JP2008290809A - Sheet feeder and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent double feeding of sheets by using a non-separated friction separation system. <P>SOLUTION: This sheet feeder 31 is provided with a sheet house 2 in which the sheets are stacked, a feed rotating body 5 contacted and rotated with the uppermost sheet to feed the uppermost sheet of the sheets stacked in the sheet house 2, a main separating member 6 for separating the double feeding sheets by holding the sheets together with the feed rotating body 5, a guide member 92 for guiding the sheets fed by the feed rotating body 5 along an outer periphery of the feed rotating body 5, and an auxiliary separating member 8 disposed along the guide member 92 to receive distal end parts of the double feeding sheets which are not separated by the main separating member 6 and separate the double feeding sheets. A downstream side end part 8b of the sheet feeding direction of the auxiliary separating member 8 is extended from an intersection D of a tangential line L of the feed rotating body 5 passing the lowest downstream position C and the guide member 92 up to the downstream side, in a contact region of the feed rotating body 5 and the main separating member 6. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a sheet feeding apparatus that feeds a sheet, and an image forming apparatus including the sheet feeding apparatus.

  2. Description of the Related Art Conventionally, an image forming apparatus forms an image with an image forming unit on a sheet fed by a sheet feeding apparatus. In this case, the sheet feeding apparatus has a sheet separation function for separating the multi-fed sheets one by one so that the sheets can be fed one by one to the image forming unit. As such a sheet feeding apparatus, there is one disclosed in Patent Document 1.

  A conventional sheet feeding apparatus is shown in FIGS. 9 to 12, a sheet feeding device 131 for feeding a sheet to the image forming apparatus 101 is incorporated. The sheet feeding device 131 supplies a sheet by the half-moon-shaped feeding rotating body 105, and when the supplied sheet is multi-feeded, the friction of the feeding rotating body 105 and the friction of the main separation member 106 are used. The sheets that are being multi-fed (hereinafter referred to as multi-feed sheets) are separated and fed one by one. Such a method of separating sheets using friction is hereinafter referred to as a friction separation method.

  The friction separation method includes a separation friction separation method and a non-separation friction separation method. The separation friction separation method is a method of separating the main separation member 106 from the feeding rotation body 105 when conveyance of the sheet fed by the feeding rotation body 105 and the main separation member 106 is started by the conveyance roller pair 110. It is. After the main separation member 106 is separated, the sheet is fed in sliding contact with guide rollers 111 that are rotatably supported on both sides of the feeding rotating body 105. As a result, when the sheet is conveyed by the conveying roller pair 110, nipping of the sheet by the feeding rotating body 105 and the main separation member 106 is released, so that the conveyance resistance can be reduced. Therefore, the conveyance roller pair 110 can be driven with a small driving force, and conveyance damage (generation of roller marks, etc.) to the sheet can be reduced. On the other hand, the non-separation friction separation method is a method in which the main separation member 106 is not separated from the feeding rotating body 105.

(Separation friction separation method)
In the separation friction separation method, after the main separation member 106 is separated from the feeding rotating body 105, the friction resistance of the main separation member 106 does not act on the next sheet to be fed, and the lower sheet is fed out. There is a risk of double feeding due to static electricity. Hereinafter, the next sheet is referred to as a lower sheet. For this reason, in many cases, a sheet feeding apparatus that employs the separation friction separation system includes a movable auxiliary separation member to ensure separation of lower-order sheets.

  The sheet feeding device 131 shown in FIGS. 9 to 12 employs a separation friction separation method and includes a movable auxiliary separation member 151. The auxiliary separation member 151 rotates around the rotation center 153 (FIG. 11). The auxiliary separating member 151 has a friction part 152 formed in a step shape at one end with a rotation center 153 in between, and a spring part 154 formed so as to generate elasticity at the other end. The auxiliary separating member 151 is disposed on both sides of the feeding rotating body 105 (FIG. 9) so as to protrude so as not to come into contact with the feeding rotating body 105, and when the middle plate 104 moving up and down is lowered, the spring portion 154 is pressed by the intermediate plate 104, and the friction part 152 protrudes on both sides of the feeding rotating body 105. Further, when the intermediate plate 104 is lifted, the auxiliary separating member 151 rotates in a direction away from the feeding rotating body 105 around the rotation center 153 by its own weight, and waits at the standby position. .

