JP2008213997A - Sheet feeder, image forming device, and image reading device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet feeder capable of preventing double-feeding by reliably interrupting a second sheet almost double-fed, even if a sheet with high stiffness pushes down a separating pad 10. <P>SOLUTION: The separating pad 10 is supported by a pad arm 9 energized by a compression spring 12 so as to move from a feeding roller. A carrying guide 30a guides a course of a sheet fed between the feeding roller 4 and the separating pad 10 while curving the course to the feeding roller 4 side. A pair of sub pads 13 is fixed to a feeding frame 30 on the outside of the carrying guide 30a. The sub pads 13 are guided by the carrying guide 30a so as to contact and interrupt a sheet fed by following a sheet pushing down the separating pad 10. The sub pads 13 are guided by the carrying guide 30a, and disposed at a height position which does not contact the sheet fed between the feeding roller 4 and the separating pad 10. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sheet feeding device that separates and feeds sheets one by one by frictional force with the separating member, and more specifically, when the sheet having high rigidity is bent and sent to the side opposite to the separating member, The present invention relates to a mechanism for preventing double feeding caused by being pushed down.

  Practical use of a sheet feeding device for nipping and conveying a sheet by a feeding rotating member that contacts the sheet surface and feeding the sheet and a separating member that rubs the back surface of the sheet, and separates the multiple fed sheets one by one ing.

  In the sheet feeding apparatus, when two sheets are about to be fed by the feeding rotating member and the separating member, as described later, μ1> between the feeding rotating member, the separating member, and the two sheets. If the frictional relationship of μ2> μ3 is established, the multifeeds are separated one by one. Here, μ1 is a frictional force between the feeding rotation member and the surface of the first sheet, μ3 is a frictional force between the two sheets, and μ2 is a frictional force between the back surface of the second sheet and the separating member. It is.

  That is, in a state where two sheets are sandwiched between the feeding rotation member and the separating member, the second sheet overcomes the frictional force of the first sheet by the relationship of μ2> μ3, and the separating member You can stop. On the other hand, according to the relationship of μ1> μ3, the first sheet overcomes the frictional force of the second sheet and is sent to the feeding rotation member.

  Patent Document 1 shows that when a sheet having high rigidity is guided to the separating member side by bending the traveling direction, the relationship of μ1> μ2> μ3 is broken and multifeed is likely to occur. Here, in order to prevent such double feeding, a pair of separation members supported by a seesaw mold is disposed opposite to the feeding rotation member. When the highly rigid sheet bent in the traveling direction toward the separating member pushes down the separating member on the downstream side, the separating member on the upstream side strongly rubs the back surface of the second sheet due to the pushing force, and double feed is performed. Separate one by one.

  Patent Document 2 discloses a sheet feeding apparatus in which a pair of auxiliary separating members are arranged with a separating member interposed in a direction orthogonal to the sheet feeding direction of the sheet surface. The auxiliary separation member is disposed with a positional relationship fixed with respect to the separation member. The auxiliary separation member is formed lower than the separation member on the upstream side of the clamping position between the feeding rotation member and the separation member, and the auxiliary separation member is formed higher than the separation member on the downstream side. As a result, the frictional force between the auxiliary separation member and the second sheet gradually increases with the progress of the sheet, and the second sheet is dammed during the process.

JP-A-7-33273 JP 62-222944 A

  As the application of the image forming apparatus expands, the sheet feeding apparatus mounted on the image forming apparatus is also required to be applied to sheets of various materials, thicknesses, and rigidity. In addition, as the machine size (installed floor area) of the image forming apparatus is reduced, the sheet feeding apparatus (between the feeding rotating member and the sheet feeding apparatus that bends the traveling direction greatly toward the feeding rotating member and sends the sheet at a position close to the feeding rotating member. 1) is also required.

  However, when the guide member is arranged at a position close to the feeding rotation member and the sheet traveling direction is bent toward the feeding rotation member, if the sheet has high rigidity, the sheet guided by the guide member strongly strengthens the separation member. Pushing down makes it easier to double feed. If the separating member is pushed down, as will be described later, the two rotatingly fed sheets cannot be normally sandwiched between the feeding rotating member and the separating member, and the relationship of μ1> μ2> μ3 is lost. is there. This is because when the clamping force is lost, the frictional force μ2 between the separation member and the second sheet decreases, while the press contact positions of the two sheets are generated at two front and rear positions, and the frictional force μ3 increases.

  In such a case, the auxiliary separating member disclosed in Patent Document 1 exerts a large clamping force on the first sheet, making it difficult to pull the first sheet downstream. Further, the auxiliary separation member disclosed in Patent Document 2 is pushed down integrally with the separation member and cannot prevent double feeding of two sheets.

  Here, if the pressure contact force of the separating member with respect to the feeding rotation member is increased, it may be possible to overcome the rigidity of the sheet guided by the guide member and maintain the nipping and conveyance between the separating member and the feeding rotation member normally. However, when the pressure contact force of the separating member with respect to the feeding rotation member is increased, the possibility of jamming is prevented in the case of a thin sheet or a sheet having a small rigidity because the penetration between the separating member and the feeding rotation member is hindered.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a sheet feeding device that can reliably dam the second sheet that has been double fed and prevent double feeding even if the separation member is pushed down by a highly rigid sheet.

  The sheet feeding device according to the present invention includes a feeding rotating member that feeds a sheet, a separating member that separates the sheet between the feeding rotating member, and the separating member that urges the feeding rotating member. A biasing member that is in pressure contact with the feed rotating member and the separating member, and the feeding rotating member is moved from the feeding rotating member to a position pressed against the separating member and the feeding rotating member. And an auxiliary separating member disposed at a position separated in the radial direction.

  Further, the present invention provides a feeding rotation member that feeds a sheet, a separation member that separates the sheet between the feeding rotation member, and urges the separation member toward the feeding rotation member. An auxiliary separation member that can come into contact with the sheet to be fed to the separation sheet when the separation member moves in a direction away from the feeding rotation member by the support mechanism to be pressed and the sheet separated by the separation member And.

