JP2013184748A - Sheet carrying device, image reader and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet carrying device capable of surely preventing a slipping-out shock even when carrying a sheet of an unrecognizable size.SOLUTION: A sheet carrying device 1 includes a pair of first carrier rollers 3 and a pair of second carrier rollers 2 arranged on the upstream side. The rear end of a sheet is detected by a detecting part 4 arranged on the upstream side of the pair of second carrier rollers 2 in the sheet carrying direction. Control of a driving part for driving the pair of second carrier rollers 2 is controlled so that a sheet carrying speed by the pair of second carrier rollers 2 is increased more than a sheet carrying speed by the pair of first carrier rollers 3 by a control part based on a detecting result of the detecting part. A loop is formed between the first pair of carrier rollers 3 and the second pair of carrier rollers 2. Thus, even when carrying the sheet of an unrecognizable size, a slipping-out shock can be surely prevented.

Description

  The present invention relates to a sheet conveying apparatus, an image reading apparatus, and an image forming apparatus.

  Conventionally, in a document conveying device provided in an image reading device that reads an image of a document or a recording sheet conveying device provided in an image forming device that forms an image on a recording sheet, a document or a recording sheet is sandwiched between a pair of rollers. Thus, a document or sheet conveying apparatus for conveying is provided.

  In such a document or sheet conveying apparatus, unevenness may occur in the sheet conveying speed when the rear end of the document or recording sheet (hereinafter, the document and recording sheet are collectively referred to as a sheet) passes through the nip of the roller pair. . This is considered to be caused by abruptly pulling out the rear end of the sheet from the nip when the sheet passes through the nip of the roller pair (hereinafter, this is referred to as a release shock).

  Therefore, in Patent Document 1, when a sheet is conveyed from the first conveying unit to the second conveying unit in order to prevent a drop shock, the sheet conveying speed by the first conveying unit is set as the sheet conveying speed by the second conveying unit. A sheet conveying device that is larger than the above is described. In the sheet conveying apparatus described in Patent Document 1, the sheet is conveyed from the first conveying means to the second conveying means that is stopped, and the leading edge of the sheet abuts against the second conveying means to form a loop on the sheet. The skew of the sheet is corrected. Then, after the skew of the sheet is corrected, the conveyance of the sheet by the second conveyance unit is started, and after the time determined for each sheet size has elapsed, the first conveyance unit is moved to the sheet conveyance of the second conveyance unit. The conveyance is started at a speed higher than the speed. As a result, a slipping shock is prevented by forming a loop on the sheet between the first conveying means and the second conveying means.

JP 2005-15100 A

However, the apparatus described in Patent Document 1 has room for improvement.
That is, since the timing for increasing the sheet conveying speed by the first conveying unit is determined based on the size of the sheet, an appropriate amount of loop for preventing a drop shock when a sheet of an unrecognizable size is conveyed. May not be formed.

  For example, an excessive amount of loops may be formed on the sheet and collide with the conveyance guide to cause a jam, or a sufficient amount of loops may not be formed, and a falling shock may not be prevented. In particular, a document conveying device provided in a document reading device that reads a document can read a document of a size that cannot be recognized. Therefore, a configuration that recognizes and controls the size of a sheet as in the device described in Patent Document 1. Then, it is impossible to reliably prevent the falling shock.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a sheet conveying apparatus that can reliably prevent a slipping shock even when conveying an unrecognizable size sheet.

  The present invention provides a first conveying roller that conveys a sheet, and a second conveying roller that is provided upstream of the first conveying roller in the sheet conveying direction, and that conveys the sheet in the sheet conveying direction. A detection unit that is provided upstream of the second conveyance roller and detects a trailing edge of the conveyed sheet; and based on a detection result of the detection unit, the conveyance speed of the sheet by the second conveyance roller is And a control unit that controls a drive unit that drives the second conveyance roller so as to increase the sheet conveyance speed of the first conveyance roller.

  According to the present invention, the trailing edge of the sheet is detected by the detection unit provided on the upstream side of the second conveyance roller in the sheet conveyance direction. Based on the detection result of the detection unit, the control of the drive unit that drives the second conveyance roller is controlled so that the control unit increases the sheet conveyance speed by the second conveyance roller. A loop is formed between the second transport rollers. Therefore, even when a sheet having an unrecognizable size is conveyed, it is possible to reliably prevent a drop shock.

