JP2013103813A - Sheet conveyance device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can suppress occurrence of poor adsorption, damage of an adsorption separation unit, and deformation of an uppermost sheet.SOLUTION: A sheet conveyance device includes: the adsorption separation unit that has an adsorption belt arranged opposite to a top of a sheet bundle and rotatably-stretched by a plurality of stretch rollers, and is swingably-supported to a support member at the upstream in a sheet conveyance direction farther than the adsorption belt; a charging means for charging a surface of the adsorption belt; and a swing means for swinging the adsorption separation unit with the support member as a fulcrum so as to reciprocate the adsorption belt between an adsorption position where the uppermost sheet of the sheet bundle is brought into contact and adsorbed to the adsorption belt and a conveyance position at which the uppermost sheet adsorbing to the adsorption belt is conveyed and which is spaced from the sheet bundle farther than the adsorption position. The device includes a swing stop means for stopping the adsorption separation unit swung by the swing means if a load equal to or more than a predetermined load is applied to the adsorption separation unit, when the adsorption belt comes into contact with the uppermost sheet.

Description

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

  As a method of separating and transporting stacked sheets such as originals and recording paper, an electrostatic adsorption separation method has been proposed in which an electric field is formed on an adsorption belt, and this is brought into contact with the sheet for adsorption and separation (for example, Patent Document 1).

  An electrostatic adsorption separation type sheet conveying device described in Patent Document 1 is a dielectric adsorption belt wound around two rollers, charge applying means for applying alternating charges to the adsorption belt, and holding these And an adsorption separation unit composed of a holder. The holder rotatably supports the two rollers, and is fixed to a rotating shaft provided on the upstream side in the sheet conveying direction from the rollers. Also, a suction position where the uppermost sheet of the sheet bundle stacked on the bottom plate of the paper tray is brought into contact with the suction belt and sucked, and a transport position farther from the sheet bundle than the suction position where the uppermost sheet sucked on the suction belt is transported Oscillating means for oscillating the adsorption / separation unit with the rotation shaft as a fulcrum is provided so that the adsorption belt can reciprocate between.

  In the previous stage of paper feeding, the suction belt held by the holder via the two rollers is located at a position away from the sheet bundle. When separating and transporting the uppermost sheet of the sheet bundle, first, the suction belt is rotated to apply an alternating charge to the suction belt. When an alternating charge is applied to the suction belt, the suction belt stops rotating, the suction separation unit is swung to the sheet bundle side by the swinging means, the suction belt is positioned at the suction position, and the suction belt is placed on the uppermost sheet of the sheet bundle. The uppermost sheet of the sheet bundle is adsorbed to the adsorbing belt. When the uppermost sheet of the sheet bundle is adsorbed by the adsorption belt, the adsorption separation unit is oscillated in the direction away from the sheet bundle by the oscillating means. Then, the uppermost sheet adsorbed on the adsorption belt is lifted by the adsorption belt and separated from the second sheet. Then, after the suction belt is positioned at the transport position, the suction belt is rotationally driven to transport the uppermost sheet adsorbed on the suction belt.

  The electrostatic attraction force generated between the adsorption belt and the uppermost sheet increases as the distance between the two becomes shorter. Therefore, in order to obtain a sufficient electrostatic attraction force so as not to cause a suction failure, the suction belt is placed on the uppermost position so that no gap is created between the suction belt and the uppermost sheet due to the undulation of the suction belt or the sheet. It is desirable to press the sheet with a certain force to bring them into uniform contact.

  Here, in continuous conveyance, the bottom plate of the paper tray is raised so that the topmost sheet reaches the preset highest position, and then the topmost sheet of the sheet bundle stacked on the bottom plate of the paper tray is sucked. Transport while turning one sheet at a time using a belt. Therefore, every time a sheet is conveyed, the sheet stacking height of the sheet bundle is lowered by one sheet, and the sheet stacking height of the sheet bundle is slightly changed. Then, when the sheet stacking height of the sheet bundle is lowered by several sheets and becomes equal to or lower than a certain height, the bottom plate of the sheet tray is raised so that the uppermost sheet reaches the highest position set in advance.

