JP2009007087A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device capable of surely separating and feeding sheets without giving damage to the sheets. <P>SOLUTION: A first sheet separating member 5 for separating sheets to be fed by a sheet feeding member 4 is brought in pressure-contact with the sheet feeding member 4 freely to be brought in contact and separated with/from the sheet feeding member 4. When the first sheet separating member 5 is separated from the sheet feeding member 4 by a predetermined quantity by the sheet passing through a pressure-contact part between the sheet feeding member 4 and the first sheet separating member 5, a second sheet separating member 8 is projected into a sheet conveyance path R so as to separate the sheet to be fed by the sheet feeding member 4. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to a configuration of a sheet separating unit that separates sheets fed by a sheet feeding member one by one.

  Some conventional image forming apparatuses form an image on a sheet using, for example, an electrophotographic image forming system. Examples of such an image forming apparatus include an electrophotographic printer such as an electrophotographic copying machine, a laser printer, and an LED printer, a facsimile apparatus, a word processor, and a multifunction printer that is a combination of these.

  Incidentally, the image forming apparatus includes a sheet feeding unit for feeding sheets stored in a sheet feeding cassette or a multi sheet feeding tray toward the image forming unit. In a small / low-cost image forming apparatus, a multi-feed tray is often used because of its high flexibility that can handle various sheets.

  Here, the sheet feeding unit prevents, for example, a sheet separation member, which is a friction member such as a separation pad, from being pressed against the sheet feeding member, and feeds only the uppermost sheet one by one. Some have a sheet separation unit of the above type (see Patent Documents 1 and 2).

  FIG. 8 is a diagram illustrating a configuration of a sheet separation unit of a conventional image forming apparatus. In FIG. 8, 103 is a paper feed roller, 85 is a separation pad, and 86 is a rotatable separation pad holder for holding the separation pad 85. The separation pad holder 86 is urged by a pad spring (not shown), so that the separation pad 85 is pressed against the paper feed roller 103.

  Reference numeral 107 denotes a swingable intermediate plate that supports a sheet to be fed. The intermediate plate 107 rotates in the vertical direction as the sheet feed roller 103 rotates. The intermediate plate 107 is rotated downward after the paper feeding operation is completed. When the intermediate plate 107 is rotated downward in this manner, the separation pad 85 is separated from the paper supply roller 103 accordingly. It is supposed to be. Reference numeral 81 denotes a separation subpad. The separation subpad 81 moves to a position (a side of the sheet feeding roller 103) to prevent the sheet from being double-fed in accordance with the downward rotation of the intermediate plate 107, and the double-fed sheet. Is to regulate.

  In the image forming apparatus including the sheet separating unit having such a configuration, when the sheet feeding roller 103 rotates, the intermediate plate 107 rotates upward to press the sheet P against the sheet feeding roller 103. Further, the separation pad holder 86 rotates upward about the rotation shaft 86a so that the separation pad 85 is pressed against the paper feed roller 103.

  As a result, the sheet P is fed out by the paper feed roller 103, and thereafter, the sheet P is separated one by one by the separation pad 85 when passing through the separation nip formed by the paper feed roller 103 and the separation pad 85. The

  When the leading edge of the sheet P reaches the downstream conveying roller pair, the intermediate plate 107 rotates downward, and accordingly, the separation pad holder 86 rotates downward to separate the separation pad 85 from the paper feed roller 103. . At the same time, the separation subpad 81 moves to a position that prevents double feeding of sheets shown in FIG. By moving the separation subpad 81 in this way, even if the paper feed roller 103 and the separation pad 85 are separated from each other, the separation subpad 81 can prevent the sheet P from being double-fed.

  Here, in the case of a sheet separation unit using such a separation subpad 81, the separation pad 85 is separated from the sheet feed roller 103 after the sheet feeding operation is completed, so that the load at the time of sheet conveyance by the pair of conveyance rollers on the downstream side is increased. Can be small. Further, the sheet can be easily removed during the jam processing. For this reason, the sheet separation unit using the separation subpad 81 is often used in an image forming apparatus using a multi-feed tray.

  FIG. 9 is a diagram illustrating another configuration of the sheet separating unit of the conventional image forming apparatus. In this case, the separation pad 85 is not separated from the sheet feeding roller 103 even after the sheet feeding operation is completed. The sheet is prevented from being double fed by the frictional force of the separation pad 85. Such a sheet separation unit is often used in an image forming apparatus using a sheet feeding cassette.

JP-A-8-81078 JP 2001-335176 A

  By the way, in an image forming apparatus including a sheet separation unit using a separation subpad, an OHT (Over-Head Transparency), a sheet with a curled tip, or the like may be fed. Here, in the case of these sheets, the leading end is not easily caught by the separation subpad, so that double feeding may occur.