  In the sheet feeding apparatus of the present invention, the separating member is pushed down by the sheet when separating a highly rigid sheet, but the sheet fed to the separated sheet is blocked by the auxiliary separating member.

  That is, the auxiliary separating member functions when the separating member is pushed down, and comes into contact with the second sheet fed to the first sheet to be separated and stops the second sheet.

  Therefore, even if the separating member is pushed down by a highly rigid sheet and the relationship of μ1> μ2> μ3 is broken, the second sheet that has been fed can be reliably damped to prevent double feeding. By using a biasing member with a weak biasing force that can be pushed down by a highly rigid sheet, it is possible to provide a sheet feeding device that is unlikely to cause a jam even with a thin sheet or a small rigid sheet.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention replaces a part or all of the configuration of the embodiment with an alternative configuration as long as the sheet is fed by bending the traveling direction from between the feeding rotation member and the separation member to the feeding rotation member side. Other embodiments can also be implemented.

  As will be described later, the sheet feeding apparatus of the present invention can be mounted not only on an image forming apparatus but also on various sheet processing apparatuses such as an image reading apparatus, a sheet processing apparatus, and the like.

  The image forming apparatus of the present invention can be implemented not only for monochrome printers but also for various applications such as electrophotographic full-color printers, copiers, FAX machines, and multifunction machines. The image forming apparatus of the present invention can be implemented not only in an electrophotographic system but also in various printing systems that form images on various types of sheet materials.

  Note that the general configuration and control of the sheet feeding apparatus and the image forming apparatus disclosed in Patent Documents 1 and 2 are not illustrated and redundant description is omitted.

<Image forming apparatus>
FIG. 1 is an explanatory diagram of the configuration of the image forming apparatus of the present embodiment. The image forming apparatus 200 is an electrophotographic monochrome printer.

  As shown in FIG. 1, in the image forming apparatus 200, a sheet feeding unit 100 is disposed in a lower housing of the apparatus main body. The uppermost sheet S stacked on the middle plate 20 of the sheet feeding unit 100 is pulled out by the feeding roller 4 and separated one by one at the contact portion between the feeding roller 4 and the separation pad 10. The sheet S sent to the feeding roller 4 is guided by the conveyance guide 30 a and delivered to the registration roller 123, and is sent out to the transfer nip between the photosensitive drum 112 and the transfer roller 116 by the registration roller 123.

  In the image forming unit 110, a charging roller 113, an exposure device 117, a developing unit 115, a transfer roller 116, and a cleaning unit 118 are arranged around a rotating photosensitive drum 112. The photosensitive drum 112, the charging roller 113, the developing unit 115, and the cleaning unit 118 are assembled in a cartridge and can be exchanged by pulling them out to the front side.

  The charging roller 113 uniformly charges the surface of the photosensitive drum 112 cleaned by the cleaning unit 118. The exposure device 117 scans the surface of the charged photosensitive drum 112 with a laser beam modulated by an image signal, and writes an electrostatic image. The developing unit 115 electrostatically attaches the toner T carried on the developing sleeve 114 to the electrostatic image on the photosensitive drum 112 to form a toner image. The transfer roller 116 is applied with a transfer voltage having a polarity opposite to the charging polarity of the toner image formed on the photosensitive drum 112, and transfers the toner image from the photosensitive drum 112 to the sheet S sent to the transfer nip. The sheet S to which the toner image is transferred is sent to the fixing device 120 and is nipped and conveyed by a fixing nip between the pressure roller 129 and the heating unit 128 to fix the toner image on the surface. The sheet S on which the toner image is fixed is discharged to the tray 126 by the discharge roller 125.

<Sheet feeding apparatus according to the first embodiment>
2 is a perspective view of the sheet feeding unit according to the first embodiment in a standby state, FIG. 3 is an explanatory diagram of assembling of the feeding roller shaft unit, and FIG. 4 is an explanatory diagram of assembling of the separation pad unit.

  As shown in FIG. 2, the sheet feeding unit 100, which is an example of a sheet feeding apparatus, pulls out the uppermost sheet stacked on the intermediate plate 20, and includes a feeding roller shaft unit 40 and a separation pad unit 41. Separate them one by one and feed them upward in the figure.

  As shown in FIG. 3, the feeding roller 4, which is an example of a feeding rotation member, contacts the upper surface of the sheet and feeds the sheet.

  As shown in FIG. 4, the separation pad 10, which is an example of a separation member, is for separating the sheet from the feeding roller 4.

  The pad arm 9 and the compression spring 12, which are an example of a support mechanism, urge the separation pad 10 toward the feeding roller 4 to be in pressure contact therewith. Accordingly, when a sheet enters between the feeding roller 4 and the separation pad 10, the separation pad 10 is separated from the feeding roller 4.

  The compression spring 12, which is an example of an urging member, urges the separation pad 10 toward the feeding roller 4 to be in pressure contact therewith.

  As shown in FIG. 2, the conveyance guide 30a, which is an example of a guide member, bends the sheet separated by the feeding roller 4 and the separation pad 10 to the feeding roller 4 side, which is an example of the feeding rotation member side. I will guide you. Further, the upstream end portion of the transport guide 30a extends to the side of the separation pad 10, and the upstream end is disposed up to substantially the same position as the vertical wall 9b of the pad arm 9 (see FIG. 4).

  A pair of conveyance guides 30a are arranged with the feeding roller shaft unit 40 interposed therebetween in a direction orthogonal to the sheet feeding direction of the sheet surface. The conveyance guide 30a is disposed along the separation pad 10 in the sheet feeding direction at a height position where the conveyance guide 30a does not contact the other surface of the sheet until it comes into contact with the position after passing the separation pad 10.