Schematic diagram of the sheet conveying apparatus of the present invention The figure which shows the 1st Embodiment of this invention Timing chart of sheet conveying operation according to the first embodiment Flowchart of sheet conveying operation according to the first embodiment Block diagram of the first embodiment The figure which shows the 2nd Embodiment of this invention

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

<First Embodiment>
A first embodiment to which the sheet conveying apparatus of the present invention is applied will be described with reference to FIG. In FIG. 2, reference numeral 5 denotes a document reading device that reads a document. The document reading device 5 automatically feeds an image reading unit that reads an image of a document and an image reading unit that will be described later of the image reading unit. Device. Hereinafter, the original is referred to as a sheet.

  First, the image reading unit will be described. As shown in FIG. 2, the image reading unit is provided with reading means 17 for reading an image of the sheet, and the reading means 17 is provided so as to be movable so as to read and fix the sheet. Further, in order to perform the flow reading for reading the sheet image while conveying the sheet, a flow reading platen glass 18 is provided at the flow reading position, and the reading means 17 is provided at the position of the flow reading platen glass 18. It is provided to be movable.

  Next, the document conveying device will be described. 7 is a paper feed tray for stacking sheets, and 9 is a pickup roller for feeding sheets stacked on the paper feed tray. A separation roller 10 separates and conveys the sheet fed by the pickup roller 9 into one sheet. Reference numeral 11 denotes a drawing roller pair that pulls out the sheet separated by the separation roller, and reference numeral 12 denotes a registration roller pair that corrects the skew of the sheet. A pre-reading conveyance roller pair 13 is arranged on the downstream side of the registration roller pair 12 and conveys the sheet to the image reading unit 50. The sheet conveyed to the image reading unit 50 by the pre-reading conveyance roller pair 13 is read by the reading unit 17 through the platen glass 18 for flow reading while being assisted by the platen roller 14. Thereafter, the sheet on which the image has been read is discharged onto the discharge tray 8 by the conveyance roller pair 15 and the discharge roller pair 16 after reading.

  Reference numerals 4a and 4b denote sensors as detection units for detecting the conveyed sheet. The sensor 4 a is a post-separation sensor provided on the upstream side of the drawing roller pair 11, and the sensor 4 b is a registration sensor provided on the upstream side of the registration roller pair 12.

  FIG. 5 is a block diagram for controlling each component of this embodiment. As shown in this block diagram, the CPU as the control unit is connected to a paper feed motor M1 as a drive unit that drives the pickup roller 9 and a registration motor M2 as a drive unit that drives the registration roller pair 12. Yes. The CPU is connected to a read motor M3 that moves the reading means 17. The CPU is also arranged on the upstream side of the document set detection sensor for detecting sheets stacked on the tray 7 and the pre-reading conveyance roller pair 13 and determines the image reading timing from the sheet detection timing. Connected to the lead sensor. The CPU is connected to the post-separation sensor 4a and the registration sensor 4b. And CPU controls each motor based on the detection result by each sensor.

  Next, a sheet conveying operation by the reading device 5 will be described. The sheet conveying operation is set to perform drive control based on the timing shown in FIG.

  When a copy operation start instruction is input from the operation panel 6, the sheets stacked on the tray 7 are conveyed to the sheet conveying apparatus 1 by the pickup roller 9. The sheets conveyed to the pickup roller 9 are separated one by one by a separation roller 10 and a separation pad (not shown) and conveyed to the drawing roller pair 11 side. The sheets separated one by one are drawn from the separation roller 10 by the drawing roller pair 11 and conveyed to the stopped registration roller pair 12. The leading edge of the sheet conveyed by the drawing roller pair 11 is abutted against the nip of the registration roller pair 12.

  At this time, when the leading edge of the sheet is abutted against the nip of the registration roller pair 12 and the sheet is further conveyed by the drawing roller pair 11, a loop is formed on the sheet. A space for allowing the formed loop is provided in the transport path on the upstream side of the registration roller pair 12. When a predetermined amount of this loop is formed, the drawing roller pair 11 starts to reduce the sheet conveyance speed, and when the drawing roller pair 11 decelerates to a predetermined speed, the registration roller pair 12 starts to be driven. The loop amount formed on the sheet by being abutted against the nip of the registration roller pair 12 is set by the drawing roller pair 11 feeding the sheet by a predetermined amount after the registration sensor 4b detects the leading edge of the sheet. The

  The sheet conveyed by the registration roller pair 12 is drawn into the pre-reading conveyance roller pair 13 and conveyed to the image reading unit 50 by the pre-reading conveyance roller pair 13. Before the leading edge of the sheet reaches the platen glass for flow reading 18 which is the reading position, the roller pair holding the sheet is decelerated to a constant speed V1 corresponding to the image reading speed.

