JP2004256229A - Document conveyance device and image reading device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading device capable of preventing the occurrence of image distortion and color deviation. <P>SOLUTION: A document conveyance unit has a conveyance roller 12 conveying a document to a reading position R, a delivery roller 14 receiving the document and delivering it, a guide plate 21 positioned between the rollers 12 and 14 and on a rear surface side of an image recording face of document to be conveyed to guide the document, flappers 31, 33 arranged by opposing to the guide plate 21 on both sides of a flowing reading platen glass 72 to support the document from an image recording face side, and a flapper driving motor driving the flappers 31, 33 to change a clearance formed among the guide plate 21 and the flappers 31, 33. By changing the clearance formed among the guide plate 21 and the flappers 31, 33 and avoiding buckling of document, abutting shock with the delivery roller at a tip of document is reduced. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a document reading apparatus and an image forming apparatus, and more particularly, to a document conveying apparatus which is mounted on an image reading apparatus having reading means for reading an image recording surface of a document at a predetermined reading position and conveys a document to be read, and The present invention relates to an image reading apparatus having reading means for reading an image recording surface of a document at a reading position via a transparent body.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an image reading apparatus equipped with a document feeder, a reading means such as an image sensor for reading a document is stopped at a predetermined reading position, and a document conveyed by the document feeder is placed on a platen glass (reading glass) or the like. Image data is obtained by reading through a transparent body (sheet-through method). That is, in the sheet-through system, the document feeder separates the document placed on the paper feed tray, and then separates the separated document with the platen glass by rollers provided on the upstream and downstream sides of the platen glass. It is transported to the reading position on the glass. The document read at the reading position is scooped up from the platen glass by a scooping member fixed to the document conveying device or the image reading device, and is discharged to a downstream discharge tray. The image reading device irradiates light from a light source, guides light reflected on an image recording surface of a document conveyed to a reading position to an image sensor via a mirror or a lens, and acquires image data (reads an image). .
[0003]
There are various types of image sensors. A linear image sensor in which photoelectric conversion elements such as a CCD device and a MOS device are linearly arranged one-dimensionally in a monochromatic manner is typical. A one-dimensional array of each of the three primary colors formed on the conversion element is arranged in parallel at a predetermined interval, and the primary color data from the three lines read synchronously is corrected by a delay corresponding to the predetermined interval, thereby providing a color image. Those that have acquired data are typical. The lines of the photoelectric conversion elements formed in such a one-dimensional array are called reading lines. In general, reading is performed at regular intervals on the assumption that a document is conveyed at a constant speed. Therefore, in order to improve the quality of image data obtained by the image reading apparatus, the document conveying apparatus is required to suppress conveyance fluctuations such as document bending and height deviation (fluttering) due to conveyance and read lines from the image recording surface. There is a demand for a function to stabilize the optical distance up to.
[0004]
In order to suppress such a document conveyance variation, it is preferable to make the gap of the conveyance path as narrow as possible. However, if the gap of the conveyance path is made narrow, the leading end of the document will be buckled. In order to solve this problem, a technique for stabilizing the optical distance by pressing a document against a platen glass of a contact sensor (CIS), a method for pressing a document against a reduced-type platen glass by an urging force of an elastic member, or a mylar (thin sheet) A technique using a plastic plate) is known (for example, see Patent Documents 1 and 2). Further, there is also known a method in which a document is received by enlarging a gap in a transport path and the document is pressed by driving a solenoid or the like after the document is received, as a thin paper having a weak stiffness (for example, see Patent Document 3).
[0005]
[Patent Document 1]
JP-A-8-65445
[Patent Document 2]
JP-A-5-236194
[Patent Document 3]
JP-A-5-103165
[0006]
[Problems to be solved by the invention]
However, according to the technique of the above-mentioned patent document, when the document is conveyed (discharged) from above the platen glass, the leading end of the document is transferred to the surface of the fixed scooping member or to a conveyance roller disposed downstream of the platen glass. At that moment, the original receives a reaction force (impact) in a direction opposite to the conveying direction. Due to this impact, the document is instantaneously stopped or accelerated (or vibrated) at the reading position, and the read image data includes positional distortion. Also, when the rear end of the document in the conveyance direction passes through the conveyance roller arranged on the upstream side of the platen glass, the document is fluttered at the reading position at the moment when the grip (nipping) of the roller with respect to the document is released. Since blurring occurs, there is a problem in that the read image data includes positional distortion and the quality of the image data deteriorates. In particular, in an image reading apparatus in which a reading sensor is composed of three lines of RGB and reads the primary color at the same time, the reading positions of the originals are different at the same time. Therefore, even if the time difference is corrected, the positions do not match between the primary colors, resulting in color shift or color bleeding. Will be reproduced as.
[0007]
SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a document conveying device and an image reading device that can prevent image distortion and image blurring and can prevent occurrence of color misalignment when reading a color document.