  The sub pad 13, which is an example of an auxiliary separation member, contacts the lower surface of a sheet (limited to the maximum thickness in which image formation is possible) guided by the conveyance guide 30 a and fed between the feeding roller 4 and the separation pad 10. It is arranged at a height position that does not. The protrusion amount of the separation pad 10 toward the feeding roller 4 with respect to the sheet guide surface for guiding the sheet at the position of the separation pad 10 in the conveyance guide 30a is the protrusion amount of the sub pad 13 toward the feeding roller 4 with respect to the separation pad 10. Bigger than.

  The sub pad 13 is disposed on the side of the feeding roller 4 and the separation pad 10, and the radial direction of the feeding roller 4 from the feeding roller 4 is larger than the pressure contact position (nip portion) between the feeding roller 4 and the separation pad 10. It is arranged at a position distant from. The subpad 13 can contact the sheet to be separated when the separation pad 10 is moved away from the feeding roller 4 by the sheet separated by the separation pad 10. The subpad 13 comes into contact with the sheet that is guided by the conveyance guide 30a and is fed to the sheet that has pushed down the separation pad 10. The sub pad 13 is arranged with a fixed positional relationship with respect to the sheet guide surface of the feeding frame 30 integrally formed with the conveyance guide 30a.

  An intermediate plate 20 which is an example of a sheet storage unit holds sheets in a stacked state. The feeding roller 4 also serves as a member that comes in contact with the held uppermost sheet and pulls it out from the intermediate plate 20. The feeding direction of the sheet by the feeding roller 4 is a direction in which the sheet is pulled out from the intermediate plate 20. is there.

  A registration roller (123: FIG. 1), which is an example of a conveyance member, receives and conveys the sheet guided by the conveyance guide 30a.

  A feeding roller 5, which is an example of a roller member, is rotatably disposed outside the feeding roller 4, and replaces the feeding roller 4 to sandwich the sheet with the separation pad 10.

  As shown in FIG. 2, the feeding frame 30 and the bottom plate 25 are fastened by screws (not shown) and constitute a frame of the sheet feeding unit 100. An intermediate plate support plate 22 is fixed to the bottom plate 25 by screws or welding. An intermediate plate shaft 21 is fixed to the side surface of the intermediate plate 20, and the intermediate plate 20 is rotatably supported by fitting the intermediate plate shaft 21 and the intermediate plate support plate 22.

  A compression spring 23 is disposed between the middle plate 20 and the bottom plate 25 and urges the middle plate 20 upward. Further, the intermediate plate separation sheet 24 is fixed to the position of the intermediate plate 20 facing the feeding roller 4 by an adhesive or a double-sided tape. The middle plate separation sheet 24 is a friction member for preventing sheets near the lowermost part of stacked sheets (for example, cut sheets) from being fed in a bundle.

  The feed roller shaft 1 is fitted in a hole provided in the feed frame 30 and is rotatably supported. The feeding roller shaft 1 is fixed to both end portions with symmetrical middle plate cams 6 and 7 using a snap fit or pins or screws (not shown). The intermediate plate cams 6 and 7 rotate integrally with the feeding roller shaft 1 and push down the intermediate plate 20 against the compression spring 23. A feeding gear 8 is fixed to the outside of the intermediate plate cam 6, and rotation is selectively transmitted to the feeding gear 8 by a solenoid, a clutch, etc. (not shown).

  A feeding roller shaft unit 40 is fixed to the feeding roller shaft 1, and a separation pad unit 41 is arranged below the feeding roller shaft unit 40 with screws to the feeding frame 30. The

  As shown in FIG. 3, a feeding roller holder 2 is fixed to a substantially central portion of the feeding roller shaft 1 of the feeding roller shaft unit 40 by a snap fit (not shown), a pin, a set screw or the like. The feed roller 5 is rotatably supported by the hollow sleeve toward the outside of the feed roller holder 2 at one place on each of the left and right sides, and the feed roller 5 is dropped from the feed holder 2 by the feed roller regulating portion 2d. It is held without.

  The feeding roller holder 2 is integrally molded with resin, and the feeding roller collar is widened by tilting the spring-like knobs 2c provided on both side surfaces of the feeding roller holder 2 outward. 3 is removable.

  The feeding roller 4 is made of an elastic material such as EPDM or elastomer and having a high friction coefficient. The feeding roller 4 is assembled by surrounding the outer side of the semi-cylindrical feeding roller collar 3. When the feeding roller 4 is fixed to the feeding roller holder 2, two positioning bosses 3 a provided on both side surfaces of the feeding roller collar 3 are provided on U side provided on both side surfaces of the feeding roller holder 2. It is engaged with the groove 2a. At the same time, the claws 3 b provided on both side surfaces of the feeding roller collar 3 are engaged with holes 2 b provided on both side surfaces of the feeding roller holder 2.

  The feeding roller 4 is assembled by pressing the inner flange portion 4 a against the feeding roller shaft 1. This pressing force pulls the outer side of the feeding roller 4 in the circumferential direction and winds it around the outer circumference of the feeding roller collar 3 without any gap.

  As shown in FIG. 4, the separation pad 10 of the separation pad unit 41 is fixed to the pad arm 9 with an adhesive or a double-sided tape. The separation pad 10 is formed of EPDM, rubber such as elastomer, resin material, natural material such as cork, artificial material such as Clarino. The pad arm 9 is rotatably held when a boss extending from the arm shaft 9 a is fitted into an arm holding portion 11 a provided in the pad holder 11. A compression spring 12 is disposed between the pad arm 9 and the pad holder 11 and generates an upward biasing force so that the separation pad 10 contacts the feeding roller 4 or the feeding roller 5 shown in FIG. I am letting. On both sides of the pad arm 9, as shown in FIG. 2, a conveyance guide 30 a is fixedly disposed on the feeding frame 30.

Here, the friction coefficient between the feeding roller 4 and the sheet S shown in FIG. 1 is μ1, the friction coefficient between the two overlapping sheets S is μ3, and the friction coefficient between the sheet S and the separation pad 10 is μ2. Further, the friction coefficient between the intermediate plate separation sheet 24 and the sheet S shown in FIG. At this time,
.mu.1>.mu.2> .mu.3 (1) is a condition in which the feeding roller 4 described above can convey the sheet S against the separation pad 10 and a condition in which the separation pad 10 can separate the sheet S.

