JP2013224199A - Automatic document conveying device and image reading device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a proper amount of loop to be held between a registering means and a pre-reading conveying means regardless of a document size or the like without causing upsizing of a device, and to prevent color deviation of a read image consequently, in an automatic document conveying device.SOLUTION: An automatic document conveying device includes: a paper feed tray 11 on which a plurality of sheets of documents can be placed; feeding means 16, 17 for separating the document stacked on the paper feed tray 11 by one sheet and feeding it; a document detection means SE11 disposed on a downstream side of the feeding means 16, 17 and detecting the fed document; registration conveying means 21 disposed on a downstream side of the document detection means SE11, for registering the fed document and then conveying it; a pre-reading conveying means 22 disposed on a downstream side of the registration conveying means 21 and conveying the fed document further to a position Y of reading by an image reading means 2; and a control means 50 for changing a document conveying speed by the registration conveying means 21 to a plurality of speeds based on signals from the document detection means SE11, SE13 when documents of a plurality of sizes are mixedly placed on the paper feed tray 11.

Description

  The present invention relates to an automatic document feeder, and more particularly, to an automatic document feeder mounted on an image reading device that optically reads a document image, and an image reading device equipped with the device.

  In general, in an image reading apparatus that optically reads a document image, a platen method that reads an image of a document placed on a platen glass with an optical system that moves in one direction, and a reading of a stationary optical system. The position is roughly divided into a sheet-through method in which the document is read while moving the document in one direction. The sheet-through method has an advantage that the reading workability is better (the reading productivity is high) than the platen method, and is mounted on an image forming apparatus such as a copying machine.

  In the sheet-through method, the image reading means is stationary at a fixed position and focuses on the surface of the document conveyed through the reading glass, so that the document conveyance speed at the image reading position is stable. It is important to let In particular, when reading in color, if the document conveyance speed slightly deviates from a predetermined speed, a correction occurs between the RGB pixels, which causes a color shift in the read image. Even a slight amount of color misregistration degrades the image quality. The shift in speed also causes a misjudgment of monochrome / color, and consumes color toner meaninglessly, which is also a cause of discomfort to the user.

  On the other hand, paper feeding performance is a factor that affects user satisfaction. In particular, as the reading speed increases, the frequency of double feeds tends to increase during paper feeding, and there is a tendency to increase the load for turning the originals one by one with high torque to ensure the performance. However, an increase in the winding load torque increases the impact when the trailing edge of the document passes through the nip portion between the paper feed roller and the separation roller, causing fluctuations in the document conveyance speed and thus color misregistration. .

  For this reason, in the conventional automatic document feeder, a loop (sag) is formed on a document fed between a registration roller arranged immediately after the paper feeding roller and a pre-reading conveyance roller arranged just before the reading position. This is dealt with by absorbing the load fluctuation (impact through the nip portion between the paper feed roller and the separating roller) on the upstream side with the slack of the original (see Patent Document 1). However, if the speed of document transport is increased and a large paper load is set, there will be a large difference in the amount of document slip between when the document is held in the paper feed unit (paper unit) and after the document has been removed. A large difference is generated in the conveyance amount of the registration rollers. Due to the difference in the transport amount, the smaller the document size, the larger the loop, and the larger the size, the smaller the loop. As described above, when the loop (sag) is excessive / small, the original is rubbed against the guide plate, and the conveyance speed at the reading position is changed, resulting in color shift in the read image.

  On the other hand, in the automatic document feeder described in Patent Document 2, by setting the distance between the reading position and the scanning portion to be longer than the length of the document, the trailing edge of the document already passes through the scanning portion before starting reading. It is composed. However, this has a problem that the apparatus becomes large.

JP 2001-146337 A JP-A-8-272006

  The object of the present invention is to prevent an increase in the size of the apparatus, and to maintain an appropriate amount of loop between the registration means and the pre-reading conveying means regardless of the size of the original, and thus to prevent color misregistration of the read image. It is an object of the present invention to provide an automatic document feeder and an image reading device that can be prevented.