[0008]
[Means for Solving the Problems]
In order to solve the above-described problems, a first aspect of the present invention is a document feeder mounted on an image reading device having a reading unit that reads an image recording surface of a document at a predetermined reading position, and transporting a document to be read. A first transport unit that transports the original placed on the tray to the reading position; a second transport unit that receives the original transported by the first transport unit and transports the original further downstream; A back guide for guiding the document, the back guide being located between the first and second conveyance means and being arranged on the back side of the document to be conveyed, and the back guide between the first conveyance means and the reading position; A first support unit that is disposed to face and supports the document from the image recording surface side; and the first support unit is configured to change a gap formed between the first support unit and the back guide. Driving means for driving That.
[0009]
In this aspect, the document placed on the tray is transported to the reading position by the first transport unit, and the document transported by the first transport unit is received by the second transport unit and further transported downstream. A back guide for guiding the document is arranged between the first and second transport means and on the back side of the document to be transported. A first support unit for supporting the document from the image recording surface side is disposed therebetween. For this reason, the document is transported between the gap formed by the back guide and the first support means, and the reading means reads the image recording surface of the document at a predetermined reading position. This gap is changed by driving the first supporting means by the driving means. According to this aspect, the gap formed between the first supporting means and the back guide is allowed to be changed by the driving means, and the document is supported from the image recording surface side by the first supporting means by narrowing the gap. Therefore, the impact that occurs on the document when the trailing edge of the document separates from the first transport unit is suppressed, and image distortion of image data read by the reading unit can be prevented. In this case, occurrence of color shift can be prevented.
[0010]
In the first aspect, if the drive means drives the first support means so as to gradually change the gap as the document is conveyed, the impact caused by the original being brought into contact with or supported by the first support means is reduced. This makes it difficult for defects such as image distortion to be included in the image data. Further, if the driving means moves the first support means to a predetermined position where the gap is narrowed before the trailing end of the document separates from the first conveyance means, the document is generated when the document separates from the first conveyance means. The impact is attenuated by the narrowed gap, and image distortion and the like can be minimized.
[0011]
Further, the image forming apparatus may further include a second support unit that is disposed between the reading position and the second transport unit so as to face the back guide, and that supports the document from the image recording surface side. In this case, the first gap formed between the back guide and the first support means and the second gap formed between the back guide and the second support means are gradually changed. Various modes are conceivable for the drive sequence of the first and second support means by the drive means, including the mode for driving the first and second support means. For example, at least the first support means may be driven so that the second gap is larger than the first gap before the leading end of the document conveyed by the first conveyance means reaches the second holding means. The original can smoothly enter the second gap. Further, after the leading end of the document conveyed by the first conveyance means reaches the second support means, if the second support means is driven so as to narrow the second gap, the conveyance resistance can be reduced while preventing the document from loosening. Can be smaller. Further, if the operation of driving the second support means to complete the operation of narrowing the second gap before the leading end of the document conveyed by the first carrying means reaches the second carrying means, the leading end of the document can be obtained. The impact caused by contact with the second conveying means can be absorbed and attenuated by the narrowed second gap. At this time, a rear end detection sensor for detecting the rear end of the document in the conveyance direction is further provided upstream of the reading position, and the driving unit detects the first gap after the rear end detection sensor detects the rear end of the document in the conveyance direction. If the first and second support means are driven so as to widen the second gap, the conveyance of the next document can be started in a short time. Furthermore, if the drive means operates the first and second support means at synchronized timing, a single drive source for the drive means can be used. If the first supporting means has a rotatable roller at the position where the document contacts the image recording surface, the friction between the document and the first supporting means can be reduced.
[0012]
According to a second aspect of the present invention, there is provided an image reading apparatus having reading means for reading an image recording surface of a document at a predetermined reading position via a transparent body. A first transport unit that transports the scanned original to the reading position; a second transport unit that receives the original transported by the first transport unit and transports the original further downstream; A back guide for guiding the document, disposed on the back side of the document to be conveyed therebetween, and disposed on the upstream side of the transparent body so as to face the back guide; And driving means for driving the supporting means so as to change a gap formed between the supporting means and the back guide.
[0013]
In the second aspect, the support means is lever-shaped, and the gap formed between the lever tip of the support means and the back guide is the same as the gap formed between the transparent body and the back guide, or In order to form a large gap, a retracting portion may be provided in the vicinity of the transparent body to allow the distal end of the lever of the supporting means to retract.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to an image reading apparatus will be described with reference to the drawings.
[0015]
(Constitution)
As shown in FIG. 1, the image reading apparatus according to the present embodiment includes an image reading unit 2 that can read a document and output image data to an external device such as a personal computer, and is mounted on the image reading unit 2 to read an image to be read. And a document transport unit 1 for transporting the document.
[0016]
The image reading unit 2 has a substantially box-shaped casing 75. A fixed document platen glass 73 serving as a document mounting table for reading a fixed document placed on the upper portion of the casing 75, and entry of dust and dirt when reading a document in a sheet-through (flow-reading) mode using the document transport unit 1. And a platen glass 72 for reading the document are fixed.