  At this time, if the force that presses the suction belt against the uppermost sheet is set to an optimum size when the uppermost sheet is at the highest position, the sheet stack height of the sheet bundle changes slightly. In addition, the force pressing the suction belt against the uppermost sheet is weakened. As a result, a gap is easily generated between the suction belt and the uppermost sheet due to the undulation of the suction belt and the sheet, and the suction belt and the uppermost sheet cannot be uniformly contacted, and sufficient electrostatic adsorption force is obtained. Cannot be obtained, resulting in poor adsorption.

  For this reason, it is conceivable to set the force that presses the suction belt to the uppermost sheet to an optimum magnitude when the sheet is conveyed immediately before the sheet stack height of the sheet bundle is slightly changed to raise the bottom plate. As a result, even if the sheet height of the sheet bundle changes slightly, the force that presses the suction belt against the uppermost sheet is prevented from weakening, and the suction belt is pressed against the uppermost sheet with a constant force to make both uniform. Can be contacted. However, in this case, when the uppermost sheet is at the highest position, if the adsorption belt is pressed too hard against the uppermost sheet and the adsorption separation unit is overloaded, the adsorption separation unit may be damaged or the uppermost sheet may be Problems such as deformation occur.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus capable of suppressing defective adsorption, damage to an adsorption separation unit, and deformation of the uppermost sheet. That is.

  In order to achieve the above-mentioned object, the invention of claim 1 has a suction belt that is arranged opposite to the upper surface of the sheet bundle and is rotatably stretched by a plurality of stretching rollers, and the sheet conveyance direction is more than that of the suction belt. An adsorption / separation unit supported swingably on a support member on the upstream side, a charging means for charging the surface of the adsorption belt, and an adsorption position for bringing the uppermost sheet of the sheet bundle into contact with the adsorption belt and adsorbing it, The adsorbing / separating unit is supported with the support member as a fulcrum so that the adsorbing belt can reciprocate between the adsorbing position for conveying the uppermost sheet adsorbed on the adsorbing belt and the conveying position away from the sheet bundle. In the sheet conveying apparatus having a swinging means for swinging, when the suction belt and the uppermost sheet are in contact with each other, a load exceeding a predetermined load is applied to the suction separation unit. It is characterized in that it has a swinging stop means for stopping the rocking of the adsorber separation unit according to.

  In the present invention, when the adsorption / separation unit is oscillated and the adsorption belt and the uppermost sheet are brought into contact with each other, if the load on the adsorption / separation unit is more than a predetermined load, the oscillation / separation unit oscillates the adsorption / separation unit. Stop. Accordingly, the suction belt can be pressed against the uppermost sheet with a constant force while suppressing the suction belt from being pressed against the uppermost sheet with a force stronger than necessary. Therefore, it is possible to uniformly contact the suction belt and the uppermost sheet while suppressing an excessive load on the suction separation unit and suppressing the force of pressing the suction belt against the uppermost sheet from becoming too weak. Therefore, even if the sheet stacking height of the sheet bundle changes minutely, it is possible to suppress occurrence of suction failure, damage to the suction separation unit, and deformation of the uppermost sheet.

  As described above, according to the present invention, there is an excellent effect that it is possible to suppress the adsorption failure, the damage to the adsorption separation unit, and the deformation of the uppermost sheet.

3 is a schematic diagram of a sheet conveying apparatus according to Configuration Example 1. FIG. 1 is a schematic diagram showing a copying machine according to an embodiment. The perspective view which shows schematic structure of a paper feed part. FIG. 3 is a schematic diagram illustrating a sheet feeding unit. The figure which shows the principal part structure of an adsorption | suction separation unit. The schematic block diagram of the drive mechanism which rotationally drives an adsorption belt. The perspective view which shows the principal part structure of an adsorption | suction separation unit. The perspective view which shows the structural example of an adsorption | suction separation unit. (A) Schematic diagram of a sheet conveying apparatus viewed from the downstream side in the sheet conveying direction, showing a state where an urging support portion is present at a position A where the belt driving shaft supporting member and the belt driving shaft are in contact, (b) belt driving shaft support FIG. 6 is a schematic diagram of the sheet conveying apparatus viewed from the downstream side in the sheet conveying direction, showing a state where the biasing support portion is located at a position B where the member and the belt drive shaft do not contact each other. The schematic diagram which looked at the sheet conveying apparatus from the upper part. The perspective view of an urging | biasing support part and a guide groove. FIG. 6 is a diagram illustrating a sheet conveying operation using the sheet conveying apparatus of the present embodiment. 10 is a schematic diagram of a sheet conveying apparatus according to Configuration Example 2. FIG. FIG. 10 is a schematic view of a sheet conveying apparatus according to Configuration Example 3 as viewed from above. The perspective view of an urging | biasing support part and a guide groove.