An automatic document feeder according to a first aspect of the present invention is:
A paper feed tray on which multiple documents can be placed;
A feeding means for separating and feeding the documents stacked on the sheet feeding tray one by one;
A document detecting means arranged on the downstream side of the feeding means for detecting a fed document;
A registration conveying means disposed downstream of the original detection means for registering and conveying the fed original;
A pre-reading conveyance unit that is arranged on the downstream side of the registration conveyance unit and further conveys the fed document to a reading position by the image reading unit;
Control means for changing the document conveying speed by the resist conveying means to a plurality of speeds based on a signal from the document detecting means when a plurality of sizes of documents are mixedly loaded on the paper feed tray;
It is provided with.

An automatic document feeder according to a second aspect of the present invention is:
A paper feed tray on which multiple documents can be placed;
A feeding means for separating and feeding the documents stacked on the sheet feeding tray one by one;
A document detecting means arranged on the downstream side of the feeding means for detecting a fed document;
A registration conveying means disposed downstream of the original detection means for registering and conveying the fed original;
A pre-reading conveyance unit that is arranged on the downstream side of the registration conveyance unit and further conveys the fed document to a reading position by the image reading unit;
Control means for changing a document transport speed by the resist transport means to a plurality of speeds based on a signal from the document detection means when an irregular-size document is placed on the paper feed tray;
It is provided with.

  An image reading apparatus according to a third aspect of the present invention includes the automatic document feeder according to the first or second aspect.

  In the automatic document feeders according to the first and second embodiments, when a plurality of sizes of documents are mixedly loaded on the sheet feed tray, or when an indeterminate size document is placed, that is, a sheet feed Even if the size of the document to be printed cannot be determined, it is determined whether or not the trailing edge of the fed document has passed through the sheet feeding unit based on the signal from the document detection unit. By changing the conveyance speed of the registration conveyance means based on the signal from the original detection means, the original fed between the registration conveyance means and the pre-read conveyance means regardless of the length of the original conveyance direction. Keep the loop formed in the proper amount. Thereby, the fluctuation | variation of the conveyance speed in a reading position is suppressed as much as possible.

  According to the present invention, it is possible to hold an appropriate amount of loop between the registration unit and the pre-reading conveyance unit regardless of the size of the original, and the variation in the conveyance speed at the reading position is suppressed as much as possible. Can be prevented. In addition, the size of the apparatus is not increased.

1 is a schematic configuration diagram illustrating an image reading apparatus including a document conveying device according to an embodiment. FIG. 6 is a flowchart showing a control procedure in a normal conveyance mode in the document conveying apparatus. FIG. 10 is a chart showing the amount of document loop that occurs during conveyance in the normal conveyance mode. FIG. 10 is a flowchart illustrating a first control procedure in a mixed document conveyance mode. FIG. 6 is a chart showing a change in loop amount in a mixed document conveyance mode. FIG. 10 is a flowchart illustrating a second control procedure in the mixed document conveyance mode. FIG. 10 is a flowchart showing a third control procedure in the mixed document conveyance mode.

  Embodiments of an automatic document feeder and an image reading apparatus according to the present invention will be described below with reference to the accompanying drawings.

  First, an image reading apparatus 1 equipped with an automatic document feeder 10 will be described with reference to FIG. This image reading apparatus 1 includes a close contact type reading optical system 2, and an image of a document placed on the platen glass 5 is read by the reading optical system 2 on the guide member 3 directly below the platen glass 5 in the direction of arrow X. Read by moving to. A reading optical system in which the documents placed on the sheet feeding tray 11 of the automatic document feeder 10 are automatically fed and conveyed one by one, and the image is stationary at the reading position Y through the reading glass 6. Read by 2. The configuration and operation of the contact-type reading optical system 2 are well known in the art and will not be described.

