JP2011084401A - Sheet carrying device, automatic document feeder, image reader and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inexpensively provide a sheet carrying device capable of improving productivity, by shortening a switching time of pullout operation from separation operation, with a simple constitution. <P>SOLUTION: A pullout roller 12 is put in a stopping state by turning off an electromagnetic clutch 40 in the separation operation. A paper feeding belt 9 operates, and butts a document P against the pullout roller 12 by separating one by one. The pullout roller 12 operates when turning on the electromagnetic clutch 40, and carries the document P to the downstream side. At this time, the paper feeding belt 9 co-rotates by a sheet by the action of a one-way clutch 43, and the document P is extracted from a separation part by carrying of the pullout roller 12. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a sheet conveying apparatus that separates and conveys a sheet into one sheet.

  An image reading apparatus for reading a document image is well known and widely used as an image reading unit provided in a scanner or an image forming apparatus. An automatic document feeder (ADF) that is mounted on the image reading apparatus and conveys a document to a reading position is also well known. In an apparatus for handling these sheet-like originals, a sheet conveying apparatus that separates and conveys sheets into one sheet is provided.

  Incidentally, as the automatic document feeder, there is a sheet-through type device that reads a document while conveying it. With this sheet-through method, it is possible to improve the reading productivity compared with the fixed reading method in which the original is stopped and then read, but on the other hand, with respect to skew, reading in a stationary state with corrected skew is possible. Compared to the fixed reading method that can be performed, the sheet-through method may cause a skew during reading in principle, and this possibility is unavoidable.

  Therefore, in the sheet-through method, with the intention of reducing the skew as much as possible, there is a technique of reading the document while conveying the document after correcting the skew by abutting the leading edge of the document with a roller or the like before reading. A technique is already known in which a document is separated at the separation unit, and at the same time, the skew is corrected by abutting the leading end against a pull-out roller stopped downstream thereof, and then conveyed to the reading unit by the pull-out roller and the downstream roller. Yes.

  Japanese Patent Laid-Open No. 6-16261 (Patent Document 1) uses one motor and two electromagnetic clutches (an electromagnetic clutch for switching driving to a registration roller and an electromagnetic clutch for switching driving transmission to a feed roller). On the other hand, for the purpose of cost reduction, a configuration is disclosed in which forward / reverse rotation of a motor and a plurality of one-way clutches are used without using an electromagnetic clutch.

  In Japanese Patent Laid-Open No. 3-36132 (Patent Document 2), skew correction is abutted against a registration roller by one-way rotation of one motor, and driving of the registration roller is switched by ON / OFF of an electromagnetic clutch. Possible configurations are disclosed.

  Japanese Patent Laying-Open No. 2001-253582 (Patent Document 3) discloses a configuration in which a pre-registration roller abuts against a registration roller, and the registration roller includes a drive electromagnetic clutch and a stop electromagnetic clutch. .

  However, in the conventional paper feed drive system in which the separation unit and the pull-out roller are driven by a single drive source, the separation operation (the separation unit operates, the pull-out roller is stopped, and the leading edge of the document is abutted against the stopped pull-out roller). A drive system that uses a one-way clutch to switch between skew correction) and pull-out operation (operating a pull-out roller with the document leading edge and pulling out the latter half of the document from the separation unit to transport it downstream, and simultaneously turning off the separation unit) It was performed by forward rotation and reverse rotation of one paper feed motor through a gear train. Therefore, when moving from the separation operation to the pullout operation, it is necessary to lower the feed motor (forward rotation) → stop → feed motor startup (reverse rotation). That is, as the switching time from the separation operation to the pullout operation, It took time to start / stop / start up. In such a system, when the required reading productivity increases, the ratio of the switching time in the operation cycle of the apparatus cannot be ignored, and there is a problem that the improvement in reading productivity is limited. It was.

  Even the one described in Patent Document 1 cannot solve the problem that it takes time to start up the motor normal rotation / reverse rotation. In addition, since the pull-out roller does not have a brake mechanism, the pull-out roller may not be stationary until the next original is abutted due to the inertia of the pull-out roller itself or the drive system after the previous operation. In some cases, the correction effect could not be obtained.

  In addition, as a skew correction method to ensure high productivity even if the skew correction effect is somewhat reduced, the roller at the abutting destination is not stopped completely but driven at some linear speed. A method of rushing a document at a high linear velocity (hereinafter referred to as linear velocity differential abutting) is known. However, the separation operation can be performed by one motor by switching between normal rotation / reverse rotation of the motor described in Patent Document 1. In the configuration in which the pull-out operation is switched, the linear speed difference cannot be abutted by the pull-out roller from the separation unit.