  For this reason, even in the multi-feed tray configured so that the middle plate rotates in the vertical direction, the separation nip is not opened even after the sheet feeding operation is completed as shown in FIG. There is a case where a configuration that is not separated from the paper roller 103 is employed.

  However, in the multi-feed tray, when the sheet separation unit is configured so that the feed roller and the separation pad are not separated from each other, when feeding a highly rigid sheet such as an envelope or cardboard, Reaction force due to rigidity is received by the separation pad. When the reaction force due to the rigidity of the sheet is received in this way, the separation pad is pushed down and double feeding may occur.

  Here, in order to prevent double feeding due to such a cause, the spring force of the pad spring may be increased so that the separation pad does not lose the rigidity of the seat. However, in this case, if the spring force is excessively increased, the basic sheet feeding / separation performance changes, and the area where sheet feeding / separation can be performed stably decreases. In other words, in order to prevent double feeding, it is only necessary to increase the spring force of the pad spring so that the separation pad is not pushed down. However, if the spring force is simply increased, problems such as poor paper feeding occur.

  In addition, in order to prevent double feeding due to the above-described causes, a configuration in which the width of the spring force of the pad spring is reduced and a separation subpad is used may be used in combination. However, depending on the magnitude of the spring force of the pad spring, when a thin sheet is conveyed, the sheet conveyance speed may be reduced. In this case, after that, when the separation subpad moves to a position to prevent double feeding, the separation subpad hits the sheet, and the sheet is damaged.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of reliably separating and feeding sheets without causing damage. .

  The present invention provides an image forming apparatus comprising: a sheet feeding member that feeds a sheet; and a sheet conveyance path that guides the sheet fed by the sheet feeding member. A first sheet separating member that separates the sheet fed by the sheet feeding member, and a second sheet separating member that is provided on the downstream side of the first sheet separating member in the sheet feeding direction and can be moved in and out of the sheet conveying path. The second sheet separating member protrudes into the sheet conveying path and separates the sheet when the first sheet separating member is separated from the sheet feeding member by a predetermined amount by the sheet to be separated. It is characterized by this.

  As in the present invention, when the first sheet separating member is separated from the sheet feeding member by a predetermined amount, the second sheet separating member is protruded into the sheet conveying path to separate the sheets, so that the damage can be ensured without causing damage. Sheets can be fed separately.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an electrophotographic printer which is an example of an image forming apparatus according to a first embodiment of the present invention.

  In FIG. 1, 50 is a printer, 51 is a printer main body, 52 is provided in the printer main body 51, and forms an image by an electrophotographic method. 53 is a sheet feeding unit that feeds a sheet P to the image forming unit 52. Part.

  Here, the image forming unit 52 includes a photosensitive drum 18 and the like that form a toner image. The process cartridge 15 that is detachably attached to the printer main body 51 and the toner image formed on the photosensitive drum 18 are formed on a sheet P. A transfer roller 12 for transferring is provided.

  The sheet feeding unit 53 includes a sheet feeding tray 17 provided in the printer main body 51, a half-moon-shaped sheet feeding roller 4 that is a sheet feeding member that feeds the sheets P stored in the sheet feeding tray 17, and a sheet feeding member 4. A sheet separation unit 54 that separates the sheet P sent out by the paper roller 4 is provided.

  Here, the sheet feeding tray 17 includes a sheet width regulating plate 9 that regulates both end positions in a direction orthogonal to the sheet feeding direction of the sheet P (hereinafter referred to as a width direction). Further, an intermediate plate 7 that presses the sheet P stacked on the paper feed tray 17 against the paper feed roller 4 is provided downstream of the paper feed tray 17 in the sheet feeding direction. The intermediate plate 7 is urged toward the paper feed roller by a spring (not shown). In FIG. 1, reference numeral 4 b denotes a sheet feeding roller having a smaller diameter than the sheet feeding roller 4 provided on the shaft 4 a of the sheet feeding roller 4.

  The sheet separation unit 54 is a separation pad 5 that is a first sheet separation member that is press-contacted to and separate from the paper feed roller 4, and a holding member that holds the separation pad 5 so as to be able to contact and separate from the paper feed roller 4. A separation pad holder 6 is provided. Further, the sheet separating unit 5 includes a separation pad spring 11 that urges the separation pad holder 6 toward the sheet feeding roller to press the separation pad 5 against the sheet feeding roller 4.