  .mu.1> .mu.4> .mu.3 (2) are conditions under which the feed roller 4 can be conveyed against the intermediate plate separation sheet 24 and conditions under which the intermediate plate separation sheet 24 can separate the sheet S.

  μ1> μ3 + μ4 (3) is a condition in which the feeding roller 4 can convey the sheet S against the separation pad and the intermediate plate separation sheet 24.

  Each coefficient of friction is determined so as to satisfy the above relationship.

  That is, the friction coefficient μ1 of the feeding roller 4 and the friction coefficient μ2 of the separation pad 10 are set so that μ1> μ2> μ3.

  When rotational driving is applied to the feeding roller 4, the uppermost sheet S <b> 1 of the sheet S bundle is fed by the frictional force of the feeding roller 4. When the sheet S1 is conveyed to the separation pad 10, the pressure applied by the compression spring 12 is N, and the force applied in the sheet conveying direction is positive. At this time, the conveyance force F1 of the feeding roller 4, the drag F2 that the separation pad 10 applies to the sheet S1, and the force F that the sheet S1 receives are calculated as follows.

F1 = μ1 * N (4)
F2 = −μ2 * N (5)
F = F1 + F2 = ([mu] 1- [mu] 2) N (6)

  Here, as described above, since μ1> μ2, F> 0, and the sheet S1 is sent downstream by the rotation of the feeding roller 4.

  Next, consider a case where the sheets S1 and S2 are simultaneously conveyed (multi-feed). The force FS1 applied to the sheet S1 is calculated as follows, assuming that the conveying force received from the feeding roller 4 is F1 and the drag received from the sheet S2 is F3.

  FS1 = F1 + F3 = μ1 * N−μ3 * N = (μ1−μ3) N (7)

  Here, as described above, since μ1> μ3, FS1> 0, and the sheet S1 is sent downstream by the rotation of the feeding roller 4.

  On the other hand, the force FS2 applied to the sheet S2 is calculated as follows since the drag force received from the separation pad 10 is F2 when the conveying force received from the sheet S1 is F4.

  FS2 = F4 + F2 = [mu] 3 * N- [mu] 2 * N = ([mu] 3- [mu] 2) N (8)

  Here, as described above, since μ2> μ3, FS2 <0, and the sheet S2 is blocked by the separation pad 10.

  When the feeding roller 4 is replaced with the feeding roller 5, μ1 is almost disappeared by the rolling contact of the feeding roller 5, but the pressure N of the compression spring 12 does not change (the relationship of μ2> μ3 is maintained). The double feeding of the sheet P2 continues to be prevented.

  By the operation as described above, the sheet feeding unit 100 can separate the sheets S one by one and supply them to the image forming unit 110.

<Normal operation of paper feed unit>
FIG. 5 is an explanatory diagram of each stage of a normal sheet feeding operation by the sheet feeding unit. In the description, (a), (b), (c)... (F) correspond to (a), (b), (c)... (F) in FIG. The feeding operation stage of the unit 100 is shown in a schematic sectional view. In order to simplify the drawing, the feeding roller collar 3 and the feeding roller holder 2 are not shown.

(A) Home position The feed roller 4 and the feed roller 5 are arranged coaxially with the feed roller shaft 1. When the radius of the feeding roller 4 is R1 and the radius of the feeding roller 5 is R2, the relationship of R1> R2 is established so that the feeding roller 4 can contact the sheet and transport the sheet. The intermediate plate cam 6 engages with a cam follower 20a formed on the side surface of the intermediate plate 20, and fixes the intermediate plate 20 to the lower side in the figure against the urging force of the compression spring 23, so that the sheets S can be stacked. Has stopped. The sheet S bundle is stacked on the intermediate plate 20. The pad arm 9 is urged in the direction B in the figure by a compression spring 12 to bring the separation pad 10 into pressure contact with the feeding roller 5.

(B) Middle plate rise When a clutch mechanism (not shown) is engaged and the feed roller shaft 1 is rotationally driven, the feed roller shaft 1 rotates in the direction C in the figure. When the intermediate plate cam 6 fixed to the feeding roller shaft 1 also rotates in the same direction and the intermediate plate 20 is disengaged from the cam follower 20a, the urging force of the compression spring 23 causes the sheet to move in the direction D in the figure. The middle plate 20 on which the S bundle is placed is pushed up. At the position where the uppermost part of the sheet S bundle is in contact with the outer periphery of the feeding roller 5, the rising of the intermediate plate 20 and the sheet S bundle is restricted and stopped.

(C) Feeding start The feeding roller shaft 1 further rotates, and the uppermost sheet S1 of the sheet S bundle contacts the feeding roller 4. Here, since “μ1> μ2” described in Expression (1), the sheet S1 is pulled out from the sheet S bundle.

(D) Separation part approach The feeding roller shaft 1 further rotates, and the feeding roller 4 conveys the sheet S1 to the contact part with the separation pad 10. In (d) to (f) of FIG. 5, one sheet is conveyed. At this time, since the feed roller shaft 1 is pivotally supported by the feed frame 30 and the feed roller 4 cannot move, the pad arm 9 fixing the separation pad 10 is opposed to the compression spring 12 in the direction F in the figure. Is moved by the thickness of the sheet S1 (about 0.05 to 0.1 mm for plain paper). In addition, when two sheets are conveyed, the double-feeded sheet that is in contact with the separation pad 10 is blocked by the separation pad 10 by the action of “μ2> μ3” described in the expression (1). . Then, only the sheet S <b> 1 in contact with the feeding roller 4 is sent out by the feeding roller 4.