  Further, in the above-mentioned Patent Document 2, the drive switching (transmission) of the paper feed roller is performed by a spring clutch, and the abutting amount (that is, the switching timing from separation to pull-out) is obtained by a mechanical mechanism. The mechanism is complicated and expensive.

And the thing of the said patent document 3 is provided with the electromagnetic clutch for a registration roller stop, and there exists a problem that a mechanism is complicated and costly.
The present invention solves the above-described problems in the conventional sheet conveying apparatus, can reduce the cost without complicating the configuration, and shortens the switching time from the separation operation to the pull-out operation in the series operation of the sheet feeding unit, thereby improving productivity. And a sheet conveying device that can reliably perform skew correction by abutting even with a high-speed operation for improving productivity, and an automatic document feeder, an image reading device, and an image forming device provided with the sheet conveying device The task is to do.

  According to the present invention, there is provided a separating unit that separates the sheets called from the sheet stacking unit one by one and conveys them downstream, a conveying unit positioned immediately downstream in the conveying direction of the separating unit, One driving means for driving the separating means and the conveying means by rotation in a fixed direction, and a drive switching means arranged in a driving system from the driving means to the conveying means for switching between transmission and interruption of driving force The driving switching means cuts off the driving force to the conveying means, the separation means separates and feeds the sheet, and the sheet is abutted against the conveying means, and then the driving switching means drives the conveying means to the conveying means. The sheet is conveyed by transmitting force, and then the drive switching unit stops the drive unit while maintaining the driving force transmission state and holds the excitation state of the drive unit for a predetermined time. Ri is resolved.

In addition, it is preferable that a predetermined amount of the sheet is conveyed by the separating unit after the leading end of the sheet is abutted against the conveying unit in a state where the driving force is interrupted.
Further, according to the present invention, there is provided a separation unit that separates the sheets called from the sheet stacking unit one by one and conveys them downstream, and a conveyance unit that is located immediately downstream in the conveyance direction of the separation unit. One driving means for driving the separating means and the conveying means by rotation in a fixed direction, and a drive switching means arranged in a driving system from the driving means to the conveying means for switching between transmission and interruption of driving force. A driving force by the drive switching means when the driving switching means cuts off the driving force to the conveying means and separates and feeds the sheet by the separating means and abuts the sheet against the conveying means. This is solved by driving the conveying means with the drive switching means in a driving force transmitting state after at least one transmission and interruption.

  Further, it is preferable that a sheet detecting unit is provided between the separating unit and the conveying unit, and when the leading end of the sheet is detected by the sheet detecting unit, the driving switching unit transmits and interrupts the driving force at least once.

Moreover, when the driving force is transmitted and interrupted by the driving switching unit a plurality of times when the sheet is abutted against the conveying unit, it is preferable that the initial driving force transmission time is shortest.
In addition, when the driving force is transferred and interrupted by the driving switching unit a plurality of times when the sheet is brought into contact with the conveying unit, it is preferable to gradually increase the driving force transmission time.

  It is preferable that the sheet conveying linear speed by the separating unit is set to be slower than the sheet conveying linear velocity by the conveying unit, and that the separating unit is provided with a one-way clutch so that it can be rotated in the sheet conveying direction. It is.

The drive switching means is preferably an electromagnetic clutch.
The driving means is preferably a stepping motor.
The sheet is preferably a recording medium.

According to the present invention, the above problem is solved by an automatic document feeder provided with the sheet conveying device according to any one of claims 1 to 9.
According to the present invention, the above problem is solved by an image reading apparatus provided with the automatic document feeder according to claim 11.

  Further, according to the present invention, the subject is a sheet conveying device according to any one of claims 1 to 10, an automatic document feeder according to claim 11, or an image reading device according to claim 12. This is solved by an image forming apparatus comprising:

  According to the sheet conveying apparatus of the first aspect, the time required for switching from the separation operation to the pull-out operation can be greatly shortened. Therefore, productivity in sheet conveyance can be improved. Further, since only one drive switching means is required and the motor as the drive means may be rotated in a certain direction, the configuration and control are simple and the productivity can be improved at low cost. In addition, the pull-out roller can be surely stopped even during high-speed operation when productivity is improved, and the abutting correction to the next pull-out roller can be ensured.

With the configuration of the second aspect, it is possible to correct the skew of the sheet by abutting against a stationary roller.
According to the sheet conveying apparatus of the third aspect, the time required for switching from the separation operation to the pull-out operation can be greatly shortened, and the productivity in sheet conveyance can be improved. Further, the configuration and control are simple, and productivity can be improved at low cost. Furthermore, it is possible to perform skew correction by linear velocity difference abutting that can further improve productivity during the pull-out operation after sheet separation.