Hereinafter, an embodiment in which the present invention is applied to a copying machine which is an electrophotographic image forming apparatus will be described.
Needless to say, the present invention can be applied not only to the image forming apparatus of the present embodiment but also to, for example, an inkjet image forming apparatus.

FIG. 2 is a schematic diagram illustrating the copying machine 100 according to the present embodiment.
The copying machine 100 includes an automatic document feeder 59 that separates documents one by one from a bundle of documents placed on a document tray 59a and automatically feeds them to a contact glass on a document reading unit 58, and an automatic document feeder 59. An image is formed based on the original image read by the original reading unit 58 on the original reading unit 58 that reads the original conveyed on the contact glass by the sheet feeding and the sheet that is a recording material fed from the paper supply unit 52. And an image forming unit 50 as image forming means. The sheet feeding unit 52 accommodates the sheet bundle 1 in which a plurality of sheets are stacked, and feeds the uppermost sheet 1 a located at the uppermost position from the sheet bundle 1 to the image forming unit 50. In the present embodiment, the image forming unit 50 and the paper feeding unit 52 can be divided.

  The image forming unit 50 includes a charging device 62, a developing device 64, a transfer device 54, a photoconductor cleaning device 65, and the like around a photoconductor 61 as a latent image carrier. The image forming unit 50 also includes an optical writing unit (not shown) for irradiating the photoreceptor 61 with a laser beam 63, a fixing device 55 for fixing the toner image on the sheet, and the like.

  In the image forming unit 50 configured as described above, as the photosensitive member 61 rotates, the surface of the photosensitive member 61 is first uniformly charged by the charging device 62. Next, a laser beam 63 from an optical writing unit (not shown) based on image data input from a personal computer, a word processor, or the like, or image data of a document read by the document reading unit 58 is irradiated onto the photoreceptor 61. An electrostatic latent image is formed. Thereafter, a toner image is formed on the photosensitive member 61 by attaching toner with the developing device 64 to visualize the electrostatic latent image. On the other hand, the sheet feeding unit 52 separates the sheets one by one, conveys the sheet through the conveyance path 51 by the conveyance roller pair 9, and abuts against the registration roller 53 to stop. Then, in synchronization with the toner image formation timing of the image forming unit 50, the sheet that is pressed against the registration roller 53 and stopped is sent to the transfer unit where the photoconductor 61 and the transfer device 54 face each other. In the transfer unit, the toner image on the photoreceptor 61 is transferred to the supplied sheet. The sheet onto which the toner image has been transferred is fixed to the toner image by the fixing device 55 and then discharged to the paper discharge tray 57 by the paper discharge roller pair 56. On the other hand, the surface of the photoconductor 61 after the toner image transfer is cleaned by removing residual toner by the photoconductor cleaning device 65 to prepare for image formation again.

[Configuration example 1]
3 is a perspective view illustrating a schematic configuration of the paper feeding unit 52, FIG. 4 is a schematic diagram illustrating the paper feeding unit 52, and FIG. 5 is a diagram illustrating a main configuration of the adsorption separation unit 110. .

  The paper feeding unit 52 is a sheet feeding cassette 11 serving as a sheet material accommodation unit that stacks and accommodates a plurality of sheets, and a sheet bundle 1 composed of a plurality of sheets on the paper feeding cassette 11 and located at the uppermost position. And a sheet conveying device 200 that separates and conveys the upper sheet 1a.

