rollers 71 and 72 constituted by a discharge drive roller 71 and a discharge pressure roller 72. The document stacker 90 is configured to be higher on the downstream side in order to prevent the ejected document from jumping out and improve the accuracy of stack document alignment.
[0038]
During continuous reading of multiple originals, the drive of the reading motor is stopped by the registration stop operation by the first advance of the original before the completion timing of the original discharge, so the discharge operation of the original that has been read is resumed when the reading of the next original starts. Thus, when the trailing edge of the document passes through the paper discharge sensor, a paper discharge completion signal is transmitted to the main body control unit to complete the process.
[0039]
When stacking small-size documents, the reversing switching claw 80 of the reversing unit 8 is switched to the state shown by the broken line by the solenoid 105 as a driving source, and the document is transported to the reversing path 85, and the reversing discharge driving roller 81 and the reversing discharge The paper is discharged from a pair of reverse conveying rollers 81 and 82 constituted by a paper driven roller 82 onto a small-size dedicated stacker 91 that forms a part on the document stacker 90. This improves the visibility after discharging a small-size document.
[0040]
Further, the document setting table 10 is configured so as to be able to retreat upward with the rotation fulcrum 15 as a center, thereby improving the stack document extraction performance. Further, when the document is discharged, the operation of the reverse switching claw 80 is synchronized with the trailing end of the discharged document, and immediately after the original is discharged, the reverse switching claw 80 is rotated in the direction of the broken line by the reverse switching solenoid 105 as a drive source, Control is also performed to strike the trailing edge of the discharged document and prevent the remaining trailing edge of the discharged document. The above is the outline of the processing for single-sided or double-sided originals with the same size original bundle.
[0041]
Next, processing of single-sided and double-sided originals when sizes are mixed will be described. When documents of different sizes are mixedly loaded, the document length varies, and the document length detection sensors 12 and 14 on the document set table 10 cannot discriminate. Therefore, after separating the original into one sheet, the size can be determined only when the rear end of the original leaves the original bundle 13 and becomes completely independent. Therefore, if you want to determine the document size before reading, set the document path configuration to a length of 1/2 or more of the maximum document length between the first document trailing edge detection position after separation and the registration sensor position before reading. Must be set to In order to satisfy this, the document setting position needs to be greatly separated from the reading position, and the part including the document setting table 10 and the conveyance path becomes large, and the entire apparatus becomes wide. Therefore, in order to make the apparatus small, it is necessary to devise a method for detecting the document length when mixed loading.
[0042]
As a countermeasure, if the original size cannot be determined before reading starts when mixed sizes are loaded, reading is not performed at all for the first conveyance, paper is passed for size reading only, and the second reading passes through the reversing unit. Sometimes a method of reading the front and back surfaces simultaneously is adopted. In this case, the conveyance operation until the first registration stop is the same as that for the document bundle 13 of the same size, but the operation after receiving the read start signal transmitted from the main body control unit (particularly the processing after the discharge unit 7). Is different.
[0043]
That is, when the document is discharged after passing through the reading unit, the reverse switching claw 80 is moved in the direction of the broken line by the reverse switching solenoid 105 before the leading edge of the document comes out of the pair of paper discharge rollers 71 and 72, and the document is reversed. Send to 85 side. Thereafter, the original is fed by the reverse paper discharge roller pair 81 and 82 driven by the reverse motor 104 until the rear end thereof passes through the paper discharge roller pair 71 and 72. This control is performed by the pulse count from the paper discharge sensor 70. . Then, after the document stops, the reverse switching claw 80 is moved in the direction of the solid line by the reverse switching solenoid 105, and the rear end of the document is directed in the nip direction of the pair of reverse conveying rollers 81 and 82. Thereafter, the reverse paper discharge driving roller 81 is rotated counterclockwise, and the document end (viewed from the initial state) is formed at the nip portion of the reverse roller pair 71 and 83 formed by the paper discharge drive roller 71 and the reverse upper roller 83 that are stopped. And the rear end) are abutted and the tip skew matching operation is performed. Thereafter, the reversing roller pair 71 and 83 are driven by the reading motor 103 to start feeding the document, and are sent again to the first reading conveyance unit 5 and the second reading conveyance unit 6 through the turn unit 4 to read the front and back sides. . At this time, since the document is in a state where the back side and the front side are reversed, the reading order is the back side first, and the front side is read later. Therefore, the back gate ON signal is transmitted first, and then the front gate signal ON signal is transmitted. Based on this signal, the page order is changed on the image processing apparatus side.
[0044]
This completes the reading operation, but if it is discharged as it is, the page order will be out of order, so that the reversing operation is repeated once before discharging. Note that the above-described conveyance only for document size reading and conveyance only for page alignment are configured to be sent at the highest conveyance speed of the apparatus for a conveyance operation that does not involve image reading, thereby reducing the loss time. Good.
[0045]
Next, a case where the second reading / conveying unit 6 is not provided will be described.
The configuration shown in FIG. 2 has a contact image sensor 61 that supports double-sided originals. However, this reading apparatus is expensive, and even if there is no such apparatus, double-sided original processing can be performed using a reversing mechanism. is there. This will be described below.