[0017]
As shown in FIG. 2, in the upper portion of the casing 75 and near both sides of the flow-reading platen glass 72, a tip receiving groove 75 a having a substantially triangular cross section for receiving the tip of the later-described upstream flapper 31 and downstream flapper 33, An upstream flapper sensor 81 and a downstream flapper sensor 82 for detecting the front ends of the upstream flapper 31 and the downstream flapper 33 are provided at the edges of the front housing grooves 75a and 75b, respectively.
[0018]
Further, as shown in FIG. 1, the image reading unit 2 has a first carriage 50 and a second carriage 51 that can move in a longitudinal direction in a casing 75 by a driving force of a stepping motor (not shown). . The first carriage 50 includes an illumination lamp 60 for illuminating the original, a reflector 64 for reflecting light from the illumination lamp 60 in the original direction, and a first mirror 61 for changing an optical path of light reflected from the original. The second carriage 51 includes a second mirror 62 that changes the optical path of the reflected light from the document changed by the first mirror 61 to be substantially vertical, and a second mirror 62 that changes the reflected light changed by the second mirror 62. And a third mirror 63 for making the optical path substantially horizontal. A lens unit 52 that collects reflected light on the sensor surface of a linear image sensor 53 such as a CCD is disposed on a horizontal extension line of the third mirror 63. The image sensor 53 of this embodiment has a reading density (resolution) of 400 dpi (400 lines per inch) in the document conveying direction.
[0019]
The image sensor 53 is mounted on an analog board 54 that operates the image sensor 53 and converts an analog signal from the image sensor 53 into a digital signal. The analog substrate 54 is connected to a processing substrate 55 that performs shading correction processing and image processing. The processing substrate 55 is connected to an interface connector 56 that is fixed to a casing 75 and allows connection to an external device.
[0020]
That is, as shown in FIG. 4, an analog substrate 54 is mounted with an image sensor 53, a clock generator 124 for operating the image sensor 53, and an A / D converter 122. A microcomputer 120 for controlling the entire unit 2, a shading correction processing unit 123 for correcting density unevenness of image data, an image processing IC 125 for performing image processing such as a time difference correction of image data, and a communication IC 126 for controlling communication with an external device are provided. Mounted. Note that the upstream flapper sensor 81 and the downstream flapper sensor 82 (see FIG. 2) are connected to the microcomputer 120, and the microcomputer 120 is connected to the document transport unit 1 via the scanner connector 128.
[0021]
As shown in FIG. 1, the document transport unit 1 has a pickup roller 10 that feeds out the uppermost document S placed on a loading tray 22. The pickup roller 10 is located downstream of the pickup roller 10 and is connected to a separation roller 11 for separating the document S by a long plate-shaped connection plate. A pulley (not shown) is fixed to the roller shafts of the pickup roller 10 and the separation roller 11, and an endless belt (not shown) is stretched between the pulleys. For this reason, the pickup roller 10 is rotatable about the roller axis of the separation roller 11 by its own weight, and comes into contact with the uppermost document S placed on the placement tray 22 and is endlessly moved from the separation roller 11 side. The uppermost document S can be fed out by the rotational driving force supplied via the belt. A rubber separation pad 16 having frictional force is in contact with the bottom peripheral surface of the separation roller 11, and the separation pad 16 is urged upward (on the peripheral surface side of the separation roller 11) by a spring 17. The loading tray 22 is provided with an empty sensor (not shown) for detecting a state where a document is not loaded.
[0022]
The document transport unit 1 is configured to move the image reading unit 2 from the loading tray 22 to the discharge tray 3 having a gentle inclined surface formed integrally with the cover 3 a that covers the fixed document platen glass 73 of the image reading unit 2. It has a substantially U-shaped transport path that allows the transport of the document S within the installation area.
[0023]
As shown in FIG. 2, on the upstream and downstream sides of the moving reading platen glass 72 of the image reading unit 2, a conveying roller 12 and a conveying roller for conveying the original S toward the reading position on the moving reading platen glass 72 are respectively provided. A discharge roller 14 is provided to receive the document S transported at 12 and transport the document S toward the paper discharge tray 3.
[0024]
A guide plate 21 that guides (guides) the back side of the image recording surface of the document S to be conveyed while being curved on both sides is disposed between the conveyance roller 12 and the discharge roller 14. A cue sensor 80 for detecting the leading and trailing ends of the document S being transported is fixed near the transport roller 12 of the guide plate 21.
[0025]
The fixing position of the cue sensor 80 will be described in detail. The image sensor 53 is set at a position 400 lines before the reading position R for reading the image recording surface of the document S. As described above, since the reading density of the image sensor 53 in the document conveying direction is 400 dpi, the image sensor 53 is located one inch (25.4 mm) before the reading position R. Actually, since the fixing position varies due to an attachment error or the like, the number of offset lines is finely adjusted by a dip switch (not shown). Therefore, the value of the dip switch is set in the assembling process of the document transport unit 1, and the number of offset lines is determined.