  As shown in FIG. 4, the paper feed cassette 11 has a bottom plate 7 on which the sheet bundle 1 in which a plurality of sheets are stacked is placed. A support member 8 that supports the bottom plate 7 is rotatably mounted between the bottom plate 7 and the bottom portion of the paper feed cassette 11. As shown in FIG. 3, the sheet feeding unit 52 is provided with a sheet detecting unit 40 that detects that the uppermost sheet 1 a of the sheet bundle 1 has reached a predetermined position. The sheet detection means 40 includes a filler 44 that is rotatably supported by a shaft 42 provided in the apparatus main body, and a transmission optical sensor 43. When the support member 8 is rotated by a drive motor (not shown) to raise the bottom plate 7, the sheet bundle 1 stacked on the bottom plate 7 rises and the uppermost sheet 1 a comes into contact with the filler 44. At this time, the light receiving unit 43a of the transmissive optical sensor 43 receives light from the light emitting unit 43b. Further, when the bottom plate 7 is raised, the filler 44 blocks the light from the light emitting portion 43b, and the light receiving portion 43a does not receive the light. Thereby, it is detected that the uppermost sheet 1a of the sheet bundle 1 has come to a predetermined position, and the rotation of the support member 8 is stopped.

The sheet conveying apparatus 200 includes an adsorption / separation unit 110, an oscillation mechanism 120 that is an oscillation unit for oscillating the adsorption / separation unit 110, a drive mechanism 230 that moves the adsorption belt 2 endlessly, and the like. As shown in FIG. 5, the adsorption separation unit 110 includes an adsorption belt 2 that is stretched between a downstream tension roller 5 and an upstream tension roller 6. The adsorption belt 2 has a surface layer made of polyethylene terephthalate with a thickness of about 50 [μm] having a resistance of 10 ⁸ [Ω · cm] or more, and a resistance of 10 ⁶ [Ω · cm] or less formed by aluminum vapor deposition. It has a two-layer structure having a conductive layer. By making the suction belt 2 have such a two-layer structure, the conductive layer can be used as a grounded counter electrode, and the electrode member 3 serving as a charging means for applying a charge to the suction belt 2 can be used as the suction belt 2. It can be provided anywhere as long as it is in contact with the surface layer. Further, a rib 23 for stopper is provided on the inner side of both side edges of the suction belt 2, and engages with both side end surfaces of the downstream tension roller 5 and the upstream tension roller 6 so as to be close to the belt. Is preventing.

  Further, the suction belt 2 is stretched so as to be slacked downward to such an extent that no idle rotation occurs between the suction belt 2 and the downstream tension roller 5, and comes into contact with the upper surface of the sheet bundle in a relaxed state. A contact area can be secured even for a sheet in which a wave is generated.

The downstream tension roller 5 is provided with a conductive rubber layer having a resistance value of 10 ⁶ [Ω · cm] on the surface, and the upstream tension roller 6 is a metal roller. Both the downstream tension roller 5 and the upstream tension roller 6 are grounded. The downstream tension roller 5 has a small diameter suitable for separating the sheet from the suction belt 2 by the curvature. That is, by setting the diameter of the downstream tension roller 5 to be small and increasing the curvature, the sheet adsorbed and conveyed by the suction belt 2 is separated from the downstream tension roller 5 and guided downstream in the conveyance direction. It can enter the conveyance path H formed by the member 10.

  Further, as shown in FIG. 5, the shaft 5 a of the downstream tension roller 5 is rotatably supported by the housing 20. The shaft 6 a of the upstream tension roller 6 is rotatably supported by a bearing 22 that is slidably held in the sheet conveyance direction with respect to the housing 20. The bearing 22 is urged to the upstream side in the sheet conveying direction by a spring 21. As a result, the upstream tension roller 6 is urged to the upstream side in the sheet conveying direction, and tension is applied to the suction belt 2.