According to the configuration of the fourth aspect, skew correction by linear velocity difference butting can be performed at an appropriate timing.
According to the configurations of the fifth and sixth aspects, the skew correction by the linear velocity difference butting can be smoothly performed at an appropriate timing.

  According to the configuration of the seventh aspect, the sheet is not loosened during the pull-out operation after the sheet separation, and at the same time, the sheet rubbing by the separating unit can be prevented.

With the configuration of the eighth aspect, by using an electromagnetic clutch as the drive switching means, it is possible to realize reliable drive switching at a low cost.
With the configuration of the ninth aspect, by using a stepping motor as the driving means, it is possible to realize accurate drive control at low cost.

  According to the configuration of the tenth aspect, productivity in transporting the recording medium can be improved. In addition, the abutting correction of the recording medium can be ensured to contribute to high-quality image output.

According to the automatic document feeder of the eleventh aspect, the productivity of document reading is excellent, and the document abutting correction can be reliably performed even during high-speed operation.
According to the image reading device of the twelfth aspect, it is possible to provide an image reading device that is excellent in document reading productivity and capable of reading a high-quality document even during high-speed operation.

  According to the image forming apparatus of the thirteenth aspect, it is possible to provide an image forming apparatus with excellent productivity by including the sheet conveying apparatus with high productivity.

1 is a cross-sectional view illustrating a configuration of a sheet-through ADF that is an example of an automatic document feeder according to the present invention. It is a schematic diagram of the reading drive system of the ADF. It is a schematic diagram of the paper discharge drive system of the same ADF. It is a block diagram which shows the control system of the same ADF. It is a block diagram which shows the structure of the 2nd image reading means for reading a back surface original. It is a schematic diagram for demonstrating a structure and operation | movement of the separation feeding part in the conventional automatic document feeder. It is a timing chart which shows the operation timing in the apparatus of FIG. It is a schematic diagram for demonstrating the structure and operation | movement of the separation feeding part and resist part in embodiment of this invention. It is a timing chart which shows the operation timing in the embodiment of the present invention. It is a schematic diagram for demonstrating the control at the time of isolation | separation operation | movement in 2nd Embodiment of this invention. It is a timing chart which shows the operation timing in a 2nd embodiment. 1 is an external perspective view illustrating an example of an image forming apparatus including an automatic document feeder according to the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The present invention is an automatic document feeder (ADF) that conveys a document to a reading unit of an image reading device such as an image reading unit or a scanner in an image forming apparatus such as a copying machine or a facsimile, or a recording medium inside the copying machine. The present invention relates to a mechanism for transporting a sheet such as a document or a sheet, such as a sheet feeding unit that transports a sheet from a sheet stacking unit to a copying machine. In the present embodiment, as a representative example, the present invention will be described by taking up the case of conveying a document of a sheet through ADF mounted on a copying machine.

  FIG. 1 is a cross-sectional view showing a configuration of a sheet-through ADF as an example of an automatic document feeder according to the present invention, FIG. 2 is a schematic diagram of a reading drive system of the ADF, and FIG. 3 is a discharge driving system of the ADF. It is a schematic diagram. FIG. 4 is a block diagram showing a control system of the automatic document feeder. FIG. 5 is a block diagram showing the configuration of the second image reading means 25 for reading the back side document. First, the basic configuration and operation of this embodiment will be described with reference to these drawings.

  The sheet-through ADF 1 according to this embodiment includes a document setting unit A for setting a read document bundle, a separation feeding unit B for separating and feeding documents one by one from the set document bundle, and a fed document. , And a turn part D that turns the conveyed original and conveys the original surface toward the reading side (downward). A first reading / conveying unit E for reading the front image of the original document from below the contact glass, a second reading / conveying unit F for reading the back side image of the original after reading, and discharging the original on which the front and back sides have been read out of the apparatus. A paper discharge unit G that performs stacking and holding a document after reading, a drive unit 101 to 105 that drives the transport operation, and a controller unit 100 that controls a series of operations. .

  The original bundle P to be read is set on the original table 2 including the movable original table 3. In this example, the document surface is set face up. The document table 2 is provided with a side guide (not shown), and the width direction of the document bundle P is positioned by the side guide in a direction orthogonal to the transport direction. The document set is detected by the set filler 4 and the set sensor 5 and transmitted to the main body control unit 111 by the I / F 107. Further, the length of the document in the conveyance direction is roughly determined by a document length detection sensor 30 or 31 (a reflective sensor or an actuator type sensor that can detect even one document) provided on the document table surface. Is determined (a sensor arrangement capable of determining at least whether the document size is vertical or horizontal is necessary).

  The movable document table 3 can be moved up and down in the directions a and b shown in FIG. 1 by a bottom plate raising motor 105. When the set filler 4 and the set sensor 5 detect that a document has been set, the bottom plate rises. The motor 105 is rotated forward to raise the movable document table 3 so that the uppermost surface of the document bundle P contacts the pickup roller 7.