  The automatic document feeder 10 includes a paper feed tray 11, a pickup roller 15, a paper feed means comprising a paper feed roller 16 and a separating roller 17, a registration roller 21 comprising a pair of rollers, a pre-reading roller 22, and a post-reading. The roller 23, the discharge roller 24, and the discharge tray 19 are configured. Further, guide plates 31 to 38 for guiding the conveyance of the document are arranged. Further, the image reading apparatus 1 includes a control unit (CPU) 50, and the control unit (CPU) 50 also controls the operation of the automatic document feeder 10.

  A plurality of originals are placed on the paper feed tray 11 with the first surface facing upward and with the front end and both sides restricted by a front end restricting plate and a side restricting plate 12 (not shown). At this time, the size of the document is detected by the size detection sensors SE1, SE2, SE3. In this embodiment, A5 vertical size or smaller, a size exceeding A5 vertical size and A4 vertical size or smaller, and a size exceeding A4 vertical size are detected. Note that “vertical size” refers to the case where the long side of the document is placed parallel to the transport direction, and “horizontal size” refers to the case where the short side of the document is placed parallel to the transport direction. The size exceeding the A4 vertical size usually means the A3 vertical size.

  However, when a plurality of sizes of originals are mixedly loaded, only the maximum size is detected, and if it is an irregular size, the size cannot be detected appropriately. Therefore, when different size originals are mixedly loaded (hereinafter referred to as a mixed original transport mode) and when an irregular size original is placed (hereinafter referred to as an irregular size original transport mode), the sensor SE1. , SE2 and SE3 are canceled, and the user separately inputs from the operation panel (not shown) that the mixed document transport mode or the unfixed size document transport mode is selected. Hereinafter, when referring to the mixed document transport mode, in principle, an irregular size document transport mode is also included.

  The conveyance of the original is started from the uppermost original. The original is first picked up by the pick-up roller 15, and is fed into one sheet by a rotation of the paper feed roller 16 at a nip portion with the separation roller 17 (hereinafter referred to as a separation nip portion). The winding roller 17 incorporates a torque limiter having a predetermined value and prevents double feed. This configuration is well known in the art. Thereafter, the document is conveyed to the registration roller 21. The registration roller 21 is in a rotation stopped state at the beginning of the paper feeding operation. When the leading edge of the fed document hits the nip portion of the registration roller 21, the leading edge portion of the document is curved and skew is corrected. When the leading edge of the document is curved (when a predetermined time has elapsed after the document is fed), the registration roller 21 is driven to rotate and the document is conveyed to the pre-reading roller 22. The pre-reading roller 22 is rotationally driven at a predetermined conveyance speed corresponding to the reading magnification. The registration roller 21 is rotationally driven at a conveyance speed that causes a predetermined loop (slack) in the document through a conveyance path 40 between the pre-reading roller 22 and the registration roller 21, and the mixed document conveyance is performed as described in detail below. In mode, it is changed to multiple speeds.

  Further, the original is conveyed on the reading glass 6 by the roller 22 before reading, and an image (image on the first surface) is read by the optical system 2 at the reading position Y. Thereafter, the document is discharged to the discharge tray 19 by the roller 23 and the discharge roller 24 after reading. When reading the image on the second surface, the document is switched back by the discharge roller 24 and conveyed again to the registration roller 21 through the guide plates 37 and 38. When reading the second surface, the sheet is conveyed in the same manner as the reading of the first surface.

  Here, a control procedure in a normal document transport mode (meaning a case of transporting documents of the same size) will be described with reference to FIG. That is, the size of the document placed on the paper feed tray 11 is detected, the registration roller 21 is set to a predetermined transport speed according to the detected document size, and the fed document is transported.

  First, the size of the document is detected by the sensors SE1, SE2, SE3 (step S1). If the document size is A5 vertical size or less (YES in step S2), the registration roller 21 transports the document of A5 vertical size or less. (Step S3). If it exceeds A5 vertical size and is A4 vertical size or less (YES in step S4), the registration roller 21 is set to a speed b for conveying a document that exceeds A5 vertical size and is A4 vertical size or less (step S5). If it exceeds the A4 vertical size (NO in step S4), the registration roller 21 is set to a speed c for conveying a document exceeding the A4 vertical size (step S6). Thereafter, the document feeding operation is started (step S7).