  As shown in FIGS. 3 and 4, the adsorption separation unit 110 is provided with brackets 12 at both ends in the belt width direction for holding the adsorption belt 2 in a swingable manner. Each bracket 12 is rotatably supported by a support shaft 14 provided on the upstream side in the sheet conveying direction from the upstream tension roller 6. Thereby, the adsorption separation unit 110 conveys the adsorption position where the uppermost sheet 1a of the sheet bundle 1 is adsorbed by the adsorption belt 2 and the uppermost sheet 1a adsorbed by the adsorption belt 2 by the swing mechanism 120 described later. Can be swung around the support shaft 14 as a fulcrum.

  Each bracket 12 is provided with a long hole 12a, and the shaft 6a of the upstream tension roller 6 passes through the long hole 12a. Thereby, the upstream tension roller 6 is held movably with respect to the bracket 12. On the other hand, the shaft 5 a of the downstream tension roller 5 passes through a hole (not shown) provided in the bracket 12, and the downstream tension roller 5 is held immovably with respect to the bracket 12. As shown in FIG. 4, when the adsorption separation unit 110 is in the feeding position, the shaft 6a of the upstream tension roller 6 is in contact with the lower end 41 of the long hole 12a.

  The long hole 12a provided in the bracket 12 allows the rotation center of the upstream tension roller 6 and the rotation of the downstream tension roller 5 even if the upstream tension roller 6 (the shaft thereof) moves in the long hole 12a. The arcuate shape is centered on the rotation center of the downstream tension roller 5 so that the distance from the center does not change. As a result, even if the upstream tension roller 6 moves in the long hole 12a, the tension of the suction belt 2 does not change. Usually, even when the tension of the suction belt 2 is 5 [N] or less, the suction belt 2 can be driven to rotate and the sheet adsorbed on the suction belt 2 can be conveyed without slipping between the rollers. However, when a sheet having a special condition such as a sheet having high adhesion is conveyed, a slip may occur between the suction belt 2 and the roller. For this reason, it is preferable that the friction coefficient of the surface of the upstream tension roller 6 or the surface of the downstream tension roller 5 is increased to make it difficult to cause slip.

FIG. 6 is a schematic configuration diagram of a drive mechanism 230 that rotationally drives the suction belt 2.
A driven first pulley 26a and a driving second pulley 26b are fixed to one end of a support shaft 14 that rotatably supports each bracket 12. A driven second pulley 25 is fixed to one end of the downstream tension roller 5, and a driven timing belt 28 is wound around the driven first pulley 26 a and the driven second pulley 25. A drive motor 24 is provided upstream of the support shaft 14 in the sheet conveying direction, and a drive first pulley 27 is fixed to the motor shaft of the drive motor 24. A drive timing belt 29 is wound around the drive first pulley 27 and the drive second pulley 26b.

  When the drive motor 24 is driven, the downstream tension roller 5 is rotationally driven via the drive timing belt 29 and the driven timing belt 28. As a result, the suction belt 2 is rotationally driven, and the upstream tension roller 6 is driven to rotate by friction of the inner surface of the suction belt 2. In the present embodiment, the driving force of the driving motor 24 is transmitted to the downstream tension roller 5 through the support shaft 14 that supports the bracket 12. With this configuration, as will be described later, the adsorption / separation unit 110 swings with the support shaft 14 as a fulcrum, so that even if the adsorption / separation unit 110 swings, it supports the downstream tension roller 5. The distance from the shaft 14 does not vary. Therefore, the tension of the driven timing belt 28 is maintained and the driving force can be transmitted to the downstream tension roller 5 satisfactorily.

  As shown in FIGS. 3 and 4, a swing mechanism 120 is provided as a swing means for swinging the bracket 12 on the downstream side in the sheet conveying direction. The swing mechanism 120 has a rack gear portion 13 as a first drive transmission portion formed at a downstream end portion of each bracket 12 in the sheet conveyance direction, and a second drive transmission fixed to the rotary shaft 16 and meshing with the rack gear portion 13. And a pinion gear 15 as a member. The swing mechanism 120 includes a swing motor 30. At one end of the rotary shaft 16, a driven gear 32 that meshes with a motor gear fixed to the motor shaft of the swing motor 30 is provided. By fixing each pinion gear 15 to the rotating shaft 16, each pinion gear 15 can be rotated by rotating the rotating shaft 16 by the swing motor 30. Thereby, the pinion gear 15 provided at both ends in the belt width direction can be rotationally driven by one swing motor 30, the number of parts can be reduced, and the apparatus can be made inexpensive. In addition, with a simple configuration, it is possible to synchronize the drive of the rack and pinion provided at both ends in the belt width direction.