(E) Feed roller conveyance completion, start of lowering of intermediate plate When the feed roller shaft 1 further rotates and the contact between the feed roller 4 and the separation pad 10 is finished, the feed roller 5 is again moved to the separation pad 10 as well. Abut. At approximately the same time, the intermediate plate cam 6 and the cam follower 20a come into contact again, and the intermediate plate 20 starts to descend in the direction E in the figure. Further, before the end of the contact of the feeding roller 4, the leading edge of the sheet S1 is transferred to the conveying roller (the registration roller 123 shown in FIG. 1) arranged downstream of the feeding roller 4.

(F) Home position return The feed roller shaft 1 further rotates, and the intermediate plate cam 6 and the cam follower 20a return to the same home position as in FIG. At substantially the same time, the clutch mechanism (not shown) is disengaged, the rotation transmission is finished, and the feeding roller shaft 1 stops.

  Thereafter, the sheet S1 sandwiched between the feeding roller 5 and the separation pad 10 which are freely rotatable is pulled out from between the feeding roller 5 and the separation pad 10 with the rotation of the registration roller 123 shown in FIG. . At this time, the sheet that has been double-fed to the sheet S1 is sandwiched between the sheet S1 and the separation pad 10 and is normally separated from the sheet S1, so that the sheet S is 2 even if the feeding roller shaft 4 is stopped. They are not sent out in layers.

<Separation of sheets with high rigidity>
FIG. 6 is an explanatory diagram of each stage of the sheet feeding operation with high rigidity by the sheet feeding unit. In the description, (a), (b), and (c) correspond to FIGS. 6 (a), (b), and (c), respectively, and the feeding roller 4 of the sheet feeding unit 100, The feeding operation stage in the vicinity of the separation pad 10 is shown enlarged.

  As shown in FIG. 6A, in a state where one sheet is sandwiched between the feeding roller 4 and the separation pad 10, the protrusion amount (L1) of the separation pad 10 toward the feeding roller 4 with respect to the conveyance guide 30a. Is larger than the protruding amount (L2) of the sub pad 13 toward the feeding roller 4 with respect to the conveyance guide 30a. Here, a portion that guides the sheet at the position of the separation pad 10 in the conveyance guide 30a is a sheet guide surface, and distances from the sheet guide surface are L1 and L2.

  This relationship is maintained even when the sheet is pulled out between the feeding roller 5 and the separation pad 10 by the registration roller 123. That is, in a state where one sheet is sandwiched between the feeding roller 5 and the separation pad 10, the protrusion amount (L1) of the separation pad 10 toward the feeding roller 5 with respect to the conveyance guide 30a is the amount of protrusion of the sub pad 13 with respect to the conveyance guide 30a. It is larger than the protruding amount (L2) toward the feeding roller 5.

  When a medium such as an envelope having a thickness greater than that of plain paper is passed, FIGS. 5 (c) and 5 (d) are as shown in FIGS. 6 (a), 6 (b), and 6 (c). proceed. Since the operations of the feeding roller 4 and the middle plate cam 6 are the same as those described with reference to FIG. 5, the description here focuses on the operations of the feeding roller 4, the separation pad 10, and the pad arm 9. To do.

(A) Start of feeding It is assumed that the uppermost sheet of the stacked sheets is S1, and the sheet stacked immediately below the sheet S1 is S2. The distance between the conveyance guide 30a and the sub pad 13 is L2, and the distance between the pad arm 9 that fixes the separation pad 10 at substantially the same position and the conveyance guide 30a is L1. The feeding roller 4 comes into contact with the sheet S1 and conveys the sheet S1 to the left side in the drawing. At this time, as shown in FIG. 6A, L1> L2.

(B) Separation pad approach The feeding roller 4 further rotates to pull out the sheet S1 from the sheet S bundle, and the leading edge of the sheet S1 comes into contact with the separation pad 10. Since the sheet S1 and the sheet S2 are sheet materials having high rigidity, the separation pad 10 and the pad arm 9 are pushed in the H direction in the figure against the urging force of the compression spring 12 due to the rigidity of the sheet S1. As a result, the pad arm 9 and the separation pad 10 move to a position lower than the subpad 13.

  However, since the sub pad 13 is fixed to the feeding frame 30 and the feeding roller shaft 1 is pivotally supported with respect to the feeding frame 30, the distance L3 between the sub pad 13 and the feeding roller 4 is rigid. Even if the strong sheets S1 and S2 enter, it does not change. As a result, the non-movable subpad 13 is exposed on the conveyance surface of the sheet S2. When the sheet S2 that has been double-fed in a form connected to the sheet S1 enters, the lower surface of the sheet S2 comes into contact with the subpad 13 at a position P shown in FIG. 6B, and the sheet S2 is subpadded by the corner portion P. 13 receives a separation resistance.

  Accordingly, the sheet S2 that has been double-fed is not fed to the sheet S1 due to the separation resistance from the sub pad 13 even if the feeding roller 4 further rotates to send out the sheet S1.

  Further, as shown in FIG. 6A, since the relationship of L1> L2 is set, neither the sheet S1 nor the sheet S2 comes into contact with the subpad 13 when a sheet having low rigidity is sent out.

(C) At the time of sheet separation When the feeding roller 4 further rotates, the sheet S1 comes into contact with the conveyance guide 30a and is guided to bend upward. At this time, the sheet S1 is bent by the outer peripheral surface of the feeding roller 4 with the contact portion Q and the corner portion P of the sub pad 13 as fulcrums. Here, when the restoring force for restoring the sheets S1 and S2 to the original horizontal state at the corner portion P is Nt and the friction coefficient of the subpad 13 is μ5, the separation resistance F received by the sheet S2 is as follows: Is calculated.

  F = μ5 · Nt (9)

  Here, in the case of a sheet feeding unit that does not include the subpad 13, the sheets S1 and S2 are bent by the outer peripheral surface of the feeding roller 4 with the feeding frame (30) and the sheet guide 30a in the vicinity of the subpad 13 as fulcrums. . Here, when the friction coefficient of the feeding frame (30) is μ6 and the restoring force of the sheets S1 and S2 is the same Nt as in this embodiment, the separation resistance F received by the sheet S2 is calculated as follows. .