  The sheet feeding device 131 feeds and rotates the sheet P placed on the middle plate 104 by raising the middle plate 104 provided in the paper storage 102 by a cam mechanism (not shown) during the sheet feeding operation. The body 105 is pressed. The feeding rotator 105 rotates to feed the sheet from the paper storage 102. At this time, the main separation member 106 is urged by the spring 156 to form a nip by being urged by the spring 156 on the downstream side of the leading end (downstream end) of the sheet fed from the intermediate plate 104. Yes. The sheet enters its nip. At this time, when the sheets are being fed in multiples, the main separation member 106 imparts frictional resistance to the lower sheet P2 to prevent the lower sheets from being fed.

The magnitude relationship of the friction of each part at this time is
Friction between feeding rotating body 105 and uppermost sheet P1> Friction between lower sheet P2 and main separation member 106> Friction between uppermost sheet P1 and lower sheet P2 (Formula 1)
It has become. Due to the magnitude relationship of the friction, the feeding rotating body 105 separates and feeds only the uppermost sheet P1 among the sheets P stacked on the intermediate plate 104.

  The main separating member 106 is configured to rotate in the vertical direction about the shaft 155 (FIG. 12) with respect to the paper storage 102. As shown in FIG. 12, in the main separating member 106, when the separated uppermost sheet P1 is fed into the conveying roller pair 110 and conveyance is started, the intermediate plate 104 is lowered by a cam mechanism (not shown). The main separating member 106 is pushed away from the feeding rotating body 105 against the spring 156 by pressing the intermediate portion 106 c having a mountain shape against the lowering intermediate plate 104. This is to reduce the sheet conveyance resistance, but the magnitude relationship of the friction shown in Formula 1 is lost, and there is a possibility that double feeding may occur on the sheet. In order to prevent this, the sheet feeding apparatus 131 includes the movable auxiliary separation member 151 described above.

  Simultaneously with the separation of the main separation member 106, the spring portion 154 of the movable auxiliary separation member 151 is pushed by the intermediate plate 104. Then, the friction part 152 of the auxiliary separating member 151 protrudes to the sheet side conveyed on both sides of the feeding rotating body 105, and the leading end of the lower sheet P2 is pressed by the friction part 152 formed in a step shape. As a result, the progress of the lower sheet P2 is stopped, the double feeding of the sheets is prevented, and only the uppermost sheet P1 is fed. The auxiliary separating member 151 is not pushed by the intermediate plate 104 while the main separating member 106 is in pressure contact with the feeding rotating body 105. The progress of the sheet P1 is not hindered.

(Non-separation friction separation method)
FIG. 13 shows a sheet feeding apparatus 132 that employs a non-separating frictional separation system in which the feeding rotating body 105 and the main separation member 206 are not separated from each other.

  Unlike the main separation member 106 used in the above-described separation friction separation method, the intermediate part of the main separation member 206 of the sheet feeding device 132 is not a mountain shape and is flat. Therefore, the main separation member 206 is urged by the spring 156 regardless of the up-and-down movement of the intermediate plate 104, and is always in a position where it can contact the arcuate portion 105a of the half-moon-shaped feeding rotating body 105. However, the main separation member 206 does not come into contact with the flat portion 105 b of the feeding rotating body 105 by the guide rollers 111.

  The non-separation friction separation method can stabilize the sheet conveyance state after feeding, and it is easy to stick on the sheet with images formed on both sides, but the separation performance is higher because the separation property of the sheet is higher than the separation separation method There is an advantage that it can be improved.

  However, the non-separation friction separation method cannot use the movable auxiliary separation member 151 as described above. The reason for this is that the non-separating friction separation method prevents the lower sheet from proceeding due to the frictional relationship of Equation 1 when the leading edge of the lower sheet is positioned between the feeding rotating body 105 and the main separating member 106. It is difficult to always stop the leading edge of the lower sheet at the same position. That is, when the leading edge of the lower sheet is sandwiched between the feeding rotating body and the main separating member due to the frictional relationship of Formula 1, the thickness of the sheet, the shape of the envelopes, the friction coefficient such as the film, etc. This is because there is a sheet whose tip position is easy to advance even if double feeding is not reached.

  In particular, a sheet having a strong force to return straight (a sheet having a high rigidity) has an uppermost position due to the strength of the rigidity when the portion of the guide member 192 on the downstream side of the feeding rotating body is sharply curved. The friction between the lower sheets becomes strong, and the tip tends to protrude downstream.

  A portion of the guide member 192 on the downstream side of the feeding rotating body 105 in the sheet feeding apparatus illustrated in FIG. 13 is abruptly curved.

  In the non-separation friction separation method, when the movable auxiliary separation member 151 (FIG. 11) is used in a state where the position of the leading edge of the sheet cannot always be constant, the friction portion 152 of the movable auxiliary separation member 151 is formed on the lower sheet P2. There is a risk of scratching the tip.