  The loop amount formed in the conveyance path 40 between the registration roller 21 and the pre-reading roller 22 in this normal conveyance mode will be described with reference to FIG. When the document to be transported is A5 vertical size, the document is transported along the transport path 40 at the speed a, the loop amount indicated by the line segment A1 is formed until the trailing edge of the document passes through the nip portion, and the trailing edge of the document is rolled. A loop amount indicated by a line segment A2 is formed until the registration roller 21 is passed after passing through the nip portion. When the document to be conveyed is A4 vertical size, the document is conveyed along the conveyance path 40 at the speed b, and the loop amount indicated by the line segment B1 is formed until the trailing edge of the document passes through the nip portion, and the trailing edge of the document is rolled. A loop amount indicated by a line segment B2 is formed after the nip portion passes through the registration roller 21. When the document to be conveyed is A3 vertical size, the document is conveyed along the conveyance path 40 at the speed c, the loop amount indicated by the line segment C1 is formed until the trailing edge of the document passes through the nip portion, and the trailing edge of the document is rolled. A loop amount indicated by a line segment C2 is formed after the nip portion passes through the registration roller 21 until it passes through the registration roller 21.

  In the above normal conveyance mode, the conveyance speeds a, b, c (a <b <c) of the registration rollers 21 are set so that the loop amount formed in any size of the document is within the range of the region R. ) Is set, and if the loop amount is within this region R, the document will not be rubbed against the guide plates 33, 34. However, even when A5 vertical size or A4 vertical size originals are mixed in an A3 vertical size document, if the normal conveyance mode is executed, the speed of the registration roller 21 is set to a speed c corresponding to the A3 vertical size. Is done. For this reason, the A5 vertical size document is formed with a loop amount indicated by the line segment A3 after its trailing edge is rolled and passes through the nip portion. In addition, the A4 vertical size document has a trailing end and a loop amount indicated by a line segment B3 is formed after passing through the nip portion. The loop amount in the line segments A3 and B3 exceeds the appropriate region R, and the original is rubbed against the guide plates 33 and 34, thereby causing fluctuations in the conveyance speed at the reading position Y.

  Therefore, the automatic document feeder 10 executes the first control procedure shown in FIG. 4 in the mixed document conveyance mode. The fact that originals of different sizes are mixedly loaded on the paper feed tray 11 is identified when the user inputs that fact on an operation panel (not shown). Further, the automatic document feeder 10 is provided with sensors SE11 to SE14 for detecting the passage of the document. The size of the document is determined by turning on / off the sensor SE11 and the sensor SE13 before reading. ON of the sensors SE11 to SE14 indicates a state where a document is detected, and OFF indicates a state where a document is not detected.

  The transport path length between the sensors SE11 and SE13 is set slightly longer than the A5 vertical size length and shorter than the A4 vertical size length. That is, the sensors SE11 and SE13 are both turned off when a document of A5 vertical size or smaller is on the transport path 40, and the sensor SE13 is turned on when a document exceeding A5 vertical size and smaller than A4 vertical size is on the transport path 40, sensor SE11. Is turned off, and the sensors SE11 and SE13 are both turned on when a document exceeding the A4 vertical size is in the transport path 40. When a document of A3 vertical size or larger is conveyed, both the post-read sensor SE14 and the post-scan sensor SE11 are turned on.

  In the mixed document conveyance mode, first, the registration roller 21 is set to a speed a for conveying a document of A5 vertical size or less (step S11), and a paper feeding operation is started (step S12). If the leading edge of the fed document is detected by the sensor SE11 after scanning (sensor SE11 is on, YES in step S13), and if both the sensor SE11 after scanning and the sensor SE13 before reading are both off (the leading edge of the document is If the trailing edge has passed the sensor SE11 without reaching the sensor SE13, YES in step S14), the document size is A5 vertical size or less, so the speed of the registration roller 21 is left as it is (A5 vertical size or less). Document transport speed a) The transport operation is continued (step S15).