[0046]
If it is not compatible with double-sided originals, the original whose surface has been read by the reading operation in the first reading conveyance unit 5 is conveyed again to the first reading conveyance unit 5 through the reversing unit 8, and the back side is read. The paper is discharged onto the document stacker 90 through the reverse discharge of the page alignment. As described above, in an apparatus having no second reading / conveying unit 6, productivity is lowered when double-sided copies are made from double-sided originals. As a countermeasure, a method is adopted in which a plurality of originals are fed into the unit and image reading and reverse document discharge are combined alternately to reduce the paper loss.
[0047]
First, the first original is fed, and one page of image is read by the first reading / conveying unit 5, which is sent to the reversing unit, and the first reading is performed again after abutting alignment with the reversing roller pair 71 and 83. The paper is fed to the transport unit 5 and the second page is read, and sent to the reversing unit in order to align the page order at the time of paper discharge. Before and after this, the second original is fed, and the first reading conveyance unit 5 reads the third page. Subsequently, reverse discharge of the first original is executed, and subsequently, the fourth page of the second original is read. Thereafter, the second original is sent to the reversing unit, the third original is sent before and after this, the fifth page is read, and then the second original is reversed and discharged. In this way, by performing the process between the reverse reading operation of the document that has already been read between the reading of the front surface and the reading of the back surface, the loss time between papers of the reverse discharging operation without reading is minimized. It is possible to stay. Note that this processing is possible only for a document having a size that fits between the pair of reverse conveyance rollers 81 and 82 and the registration sensor 40.
[0048]
FIG. 4 is a cross-sectional view (A) showing a configuration related to the scooping guide in an embodiment of the automatic document feeder according to the present invention, and a diagram showing a simulation result of a distance between the white background plate and the scooping guide and a color shift prediction value ( B). In this example, the pressure plate reading glass 58 and the scooping guide 59 are shifted to the right in the horizontal direction in the drawing with respect to the conventional example shown in FIG. 7, and the original of the scooping guide 59 first comes in contact with the right end of the white background plate 51 in the document transport direction. The distance to the part, that is, the distance L that indirectly represents the conveyance gap is increased, and the reading glass 54 is extended by that amount. The inclination angle θ of the inclined surface of the scooping guide 59 remains constant.
[0049]
When the distance L is increased with the inclination angle θ kept constant, as shown in FIG. 4B, the amount of jitter and color misregistration tends to decrease as the distance L increases. As shown in the figure, when the distance L is set to 3 mm or more, the conveyance resistance of the original is small, and the result that the jitter or color misregistration becomes a level with no problem is obtained.
[0050]
FIG. 5 is a cross-sectional view (A) showing another configuration relating to the scooping guide in an embodiment of the automatic document feeder according to the present invention, and a diagram showing a simulation result of the inclination angle and the color misregistration prediction value of the inclined surface of the scooping guide ( B). With the configuration of the embodiment of FIG. 4, not only the size of the reading glass 54 or the reading glass bracket 55 is changed, but also the reading reference position in the pressure plate reading mode and the component layout downstream of the reading unit are changed. It will be necessary to review many parts shapes and, in some cases, the aircraft size. Therefore, in this example, the distance L is the same as that of the conventional example, the extending portion 59b is provided on the side of the reading glass 54 of the scooping guide 59a so as to form a surface connected to the upper surface of the reading glass 54, and the scooping guide 59a is inclined. The inclination angle θ of the surface is increased. By doing so, the layout space required for the scooping guide 59a can be reduced, and the arrangement of parts can be afforded. However, if the inclination angle θ is too large, a large shock occurs at the moment when the leading edge of the document comes into contact with the scooping guide 59a, causing jitter and color misregistration. Therefore, the inclination angle θ is approximately 45 ° or less. As shown in FIG. 5B, at such an angle, the shock at the moment when the leading edge of the document comes into contact with the scooping guide 59a is small, and there is no problem with jitter and color misregistration. Moreover, it is good also as a clearance gap or an empty space, without providing the extending part 59b. In this case, however, a situation may occur in which the leading edge of the document enters a gap or a space, so that a gap or the like may not be generated by a separate member.
[0051]
FIG. 6 is a cross-sectional view showing still another configuration relating to the scooping guide in the embodiment of the automatic document feeder according to the present invention. This example has a configuration in which the embodiments of FIGS. 5 and 6 are combined, and is a scooping guide 60a that fits in a layout space similar to the conventional one, but takes a large distance L and the inclination angle θ is equal to or less than the upper limit value. Thus, an appropriate range can be set for both. With this configuration, it is possible to reduce jitter and color misregistration caused by a shock at the moment when the leading edge of the document comes into contact with the scooping guide inclined portion and a speed fluctuation at the reading position that occurs when the document approaches. . Note that the inclination angle θ of the inclined portion is sufficient if the angle of only the inclined surface 60b in the vicinity of the leading edge of the document 57 starts to meet the above-mentioned condition, and the inclination of the other portions is not necessarily uniform as shown in the figure. Good. In addition, the inclination angle θ formed by the inclined surface 60b in the example of FIG. 6 is 36 °, and the distance L is 3 mm.