[0026]
As shown in FIGS. 2 and 3, the transport roller 12 is fixed to the transport shaft 18, and a gear pulley 44 is fitted on one side of the transport shaft 18. A gear pulley (not shown) is fitted on the motor shaft of the transport motor 20 serving as a drive source of the transport roller 12, and a timing belt 43 is stretched between the gear pulley (not shown) and the gear pulley 44. A stepping motor is used as the transport motor 20, and one step is set so as to correspond to one line of document reading by the image sensor 53.
[0027]
An upstream roller 13 that is rotatable and driven by the transport roller 12 is in contact with the transport roller 12. The upstream roller 13 is supported by the upstream shaft 30 with a certain clearance. A lever-shaped upstream flapper 31 for supporting the image recording surface side of the document S to be conveyed is fixed to the upstream shaft 30, and a gear 42 is fitted on one side of the upstream shaft 30. The gear 42 is meshed with a gear 41 having a larger diameter than the gear 42, and the gear 41 is fitted to a motor shaft of a flapper drive motor 40 (stepping motor) that can rotate forward and reverse. Accordingly, as shown in FIG. 2, the upstream flapper 31 has a gap formed by the rotation driving force of the flapper drive motor 40 between the guide plate 21 and the tip of the upstream flapper 31 (hereinafter, referred to as a first gap). The gap (transport path) can be gradually changed between a position A where the first gap is the narrowest, and a position C where the tip is housed in the tip housing groove 75a of the image reading unit 2 and the first gap is the widest. Have been.
[0028]
On the other hand, the discharge roller 14 has a similar structure. That is, the discharge roller 14 is fixed to the discharge shaft 19. A timing belt is stretched between a gear pulley (not shown) fitted to the discharge shaft 19 and a gear pulley (not shown) fitted to the motor shaft of the transport motor 20, and the rotation from the transport motor 20 is performed. The driving force is also transmitted to the discharge roller 14. A downstream roller 15 that is rotatable following the discharge roller 14 is in contact with the discharge roller 14, and the downstream roller 15 is supported by the downstream shaft 32 with a certain clearance. A lever-shaped downstream flapper 33 that supports the image recording surface side of the conveyed document S in cooperation with the upstream flapper 31 is fixed to the downstream shaft 32. A gear pulley (not shown) is fitted to the downstream shaft 32 and the upstream shaft 30, and the rotational driving force of the flapper drive motor 40 is synchronized with the upstream shaft 30 by the timing belt stretched between the gear pulleys, and the downstream shaft 32. Is transmitted to. Like the upstream flapper 31, the downstream flapper 33 has a gap (hereinafter, referred to as a second gap) formed between the guide plate 21 and the distal end of the downstream flapper 33 by the rotational driving force of the flapper drive motor 40. The gap (conveyance path) can be gradually changed between a position B where the width becomes narrower and a position D where the front end portion is housed in the front end housing groove 75b of the image reading unit 2 and the second gap is the widest.
[0029]
As shown in FIG. 4, the document transport unit 1 includes a microcomputer 100 that controls the document transport unit 1. The microcomputer 100 is connected to a cue sensor 80, a driver 101 for driving the transport motor 20, and a driver 110 for driving the flapper drive motor 40. The drivers 101 and 110 are connected to the transport motor 20 and the flapper drive motor 40, respectively. ing. The microcomputer 100 is connected to the image reading device 2 via the ADF connector 102. In FIG. 4, a stepping motor for driving the separation roller 11 and the pickup roller 10 and its driver, an empty sensor disposed on the loading tray 22, and the like are omitted.
[0030]
The document reading device of the present embodiment can also place a document on the fixed document platen glass 73 and read the document in the same manner as a known document reading device, and can place a document on the fixed document platen glass 73. As described above, the document transport unit 1 is configured to be able to open and close (rotate) with respect to the image reading unit 2.
[0031]
(motion)
Next, the operation of the image reading apparatus of the present embodiment in the sheet through mode will be described.
[0032]
When the microcomputer 120 receives an instruction to read a document in the sheet-through mode from an external device via the communication IC 126, the microcomputer 120 turns on the illumination lamp 60, activates the image sensor 53 (see time A in FIG. 6), and illustrates the same. The first carriage 50 and the second carriage 51 are moved to the reading position R by driving the stepping motor which is not performed (the state of FIG. 1). Further, the microcomputer 120 notifies the microcomputer 100 that there is a read command. In this state, the distal ends of the upstream flapper 31 and the downstream flapper 33 are located at positions C and D, respectively, and are housed in the front end housing grooves 75a and 75b.
[0033]
The microcomputer 100 that has received the notification of the reading command from the microcomputer 120 determines whether or not a document is placed on the placing tray 22 based on the output from the empty sensor. When it is determined that the original is not placed, the microcomputer 120 is notified of the fact and stands by until the original is placed. The microcomputer 120 notifies the external device via the communication IC 126 that the document should be placed on the loading tray 22.