  If the pre-reading sensor SE13 is ON and the post-scanning sensor SE11 is OFF (when the leading edge of the document reaches the sensor SE13 and the trailing edge passes the sensor SE11, YES in step S16), the size of the document is A5 vertical size. Therefore, the speed of the registration roller 21 is changed to the document conveying speed b exceeding the A5 vertical size and below the A4 vertical size (step S17), and the conveying operation is continued (step S18). If sensors SE11 and SE13 are both on (if the leading edge of the document has reached sensor SE13 and the trailing edge has not yet passed through sensor SE11, YES in step S19), the size of the document exceeds the A4 vertical size. Therefore, the speed of the registration roller 21 is changed to the document transport speed c exceeding the A4 vertical size (step S20), and the transport operation is continued (step S21).

  In the first control procedure, the loop amount formed in the conveyance path 40 between the registration roller 21 and the pre-reading roller 22 will be described with reference to FIG. When the original to be conveyed is A5 vertical size, the original is conveyed along the conveyance path 40 at the speed a, and the loop amount indicated by the line segment A1 is formed until the rear end of the original passes through the nip portion, and the rear end of the original is formed. The loop amount indicated by the line segment A2 is formed until the roller passes through the nip portion and passes through the registration roller 21. When the document to be conveyed is A4 vertical size, the document is first conveyed on the conveyance path 40 at the speed a, changed to the speed b after the trailing edge of the document passes through the nip portion, and the trailing edge of the document turns to the nip portion. A loop amount indicated by a line segment B2 is formed until the registration roller 21 is exited after exiting. When the document to be conveyed is A3 vertical size, the document is first conveyed on the conveyance path 40 at the speed a, changed to the speed c after the leading edge of the document is detected by the sensor SE13 before reading, and the trailing edge of the document is turned to the nip nip. A loop amount indicated by a line segment C2 is formed until the registration roller 21 is exited after exiting the portion.

  In FIG. 5, the loop amount indicated by the dotted line is that in the normal conveyance mode. In the first control procedure of the mixed document conveyance mode, the maximum value of the loop amount is within the region R, as is clear when compared with the loop amount in the normal conveyance mode. In this case, the document is not rubbed against the guide plates 33 and 34.

  FIG. 6 shows a second control procedure in the mixed document conveyance mode. This second control procedure assumes that the document placed on the paper feed tray 11 includes a document having a size exceeding the A3 vertical size. In other words, the second control procedure corresponds to an irregular-size document transport mode. It can be said. The processing in steps S11 to S21 is the same as in the first control procedure (see FIG. 4). When the sensor SE11 after turning is on and the sensor SE14 is on after reading (the leading edge of the document reaches the sensor SE14, If the trailing edge has not yet passed through the sensor SE11 (YES in step S22), since the document size exceeds the A3 vertical size, the speed of the registration roller 21 is changed to a document conveyance speed d exceeding the A3 vertical size ( Step S23), the carrying operation is continued (step S24). The speed d is larger than the speed c. As a result, the loop amount can be stored in the region R even for an irregular document exceeding the A3 vertical size.

  Next, a third control procedure in the mixed document conveyance mode will be described with reference to FIG. In the third control procedure, after the leading edge of the fed document is detected by the sensor SE11, the time is counted by a timer built in the control means (CPU) 50, thereby the size (length) of the document. ), That is, based on the signal from the sensor SE11, the conveyance speed by the registration roller 21 is changed to a speed corresponding to the document length, and the loop amount is controlled to fall within a predetermined region R.

  Specifically, after the paper feeding operation is started, the registration roller 21 is driven to rotate at the speed a (step S31), and when T1 seconds have passed since the leading edge of the original is detected by the sensor SE11 after being turned (in step S32). If the sensor SE11 is turned off (NO in step S33), the document is A5 vertical size or smaller in this case, and the registration roller 21 is driven at the speed a as it is. If sensor SE11 is turned on after T1 seconds have elapsed (YES in step S33), the document exceeds the A5 vertical size, so registration roller 21 is changed to speed b (step S34).