  F = μ6 · Nt (10)

  Here, it is assumed that the material of the sub pad 13 is EPDM and the material of the feeding frame 30 is ABS or a similar material. The friction coefficient μ5 between low hardness EPDM and plain paper is generally about 1.6 to 2.0. On the other hand, the friction coefficient μ6 of ABS is about 0.1 to 0.3. For this reason, the sheet feeding unit 100 including the sub pad 13 can generate a separation resistance F that is approximately 5 to 20 times that of the sheet feeding unit not including the sub pad 13. In addition, since the restoring force Nt increases as the rigidity of the sheet increases, the separation resistance F increases accordingly, and effective double feed performance can be exhibited.

  In the first embodiment, the relationship between the protrusion amount L2 of the sub pad 13 relative to the transport guide 30a and the protrusion amount L1 of the separation pad 10 relative to the transport guide 30a is defined as follows.

  L1> L2 (11)

  In other words, the sub pad 13 is arranged with a fixed positional relationship with respect to the conveyance guide 30a, and the separation pad 10 and the sub pad 13 are located at the back side position where the feeding roller 4 is in contact with the conveyance guide 30a. Projects to the 4th side. Then, the protruding amount of the separation pad 10 toward the feeding roller 4 at the back side position where the feeding roller 4 contacts is larger than the protruding amount of the sub pad 13.

  For this reason, when the sheet S1 having low rigidity is passed, the conveyance resistance F is not received from the sub pad 13, and skewing caused by the sub pad 13, corner breakage of the sheet leading edge, paper jam caused by the corner breakage, etc. are generated. do not do. In addition, when the highly rigid sheets S1 and S2 are conveyed, the separation pad 10 that is retracted with respect to the feeding roller 4 cannot exhibit sufficient separation. However, when the subpad 13 is exposed on the conveyance surface and the separation resistance F is added, the sheets S1 and S2 having high rigidity can be separated, and the sheet corresponding to the medium can be separated.

  Even when the sheet S1 is sandwiched between the feeding roller 5 and the separation pad 10 in place of the feeding roller 4 and the sheet is left to be pulled out by the registration roller (123: FIG. 1), the sub pad 13 is placed on the conveying surface. An isolation resistor F is added by exposure. Thereby, separation of the sheets S1 and S2 having high rigidity is reliably maintained.

  Further, since the feeding roller 5 is in rolling contact with the sheet S1, the conveyance of the sheet S1 by the registration roller (123: FIG. 1) is not hindered, and stable image formation in the image forming unit 110 is realized.

  In a plain paper copier (PPC), a facsimile, a printer, and the like, it is necessary to separate and feed the stacked sheets one by one. There are various methods as such a sheet feeding device, but a method using a frictional force such as an FRR (Feed Reverse Roller) method and a friction separation pad method is most popular. Among these, the friction separation pad system has the features that the structure is the simplest and the size can be easily reduced.

However, in recent years, in a printer or copier, in addition to printing a basis weight of ^60g / ^{m 2 ~100g} / m 2 about a single cut sheet, and 160 g / ^{m 2} or more thick, labels, various media, such as envelopes It is hoped that When these thick sheets are multi-fed, the separation pad may be more than the predetermined amount because the sheet is several times to several tens of times thicker than the above-mentioned single-cut sheet, and the sheet itself has high rigidity. was there. For this reason, the contact portion between the second and subsequent sheets and the separation pad could not be secured, and sometimes the paper was frequently fed.

  When such an issue is dealt with by providing an auxiliary pad on the upstream side of the separation pad, as shown in Patent Document 1, the pad protrudes from the sheet stacking surface, so there is no auxiliary pad. The sheet stacking performance is lower than that of the sheet. In order to bring the downstream separation pad into contact with the sheet, it is necessary to use a large-diameter feeding roller, and the size and cost of the sheet feeding apparatus cannot be denied.

Moreover, as shown in Patent Document 2, when an auxiliary pad that is fixed in positional relation with the separation pad and is protruded from the separation pad is disposed, the sheet is bent into a wavy shape at the time of feeding. For this reason, when thin paper of 50 g / m ² or less is fed, wrinkles are likely to be generated in the separation unit, and measures for these thin papers are desired.

  On the other hand, in the sheet feeding apparatus 100 according to the first embodiment, since the sub pad 13 is arranged lower than the sheet conveyance surface with respect to the separation pad 10, the sub pad 13 is passed when plain paper or thin paper is passed. Does not contact the sheets S1 and S2. For this reason, the transportability of the sheet S1 is not impaired by the addition of the sub pad 13. In addition, this prevents the skew of the sheet due to the subpad 13 and the printing accuracy from occurring.

  Further, when the thick and rigid sheets S1 and S2 such as thick paper and envelope are passed, the separation pad 10 is pushed down by the thickness and rigidity of the sheet S1 itself. As a result, the corners of the subpads 13 protrude on the apparent sheet conveyance path, so that the separation resistance of the subpads 13 is added in addition to the separation pads 10, so that higher separation performance of the sheets S1 and S2 can be realized. Further, since the corner portion of the subpad 13 is exposed on the apparent sheet conveyance path, a high surface pressure can be obtained. As a result, it is possible to dramatically increase the separation resistance, and it is possible to more effectively prevent double feeding.

  In addition, by fixing the subpad 13 to the transport surface, it is possible to position the transport surface of the subpad 13. Accordingly, it is possible to provide the sheet feeding apparatus 100 that can feed various media while improving the multi-feed resistance.

  Further, unlike the auxiliary separating member disclosed in Patent Document 2, the subpad 13 does not increase the rigidity by undulating the sheet in the direction orthogonal to the sheet feeding direction of the sheet surface. The traveling direction of the sheet can be easily bent and guided toward the feeding roller 4 side. Therefore, the first sheet fed to the feeding roller 4 can be smoothly fed downstream by being guided by the conveyance guide 30a without being affected by the sub pad 13.