  In the present embodiment, the separation pad 5 is urged by the separation pad spring 11 so as to come into pressure contact with the sheet feeding roller 4 when the sheet is fed by the sheet feeding roller 4, and the sheet is fed by the sheet feeding roller 4. After being pushed, it is urged so as to come into pressure contact with the paper feed roller 4b.

  Next, an image forming operation in the printer 50 having such a configuration will be described.

  When a print start signal is input after the sheet P to which toner is transferred is set on the paper feed tray 17 and the intermediate plate 7, a driving force is applied by a drive gear train (not shown), and the paper feed roller 4 The roller 10, the photosensitive drum 18 and the like are driven.

  Here, when the paper feed roller 4 rotates in the direction of the arrow, a shaft (4a) of the paper feed roller 4 is provided with a paper feed cam (not shown) that regulates the position of the rotatable intermediate plate 7. The paper cam also rotates with the paper feed roller 4. Then, the intermediate plate 7 rotates upward in conjunction with the rotation of the sheet feeding cam to press the sheet P against the sheet feeding roller 4.

  As a result, first, the sheet P set on the paper feed tray 17 and the intermediate plate 7 is sent out by friction with the paper feed roller 4. Further, when the sheet P is fed by the sheet feeding roller 4, the sheet P is guided by the sheet width regulating plate 9.

  On the other hand, simultaneously with the rotation of the sheet feeding roller 4, the uppermost sheet P1 is separated from the next sheet P2 by the separation pad 5 as shown in FIG. 3 to be described later by the separation pad 5 biased by the separation pad spring 11. The Accordingly, the fed uppermost sheet P1 is conveyed to the image forming unit 52 by the conveying roller pair 10 provided in the sheet conveying path R for guiding the uppermost sheet P1. Immediately before the end of one rotation of the paper feed roller 4, the paper feed cam provided on the shaft 4a of the paper feed roller 4 pushes down the middle plate 7 to the paper feed standby position. Return to position.

  Next, when the sheet P1 is conveyed by the conveying roller 10, the laser exposure device 16 irradiates the photosensitive drum 18 with laser light at a predetermined timing. As a result, an electrostatic latent image is formed on the photosensitive drum 18, and this electrostatic latent image is developed with toner and visualized. Thereafter, the visualized toner image on the photosensitive drum 18 is transferred onto the sheet P 1 by the transfer roller 12.

  Next, the sheet P1 on which the toner image is formed is heated and pressed by the fixing device 13, whereby the toner image is permanently fixed on the sheet P1. Thereafter, the sheet P1 on which the toner image is fixed is discharged out of the printer main body by a paper discharge roller 19 and stacked on a paper discharge tray 14 provided on the upper surface of the printer main body.

  FIG. 2 is a perspective view showing the configuration of the sheet separation unit 54 and the sheet conveyance path R. In FIG. 2, reference numeral 1 denotes a frame that forms the sheet conveyance path R, and 8 is a separation subpad that is provided on the downstream side of the separation pad 5 in the sheet feeding direction, and is a second sheet separation member that can appear and disappear in the sheet conveyance path R. is there.

  Here, as shown in FIG. 3, the separation subpad 8 is swingably provided on the frame 1 with the swing shaft 8a as a fulcrum. As will be described later, one end of the separation subpad 8 is provided with a pressing portion 8b that is pressed by the separation pad holder 6 when the separation pad holder 6 moves by a predetermined amount, and a stopper portion 8c that is a contact portion is provided at the other end. I have.

  Further, when the pressing portion 8b is pressed by the separation pad holder 6, the separation subpad 8 swings with the swing shaft 8a as a fulcrum. At this time, the separation subpad 8 protrudes into the sheet conveyance path R to prevent double feeding of sheets. And a stopper portion 8c which is a contact portion. The separation subpad 8 is normally held at a position where the stopper portion 8c is retracted from the sheet conveying path R by a biasing member (not shown).

  FIG. 3 shows a state in which the separation pad 5 is pressed against the sheet feed roller 4 by the spring force of the separation pad spring 11 without being pushed down by the sheet P when the sheet P is fed by the sheet feed roller 4. Yes. That is, the sheet feeding state in the case where the rigidity of the sheet to be fed is not so great as to push down the separation pad 5 is shown.

  In this configuration, the separation pad 5 is pressed against the sheet feeding roller 4 b by the spring force of the separation pad spring 11, thereby forming a separation nip that is a pressure contact portion between the sheet feeding roller 4 b and the separation pad 5. Then, by passing through the formed separation nip, the uppermost sheet P1 is separated from the next sheet P2 by the separation pad 5, and the occurrence of double feeding can be prevented.