  Further, the swing motor 30 and the pinion gear 15 are connected via a torque limiter (not shown) that restricts transmission of a driving force above a certain level, and a load torque that exceeds a predetermined threshold when the adsorption separation unit 110 swings. The drive transmission is limited so as not to be applied.

  The rack gear portion 13 has an R shape centered on the support shaft 14. The rack gear portion 13 formed on the bracket 12 swings around the support shaft 14 when the adsorption separation unit 110 swings. Therefore, by making the rack gear portion 13 R-shaped around the support shaft 14, the meshing between the rack gear portion 13 and the pinion gear 15 can be maintained even when the adsorption / separation unit 110 is swung. Further, by forming the rack gear portion at the downstream end of the bracket 12 in the sheet conveying direction, the number of parts can be reduced and the configuration can be simplified as compared with the case where the rack gear separate from the bracket 12 is attached to the bracket 12. Can do. In addition, by providing a pinion on the device side of the rack and pinion of the swing mechanism 120, the configuration for transmitting the drive to the pinion is simplified compared to the case where the pinion is provided in the adsorption separation unit. Can do.

  By driving the swing motor 30, each pinion gear 15 rotates, and the rack gear portion 13 moves in a direction in which the rack gear portion 13 contacts and separates from the sheet bundle 1. Thereby, each bracket 12 swings around the support shaft 14 as a fulcrum.

  Each bracket 12 is connected and fixed by a reinforcing member 70. By connecting and fixing each bracket 12 with the reinforcing member 70, one bracket and the other bracket can be integrally swung, and the suction belt 2 held by the bracket is twisted when the bracket is swung. The uppermost sheet 1a adsorbed on the adsorption belt 2 can be prevented from being separated from the adsorption belt 2.

  As shown in FIG. 7, a blade-like electrode member 3 as a charging unit that charges the surface of the suction belt 2 is in contact with the surface of the suction belt 2. The electrode member 3 is connected to a charging power source 4 that generates alternating current. By making the electrode member 3 into a blade shape, the alternating charging interval can be easily reduced in pitch, and stable charging can be performed even if the adsorption belt 2 has a minute wave. In this embodiment, the blade-like electrode member 3 is used as the charging means, but a roller-like electrode member 103 as shown in FIG. 8 may be used.

  FIG. 9 is a schematic view of the sheet conveying apparatus viewed from the downstream side in the sheet conveying direction. FIG. 10 is a schematic view of the sheet conveying apparatus as viewed from above. FIG. 11 is a perspective view of the urging support portion 112 and the guide groove 125.

  In this configuration example, a biasing member that applies a biasing force to the suction belt 2 in a direction in which the suction belt 2 is separated from the uppermost sheet 1a when the suction belt 2 and the uppermost sheet 1a of the sheet bundle 1 are in contact with each other. A compression spring 81 is provided. A configuration is adopted in which the belt drive shaft support member 80 is brought into contact with the belt drive shaft 17 by the bias of the compression spring 15.

  A compression spring 81 is provided on each of the biasing support portion 112 and the biasing support portion 124 which are a pair of biasing support portions opposed to each other with the suction belt 2 sandwiched in the axial direction, and is provided on one end side of the compression spring 15. The belt drive shaft support member 80 is supported by contacting the belt drive shaft 17 which is the shaft of the downstream tension roller 5.

  A guide groove 125 is formed at the bottom of the sheet conveying apparatus 200 along the Y direction, which is a direction orthogonal to the paper feeding / conveying direction X shown in FIG. 10, and the urging support portion 112 and the urging support portion 124. Is slidable in the Y direction along the guide groove 125. As a result, the urging support portion 112 and the urging support portion 124 are shown in FIG. 9B as the position A where the belt drive shaft support member 80 and the belt drive shaft 17 contact each other as shown in FIG. The belt drive shaft support member 80 and the position B where the belt drive shaft 17 does not contact can be translated in the Y direction.