  Thereafter, when T2 seconds elapse (YES in step S35), if the sensor SE11 after turning is turned off (NO in step S36), in this case, the document exceeds the A5 vertical size and is not larger than the A4 vertical size. Therefore, the registration roller 21 is driven at the speed b. If the sensor SE11 is turned on after T2 seconds have elapsed (YES in step S36), the document exceeds the A4 vertical size, so the registration roller 21 is changed to the speed c (step S37). Thereafter, when T3 seconds have elapsed (YES in step S38), the process waits for the sensor SE11 to turn off after turning (NO in step S39), and the process here ends. That is, if the document exceeds the A4 vertical size, the registration roller 21 is driven at the speed c.

  The automatic document feeder and the image reading device according to the present invention are not limited to the above-described embodiments, and can be variously modified within the scope of the gist thereof.

  In particular, various configurations of various rollers and guide members for feeding and conveying a document are arbitrary. The image reading apparatus may or may not use a platen method. The configuration of the reading optical system is also arbitrary.

  As described above, the present invention is useful for an automatic document conveyance device and an image reading device, and in particular, can maintain an appropriate amount of loop between the registration unit and the pre-read conveyance unit regardless of the size of the document. Are better.

DESCRIPTION OF SYMBOLS 1 ... Image reading apparatus 10 ... Automatic document conveying apparatus 11 ... Paper feed tray 16 ... Paper feed roller 17 ... Paper feed roller 21 ... Registration roller 22 ... Roller before reading 50 ... Control part (CPU)
SE11: Sensor after firing SE13: Sensor before reading Y: Reading position

Claims (7)

A paper feed tray on which multiple documents can be placed;
A feeding means for separating and feeding the documents stacked on the sheet feeding tray one by one;
A document detecting means arranged on the downstream side of the feeding means for detecting a fed document;
A registration conveying means disposed downstream of the original detection means for registering and conveying the fed original;
A pre-reading conveyance unit that is arranged on the downstream side of the registration conveyance unit and further conveys the fed document to a reading position by the image reading unit;
Control means for changing the document conveying speed by the resist conveying means to a plurality of speeds based on a signal from the document detecting means when a plurality of sizes of documents are mixedly loaded on the paper feed tray;
An automatic document feeder characterized by comprising: A paper feed tray on which multiple documents can be placed;
A feeding means for separating and feeding the documents stacked on the sheet feeding tray one by one;
A document detecting means arranged on the downstream side of the feeding means for detecting a fed document;
A registration conveying means disposed downstream of the original detection means for registering and conveying the fed original;
A pre-reading conveyance unit that is arranged on the downstream side of the registration conveyance unit and further conveys the fed document to a reading position by the image reading unit;
Control means for changing the document transport speed by the resist transport means to a plurality of speeds based on a signal from the document detection means when an irregular-size document is placed on the paper feed tray;
An automatic document feeder characterized by comprising:   The control unit determines a length of a fed document in a conveyance direction based on a signal from the document detection unit, and increases a document conveyance speed by the registration conveyance unit as the conveyance direction length increases; The automatic document feeder according to claim 1 or 2, characterized in that: In addition to the original detection means arranged on the downstream side of the feeding means, another original detection means arranged on the downstream side of the registration conveying means,
The control means discriminates the transport direction length of the fed document based on the signals from the two document detection means;
The automatic document feeder according to any one of claims 1 to 3, wherein   4. The control unit according to claim 1, wherein the control unit determines a length in a conveyance direction of the fed document from a signal from the document detection unit and a count signal of a timer. The automatic document feeder described.   When a plurality of sizes of originals are mixedly loaded on the paper feed tray, or when an irregular-size original is mixedly loaded, the control means feeds the original transport speed by the resist transport means. The first speed is set until the trailing edge of the document exits the paper feeding means, and the second speed is set to be higher than the first speed after the trailing edge of the fed document exits the paper feeding means. 6. An automatic document feeder according to claim 1, wherein the automatic document feeder is set.   An image reading apparatus comprising the automatic document feeder according to any one of claims 1 to 6.

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