  The pickup roller 7 is operated by a pickup motor 101 in the directions c and d by a cam mechanism, and the movable table 3 is lifted and pushed by the upper surface of the original on the movable table 3 to rise in the c direction, and the table lift detection sensor 8. The upper limit can be detected.

  When the enter key is pressed from the main body operation unit 108 and a document feed signal is transmitted from the main body control unit 111 to the controller unit 100 via the I / F 107, the pick-up roller 7 rolls by the forward rotation of the paper feed motor 102. Rotation is driven to pick up several (ideally one) originals on the original table 2. The rotation direction is a direction in which the uppermost document is conveyed to the sheet feeding port.

  The paper feed belt 9 is driven in the paper feed direction by the normal rotation of the paper feed motor 102, and the reverse roller 10 is driven to rotate in the reverse direction to the paper feed by the normal rotation of the paper feed motor 102. The document is separated, and only the uppermost document can be fed. More specifically, the reverse roller 10 is in contact with the paper feeding belt 9 at a predetermined pressure, and is rotated by the paper feeding belt 9 when in contact with the paper feeding belt 9 directly or through a document. When the document enters between the paper feeding belt 9 and the reverse roller 10 in the unlikely event that the original is in the counterclockwise direction, the revolving force is set to be lower than the torque of the torque limiter. 10 rotates in the clockwise direction, which is the original driving direction, and pushes back an extra original, thereby preventing double feeding.

  The original separated by the action of the paper feeding belt 9 and the reverse roller 10 is further fed by the paper feeding belt 9, and the leading edge is detected by the abutting sensor 11 and further abuts against the pull-out roller 12 stopped. Thereafter, the sheet feeding motor 102 is stopped in a state where it is fed a predetermined amount from the detection of the abutting sensor 11 and as a result is pressed against the pull-out roller 12 with a predetermined amount of bending. By doing so, the driving of the paper feed belt 9 is stopped. At this time, the pickup motor 101 is rotated so that the pickup roller 7 is retracted from the upper surface of the original and the original is fed only by the conveying force of the paper feed belt 9, whereby the leading edge of the original enters the nip between the upper and lower roller pairs of the pull-out roller 12. Then, tip alignment (skew correction) is performed.

  The pull-out roller 12 has the skew correction function and is a roller for conveying the skew-corrected document after separation to the intermediate roller 14 and is driven by the reverse rotation of the paper feed motor 102. At this time (at the time of reverse rotation of the paper feed motor 102), the pull-out roller 12 and the intermediate roller 14 are driven, but the pickup roller 7 and the paper feed belt 9 are not driven.

  A plurality of document width sensors 13 are arranged in the depth direction and detect the size in the width direction perpendicular to the conveyance direction of the document conveyed by the pull-out roller 12. Further, the length of the document in the conveying direction is detected from the motor pulse by reading the leading edge and the trailing edge of the document with the butting sensor 11.

  When the document is transported from the resist section C to the turn section D by driving the pull-out roller 12 and the intermediate roller 14, the transport speed at the resist section C is set to be higher than the transport speed at the reading transport section E. The processing time for sending the document to the reading unit is shortened.

  When the leading edge of the document is detected by the reading entrance sensor 15, before the leading edge of the document enters the nip of the upper and lower roller pairs of the reading entrance roller 16, deceleration is started in order to make the document transportation speed the same as the scanning transportation speed. At the same time, the reading motor 103 is driven forward to drive the reading inlet roller 16, the reading outlet roller 23, and the CIS outlet roller 27. When the registration sensor 17 detects the leading edge of the document, the registration sensor 17 decelerates over a predetermined conveyance distance, temporarily stops in front of the reading position (reading means) 20, and stops the registration in the main body control unit 111 via the I / F 107. Send a signal. Subsequently, when a reading start signal is received from the main body control unit 111, the document whose registration has been stopped is accelerated and conveyed so as to rise to a predetermined conveying speed until the leading edge of the document reaches the reading position. At the timing when the leading edge of the document detected by the pulse count of the reading motor 103 reaches the reading unit, a gate signal indicating an effective image area in the sub-scanning direction on the first surface is sent to the main body control unit 111 and the first reading unit is set to the document. Sent until the trailing edge is removed.

  In FIG. 2, reference numeral 16a is a reading inlet roller driving pulley, 23a is a reading outlet roller driving pulley, 26a is a white roller driving pulley, 27a is a CIS outlet roller driving pulley, 51 and 52 are timing belts, 53 is an idler pulley, 54 is a connecting pulley, and 103 is a reading motor. In FIG. 3, reference numeral 28a is a paper discharge roller drive pulley, 55 is a connecting pulley, 56 to 57 are timing belts, and 104 is a paper discharge motor.