  An image is read by the reading unit 17 on the sheet conveyed on the platen glass 18 for flow reading at the speed V1 by the platen roller 14 rotating at the reading speed V1. At this time, after the leading edge of the sheet reaches the platen glass 18 for flow reading, the trailing edge of the sheet may pass through the nip of the separation roller 10, the drawing roller pair 11, and the registration roller pair 12. In this case, the sheet conveying speed of the most upstream roller or roller pair holding the sheet is increased by about 4% to 10%.

  Thus, in this embodiment, when the trailing edge of the sheet passes through the nip of the roller pair, the sheet conveyance speed of the roller pair is increased. Here, the reason why the sheet conveyance speed is increased will be described.

  In general, when a sheet is conveyed by an upstream roller pair and a downstream roller pair in the sheet conveying direction, control is performed so that the sheet conveying speeds of the upstream roller pair and the downstream roller pair are the same. Done. However, due to manufacturing tolerances in the diameter of the rollers and deterioration over time due to durability deterioration due to conveyance, etc., the sheet conveyance speed by the upstream roller pair is about 2-3% slower than the sheet conveyance speed by the downstream roller pair. May end up. In such a state, since the sheet is conveyed while being pulled by the downstream roller pair, unevenness occurs in the sheet conveying speed when the trailing end of the sheet passes through the nip of the upstream roller pair.

  In general, the registration roller pair 12 is often set to increase the nip pressure in order to correct sheet skew. Further, the drawing roller pair 11 is also set so that the nip pressure is increased because it is necessary to stably pull out the sheet from the separation unit. Further, in the separation unit using the separation roller 10 and a separation pad, the conveyance resistance is large in order to ensure the sheet separation performance. In this way, the pair of conveying rollers arranged on the upstream side of the image reading unit has a large nip pressure and a large conveying force, and therefore has a great influence on the conveying speed of the sheet being read.

  When the sheet conveyance speed of these roller pairs is low, the conveyance load increases in accordance with the nip pressure, which becomes the conveyance resistance of the downstream roller pair. Then, when the trailing edge of the sheet comes out from the nip of the uppermost conveying roller pair that holds the sheet, the conveying load is released at a stretch, so that the entire sheet conveying speed is temporarily increased, and the sheet It will cause the conveyance speed fluctuation. That is, a slipping shock occurs when the trailing edge of the sheet passes through the nip of the roller pair.

  In addition, when transporting thick paper or recycled paper mixed with foreign matter, the surfaces of the roller pair are likely to be worn, and it is considered that the impact of the falling shock increases. Then, in order to prevent a drop-off shock, it is not preferable to replace the roller pair or use a roller pair that is difficult to scrape, resulting in an increase in cost and a limit in design freedom.

  For the above reasons, in this embodiment, in order to prevent a sheet slipping shock, the upstream roller pair is increased by about 4% to 10% with respect to the downstream roller pair. As a result, a loop can be formed on the sheet while compensating for a deceleration of about 2-3% of the sheet conveyance speed.

  This will be described with reference to the schematic diagram of FIG. Reference numerals 2 and 3 denote a pair of rollers for conveying the sheet in the left direction in FIG. 1, 3 denotes a first conveyance roller pair provided on the downstream side, and 2 denotes a second conveyance roller provided on the upstream side. It is a pair. A sensor 4 is provided on the upstream side of the second conveyance roller pair 2 and serves as a detection unit that detects the conveyed sheet, and detects that the trailing edge of the sheet has passed. When the sensor 4 detects that the trailing edge of the sheet has passed, the CPU as a control unit (not shown) controls a motor (not shown) to increase the speed of the second conveyance roller pair, and FIG. As shown in the figure, a loop is formed on the sheet.

  Hereinafter, the specific operation of the present embodiment will be described with reference to the flowchart of FIG.