  Therefore, in the non-separating friction separation type sheet feeding device 132, the movable auxiliary separation member 151 cannot be attached, and the lower sheet is pressed only by the friction of the main separation member 206 to prevent double feeding. It has become.

  Here, when the lower sheet P2 cannot be pressed only by the friction of the main separation member 206, a technique of using a non-movable auxiliary separation member (not shown) having friction may be taken. Conventionally, the non-movable auxiliary separating member used in such a non-separating friction separating method is the inlet of the main separating member 206 in the sheet width direction and from the paper storage 102 to the feeding rotating body 105, that is, the feeding. It is provided on the upstream side of the guide member 192 so as to be located on the inlet side.

  The lower sheet P2 that cannot be stopped by the friction of the main separation member 206 is often a rigid sheet. The sheet having high rigidity pushes down the main separation member 206 to the opposite side to the feeding rotary body 105 (in a direction away from the feeding rotary body 105), and a gap is formed between the main separation member 206 and the feeding rotary body 105. This is because it is generated.

  In this way, double feeding that occurs due to the main separation member 206 being pushed down can be prevented by the non-movable auxiliary separation member provided at the aforementioned position. That is, when the main separation member 206 is in pressure contact with the feeding rotary body 105, the main separation member 206 is closer to the feeding rotary body 105 than the non-movable auxiliary separation member. However, when the main separation member 206 is pushed down by a rigid sheet, the main separation member 206 becomes flush with the non-movable auxiliary separation member, and the non-movable auxiliary separation member prevents the lower sheet P2 from being fed. As a result, only the uppermost sheet P1 among the sheets P stored in the paper storage 102 is fed.

JP-A-6-312846

  However, in the sheet feeding device 132 of the non-separation friction separation type incorporated in the image forming apparatus that has been recently increased in speed and size, it is very difficult to prevent the strong feeding of the sheets. is there. This is because the sheet conveyance speed is increased by the increase in speed, and the subsequent sheet is easily taken out by the preceding sheet. Further, for miniaturization, the guide member 192 from the feed rotating body 105 to the conveying roller pair 110 may be formed in a very steep curve. In such a case, the highly rigid sheet pushes the main separation member 206 away from the feed rotating body 105 due to the force (rigidity) of returning to the straightness of the sheet itself. This tendency is stronger as the curve of the guide member 192 becomes sharper.

  For this reason, the conventional non-separating friction separation type sheet feeding apparatus 132 can suppress the occurrence of double feeding of sheets, which is sufficient only by a non-movable auxiliary separation member (not shown) installed on the feeding inlet side. Can not.

  In order to suppress the occurrence of these double feeds, it is conceivable to increase the pressing force of the main separating member 206 against the feed rotating body 105. However, the main separation member 206 is always in contact with the sheet, and the pressing force cannot be easily increased in consideration of durability from the recent increase in speed.

  It is also conceivable to use a movable auxiliary separation member 151 that is provided in the separation friction separation type sheet feeding device 131 and interlocks with the intermediate plate 104. However, in this case, the leading edge of the subsequent sheet may be damaged, which is not preferable.

  An object of the present invention is to provide a sheet feeding apparatus that prevents double feeding of sheets by using a non-separating friction separation system.

  An object of the present invention is to provide an image forming apparatus that includes a sheet feeding device that prevents double feeding of sheets and forms an image on each sheet.

  The sheet feeding device of the present invention feeds the uppermost sheet by contacting and rotating the uppermost sheet among the sheet stacking means on which the sheet is placed and the sheets placed on the sheet stacking means. A first separation member that separates a multi-feed sheet by sandwiching a sheet between the feeding rotator and the feeding rotator, and a sheet fed by the feeding rotator on the outer periphery of the feeding rotator And a guide member that guides along the guide member. The guide member is disposed along the guide member and receives a leading end portion of the multi-feed sheet that has not been separated by the first separation member, and separates the multi-feed sheet. The feeding rotation provided with two separating members, and the downstream end of the second separating member in the sheet feeding direction passes through the most downstream position in the contact area between the feeding rotating body and the first separating member. Extends downstream from the intersection of the body tangent and the guide member It is characterized in that.

  In the sheet feeding device of the present invention, when there is a lower sheet that is not separated by the first separating member among the multi-feed sheets, the non-movable sheet extends to the downstream side in the sheet feeding direction. The sheet is received by the second separation member to prevent feeding. Therefore, the sheet feeding apparatus of the present invention can prevent double feeding of sheets without complicating the structure in the non-separation friction separation system having a simple structure.