  In the case of single-sided document reading, the document that has passed through the reading conveyance unit E is conveyed to the paper discharge unit G through the second reading unit F. At this time, when the leading edge of the original is detected by the paper discharge sensor 24, the paper discharge motor 104 is driven to rotate forward to rotate the paper discharge roller 28 counterclockwise. Further, the discharge motor driving speed is reduced immediately before the trailing edge of the document exits the nip between the upper and lower roller pairs of the discharge roller 28 by the pulse count of the discharge motor 104 from the detection of the leading edge of the document by the discharge sensor 24. Control is performed so that the document discharged onto the discharge tray 29 does not jump out.

  In the case of double-sided document reading, the second image reading unit 25 is detected at the timing when the document leading end reaches the second image reading unit 25 by the pulse count of the reading motor 103 after the discharge sensor 24 detects the document leading end. Then, a gate signal indicating an effective image area in the sub-scanning direction is transmitted from the controller unit 100 until the trailing edge of the document passes through the reading unit. The second reading roller 26 serves as a reference white part for obtaining shading data in the second reading unit as well as suppressing floating of the original in the second reading unit.

Here, the separation feeding unit in the conventional automatic document feeder will be described with reference to FIG. The same parts as those in the embodiment will be described using the same reference numerals.
FIG. 6A shows a separation operation for separating a document, and FIG. 6B shows a pull-out operation for feeding the separated document. First, as shown in FIG. 6A, when the paper feed motor 102 rotates in the direction of the arrow during the separation operation, the one-way clutch 141 is idled and the pull-out roller 12 is not driven and is stopped. On the other hand, the one-way clutch 142 is engaged to operate the paper feeding belt 9 to convey the original P and abut against the pull-out roller 12 stopped as described above. At this time, the abutting sensor 11 detects the tip and then conveys and abuts a predetermined amount.

  At this time, when the one-way clutch 145 is engaged, the reverse roller 10 is rotationally driven in the reverse direction to the paper feeding via the torque limiter 146, and separates the uppermost document from the original document below it and feeds only the uppermost document. The paper can be configured. More specifically, the reverse roller 10 is in contact with the paper feed belt 9 at a predetermined pressure. When the reverse roller 10 is in direct contact with the paper feed belt 9 or in contact with a single original, the reverse roller 10 is rotated. The counterclockwise direction is set so that when the original enters between the sheet feeding belt 9 and the reverse roller 10 by two or more sheets, the revolving force is lower than the torque of the torque limiter. Rotates clockwise, which is the original driving direction, to push back excess originals and prevent double feeding.

  Subsequently, as shown in FIG. 6B, when the paper feed motor 102 rotates in the direction of the arrow during the pull-out operation (the direction opposite to that during the separation operation), the one-way clutch 141 is engaged and the pull-out roller 12 operates, and the document P is transported downstream. On the other hand, at this time, the one-way clutch 142 idles and the sheet feeding belt 9 is not driven. The one-way clutch 143 causes the document P to be pulled out from the separation unit by the conveyance of the pull-out roller 12. At that time, the paper feed belt 9 is rotated by the document to be pulled out. At this time, the reverse roller 10 is rotationally driven in the reverse direction to the paper feed via the torque limiter 146 when the one-way clutch 144 is engaged.

  Thereafter, the document is delivered to a reading entrance roller 16 driven by a reading motor 103 via an intermediate roller 14 shown in FIG. Since the reading inlet roller 16 is driven by the reading motor 103 at a reading linear speed, the pull-out roller 12 and the intermediate roller 14 driven by the paper feeding motor 102 are also read when the original is transferred to the reading inlet roller 16. Need to be the same speed as the linear speed (read assist operation).

FIG. 7 is a timing chart showing the operation timing at this time.
Conventionally, by switching between forward / reverse rotation of the motor with the configuration and control as described above, it is possible to switch between the separation operation and the pull-out operation with one motor. However, when switching from the separation operation to the pull-out operation, as shown in FIG. 7A surrounded by a dotted line (in FIG. 7B, the abutting operation is shown enlarged), the feed motor 102 is lowered. In the past, it took less than 100 ms, which was an obstacle to the pursuit of higher speed.

  Further, since the pull-out roller 12 is not provided with a brake mechanism, the pull-out roller 12 is not stationary by the pull-out roller 12 itself or the inertia force of the drive system after the above-described reading assist operation until the next original is abutted. In some cases, the desired skew correction effect cannot be obtained.