[0034]
On the other hand, when it is determined that a document is placed on the loading tray 22, the microcomputer 100 drives the stepping motor and the transport motor 20 that supply a rotational driving force to the separation roller 11. As a result, the document S placed on the uppermost portion of the loading tray 22 is fed out by the pickup roller 10 (for convenience, this time is referred to as “document feeding out”), and the frictional force between the separation roller 11 and the separation pad 16 causes the original S to be removed. The document S is conveyed downstream by the separation roller 11, and the leading end of the document S is nipped by the conveyance roller 12 and the upstream roller 13 (the state shown in FIG. 5A). The sheet is further transported downstream via the reading position R. In this state, the upstream flapper 31 and the downstream flapper 33 are retracted into the front end accommodation grooves 75a and 75b in the initial state, and the front end of the document S is conveyed on the upstream flapper 31.
[0035]
When the cueing sensor 80 detects the leading end of the document S, the microcomputer 100 sets the internal counter (see FIG. 6) to 0 and increments the internal counter by one each time the transport motor 20 rotates one step. 400, in other words, whether the leading edge of the document S has been conveyed to the reading position R is determined. If the determination is negative, the determination is continued. To inform.
[0036]
On the other hand, the microcomputer 120 that has received the reading start command causes the A / D converter 122 to start A / D conversion (time B in FIG. 6). Thus, the image sensor 53 of the image reading unit 1 reads the image recording surface of the document S. That is, the light emitted from the illumination lamp 60 or via the reflector 64 is reflected on the image recording surface of the document S at the reading position R, and is reflected by the first to third mirrors 61 to 63 via the casting platen glass 72. The optical path is changed, and the light is condensed by the lens unit 52 and enters the image sensor 53. The output from the image sensor 53 is sequentially converted by the A / D converter 122 by the number of pixel rows of the photoelectric conversion elements arranged in a line in the transport direction of the document S, and becomes one line of image data, with a line delay. The shading correction processing unit 123 performs density correction of one line in the main scanning direction. Further, image processing such as time difference correction is performed by the image processing IC 125, and output to an external device via the interface connector 56 by the communication IC 126. When the image sensor 53 reads one line, the conveyance of the document S by the conveyance motor 20 is also sent by one step (one line).
[0037]
Next, the microcomputer 100 determines whether the leading end of the document S has contacted the downstream flapper 33 by determining whether the value of the internal counter has reached 600. That is, the leading edge of the document S contacts the downstream flapper 33 at a position where the document S is transported by the transport motor 20 by 600 steps after the cueing sensor 80 detects the leading edge of the document S. When the determination is negative, the transport of the document S by the transport motor 20 is continued, and when the determination is affirmative, the flapper drive motor 40 is driven to rotate forward (time C in FIG. 6).
[0038]
By the forward rotation of the flapper drive motor 40, the leading ends of the upstream flapper 31 and the downstream flapper 33 located at the positions C and D are synchronously supported on the image recording surface side of the conveyed document S while the upstream shaft It gradually moves (rises) as the rotation of the shaft 30 and the downstream shaft 32 rotates, and reaches the positions A and B. The number of steps for transporting the document S by the transport motor 20 during this time is set to less than 200. That is, the microcomputer 100 determines whether or not the value of the internal counter has reached a predetermined value (for example, 570) of less than 600. If the determination is negative, the microcomputer 100 continues the normal rotation drive of the flapper drive motor 40, and makes an affirmative determination. At this time, the drive of the flapper drive motor 40 is stopped (time D in FIG. 6).
[0039]
As a result, the transport path of the document S formed by the first gap and the second gap becomes the narrowest state, and the document S is transported in the narrowed transport path thereafter. Note that when the internal counter is 800, the leading end of the document S transported by the transport roller 12 is set to abut on the discharge roller 14 or the downstream roller 15.
[0040]
Next, the microcomputer 100 determines that the value of the internal counter has increased by 400 from the time when the cue sensor 80 detects the trailing end of the document S (time E in FIG. 6) (time F in FIG. 6). ), The reading end command is notified to the microcomputer 120 assuming that the rear end of the document S by the transport motor 20 has reached the reading position R (time F in FIG. 6). The microcomputer 120 that has received the reading end command ends the A / D conversion by the A / D converter 122. In the image reading unit 1, the shading correction, the image processing, and the transmission of the image data to the external device are continued thereafter, and the reading of one document S is completed by the end of the transmission of the image data of the last line.
[0041]
When the rear end of the document S reaches the reading position R, there is no need to support the image recording surface of the document S, and the microcomputer 100 drives the flapper drive motor 40 in the reverse direction (time F in FIG. 6). The reverse drive of the flapper drive motor 40 is continued until a stop command is issued. The microcomputer 120 sends a stop command to the microcomputer 100 when the upstream flapper sensor 81 and the downstream flapper sensor 82 detect the leading ends of the upstream flapper 81 and the downstream flapper 33. Upon receiving the stop command, the microcomputer 100 stops the reverse drive of the flapper drive motor 40 (time G in FIG. 6).