<Sheet Feeding Device of Second Embodiment>
7 is a perspective view of the vicinity of a feeding unit and a separation unit in the sheet feeding apparatus of the second embodiment, FIG. 8 is a perspective view of a subpad having a cut, and FIG. 9 is an explanatory diagram of a separation resistance by the subpad having a cut. It is.

  The sheet feeding apparatus according to the second embodiment is configured by replacing the subpad 13 shown in FIG. 1 with a subpad 50 having a cut, but the other configuration is the same as that of the first embodiment. Therefore, the sheet feeding apparatus of the second embodiment is also collectively referred to as the sheet feeding apparatus 100, and the same components as those of the first embodiment are denoted by the same reference numerals and redundant description is omitted. In the following description, FIGS. 1 to 6 are also referred to.

  The subpad 50 has at least one block 50b, 50c, 50d, which is an example of a corner portion having a ridge line in a direction orthogonal to the sheet feeding direction, on the opposite surface of the sheet. Blocks 50b, 50c, and 50d are edges of cuts 50a that are an example of a plurality of parallel grooves formed by crossing the subpad 50 in a direction orthogonal to the sheet feeding direction.

  As shown in FIG. 7, the feed roller shaft 1 is pivotally supported by the feed frame 30 shown in FIG. 2, and the feed roller 4 is fixed to the feed roller shaft 1. The feed roller 5 is rotatably supported with respect to the feed roller shaft 1, and the pad arm 9 is urged upward by a compression spring 12 as shown in FIG. In 3), the separation pad 10 is pressed.

  The conveyance guide 30 a is a rib-like convex portion formed of ABS resin integrally with the feeding frame 30 so as to sandwich the pad arm 9. A sub pad 50 is fixed to the inner cylindrical surface of the feeding frame 30 sandwiching the conveyance guide 30a by double-sided tape or adhesion.

  As shown in FIG. 8, the subpad 50 is formed with an infinite number of cuts 50a in a direction orthogonal to the sheet feeding direction of the sheet surface. This cut 50a forms blocks 50b, 50c, 50d,... With the number of cuts plus one on the sheet contact surface of the subpad 50. The notch 50a is not formed in the left side portion in the drawing that is lower than the sheet guide surface of the conveyance guide 30a in the attached state.

  As shown in FIG. 9, when the sheet S1 having high rigidity is passed, the sheet S2 is about to be fed to the sheet S1 in the vicinity of the feeding unit. As described in the first embodiment, the lower portion of the sheet S2 presses down a pad arm (not shown) (9: FIG. 6B) and comes into contact with the edges of the blocks 50b, 50c, and 50d of the subpad 50. At this time, since the notch 50a is present, the sub pad 50 is bent in the sheet conveying direction to stand up the edges of the blocks 50b, 50c, and 50d. As a result, the corners of the blocks 50b, 50c, and 50d abut against the leading edge of the sheet S2, and a large separation resistance F is exhibited at each location.

  In the second embodiment, it is possible to make a large number of corners abut on the second sheet S2 by carving the notches 50a in the subpad 50, so a larger double feed prevention effect than in the first embodiment is expected. it can.

  In the second embodiment, the rectangular cut is engraved. However, the present invention is not limited to this, and it is of course possible to form a three-dimensional groove in which the triangle or the groove section changes. It goes without saying that the blocks may be formed in a pseudo manner by separating the subpads into a plurality of pieces and arranging them in a tile shape.

<Sheet Feeding Device of Third Embodiment>
FIG. 10 is a perspective view of the pad holder attached in the third embodiment, FIG. 11 is a perspective view of the entire pad holder to which the subpad is fixed, and FIG. 12 is an explanatory diagram of a method for attaching the pad holder to which the subpad is fixed. .

  The sheet feeding apparatus according to the third embodiment is the same as that according to the first embodiment except that the pad arm 9, the conveyance guide 30a, and the sub pad 13 in the first embodiment are integrally detachably united. Accordingly, the sheet feeding apparatus according to the third embodiment is also collectively referred to as the sheet feeding apparatus 100, and the same components as those in the first embodiment are denoted by the same reference numerals, and descriptions of overlapping operations and the like are omitted. In the following description, FIGS. 1 to 6 are also referred to.

  As shown in FIG. 10, the pad holder 63 is detachably assembled to the bottom plate 25 of the feeding frame 30. Two holes 25 a are formed in the bottom plate 25 of the feeding frame 30, and two claws 63 b formed in the pad holder 63 are fitted in this.

  As shown in FIG. 11, the pad holder 63 is detachable as a whole. The pad holder 63 includes a separation pad 62 as an example of a separation member, a pad arm 61 as an example of a support mechanism, a compression spring (12: FIG. 4) as an example of a biasing member, and a conveyance guide 63c as an example of a guide member. The sub pad 64 which is an example of the auxiliary separating member is integrally assembled.

  The sub pad 64 is disposed at the back side position where the feeding roller (4: FIG. 10) contacts, and is brought into contact with the sheet fed to the sheet guided by the conveyance guide 63c and depressing the separation pad 62, and stops. The sub pad 64 is disposed at a height position that does not contact the sheet guided by the conveyance guide 63c and fed between the feeding roller (4: FIG. 10) and the separation pad 62.

  The pad holder 63 is provided with bearings 63 a on the left and right sides, and is fitted to the boss 61 a of the pad arm 61. The pad arm 61 is rotatably supported around a boss 61a, and the separation pad 62 is fixed to the pad arm 61 using an adhesive (not shown) and double-sided tape. In the pad holder 63, two conveyance guides 63c are formed so as to sandwich the pad arm 61, and two sub pads 64 are arranged so as to sandwich the conveyance guide 63c.