[0052]
【The invention's effect】
The automatic document feeder and the image forming apparatus using the automatic document feeder according to claim 1 have a horizontal distance of 3 mm or more from the downstream end of the reading portion of the guide plate to the inclined portion of the scooping guide. Therefore, it is possible to prevent a reading image defect caused by the conveyance resistance of the document.
[0053]
In the automatic document feeder according to claim 2 and the image forming apparatus using the automatic document feeder, the inclined portion of the scooping guide has an inclination angle of 45 ° or less obliquely upward from the incident direction of the document tip. It is possible to prevent a read image defect due to a shock at the moment when light enters.
[0054]
In the automatic document feeder and the image forming apparatus using the same according to the third aspect, the horizontal distance from the downstream end of the reading unit of the guide plate to the inclined portion of the scooping guide is 3 mm or more. In this case, it is possible to prevent the reading image defect due to the conveyance resistance of the original document generated in step 1 and the inclined portion of the scooping guide has an inclination angle of 45 ° or less obliquely upward from the incident direction of the original document end. It is possible to prevent a read image defect due to a shock at the moment of incidence, and it is not necessary to increase the layout space of the scooping guide.
[Brief description of the drawings]
FIG. 1 is a conceptual cross-sectional view showing an image forming apparatus according to an embodiment of an image forming apparatus according to the present invention.
2 is an enlarged cross-sectional view of the automatic document feeder (ADF) shown in FIG.
FIG. 3 is a control block diagram thereof.
FIG. 4 is a cross-sectional view (A) showing a configuration related to a scooping guide in an embodiment of an automatic document feeder according to the present invention, and a diagram showing a simulation result of a distance between a white background plate and the scooping guide and a predicted color misregistration value. (B).
FIG. 5 is a cross-sectional view (A) showing another configuration relating to the pick-up guide in the embodiment of the automatic document feeder according to the present invention, and a diagram showing a simulation result of the inclination angle and the color misregistration prediction value of the inclined surface of the pick-up guide; (B).
FIG. 6 is a cross-sectional view showing still another configuration related to the scooping guide in the embodiment of the automatic document feeder according to the present invention.
FIG. 7 is a cross-sectional view illustrating a configuration of a reading unit in a conventional example of an automatic document feeder including a sheet-through type image reading unit.
[Explanation of symbols]
1 Document set section
2 Separate feeding section
3 resist section
4 Turn part
5 First reading transport unit
6 Second reading transport section transport section
7 Output section
8 Reversing part
9 Stack part
10 Document setting table
11 Side guide
12, 14 Document length detection sensor
13 Document bundle
15 fulcrum
19 Home position sensor
20 Pickup roller
21 Document set detection filler
22 Belt pulley
23 Paper feed belt
25 Document stopper
26 Separation roller
27 Paper feed path
28 Document set detection sensor
29 sensors
30 Pull-out driven roller
31 Pull-out roller
32 size detection sensor
34 Tip detection sensor
35 Pressure roller
40 resist sensor
41 Pressure roller
42 Reading Entrance Guide
43 Conveyance roller
51 white background board
52 Pickup Guide
53 Intermediate transfer pressure roller
54 Reading glass
55 Reading glass bracket
56 Reading position
57 Manuscript
58 Pressure plate reading glass
59, 59a, 60, 60a Skim guide
60b inclined surface
61 Contact image sensor
62 Pressing member
70 Paper discharge sensor
71 Paper discharge drive roller
72 Paper discharge pressure roller
80 nails
81 Reverse paper discharge drive roller
82 Reversed discharge driven roller
83 Reverse upper roller
85 Reverse path
90 Document stacker
91 Small size stacker
100 Controller
101 Calling motor
102 Paper feed motor
103 motor
104 reverse motor
105 Solenoid
107 I / F section
111 Main unit controller
121 Reading unit
122 Image forming unit
123 Automatic document feeder (ADF)
125-128 paper cassette
129 Paper feed unit
130 Output tray
131 Intermediate transfer belt
132 Imaging Department
133 photoconductor
L Distance between white background board and scoop guide
θ Inclination angle of inclined surface of scoop guide

Claims (3)

In an automatic document feeder having a sheet-through type image reading unit, the image reading unit scoops up the document leading end on the transparent reading member, a guide plate facing the reading member, and the reading member downstream in the document conveying direction. A scooping guide having an inclined portion for the scooping guide, and a horizontal distance from the downstream end of the image reading portion of the guide plate in the document feeding direction to the inclined portion of the scooping guide is 3 mm or more, and the scooping guide is read. An extending portion is provided on the side of the reading member so as to form a surface connected to the upper surface of the reading member. An automatic document feeder provided at a position between the two.   2. The automatic document feeder according to claim 1, wherein at least the vicinity of the leading edge of the inclined portion of the scooping guide has an inclination angle of 45 ° or less obliquely upward from the incident direction of the leading edge of the document. Automatic document feeder.   An image forming apparatus comprising the automatic document feeder according to claim 1.

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