  Hereinafter, a sheet feeding apparatus according to an embodiment of the present invention and an image forming apparatus including the sheet feeding apparatus will be described with reference to the drawings.

(Image forming device)
FIG. 1 is a cross-sectional view of the image forming apparatus according to the embodiment of the present invention along the sheet conveying direction.

  The sheet feeding device 31 incorporated in the image forming apparatus 1 sandwiches the sheet fed from the paper storage 2 by the feeding rotating body 5 by a non-separating frictional separation method between the feeding rotating body 5 and the main separation member 6. Thus, the double feeding is prevented and the sheets are fed one by one. The fed sheet is fed into the image forming unit 27 by the conveying roller pair 10. A latent image is formed on the photosensitive drum 28 of the image forming unit 27 by the laser scanner 16, and a toner image in which the latent image is visualized by toner stored in the toner cartridge 15 is formed.

  The sheet sent to the image forming section 27 is transferred with the toner image on the photosensitive drum 28 by the transfer roller 12 and sent to the fixing device 13 to fix the toner image. Finally, the sheet is discharged to the tray 14 by the discharge roller pair 22.

  As shown in FIG. 5, the image forming apparatus 1 also incorporates a sheet feeding device 32 according to another embodiment.

  In addition, the image forming apparatus includes a reversing mechanism for forming a toner image on both sides of the sheet, and a photosensitive drum, a transfer roller according to the number of colors for forming a color toner image on the sheet. Some of them have more than one. The sheet feeding devices 31 and 32 are also incorporated in each image forming apparatus (not shown). The sheet feeding devices 31 and 32 are not provided only in the image forming apparatus, but are also incorporated in an automatic document feeder (not shown) that automatically supplies a document to the image reading device. .

(Sheet feeding device of the first embodiment)
The sheet feeding apparatus according to the first embodiment of the present invention shown in FIGS. 1 to 4 employs a non-separating friction separating system in which the feeding rotating body 5 and the main separating member 6 are not separated from each other. The non-separation friction separation method can stabilize the sheet conveyance state after feeding, can improve the separation performance of the sheet on which images are formed on both sides, and the main separation member 6 in accordance with the feeding operation. There is an advantage that the structure is simple because it does not need to be operated.

  The sheet feeding device 31 includes a paper storage 2 as a sheet stacking unit, a feeding rotating body 5, a main separation member 6 as a first separation member, a guide roller 11, a guide member 92, and an auxiliary as a second separation member. The separation member 8 and the spring 56 are provided.

  The paper storage 2 has an intermediate plate 4 on which a plurality of sheets P are placed, and stores the sheets.

  The feeding rotating body 5 is formed in a half-moon shape with an arc portion 5a and a flat portion 5b. When the uppermost sheet P1 is press-contacted among the plurality of sheets P stacked on the intermediate plate 4 and pushed up by the intermediate plate 4, the feeding rotating body 5 rotates in contact with the arc portion 5a. The uppermost sheet is sent out from the paper vault 2.

  The main separating member 6 (FIG. 3) has a base end portion 6a supported by the paper storage 2 by a shaft 55, and a rotating end portion 6b pressed against the arc portion 5a of the feeding rotating body 5 by a spring 56. It has become. The main separating member 6 is urged by the spring 56 on the downstream side of the front end of the sheet fed by the arc portion 5a of the feeding rotating body 5, contacts the arc portion 5a to form a nip, and enters the nip. A friction resistance is imparted to the lower sheet P2 of the multi-feed sheets. Therefore, the main separating member 6 is a member that allows the feeding rotating body 5 to separate and feed only the uppermost sheet P1 by applying a frictional resistance to the lower sheet P2.

  When the sheet is conveyed by the conveying roller pair 10, the guide roller 11 receives the sheet instead of the feeding rotating body 5 because the flat portion 5 b of the feeding rotating body 5 faces the sheet. It is designed to guide the feeding. The guide roller 11 is not in contact with an auxiliary separating member 8 described later.

  A guide member 92 that guides the sheet is provided along the outer periphery of the feeding rotating body 5 and the guide rollers 11. The guide member 92 includes an arcuate arc guide surface 92a along the outer periphery of the feed rotating body 5 and the guide rollers 11, and a substantially vertical vertical guide surface 92b. A conveyance roller pair 10 is provided on the vertical guide surface 92b.

  The auxiliary separation member 8 will be described later.

  The pair of conveying rollers 10 receives the uppermost sheet fed by the feeding rotating body 5 and the main separating member 6 and continuously conveys it.