  First, the sheet to be conveyed is detected by the post-separation sensor 4a as to whether the sheet size is equal to or larger than a predetermined size (S401, S402). Here, the sheet size means the length in the sheet conveyance direction, and the predetermined size is the length of the conveyance path from the nip position of the drawing roller pair 11 to the platen glass 18 for flow reading which is the reading position. Means.

  Further, the determination as to whether or not the sheet size is equal to or larger than a predetermined size is made by determining that the trailing edge of the sheet has passed after the leading edge of the conveyed sheet is detected by the post-separation sensor 4a and a predetermined time has elapsed. This is determined by whether or not the post-separation sensor 4a has detected this. The predetermined time here means the time until the leading edge of the conveyed sheet reaches the flow reading platen glass 18 from the nip position of the drawing roller pair 11 and is stored in the CPU in advance. .

  When the CPU determines that the sheet is smaller than the predetermined size, the sheet conveyance speed of the drawing roller pair 11 is not increased, and the sheet is normally conveyed (S403). This is because, even if a slipping shock occurs when the trailing edge of the sheet passes through the nip of the drawing roller pair 11, the leading edge of the sheet does not reach the platen glass 18 for flow reading, so that the reading of the sheet is less affected. .

  On the other hand, if the CPU determines that the sheet is a predetermined size or larger, the CPU controls the paper feed motor M1 to increase the sheet conveyance speed of the pulling roller pair 11 (S406). This is because when the trailing edge of the sheet nipped by the drawing roller pair 11 comes off, the leading edge of the sheet reaches the reading unit 50, so that a falling shock is prevented.

  Specifically, the sheet is pulled out after the trailing edge of the sheet is detected by the post-separation sensor 4 a disposed upstream of the nip of the drawing roller pair 11 and until the trailing edge of the sheet comes out of the nip of the drawing roller pair 11. The sheet conveying speed of the roller pair 11 is increased by about 4% to 10%. Then, after the trailing edge of the sheet passes through the nip of the drawing roller pair 11, the driving of the drawing roller pair 11 is stopped after a predetermined time has elapsed.

  Similarly, the registration sensor 4b also detects whether or not the sheet size is equal to or larger than a predetermined size (S404, S406). The size of the sheet here means the length in the sheet conveyance direction as in the above description, but the predetermined size is the platen glass 18 for flow reading which is a reading position from the nip position of the registration roller pair 12. This means the length of the transport path to

  If the CPU determines that the sheet is smaller than the predetermined size, the sheet conveyance speed of the registration roller pair 12 is not increased, and the sheet is normally conveyed (S407). On the other hand, if the CPU determines that the sheet is a predetermined size or larger, it controls the registration motor M2 to increase the sheet conveying speed of the registration roller pair 12 (S408).

  Thereafter, the sheet that has passed through the platen glass 18 for flow reading is conveyed by the conveyance roller pair 15 and the discharge roller pair 16 after reading, and is discharged and stacked on the discharge tray 8.

  As described above, according to the first embodiment, when the trailing edge of the sheet passes through the nip of the upstream roller pair, the sheet conveyance speed by the upstream roller pair is set to the sheet by the downstream roller pair. Increase the speed of transport. As a result, a loop is formed on the sheet, and it is possible to reliably prevent a slipping shock when the trailing edge of the sheet passes through the nip of the roller pair.

  In the first embodiment, after the sensor for detecting the conveyed sheet detects the trailing edge of the sheet, a minute loop is formed immediately before the trailing edge of the sheet passes through the nip of the roller pair. Since it is controlled, it is not necessary to secure a large loop space.

  Further, in the above description of the first embodiment, when the sheet size is less than the predetermined size, there is little need to prevent the slipping shock, so the sheet conveying speed of the roller pair is not increased. The control has been described. However, the present invention should not be limited to this, and the sheet conveyance speed of the roller pair may be increased uniformly for all sheets without determining the sheet size.

  In this way, by controlling the conveyance speed based on the trailing edge of the sheet, it is possible to prevent a drop shock with the same control regardless of the length of the sheet. Falling shock can be prevented.

<Second Embodiment>
Next, a second embodiment of the present invention will be described with reference to FIG.