  Note that the separation pad 5 is pushed down by the thickness of the sheet P1 when the sheet P1 passes through the separation nip, but the amount by which the separation pad 5 is pushed down is small. For this reason, even if the separation pad holder 6 rotates integrally with the separation pad 5, the separation subpad 8 does not swing when pressed against the separation pad holder 6. For this reason, the stopper portion 8c of the separation subpad 8 is in a position retracted with respect to the sheet conveyance path R, and does not affect the sheet feeding.

  On the other hand, in the case where the sheet is a highly rigid sheet such as an envelope or cardboard, the sheet is bent along the outer periphery of the sheet feeding roller 4b, and thus has a large force to return (try to return). A pressing force is applied to the separation pad 5 shown in FIG. When the force at this time exceeds the spring force of the separation pad spring 11, the separation pad 5 rotates downward integrally with the pad holder 6 that can rotate (movable) about the rotation shaft 6A. Separated from the paper roller 4b.

  Even when the separation pad 5 is separated from the sheet feeding roller 4b as described above, when the separation pad 5 protrudes into the sheet conveyance path R, the separation pad 5 can prevent the occurrence of double feeding to some extent. However, if the separation pad 5 is pushed down until it does not protrude from the sheet conveyance path R, the separation pad 5 cannot prevent the occurrence of double feeding.

  Here, in the present embodiment, the separation pad 5 is pushed down in this way, and the pressing portion 8b of the separation subpad 8 is pressed by the separation pad holder 6 that rotates downward along with this. Then, the separation subpad 8 swings around the swinging shaft 8a, and the stopper portion 8c protrudes into the sheet conveyance path R. That is, when the separation pad 5 is separated from the sheet feeding roller 4b by a predetermined amount, the stopper portion 8c protrudes into the sheet conveyance path R.

  When the stopper portion 8c protrudes into the sheet conveyance path R in this way, the next sheet P2 fed together with the uppermost sheet P1 comes into contact with the protruded stopper portion 8c in sliding contact with the back surface of the uppermost sheet P1. The sheet P2 is regulated. Thereby, it is possible to prevent double feeding of the uppermost sheet P1 and the next sheet P2.

  Further, the timing at which the separation subpad 8 protrudes is when the separation pad 5 is separated from the sheet feeding roller 4b by a predetermined amount by being pressed by a rigid sheet. Therefore, for example, when a thin sheet is fed, the normal separation operation by the separation pad 5 is performed, and the separation subpad 8 does not protrude, so that the sheet is not damaged.

  In this way, when the separation pad 5 is separated from the sheet feeding roller 4b by a predetermined amount, the separation subpad 8 protrudes into the sheet conveyance path R, thereby reliably separating and feeding the sheet without causing damage. Can do.

  That is, when the separation pad 5 is pushed down due to the rigidity of the sheet, the separation subpad 8 is projected to prevent double feeding of a rigid sheet, poor feeding of a thin sheet, and occurrence of damage. Can do. In the case of an ordinary sheet, since the sheet is fed without the separation nip being opened, a stable separation performance can be exhibited even with a sheet having a curled tip such as a backing paper.

  Next, a second embodiment of the present invention will be described.

  FIG. 5 is a perspective view showing a sheet feeding / conveying section of the image forming apparatus according to the present embodiment, and FIG. 6 is a sectional view thereof. 5 and 6, the same reference numerals as those in FIGS. 2 and 3 described above indicate the same or corresponding parts.

  In FIGS. 5 and 6, reference numeral 28 denotes a separation subpad capable of appearing and retracting in the sheet conveyance path R. As shown in FIG. 6, the separation subpad 28 is swingably provided on the frame 1 with a swing shaft 28a as a fulcrum, and when the separation pad holder 6 is moved by a predetermined amount as will be described later, A pressing portion 28b to be pressed is provided.

  Further, when the pressing portion 28b is pressed by the separation pad holder 6, the separation subpad 28 swings with the swing shaft 28a as a fulcrum. At this time, the separation subpad 28 protrudes into the sheet conveyance path R to prevent double feeding of sheets. And a stopper portion 28c. The separation subpad 28 is normally held at a position where the stopper portion 28c is retracted from the sheet conveyance path R by a biasing member (not shown).

  In the present embodiment, the contact portion 28d that contacts the sheet of the stopper portion 28c is provided with a step portion having at least two steps or more formed so that the downstream side in the sheet feeding direction is sequentially increased. ing.

  FIG. 6 shows a state in which the separation pad 5 is pressed against the sheet feeding roller 4 b by the spring force of the separation pad spring 11 without being pushed down by the sheet P. That is, the sheet feeding state in the case where the rigidity of the sheet to be fed is not so great as to push down the separation pad 5 is shown.