[0042]
As shown in FIG. 6, in order to shorten the time until the next document is read, the reverse rotation driving time of the flapper driving motor 40 is shorter than the normal rotation driving time (the time FG between the time G and the time F is shorter than the time FG). The number of pulses per unit time of the driver 110 is set such that the rotation speed of the flapper drive motor 40 during the reverse rotation is higher than the rotation speed during the forward rotation, which is shorter than the time CD between D and the time C). Have been. For this reason, the upstream flapper 31 and the downstream flapper 33 descend in a shorter time than the time to ascend to the positions A and B, and are located at the positions C and D.
[0043]
The reading of the document S in the sheet-through mode is performed until the empty sensor detects that no document is present on the loading tray 22 or until a reading stop command is received from an external device. The process is continued for the next document placed on the loading tray 22.
[0044]
(Action, etc.)
Next, the operation of the document reading apparatus according to the present embodiment will be described.
[0045]
In the document reading apparatus according to the present embodiment, when the leading end of the document S comes into contact with the downstream flapper 33 (time C in FIG. 6), the leading end is moved into the leading end receiving grooves 75a and 75b by the driving force of the flapper driving motor 40. The contained upstream flapper 31 and the downstream flapper 33 (located at the positions C and D) gradually move to the positions A and B in synchronization with each other. Since the first gap and the second gap are open and wide until the leading end of the document S contacts the downstream flapper 33, buckling of the document S due to contact with the downstream flapper 33 can be prevented. . In addition, the upstream flapper 31 and the downstream flapper 33 simultaneously and gradually ascend, and support the image recording surface side of the document S at the substantially same height position (substantially horizontally) from the platen glass 72 for reading. S is stably conveyed between the back platen 21 and the influence (shock) of the document S caused by the rise of the upstream flapper 31 and the downstream flapper 33 can be reduced. Even if the rear end of the document S passes the grip position between the transport roller 12 and the upstream roller 13, the document S is supported by the upstream flapper 31, so that stable transport is continued to the reading position R. Further, the document S comes into contact with the discharge roller 14 or the downstream roller 15 with the upstream flapper 31 and the downstream flapper 33 located at the positions A and B and the conveyance path narrowed. Therefore, the impact generated there is absorbed by the second gap narrowed by the downstream flapper 33 at the position B, and the influence on the document S is attenuated. Similarly, an impact generated when the rear end of the document S separates from the grip between the transport roller 12 and the upstream roller 13 is also absorbed by the first gap narrowed by the upstream flapper 31 at the position A, and Effect is attenuated. Therefore, in the image reading apparatus of the present embodiment, the configuration is such that the impact is not applied to the conveyed document S. Therefore, even if the image sensor 53 reads the image recording surface of the document S at the reading position R, the image distortion or The occurrence of color shift can be prevented.
[0046]
In the present embodiment, an example is shown in which the upstream flapper 31 and the downstream flapper 33 are disposed on both sides of the sink reading platen glass 72. For example, a configuration having only the upstream flapper 31 without the downstream flapper 33 is adopted. You may make it.
[0047]
In the present embodiment, an example is shown in which the document transport unit 1 and the image reading unit 2 are configured separately, but if only reading in the sheet-through mode is performed without reading a fixed document, the document The fixed platen 221 is not required, and the projection area of the entire document reading apparatus can be made considerably small, and can be integrated with one another except for the cancellation of the conveyance failure.
[0048]
Further, in the present embodiment, an example has been described in which the transport roller 12 and the discharge roller 14 are rotated synchronously by one transport motor 20, but they may be rotated by independent (two) motors. In this way, the original S can be intentionally slackened or stretched, so that the impact applied to the original S can be further reduced.
[0049]
Furthermore, in the present embodiment, an example has been described in which the leading edge position of the document S is detected by the cueing sensor 80 and the number of steps (pulses) of the transport motor 20 is counted, but the transporting distance from the position of the cueing sensor 80 is long. In this case, for example, as shown in FIG. 2, a discharge sensor 83 for detecting the leading end of the document S may be fixed to the guide roller 21 on the discharge roller 14 side. In this way, the impact caused by the contact between the document S and the discharge roller 14 or the downstream roller 15 caused by a slight difference between the distance that the document S is transported and the number of counted steps is reliably eliminated. be able to. Also, if the transport path is narrowed too quickly, the transport of the document S becomes large, and the document S may be loosened before the downstream flapper 33. For this reason, until the discharge sensor 83 detects the leading edge of the document S and the nip is performed by the conveyance of the predetermined number of pulses, the path changes slightly before the minimum path interval, and the minimum path width is adjusted in accordance with the arrival at the nip position. The downstream flapper 33 may be controlled to be at the position B.