  As shown in FIG. 6, the sheet conveying apparatus of the second embodiment is provided inside the image forming apparatus 100. The sheets P stacked on the paper feed tray 20 to be supplied to the image forming unit are sent out to the conveyance path by the pickup roller 21 and separated one by one by the separation unit including the separation roller 22 and the separation roller. The sheets that are separated and conveyed one by one are conveyed toward the registration roller pair 24 arranged on the downstream side of the conveyance path by the intermediate conveyance roller pair 23. The sheet conveyed to the intermediate conveyance roller pair 23 comes into contact with the registration roller pair 24 whose leading edge is stopped, thereby forming a loop and correcting the skew of the sheet. When a predetermined amount of loop is formed, the registration roller pair 24 starts to be driven and is controlled so as to drive at a constant speed with the intermediate conveyance roller pair 23.

  Thereafter, the skew-corrected sheet is conveyed by the registration roller pair 24 to a transfer position 25 where the toner image is transferred by the transfer unit. At the transfer position 25, since the sheet needs to be conveyed at a constant speed, it is necessary to prevent a drop shock when the trailing edge of the sheet passes through the nip of the roller pair upstream of the registration roller pair 24. .

  Therefore, also in the second embodiment, when the sheet size is longer than the length of the conveyance path from the intermediate conveyance roller pair 23 to the transfer position 25, the trailing edge of the sheet passes through the nip of the intermediate conveyance roller pair 23. Before, the sheet conveyance speed of the intermediate conveyance roller pair 23 is increased. Similarly, when the sheet size is longer than the length of the conveyance path from the separation roller 22 to the transfer position 25, the sheet conveyance speed of the separation roller 22 is removed before the trailing edge of the sheet passes through the nip of the separation roller 22. Is increased. As a result, a loop is formed in the sheet to prevent a falling shock.

  In addition, the detection of the sheet size and the passage of the trailing edge of the sheet is performed by a sensor (not shown) provided on the upstream side of each roller pair, as in the first embodiment.

  As described above, according to the first embodiment and the second embodiment, the trailing edge of the sheet passes through the nip of the roller pair that conveys the sheet to a position where image processing such as a reading position and a transfer position is performed. At this time, the sheet conveying speed of the roller pair is increased. Accordingly, it is possible to prevent a drop shock at a portion that affects the image, such as reading a document or transferring a toner image.

  In addition, a reading apparatus to which the first embodiment is applied may be provided on the upper part of the image forming apparatus to which the second embodiment is applied.

DESCRIPTION OF SYMBOLS 1 Sheet conveying apparatus 2 2nd conveying roller pair 3 1st conveying roller pair 4 Detection part 5 Reading apparatus 11 Pull-out roller pair 12 Registration roller pair 17 Reading means 18 Platen glass for flow reading (reading position)
23 Intermediate conveyance roller pair 24 Registration roller pair 25 Transfer position 100 Image forming apparatus P Sheet M1 Paper feed motor M2 Registration motor M3 Lead motor

Claims (5)

A first conveying roller pair for conveying a sheet;
A second conveying roller pair that is provided upstream of the first conveying roller pair and conveys the sheet in the sheet conveying direction;
A detection unit that is provided on the upstream side of the second conveyance roller pair in the sheet conveyance direction and detects a trailing edge of the conveyed sheet;
Based on the detection result of the detection unit, the second conveyance roller pair is driven so that the sheet conveyance speed by the second conveyance roller pair is increased more than the sheet conveyance speed by the first conveyance roller pair. A control unit for controlling the driving unit to perform,
A sheet conveying apparatus comprising:   The controller increases the conveyance speed of the second conveyance roller pair after the trailing edge of the sheet is detected by the detection unit and before the trailing edge of the sheet passes the second conveyance roller pair. The sheet conveying apparatus according to claim 1.   The control unit increases the sheet conveyance speed by the second conveyance roller pair when the size of the sheet detected by the detection unit is equal to or larger than a predetermined size. The sheet conveying apparatus according to 1. A sheet conveying device according to any one of claims 1 to 3,
Reading means for reading an image of a sheet conveyed by the first conveyance roller pair and the second conveyance roller pair of the conveyance device;
An image reading apparatus comprising: A sheet conveying device according to any one of claims 1 to 3,
An image forming unit that forms an image on a sheet conveyed by the first conveyance roller pair and the second conveyance roller pair of the conveyance device;
An image forming apparatus comprising:

Images