  Then, before the operation of the apparatus is started, the biasing support portion 112 and the biasing support portion 124 are positioned at either the position A or the position B, so that the belt drive shaft 17 is biased by the compression spring 81. It is possible to switch whether to activate or not energize. Thereby, the finer adjustment of the surface contact force generated between the suction belt 2 and the uppermost sheet 1a can be performed.

  Next, a sheet conveying operation using the sheet conveying apparatus 200 will be described with reference to FIG.

  As shown in FIG. 12A, the bottom plate 7 is normally in the lowered position, and the adsorption separation unit 110 is in the adsorption position. First, when a paper feed signal is input, the swing motor 30 is driven to rotate the pinion gear 15 clockwise in the figure, and the suction separation unit 110 is rotated counterclockwise in the figure (from the sheet bundle) with the support shaft 14 as a fulcrum. Rock in the direction of separation). Then, when the adsorption separation unit 110 swings to the feeding position, the drive of the swing motor 30 is stopped.

  When the adsorption separation unit 110 stops at the feeding position, as shown in FIG. 12B, the drive motor 24 is driven to move the adsorption belt 2 endlessly. Next, an alternating voltage is applied to the suction belt 2 that moves endlessly by the charging power source 4 via the electrode member 3, and a pitch (pitch is determined) on the surface of the suction belt 2 according to the AC power frequency and the circumferential speed of the suction belt 2. 4 [mm] to 16 [mm] is preferable, and an alternating charge pattern is formed. In addition to alternating current, the charging power source 4 may be one in which direct current is changed to high and low alternate potentials, such as a rectangular wave or a sine wave. In the present embodiment, a rectangular wave having an amplitude of 4 [kV] is applied to the surface of the suction belt 2. When charging of the suction belt 2 is completed, the rotation of the suction belt 2 is stopped and the bottom plate 7 that has been waiting at the lowered position is started to rise.

  Further, before and after the start of the rise of the bottom plate 7, as shown in FIG. 12C, the swing motor 30 is reversely rotated and the pinion gear 15 is rotated counterclockwise in the figure to support the adsorption separation unit 110. The shaft 14 is pivoted clockwise (in the direction approaching the sheet bundle) in the drawing. When the bottom plate 7 is raised and the adsorption separation unit 110 is lowered, the uppermost sheet 1 a of the sheet bundle 1 comes into contact with the upstream tension roller 6 through the adsorption belt 2. Further, when the bottom plate 7 is raised and the adsorption separation unit 110 is lowered, the upstream tension roller 6 is pushed up by the sheet bundle 1 and is in contact with the lower end 41 of the long hole 12a. It moves upward while being guided by the long hole 12a.

  Further, as the bottom plate 7 is raised, the filler 44 rotates counterclockwise in the drawing. When the uppermost sheet 1a of the sheet bundle 1 comes to a predetermined position, the filler 44 blocks the light from the light emitting portion 43b of the transmission optical sensor 43, and the transmission optical sensor 43 becomes the uppermost sheet 1a of the sheet bundle 1. Is detected, and the ascent of the bottom plate 7 is stopped.

  Further, the adsorption separation unit 110 stops the rotation of the swing motor 30 that has reached the adsorption position. When the swing motor 30 is a stepping motor, the suction separation unit 110 can be accurately stopped at the suction position by controlling the swing motor 30 based on the rotation angle (number of pulses). When the swing motor 30 is a DC motor, the adsorption / separation unit 110 can be accurately stopped at the suction position by controlling the swing motor 30 based on the driving time.

  As shown in FIG. 12D, when the bottom plate 7 stops rising and the adsorption separation unit 110 stops descending (swinging), the region facing the sheet bundle 1 of the adsorption belt 2 is the maximum of the sheet bundle 1. It contacts the upper sheet 1a. When the suction belt 2 comes into contact with the uppermost sheet 1a, Maxwell's stress acts on the dielectric sheet due to an unequal electric field formed by the charge pattern on the surface of the suction belt 2, and the uppermost sheet of the sheet bundle 1 1a is adsorbed to the adsorbing belt 2.