  In addition, as a skew correction method to ensure high productivity even if the skew correction effect is somewhat reduced, a line that is faster than that where it is driven at some linear speed without completely stopping the abutting roller. There is known a method of rushing a document at a high speed (hereinafter referred to as “linear speed difference butting”), but switching between separation operation and pull-out operation with a single motor by switching between normal rotation and reverse rotation of the motor. With this configuration, the linear velocity difference butting between the separating portion and the pull-out roller could not be performed.

  FIG. 8 is a schematic diagram for explaining the configuration and control of the separation feeding unit B (FIG. 1) and the registration unit C (FIG. 1) in the present embodiment. FIG. 8A shows a separation operation for separating a document, and FIG. 8B shows a pull-out operation for feeding the separated document.

  In FIG. 8, the paper feed motor 102 uses a stepping motor in this example, and rotates in a fixed direction indicated by an arrow in the drawing. The driving force from the paper feeding motor 102 is transmitted to the reverse roller 10 via the paper feeding belt 9, the pull-out roller 12 and the torque limiter 46 by an appropriate driving system such as a gear and a pulley. Here, in the middle of the drive system from the paper feed motor 102 to the pull-out roller 12, drive switching means 40 for switching between transmission and interruption of the driving force is provided. In this example, an electromagnetic clutch is used as the drive switching means, and will be referred to as an electromagnetic clutch 40 hereinafter. A driving force is always transmitted to the sheet feeding belt 9 and the reverse roller 10 when the sheet feeding motor 102 is operated. The sheet feeding belt 9 and the pull-out roller 12 driven by the same sheet feeding motor 102 have different sheet conveyance speeds (linear speeds), and the sheet feeding belt 9 is higher than the conveyance speed (linear speed) of the pull-out rollers 12. Is set so as to be slower (depending on gear ratio, pulley diameter, etc.). A one-way clutch 43 is provided on the shaft of the roller around which the paper feeding belt 9 is stretched so that the paper feeding belt 9 can be rotated in the sheet conveying direction. As will be described later, when the sheet is sandwiched between the paper feed belt 9 and the pull-out roller 12, the pull-out roller 12 has a higher linear velocity than the paper feed belt 9, so that the pull-out roller 12 holds the sheet. When the sheet is conveyed, the sheet feed belt 9 is rotated in the sheet conveying direction by the sheet.

  Now, as shown in FIG. 8A, the paper feed motor 102 rotates in the direction of the arrow during the separation operation. At this time, the pull-out roller 12 is not driven and stopped by turning off the electromagnetic clutch 40. On the other hand, since the drive to the paper feeding belt 9 is engaged, the paper feeding belt 9 operates to separate and feed the document P into one sheet, and abut against the pull-out roller 12 stopped as described above. . At this time, the abutting sensor 11 detects the tip and then conveys and abuts a predetermined amount. The reverse roller 10 is driven in the direction of the arrow through the torque limiter 46.

  Subsequently, as shown in FIG. 8B, the paper feed motor 102 rotates in the arrow direction (the same direction as in the separation operation) during the pull-out operation. When the electromagnetic clutch 40 is turned on, the pull-out roller 12 operates to convey the document P downstream. On the other hand, since the drive to the paper feed belt 9 is engaged, the paper feed belt 9 is driven, but the drive to the paper feed belt 9 is decelerated via a drive element (gear, pulley, etc.) and pulled out. By setting the conveyance speed (linear speed) of the paper feed belt 9 to be slower than the conveyance speed (linear speed) of the roller 12, the one-way clutch 43 pulls out the document P from the separation unit by the conveyance of the pull-out roller 12. . The reverse roller 10 is driven in the direction of the arrow through the torque limiter 46.

FIG. 9A is a timing chart showing the operation timing at this time. FIG. 9B is an enlarged view at the time of the abutting operation.
When switching from the separation operation to the pull-out operation, as shown by a dotted line in FIG. 9A, the required time is only the operation time of the electromagnetic clutch 40 in the present invention, which is generally about 20 ms to 40 ms, Compared to the conventional one, it is considerably shortened.

  Further, the feed motor 102 is stopped while the electromagnetic clutch 40 is in the connected state, and the excitation state is maintained for a predetermined time T. Therefore, the pull-out roller 12 is interlocked with the stop of the feed motor 102, The pull-out roller 12 can be surely kept stationary before the next abutment, and the abutment correction can be surely performed.

  Next, a second embodiment of the present invention will be described with reference to FIGS. Note that the mechanical configuration of the second embodiment is the same as that of the first embodiment described above, and the description thereof will be omitted here, with a focus on different control portions.

  As shown in FIG. 10, the sheet feeding motor 102 rotates in the direction of the arrow during the separation operation. At this time, the electromagnetic clutch 40 is turned off. Then, the electromagnetic clutch 40 is turned on / off at least once before the abutment is completed until the abutment is completed, and the pull-out roller 12 is slightly driven. On the other hand, the paper feed belt 9 operates in the same manner as in the first embodiment, and the original is abutted against the pull-out roller 12. The reverse roller 10 is driven in the direction of the arrow through the torque limiter 46.