[0050]
Further, in the present embodiment, the example in which the upstream flapper 31 and the downstream flapper 33 are raised in synchronization with each other to support the document S has been described. However, as shown in FIG. You may do so. In this way, it is possible to reliably prevent the leading end of the document S from contacting or slidingly contacting the scanning platen glass 72, so that there is an advantage that an impact that can potentially be applied to the document S can be eliminated. Have.
[0051]
In the present embodiment, the lever-shaped upstream flapper 31 and the downstream flapper 32 are exemplified. However, as shown in FIGS. 7 and 8, rotatable rollers 35 and 36 are provided at the tips of the upstream flapper 31 and the downstream flapper 32. It may be provided. In this way, the impact and friction when the document S comes into contact with the upstream flapper 31 and the downstream flapper 32 can be further reduced, and damage to the image recording surface can be prevented. In this case, as shown in FIG. 7, it is preferable that the shape of the distal end accommodation grooves 75a and 75b be arc-shaped.
[0052]
Furthermore, in the present embodiment, an example is shown in which the upstream flapper sensor 81 and the downstream flapper sensor 83 are provided on the image reading unit 2 side. However, for example, an encoder is disposed on the upstream shaft 30 or the motor shaft of the flapper drive motor 40. Alternatively, the positions of the upstream flapper sensor 81 and the downstream flapper sensor 83 may be grasped on the document transport unit 1 side.
[0053]
Further, in the present embodiment, an example has been described in which the contact point at the nip point between the discharge roller 14 and the downstream roller 32 is predicted based on the count from the cue sensor 80. Is performed gently, so there is no impact on the image. However, when the document S rises, the height position of the image recording surface changes, and a change in the magnification of the image caused by a change in the focal position occurs. I do. For example, if the height change is 1 mm and the path length of the optical system is 500 mm, the change rate is only 0.2%, and if the above-described displacement is performed over 30 mm in the length of the document S, In an image reading apparatus in which this magnification change cannot be tolerated by almost no eyes, as shown in FIG. 1, the lens unit 52 inserted in the light beam can be changed in focus position by an actuator such as a piezo element. You may make it. That is, a negative magnification change may be given to the lens unit 52 in accordance with the magnification change by the upstream flapper 31 and the downstream flapper 33. Such a change in magnification can be eliminated by correcting the position of the lens unit 52 to an optimum position by the actuator 77.
[0054]
In the present embodiment, the document is passed from the upstream transport roller 12 and the upstream roller 13 to the reading position R on the flow-reading platen glass 72, and is transferred to the downstream discharge roller 14 and the downstream roller 15 in one direction. However, the present invention is not limited to this. For example, first, it is determined whether or not the original includes a color image by passing the reading position R on the platen glass 72 from the transport roller 12 and after the completion of this determination, the transport roller 12 and the discharge roller 14 are moved. The present invention is also applicable to an image reading apparatus that reverses and reads a document according to the result of color discrimination of the document.
[0055]
An example of application to such an image reading apparatus will be described in detail. In the first color discrimination feed, the upstream flapper 31 and the downstream flapper 33 are positioned (downward) at the positions C and D in FIG. The upstream flapper 31 is positioned at the position A in FIG. 2 before the end is separated from the transport roller 12. Thereby, it is possible to determine the color without any image blurring. After passing through the reading position R, the conveying roller 12 and the discharge roller 14 are rotated in reverse to execute image reading according to the color determination result. At this time, the upstream flapper 31 is quickly retracted downward. Thereafter, a document returning operation is performed. At this time, since the document is not read, the downstream flapper 33 does not move downward even when the document separates from the discharge roller 14. When the return operation is completed, the transport roller 12 and the discharge roller 14 are again rotated reversely, and the original is transported in the original reading direction in the same direction as the original. At this time, if the original is a color document, by raising the upstream flapper 31 before the original separates from the transport roller 12, fluttering of the rear end of the original when the original is separated from the transport roller 12 is suppressed, It is possible to prevent blurring of a document read image and color shift of a color image. Further, when the downstream flapper 33 moves upward, the vertical movement of the document before and after the reading position R is suppressed, so that a more appropriate image can be obtained. As described above, if the upstream flapper 31 and the downstream flapper 33 are moved in accordance with the timing of document conveyance and image reading, more appropriate images can be acquired by various image reading devices.
[0056]
【The invention's effect】
As described above, according to the present invention, the drive unit allows the gap formed between the first support unit and the back guide to be changed, and by narrowing this gap, the document can be moved by the first support unit. Since the document is supported from the image recording surface side, the impact on the document when the trailing edge of the document separates from the first transport unit is suppressed, and image distortion of image data read by the reading unit can be prevented. In addition, it is possible to obtain an effect that color misregistration can be prevented when reading a color original.
[Brief description of the drawings]
FIG. 1 is a schematic front sectional view of an embodiment of an image reading apparatus to which the present invention can be applied.