  The sheet feeding device 31 feeds and rotates the sheet P placed on the intermediate plate 4 by raising the intermediate plate 4 provided in the paper storage 2 by a cam mechanism (not shown) during the sheet feeding operation. It is brought into pressure contact with the arc portion 5 a of the body 5. Then, the feeding rotating body 5 rotates to feed the sheet from the paper storage 2. The sheet enters a nip formed by the feeding rotating body 5 and the main separation member 6. At this time, if the sheets are being fed in multiples, the main separation member 6 imparts a frictional resistance to the lower sheet P2 to prevent the lower sheets from being fed. Therefore, only the uppermost sheet is fed to the conveying roller pair 10 regardless of whether or not the sheets are double fed.

  When the conveyance of the sheet is started by the conveyance roller pair 10, the sheet feeding device 31 ends the feeding operation and enters a rest state. However, the upstream end portion from the middle portion of the uppermost sheet P1 immediately after the sheet feeding device 31 enters the resting state is sandwiched between the arc portion 5a of the feeding rotating body 5 and the main separation member 6. ing.

The magnitude relationship of the friction of each part at this time is
Conveying force of the conveying roller pair 10> (friction between the feeding rotating body 5 and the uppermost sheet P1), and (friction between the main separation member 6 and the uppermost sheet P1) (Formula 2)
It has become. Due to the magnitude relationship of this friction, the uppermost sheet is pulled by the conveying roller pair 10 and conveyed while sliding between the feeding rotating body 5 and the main separating member 6.

  A bundle of sheets P on the paper storage 2 is placed substantially horizontally on the intermediate plate 4. The vertical guide surface 92 b of the guide member 92 is formed substantially perpendicular to the sheet on the intermediate plate 4. For this reason, the arc guide surface 92a is formed in a sharp curve, and the sheet fed by the feeding rotating body 5 runs up the arc guide surface 92a in the sharp curve so that the conveying roller on the vertical guide surface 92b. It will be conveyed to the pair 10. In particular, as the image forming apparatus is reduced in size, the radius of curvature of the arc guide surface 92a becomes smaller, and the arc guide surface 92a becomes steeper.

  Thus, as the arc guide surface 92a becomes steeper, the sheet feeding device 31 becomes more difficult to convey while curving the sheet along the arc guide surface 92a. In particular, a thick sheet called heavy media or a sheet having a strong force to return straight (such as a “stiff sheet” hereinafter) such as envelopes is difficult to pass through the arc guide surface 92a.

  When a sheet having a high rigidity passes through the arc guide surface 92a, the main separating member 6 is moved to the opposite side of the feeding rotating body 5 (in a direction away from the feeding rotating body 5) by the force of returning to the straightness of the sheet itself. ) May be pushed down to create a gap between the main separating member 6 and the feeding rotating body 5. As a result, the main separation member 6 may not be able to sufficiently press the lower sheet P2 and may not be able to prevent double feeding of sheets.

  Here, it is conceivable to use the movable auxiliary separating member 151 (FIGS. 9 to 11) described in the conventional sheet feeding apparatus. However, as described in the conventional sheet feeding apparatus, the stiffer sheet has a stronger force to return straight as the curve of the arc guide surface 92a of the guide member becomes steeper, and the uppermost sheet and the lowermost sheet. Friction with the other sheet becomes strong, and the tip of the lower sheet tends to protrude downstream. For this reason, the movable auxiliary separation member 151 cannot be used.

  Therefore, the sheet feeding device 31 includes the auxiliary separating member 8 on the guide member 92. As shown in FIG. 2, the auxiliary separating member 8 is disposed on the left and right of the main separating member 6 (on both sides in the sheet width direction). An upstream end portion 8 a of the auxiliary separating member 8 in the sheet feeding direction A (FIG. 2) is located at a boundary between the paper storage 2 and the guide member 92 on the inlet side of the feeding rotating body 5. The boundary is also in the vicinity of the most upstream position of the contact area W (FIG. 4) of the main separation member 6 with respect to the arc portion 5 b of the feed rotating body 5. The downstream end portion 8b in the sheet feeding direction passes through the most downstream position C in the contact area W of the main separation member 6 with respect to the feeding rotating body 5, as shown in FIG. Is located downstream of the intersection D between the outer circular tangent line L and the guide member 92.

  The function of the auxiliary separating member 8 will be described.

  First, the function of the auxiliary separating member 8 when the sheet feeding device 31 feeds a general sheet that is not rigid is described.