  FIG. 11A is a timing chart at the time of the separation operation, and FIG. 11B is an enlarged view at the time of abutment. That is, unlike the case where the electromagnetic clutch 40 is turned on and off for a short time before the leading edge of the original comes into contact with the pull-out roller 12 and is brought into contact with the pull-out roller 12 in a completely stopped state, the original is separated from the pull-out roller. 12 is abutted in a state where it is slightly rotated and rotated by inertial force. Therefore, the linear velocity difference is abutted. In addition, it becomes a break-in operation from a completely stopped state. Accordingly, simultaneously with the linear velocity difference butting, the instantaneous drive load fluctuation can be reduced, and the stepping motor (paper feed motor 102) as the drive source can be prevented from stepping out.

  In addition, before and after the abutment, the short-time electromagnetic clutch ON / OFF is performed a plurality of times, and when the electromagnetic clutch is connected a plurality of times, the first time is the shortest, and the connection time is set to the next time and the next time. If it is gradually extended (refer to the connection state of the electromagnetic clutch in FIG. 11B), the linear velocity difference butting can be performed more smoothly. Therefore, skew correction can be performed while ensuring high productivity.

  The electromagnetic clutch 40 is turned on and off at least once (including a plurality of times) after the abutting sensor 13 detects the leading edge of the document (see FIG. 11). The control during the pull-out operation is the same as in the first embodiment.

  By the way, in the conventional configuration, as described above, during the conveyance of the preceding paper (during the pull-out operation), the paper feeding belt 9 is not driven, so that even if the leading edge of the succeeding paper is in the separation nip, no paper is fed. On the other hand, in the configuration of the present invention, since the drive of the paper feeding belt 9 is always connected, the leading edge of the succeeding paper is fed immediately after the trailing edge of the preceding paper has passed through the separating section. It is theoretically possible. If this state occurs, the operation of the paper feed motor 102 is stopped after the trailing edge of the preceding sheet has passed through the pull-out roller 12 due to the pulse count from the trailing edge detection of the preceding sheet by the abutting sensor 11, Alternatively, the electromagnetic clutch 40 is turned off and the pull-out roller 12 is stopped. Therefore, in the configuration of the present invention, even if the leading edge of the succeeding paper is conveyed close to the trailing edge of the preceding paper, the leading edge of the succeeding paper hits the pull-out roller 12 here, and the double feed of the document is prevented. The Thereafter, the operation is performed as described with reference to FIG.

  As described above, in the automatic document feeder of this embodiment, the time required for switching from the separation operation to the pull-out operation is significantly reduced to less than half that of the conventional device. Therefore, productivity in the document conveying device can be improved. Further, as described above, only one electromagnetic clutch is required, and the configuration is simple and the productivity can be improved at a low cost.

  In the embodiment, as shown in FIGS. 8 and 10, there is one paper feed motor 102 which is a driving unit of the document paper feed unit, and the rotation direction thereof is a constant direction. The switching from the separation operation to the pull-out operation does not stop the motor or reverse the rotation direction (reverse rotation) as in the conventional device, and the electromagnetic clutch can be connected while the feed motor is rotating in a fixed direction. / It is done by disconnection. The operation time for connecting / disconnecting the electromagnetic clutch is shorter than the total required time for starting, stopping, and starting the motor in the conventional device, and the time required for switching from the separation operation to the pull-out operation is greatly increased as described above. Can be shortened.

Finally, an image forming apparatus provided with the automatic document feeder of the above embodiment will be briefly described.
The image forming apparatus shown in FIG. 12 is configured as a digital copying machine, and includes a main body unit 310, a paper feeding unit 320, an operation unit 330, a double-sided device 350, and the like. Reference numeral 360 denotes an in-body discharge unit. The automatic document feeder (ADF) 1 described above is mounted at the top of the copying machine.

  The main body unit 310 includes an image reading unit and an image forming unit. The image reading unit used in the digital copying machine of this example is a device having a function of irradiating a document with a light source, converting the reflected light into an electrical signal with a solid-state imaging device such as a CCD, and performing necessary image processing. is there. The image forming unit is an apparatus that forms an image image sent as an electric signal on a recording medium (transfer paper or the like) by an electrophotographic method. As an image forming method in the main body 310, a thermal method, a thermal transfer method, an ink jet method, or the like can be used in addition to the electrophotography. Since the image forming methods are all well known, detailed description thereof is omitted.