FIG. 2 is a front cross-sectional view of the vicinity of a platen glass plate of the image reading apparatus according to the embodiment;
FIG. 3 is a plan view near a conveyance roller of the image reading unit according to the embodiment.
FIG. 4 is a schematic block circuit diagram of the image reading apparatus of the embodiment.
FIGS. 5A and 5B are explanatory diagrams of the state of the upstream and downstream flapper, and FIG. 5A illustrates the state of the upstream and downstream flapper of the image reading apparatus of the embodiment when the document S is nipped by the conveyance roller and the upstream roller; (B) shows the state of the upstream and downstream flapper of the image reading apparatus of the embodiment when the document S is nipped by the discharge roller and the downstream roller, and (C) shows the upstream and downstream flapper of the image reading apparatus of another embodiment. The state of is shown.
FIG. 6 is a timing chart illustrating operation timings of main components of the image reading apparatus according to the embodiment.
FIG. 7 is a front cross-sectional view of the vicinity of a scanning platen glass of an image reading apparatus according to another embodiment to which the present invention can be applied.
FIG. 8 is a plan view near a conveyance roller of an image reading unit according to another embodiment.
[Explanation of symbols]
1 Document transport unit (document transport device)
2 Document reading unit (image reading device)
12 Transport rollers (part of the first transport unit)
14. Discharge roller (part of the second transport unit)
21 Guide plate (back platen)
31 upstream flapper (part of support means, first support means)
33 Downstream flapper (part of support means, second support means)
35, 36 Coro
40 Flapper drive motor (part of drive means)
53 line sensor (part of reading means)
72 Reading platen glass (transparent for reading)
75a, 75b Tip accommodation groove (evacuation part)
80 Cueing sensor (rear end detection sensor)
R reading position

Claims (13)

In a document transport device that is mounted on an image reading device having a reading unit that reads an image recording surface of a document at a predetermined reading position and transports a document to be read,
First transport means for transporting the original placed on the tray to the reading position;
A second transport unit that receives the document transported by the first transport unit and transports the document further downstream;
A back guide for guiding the document, the back guide being disposed between the first and second conveyance means and arranged on the back side of the document to be conveyed;
First support means disposed between the first transport means and the reading position so as to face the back guide, and supporting the document from the image recording surface side;
Driving means for driving the first support means so as to change a gap formed between the first support means and the back guide;
Document feeder provided with 2. The document feeder according to claim 1, wherein the drive unit drives the first support unit so as to gradually change the gap as the document is conveyed. 3. 3. The document according to claim 2, wherein the driving unit moves the first support unit to a predetermined position where the gap is narrowed until the rear end of the document separates from the first transport unit. Transport device. 2. The image forming apparatus according to claim 1, further comprising a second support unit disposed between the reading position and the second transport unit so as to face the back guide, and supporting the document from an image recording surface side. Document transport device according to the above. The driving means gradually changes a first gap formed between the back guide and the first support means and a second gap formed between the back guide and the second support means. 5. The document reading apparatus according to claim 4, wherein the first and second support means are driven so as to perform the operation. The driving unit is configured to at least support the first support so that the second gap is larger than the first gap before the leading end of the document conveyed by the first conveyance unit reaches the second support unit. 6. The document feeding device according to claim 5, wherein the driving unit drives the unit. The driving means drives the second support means so as to narrow the second gap after the leading end of the document conveyed by the first conveyance means reaches the second support means. The document feeder according to claim 5. The driving unit drives the second support unit before the leading end of the document conveyed by the first conveyance unit reaches the second conveyance unit to narrow the second gap. The document feeder according to claim 5. An upstream end of the reading position further includes a trailing edge detection sensor that detects a trailing edge of the document in the transport direction, and the driving unit detects the first edge after the trailing edge sensor detects the trailing edge of the document in the transport direction. 9. The document feeder according to claim 8, wherein the first and second support units are driven so as to widen the gap between the first and second sections. 10. 10. The document feeder according to claim 8, wherein the drive unit drives the first and second support units at synchronized timing. 2. The document feeder according to claim 1, wherein the first support means has a rotatable roller at a position where the document comes into contact with an image recording surface. An image reading apparatus having reading means for reading an image recording surface of a document at a predetermined reading position via a transparent body,
First transport means for transporting the original placed on the tray to the reading position;
A second transport unit that receives the document transported by the first transport unit and transports the document further downstream;
A back guide for guiding the document, the back guide being disposed between the first and second conveyance means and arranged on the back side of the document to be conveyed;
Support means arranged on the upstream side of the transparent body so as to face the back guide, and supporting the document from the image recording surface side,
Driving means for driving the support means to change a gap formed between the support means and the back guide,
An image reading device comprising: The supporting means is in the form of a lever, and a gap formed between the lever tip of the supporting means and the back guide is equal to or larger than a gap formed between the transparent body and the back guide. 13. The image reading apparatus according to claim 12, further comprising a retractable portion near the transparent body, the retractable portion permitting retreat of a lever tip of the support means.

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