  Of the sheets P stacked substantially horizontally on the paper stock 2, the uppermost sheet P <b> 1 is fed by the operation of the feeding rotating body 5 and the main separation member 6. Since the arcuate guide surface 92a has a sharp curve, the uppermost sheet P1 is fed while applying a force in a direction away from the feeding rotating body 5 to the main separating member 6 by the force of returning to the straightness of the sheet itself. The Then, the leading end of the uppermost sheet P1 is abutted against the auxiliary separation member 8. Thereafter, the uppermost sheet P <b> 1 receives a feeding force due to the rotation of the feeding rotating body 5 and is fed to the conveying roller pair 10 while sliding on the auxiliary separating member 8 and the guide member 92.

  At this time, even if it is a general sheet that does not have high rigidity, if it is in close contact with static electricity or if the sheet is in close contact with an easy-to-adhere sheet such as art paper, the overlapping lower sheets are the main ones. It is separated from the upper sheet by the separating member 6 and left behind. Even if the lower sheet is not separated from the upper sheet by the main separating member 6, the lower sheet is separated from the uppermost sheet by the auxiliary separating member 8. As a result, only the uppermost sheet P1 is fed.

  After the uppermost sheet P1 reaches the conveying roller pair 10 and starts to be fed, the feeding rotating body 5 stops rotating with the flat portion 5b facing the sheet. On both sides in the sheet width direction of the feeding rotator 5, guide rollers 11 are rotatably provided coaxially with the feeding rotator 5. The guide roller 11 and the main separating member 6 are disposed so as to be displaced from each other in the width direction of the sheet. The uppermost sheet P <b> 1 is fed by the conveying roller pair 10 so as to be pulled out while sliding between the guide roller 11 and the main separation member 6 or while receiving a small resistance by the follow-up rotation of the guide roller 11.

  The feeding rotating body 5 does not need to be formed in a half moon shape. It may be a perfect circle. In this case, the feeding rotating body 5 needs to be rotatable when the rotation is stopped, and the guide roller 11 is not required.

  In any case, when the uppermost sheet is conveyed to the conveying roller pair 10, it becomes a smooth curved surface connecting the guide roller 11 or the perfect circular feeding rotating body and the conveying roller pair 10.

  Next, the function of the auxiliary separation member 8 when the sheet feeding device 31 feeds a rigid sheet will be described.

  The uppermost sheet P <b> 1 fed by the sheet feeding device 31 has a smooth curved surface connecting the paper storage 2, the feeding rotating body 5, and the conveying roller pair 10. However, the uppermost sheet P <b> 1 presses the main separation member 6 in a direction in which the main separation member 6 is separated from the feeding rotating body 5 in an attempt to return to a flat state by a force of returning to the straightness of the sheet itself.

  This tendency indicates that the smaller the rear portion of the uppermost sheet P1 that is being transported remaining on the paper storage 2, the shorter the distance from the feeding rotating body 5 to the rear end of the uppermost sheet P1 and the higher the rigidity. Because it becomes difficult to bend, it appears remarkably. Also, when the uppermost sheet P1 passes through the arcuate guide surface 92a of the sharp curve of the guide member, the path length is different between the inner side and the outer side of the sheet. Therefore, when the uppermost sheet is an envelope, the surface of the envelope is A wave is applied and the main separation member 6 is pressed more strongly in a direction in which the main separation member 6 is separated from the feeding rotating body 5. In addition, some envelopes have an envelope opening formed in a direction intersecting the feeding direction. Such an envelope is taken out by feeding a lower envelope through the envelope opening during feeding. It may become a sending state.

  In this way, when the sheet feeding device 31 feeds a rigid sheet, the main separation member 6 is separated from the feeding rotating body 5 by the rigid sheet, and the main separation member 6 and the feeding rotation are separated. A gap may be formed between the body 5 and the body 5. When the feeding rotating body 5 feeds the sheet in this state, it becomes difficult for the main separating member 6 to prevent the lower sheet P2 from being fed following the uppermost sheet P1. As described above, the sheet feeding device 31 tends to have difficulty in preventing the multi-feeding of rigid sheets.

  Therefore, the auxiliary separating members 8 provided on the left and right sides of the main separating member 6, in particular, the upstream end portion (tip portion) 8 a in the sheet feeding direction of the auxiliary separating member 8 prevents the strong feeding of the strong sheet. To play a role.