  As a major feature of the digital copying machine as in this example, an image is converted into an electric signal and read, and when the electric signal is restored in the image forming unit, the copying machine has various changes and transmission means. It can be applied to other uses. This example also has functions as a facsimile machine and a printer in addition to a copying machine. In addition to this, the application range such as a scanner (image reading apparatus), a filing system, etc. is very wide.

  As mentioned above, although this invention was demonstrated by the example of illustration, this invention is not limited to this. For example, as the transmission means for transmitting the driving force from the sheet feeding motor to the sheet feeding belt or the pull-out roller, an appropriate one such as a gear or a pulley can be used. Also, a clutch having an appropriate configuration can be employed.

The present invention can be applied not only as a sheet conveying apparatus for sending a document but also as a sheet conveying apparatus for conveying a sheet as a recording medium.
The automatic document feeder to which the present invention is applied is not limited to the sheet-through method, and can be mounted on an image reading device that reads a document stopped on the contact glass surface while the reading unit is running (document stopping method). is there. Further, the image forming apparatus is not limited to a full-color machine, and may be a multi-color machine or a monochrome apparatus having a plurality of colors. Of course, the image forming apparatus is not limited to a copying machine, but may be a facsimile machine or a multifunction machine having a plurality of functions.

1 Seat-through ADF
DESCRIPTION OF SYMBOLS 3 Movable original table 2 Original table 4 Set filler 5 Set sensor 7 Pickup roller 8 Table rise detection sensor 9 Paper feed belt 10 Reverse roller 20 Reading means 40 Electromagnetic clutch 46 Torque limiter 100 Controller part 102 Paper feed motor 310 Copying apparatus main body 320 Feed Paper

JP-A-6-16261 JP-A-3-36132 JP 2001-253582 A

Claims (13)

Separating means that separates the sheets called from the sheet stacking unit one by one and conveys them downstream; conveying means positioned immediately downstream in the conveying direction of the separating means; and the separating means and the conveying means in a fixed direction One drive means that is driven by rotation of the motor, and a drive switching means that is arranged in a drive system from the drive means to the transport means and switches between transmission and interruption of the driving force,
After the driving switching means cuts off the driving force to the conveying means, the separation means separates and feeds the sheet, and the sheet is abutted against the conveying means, and then the driving switching means drives the conveying means to the conveying means. And then the sheet is conveyed, and then the drive switching unit stops the driving unit while maintaining the driving force transmission state and holds the excitation state of the driving unit for a predetermined time. apparatus.   The sheet conveying apparatus according to claim 1, wherein a sheet is conveyed by a predetermined amount by the separating unit after the leading end of the sheet is abutted against the conveying unit in a state where the driving force is blocked. Separating means that separates the sheets called from the sheet stacking unit one by one and conveys them downstream; conveying means positioned immediately downstream in the conveying direction of the separating means; and the separating means and the conveying means in a fixed direction One drive means that is driven by rotation of the motor, and a drive switching means that is arranged in a drive system from the drive means to the transport means and switches between transmission and interruption of the driving force,
When the driving switching means cuts off the driving force to the conveying means and the separating means separates and feeds the sheet, the driving switching means transmits the driving force when the sheet is abutted against the conveying means. A sheet conveying apparatus characterized in that after the blocking is performed at least once, the conveying means is driven with the drive switching means in a driving force transmission state.   A sheet detecting means is provided between the separating means and the conveying means, and after the leading edge of the sheet is detected by the sheet detecting means, the driving force is transmitted and interrupted by the drive switching means at least once. Item 4. The sheet conveying apparatus according to Item 3.   5. The driving force transmission time for the first time is the shortest when the driving force is transmitted and interrupted by the driving switching unit a plurality of times when the sheet is abutted against the conveying unit. The sheet conveying apparatus according to the description.   6. The driving force transmission time is gradually increased when the driving force is transferred and blocked by the driving switching unit a plurality of times when the sheet is brought into contact with the conveying unit. 6. The sheet conveying apparatus according to claim 1.   The sheet conveying linear speed by the separating means is set to be slower than the sheet conveying linear speed by the conveying means, and a one-way clutch is provided in the separating means so as to be able to follow in the sheet conveying direction. The sheet conveying apparatus according to any one of claims 1 to 6.   The sheet conveying apparatus according to claim 1, wherein the drive switching unit is an electromagnetic clutch.   The sheet conveying apparatus according to claim 1, wherein the driving unit is a stepping motor.   The sheet conveying apparatus according to claim 1, wherein the sheet is a recording medium.   An automatic document feeder comprising the sheet conveying device according to claim 1.   An image reading apparatus comprising the automatic document feeder according to claim 11. An image forming apparatus comprising the sheet conveying device according to claim 1, the automatic document feeder according to claim 11, or the image reading device according to claim 12.

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