  As shown in FIG. 12, when the sheet feeding apparatus 100 is viewed from the back side of the bottom plate (25: FIG. 10), the feeding frame 69 has two screw holes 69a and two positioning bosses 69b. Yes. On the other hand, the pad holder 63 is provided with two screw fixing holes 63d and two positioning holes 63e corresponding to the screw holes 69a and the positioning bosses 69b. As indicated by a one-dot chain line in the figure, the positioning boss 69b is fitted into the positioning hole 63e, and the screw hole 69a is fastened to the screw fixing hole 63d by using the screw 68. In this way, the pad holder 63 is detachably fixed to the feeding frame 69. As described above with reference to FIG. 10, the side opposite to the sheet feeding direction of the pad holder 63 is fixed by inserting the claw 63b into the square hole 25a.

  In the third embodiment, by arranging the sub pad 64 on the pad holder 63, the pad can be easily exchanged and the maintainability is improved. Further, since it is possible to replace the feeding roller 4 and the separation pad 62 at the same time, the sheet feeding unit 100 including the pad holder 63 is also applied to a high-speed machine that requires periodic replacement of these parts. Is possible.

  In the third embodiment, the sub pad 64 is fixed on the pad holder 63. However, the sub pad 64 may be detached and attached independently.

<Other embodiments>
The image forming unit 110 illustrated in FIG. 1 may be replaced with a line image reading head which is an example of an image reading unit. A line image reading head using a CMOS or CCD is arranged in a direction orthogonal to the sheet feeding direction of the sheet surface, and each color density distribution on the image surface of the conveyed sheet is detected to generate image data.

  Such an image reading device may include a character information recognition device to constitute an optical character information reading device (OCR). In these cases, the image forming apparatus 200 is an image reading apparatus that reads and reads an image on the sheet original surface.

  The image forming unit 110 shown in FIG. 1 may be replaced with a full-color image forming unit that superimposes yellow, magenta, cyan, and black toner images and transfers them onto a sheet.

  The image forming unit 110 illustrated in FIG. 1 may be replaced with a sheet processing unit such as a punching device, a gluing device, a bookbinding device, or a needle binding device.

1 is an explanatory diagram of a configuration of an image forming apparatus according to an exemplary embodiment. FIG. 6 is a perspective view of the sheet feeding unit according to the first embodiment in a feeding standby state. It is explanatory drawing of the assembly of a feed roller shaft unit. It is explanatory drawing of the assembly of a separation pad unit. FIG. 5 is an explanatory diagram of each stage of a normal sheet feeding operation by a sheet feeding unit. FIG. 10 is an explanatory diagram of each stage of a sheet feeding operation with high rigidity by the sheet feeding unit. FIG. 10 is a perspective view of the vicinity of a feeding unit and a separation unit in a sheet feeding apparatus according to a second embodiment. It is a perspective view of the subpad which formed the notch | incision. It is explanatory drawing of the isolation resistance by the subpad which formed the notch | incision. It is a perspective view of the attachment state of the pad holder in a 3rd embodiment. It is a perspective view of the whole pad holder to which the subpad was fixed. It is explanatory drawing of the attachment method of the pad holder to which the subpad was fixed.

Explanation of symbols

1 Feed roller shaft 4 Feed rotation member (feed roller)
5 Roller member (feed roller)
6, 7 Middle plate cam 9, 12 Support mechanism (pad arm, compression spring)
10 Separation member (separation pad)
11 Pad holder 12 Biasing member (compression spring)
13, 50, 64 Auxiliary separation member (subpad)
20 Middle plate 20a Cam follower 25 Bottom plate 30 Device body, housing, guide member (feeding frame)
30a, 63c Guide member (conveyance guide)
50a Notches 50b, 50c, 50d Block 63 Pad holder 100 Sheet feeding device (sheet feeding unit)
110 Image forming means (image forming unit)
123 Conveying means (registration roller)
200 Image forming apparatus S, S1, S2 Sheet

Claims (9)

A feeding rotating member for feeding out the sheet;
A separation member for separating the sheet from the feeding rotation member;
A biasing member that biases and presses the separation member against the feeding rotation member;
It is arranged on the side of the feed rotating member and the separating member, and is located farther from the feeding rotating member in the radial direction of the feeding rotating member than the pressure contact position between the separating member and the feeding rotating member. A sheet feeding device comprising: an auxiliary separating member disposed. A feeding rotating member for feeding out the sheet;
A separation member for separating the sheet from the feeding rotation member;
A support mechanism that urges and presses the separating member toward the feeding rotation member;
An auxiliary separation member that can come into contact with the sheet fed to the sheet to be separated when the separation member moves in a direction away from the feeding rotation member by the sheet separated by the separation member. A sheet feeding device characterized by the above. A guide member configured to bend and guide the sheet separated by the feeding rotation member and the separation member toward the feeding rotation member;
Extending the upstream side of the guide member to the side of the separating member;
The amount of protrusion of the separation member toward the feeding rotation member with respect to the sheet guiding surface that guides the sheet at the position of the separation member in the guide member is the feeding rotation member of the auxiliary separation member with respect to the guide member. The sheet feeding device according to claim 1, wherein the sheet feeding device is larger than a protruding amount toward the side.   The sheet feeding apparatus according to claim 3, wherein the auxiliary separating member is disposed with a positional relationship fixed to a sheet guiding surface of the guiding member.   5. The sheet feeding apparatus according to claim 1, wherein the auxiliary separating member has a corner portion having a ridge line in a direction orthogonal to the sheet feeding direction on a facing surface of the sheet.   6. The sheet feeding apparatus according to claim 1, wherein a plurality of parallel cuts are formed in the auxiliary separating member in a direction orthogonal to the sheet feeding direction.   The sheet feeding apparatus according to any one of claims 1 to 6, wherein the auxiliary separating member is detachably assembled to the sheet feeding apparatus. A sheet feeding device according to any one of claims 1 to 7,
An image forming apparatus comprising: an image forming unit that forms an image on a sheet fed from the sheet feeding apparatus. A sheet feeding device according to any one of claims 1 to 7,
An image reading device comprising: an image reading unit that reads an image of a sheet fed from the sheet feeding device.

Images