  That is, the uppermost sheet P <b> 1 is received by the auxiliary separating member 8 by pressing the main separating member 6 against the spring 56 in a direction away from the feeding rotating body 5 with a force of returning straight. For this reason, the sheet separating surface 6d in which the main separating member 6 faces the feeding rotating body 5 and the sheet separating surface 8d in which the auxiliary separating member 8 faces the feeding rotating body 5 are flush with each other. In addition, when the uppermost sheet P1 is a sheet that tends to generate wrinkles such as an envelope, wrinkles may occur, and the wrinkles may push the main separating member 6 and the auxiliary separating member 8 may protrude. .

  As a result, the main separation member 6 and the auxiliary separation member 8 come into contact with the uppermost sheet P1, and the lower sheet P2 advances due to friction between the members 6, 8 and the uppermost sheet P1. To prevent. When the auxiliary separating member 8 protrudes as described above, the auxiliary separating member 8 comes into contact with the uppermost sheet P1, and friction between the auxiliary separating member 8 and the uppermost sheet P1 The progress of the lower sheet P2 is prevented. Therefore, the sheet feeding device 31 can prevent double feeding with the help of the auxiliary separating member 8 even if the sheet is a rigid sheet.

  Further, the downstream end portion 8b of the auxiliary separating member 8 has the most downstream position C in the contact area W so that the double feeding of sheets can be prevented even when the arc guide surface 92a of the guide member is sharply curved. It extends to the downstream side from the intersection D between the outer circumferential circle tangent L of the feed rotating body 5 and the guide member 92 that passes therethrough.

  Next, the effect of extending the auxiliary separation member 8 downstream from the intersection D will be described.

  When the main separating member 6 is pushed by the rigid sheet and is moved away from the feeding rotating body 5, the leading edge of the lower sheet P2 when the sheets are multi-feeded draws a locus along the tangent line L, Abuts on the intersection D.

  As a result, the auxiliary separating member 8 receives the leading end (downstream end) of the lower sheet P2 that has traveled over the main separating member 6, and the lower sheet P2 is frictioned between the auxiliary separating member 8 and the lower sheet P2. It is possible to prevent the double feed of the sheet by preventing the progress of P2.

  Further, the uppermost sheet P <b> 1 that has been prevented from being double fed and has reached the conveyance roller pair 10 is conveyed to the conveyance roller pair 10. At this time, as shown in FIG. 4, the downstream side of the uppermost sheet P <b> 1 is pulled by the conveying roller pair 10, and the upstream side is sandwiched between the feeding rotating body 5 or the guide roller 11 and the main separation member 6. Yes. For this reason, the uppermost sheet P1 does not come into contact with the auxiliary separation member 8 when being fed. For this reason, the sheet feeding apparatus 31 can feed the sheet without affecting other parts.

  Therefore, in the sheet feeding apparatus, the downstream end portion 8b of the auxiliary separating member extends to the downstream side from the intersection D between the tangent L of the feeding rotating body and the guide member 92, so that the guide member has a sharp curve. Even if the sheet is a rigid sheet, it is possible to prevent the sheets from being double-fed.

(Sheet feeding device of the second embodiment)
By the way, since the auxiliary separating member 8 described above is disposed on both sides of the main separating member 6, the uppermost sheet may be inclined due to a difference in left and right friction and an error in the left and right attachment positions. is there. When the sheet is slanted, it causes a sheet jam and an error in the toner image forming position on the sheet in the image forming apparatus 1.

  Therefore, as in the sheet feeding device 32 shown in FIGS. 5 to 8, one auxiliary separation member 25 is installed on the downstream side of the feeding rotating body 5 and the main separation member 6 so that the sheet is not inclined. Can be. This eliminates the cause of the sheet jam and reduces the occurrence of an error in the toner image formation position on the sheet in the image forming apparatus 1.

  In this case, the upstream end 25a, which is the upstream side of the auxiliary separating member 25 in the sheet feeding direction, is embedded under the arc guide surface 92a of the guide member 92 as shown in FIG. The downstream end portion 25b of the auxiliary separation member 25 in the sheet feeding direction protrudes from the vertical guide surface 92b of the guide member 92 toward the feeding rotating body. For this reason, the sheet separating surface 25d of the auxiliary separating member 25 is an inclined surface that is inclined from the vertical guide surface 92b of the guide member 92 toward the feeding rotating body as it goes downstream. The downstream end 25b is located downstream from the intersection D.

  Also in the sheet feeding device 32 of the present embodiment, the uppermost sheet P1 that has been prevented from being double fed and has reached the pair of transport rollers 10 is transported to the transport roller pair 10. At this time, as shown in FIG. 8, the downstream side of the uppermost sheet P <b> 1 is pulled by the conveying roller pair 10, and the upstream side is sandwiched between the feeding rotating body 5 or the guide roller 11 and the main separation member 6. Yes. For this reason, the uppermost sheet P1 does not come into contact with the auxiliary separation member 25 when being fed. Therefore, the sheet feeding device 32 can feed the sheet without affecting other parts.