  At this time, since the separation pad 5 is not pushed down, the separation subpad 28 is not pressed by the separation pad holder 6 and swings. Therefore, the stopper portion 28c of the separation subpad 28 is in a position retracted with respect to the sheet conveyance path R, and does not affect the sheet feeding.

  On the other hand, when the sheet is a highly rigid sheet such as an envelope or cardboard, the sheet cannot be bent along the outer periphery of the sheet feeding roller 4b, and the separation pad 5 indicated by the arrow 5A in FIG. A force to push down will be given. When the force at this time exceeds the spring force of the separation pad spring 11, the separation pad 5 rotates together with the pad holder 6 about the rotation shaft 6A and is separated from the paper supply roller 4b.

  When the separation pad 5 is pushed down in this way and the separation pad 5 is separated from the paper supply roller 4b by a predetermined amount, the pressing portion 8b is pressed by the separation pad holder 6 that rotates downward along with this. As a result, the separation subpad 28 swings around the swinging shaft 28a, and the stopper portion 28c projects into the sheet transport path R.

  When the stopper 28c protrudes into the sheet conveyance path R in this way, the next sheet P2 fed together with the uppermost sheet P1 is regulated by sliding against the protruding stopper 28c on the back surface of the uppermost sheet P1. To do. As a result, the uppermost sheet P1 and the next sheet P2 come into contact with each other, and this double feeding of the sheet P2 can be prevented.

  In this way, when the separation pad 5 is separated from the sheet feeding roller 4b by a predetermined amount, the separation subpad 8 protrudes into the sheet conveyance path R, thereby reliably separating and feeding the sheet without causing damage. Can do.

  In addition, by providing a step portion having at least two steps or more in the contact portion 28d of the separation subpad 28, even when a plurality of sheets are sent to the uppermost sheet P1, The leading edge of the sheet can be regulated. Thereby, the double feed prevention effect can be further enhanced.

1 is a diagram illustrating a schematic configuration of an electrophotographic printer which is an example of an image forming apparatus according to a first embodiment of the present invention. FIG. 3 is a perspective view illustrating a configuration of a sheet separation unit and a sheet conveyance path provided in the printer. Sectional drawing which shows the structure of the said sheet | seat separation part and a sheet conveyance path. Sectional drawing which shows a state when feeding the sheet | seat with a large rigidity of the said sheet | seat separation part. FIG. 9 is a perspective view illustrating a configuration of a sheet separation unit and a sheet conveyance path provided in an image forming apparatus according to a second embodiment of the present invention. Sectional drawing which shows the structure of the said sheet | seat separation part and a sheet conveyance path. Sectional drawing which shows a state when feeding the sheet | seat with a large rigidity of the said sheet | seat separation part. FIG. 10 is a diagram illustrating a configuration of a sheet separation unit of a conventional image forming apparatus. FIG. 10 is a diagram illustrating another configuration of a sheet separation unit of a conventional image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Frame 4 Feed roller 4b Feed roller 5 Separation pad 6 Separation pad holder 7 Middle board 8 Separation sub pad 8c Stopper part 11 Separation pad spring 17 Feed tray 28 Separation sub pad 28c Stopper part 28d Contact part 50 Printer 51 Printer main body 52 Image forming unit 53 Sheet feeding unit 54 Sheet separating unit R Sheet conveying path P Sheet

Claims (3)

In an image forming apparatus comprising: a sheet feeding member that feeds a sheet; and a sheet conveyance path that guides a sheet fed by the sheet feeding member.
A first sheet separating member that is press-contactable to the sheet feeding member so as to be separated from the sheet feeding member and separates the sheet fed by the sheet feeding member;
A second sheet separating member provided on the downstream side in the sheet feeding direction of the first sheet separating member, and capable of appearing and retracting in the sheet conveying path,
The second sheet separating member protrudes into the sheet conveying path and separates the sheet when the first sheet separating member is separated from the sheet feeding member by a predetermined amount by the sheet to be separated. Image forming apparatus. A movable holder for holding the first sheet separating member so as to be able to contact and separate from the sheet feeding member;
The second sheet separating member is provided with a pressing portion at one end and a stopper portion at the other end so as to be swingable. When the first sheet separating member is separated from the sheet feeding member, the first sheet separating member is The image forming apparatus according to claim 1, wherein the pressing portion is pressed by the holder that moves integrally with the sheet separating member, and the stopper portion protrudes into the sheet conveyance path to separate the sheet.   The image forming apparatus according to claim 2, wherein the stopper portion of the second sheet separating member is provided with a step portion formed so that the downstream side in the sheet feeding direction becomes higher sequentially.

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