  Thus, since the upstream side end 25a of the auxiliary separating member 25 is buried under the arc guide surface 92a of the guide member 92, when feeding the uppermost sheet P1 and lower sheets, The sheet is not caught by the upstream end 25 a of the auxiliary separation member 25. Therefore, the sheet feeding device 32 can smoothly feed the sheet.

  Note that the sheet guide surface of the auxiliary separating member is inclined, and the auxiliary separating member 8 provided in the sheet feeding device of the first embodiment may be similarly formed with an inclined surface.

FIG. 3 is a cross-sectional view of the image forming apparatus including the sheet feeding device according to the first embodiment of the present invention along the sheet conveying direction. FIG. 5 is a perspective view of the sheet feeding apparatus according to the embodiment of the present invention with a feeding rotating body removed. FIG. 3 is a cross-sectional view of the sheet feeding apparatus according to the first embodiment of the present invention along the sheet feeding direction. FIG. 4 is a diagram for explaining an operation in the sheet feeding apparatus of FIG. 3. FIG. 6 is a cross-sectional view of an image forming apparatus including a sheet feeding device according to a second embodiment of the present invention along a sheet conveying direction. FIG. 5 is a perspective view of the sheet feeding apparatus according to the embodiment of the present invention with a feeding rotating body removed. It is sectional drawing along the sheet feeding direction of the sheet feeding apparatus which concerns on 2nd Embodiment of this invention. FIG. 8 is a diagram for explaining an operation in the sheet feeding apparatus of FIG. 7. FIG. 10 is a cross-sectional view of an image forming apparatus provided with a conventional sheet feeding device along a sheet conveying direction. FIG. 10 is a perspective view of a conventional sheet feeding apparatus with a feeding rotating body removed. It is a perspective view of an auxiliary separation member. FIG. 11 is a diagram for explaining an operation in the sheet feeding apparatus of FIG. 10. It is sectional drawing along the sheet feeding direction of the other conventional sheet feeding apparatus.

Explanation of symbols

P sheet P1 uppermost sheet P2 lowermost sheet C most downstream position L tangent line D intersection point W contact area 1 image forming apparatus 2 paper storage (sheet stacking means)
DESCRIPTION OF SYMBOLS 5 Feeding rotary body 5a Arc part 5b Flat part 6 Main separation member (1st separation member)
6a Base end portion 6b Rotating end portion 6d Sheet separation surface 8 Auxiliary separation member (second separation member)
8a Upstream end 8b Downstream end 8d Sheet separation surface 10 Conveying roller pair 25 Auxiliary separation member (second separation member)
25a Upstream end portion 25b Downstream end portion 25d Sheet separation surface 27 Image forming portion 31 Sheet feeding device of first embodiment 32 Sheet feeding device of second embodiment 92 Guide member 92a Arc guide surface 92b Vertical guide surface

Claims (5)

Sheet stacking means on which sheets are placed;
Among the sheets placed on the sheet stacking means, a feeding rotating body that rotates in contact with the uppermost sheet and feeds the uppermost sheet;
A first separation member that separates the multi-feed sheet by sandwiching the sheet with the feeding rotating body;
In a sheet feeding apparatus comprising: a guide member that guides a sheet fed by the feeding rotating body along an outer periphery of the feeding rotating body;
A second separation member that is disposed along the guide member and receives a leading end portion of the multi-feed sheet that has not been separated by the first separation member and separates the multi-feed sheet;
The downstream end of the second separating member in the sheet feeding direction passes through the most downstream position in the contact area between the feeding rotating body and the first separating member, and the tangent line of the feeding rotating body and the guide Extending from the intersection with the member to the downstream side,
A sheet feeding apparatus characterized by that. The second separation member is provided on both sides of the first separation member in the sheet width direction.
The sheet feeding apparatus according to claim 1. The second separation member is provided downstream of the first separation member;
The sheet feeding apparatus according to claim 1. The sheet separation surface of the second separation member has an upstream end that is flush with the sheet guide surface of the guide member, and the feed rotation from the sheet guide surface of the guide member toward the downstream side. It is an inclined surface inclined toward the body,
The sheet feeding device according to any one of claims 1 to 3, wherein the sheet feeding device is provided. The sheet feeding device according to any one of claims 1 to 4,
An image forming unit that forms an image on the sheet fed by the sheet feeding device,
An image forming apparatus.

Images