  In the state shown in FIG. 12 (d), when the uppermost sheet 1a is adsorbed on the adsorbing belt 2, the swing motor 30 is driven to rotate the pinion gear 15 in the clockwise direction in FIG. 110 is swung counterclockwise in the figure using the support shaft 14 as a fulcrum. Then, the downstream tension roller 5 moves together with the bracket 12 in a direction away from the sheet bundle 1. On the other hand, the upstream tension roller 6 does not move from the upper surface of the sheet bundle 1 due to its own weight, but moves relative to the bracket 12 in the sheet bundle direction. As a result, the suction belt 2 moves so as to swing around the rotation center of the upstream tension roller 6, and the uppermost sheet 1 a adsorbed to the suction belt 2 becomes the upstream tension roller of the suction belt 2. The portion wound around 6 is bent as a fulcrum. As a result, the restoring force acts on the sheet adsorbed on the adsorption belt 2, and only the uppermost sheet 1a can be adsorbed on the adsorption belt 2, and the second sheet 1b can be separated by the restoring force of the sheet.

  When the adsorption separation unit 110 further swings counterclockwise in the figure with the support shaft 14 as a fulcrum, the upstream tension roller 6 abuts against the lower end 41 of the long hole 12a. In this way, when the adsorption separation unit 110 is further swung from the state in which the upstream tension roller 6 hits the lower end 41 of the long hole 12a, the upstream tension roller 6 also moves together with the bracket 12, and the upstream tension roller 6 moves. The bridge roller 6 is separated from the upper surface of the sheet bundle 1.

  As shown in FIG. 12E, when the adsorption separation unit 110 reaches the feeding position for conveying the sheet, the drive of the swing motor 30 is stopped. Then, the drive motor 24 is driven to move the suction belt 2 endlessly in the counterclockwise direction in the drawing, and the uppermost sheet 1 a sucked on the suction belt 2 is conveyed toward the conveyance roller pair 9. When the leading edge of the uppermost sheet 1a electrostatically attracted to the suction belt 2 reaches the winding portion of the downstream tension roller 5 of the suction belt 2, it is separated from the suction belt 2 by the curvature separation and is directed toward the conveying roller pair 9. Move. After feeding, the drive of the drive motor 24 is stopped, and the endless movement of the suction belt 2 is stopped.

  The linear speeds of the conveyance roller pair 9 and the suction belt 2 are set to be the same, and when the conveyance roller pair 9 is intermittently driven at a timing, the suction belt 2 is also driven to be intermittently driven. The motor 24 is controlled.

  In the present embodiment, the uppermost sheet is electrostatically adsorbed to the adsorption belt 2 and the uppermost sheet is separated from the second sheet, so that the contact pressure between the adsorption belt 2 and the sheet bundle is sufficiently small. can do. Therefore, it is possible to suppress the occurrence of double feeding due to friction as in the separation method using frictional force.

  Further, by installing and removing the urging support portion 112 and the urging support portion 124 before starting the operation, the urging can be switched with respect to the belt drive shaft 17 and the surface contact force can be switched more finely. .

  In this configuration example, as shown in FIG. 1, the swing motor 30 transmits a predetermined torque to the pinion gear 15, and the driving force is applied to the pinion gear 15 when the adsorption separation unit 110 is moved from the feeding position to the adsorption position. It is made to rotate in the rotation direction of the oscillating motor 30 that transmits. In other words, the driving force is transmitted from the swing motor 30 to the pinion gear 15 via the torque limiter 33.

  The torque limiter 33 stops driving transmission from the swing motor 30 to the pinion gear 15 when a load torque as a driving load equal to or greater than a predetermined threshold value is applied to the pinion gear 15.

  Thus, by installing the torque limiter 33 between the swing motor 30 and the pinion gear 15, the adsorption separation unit 110 is swung by the driving force transmitted from the swing motor 30 through the pinion gear 15, etc. If the suction separation unit 110 is overloaded when the suction belt 2 is brought into contact with the upper surface of the sheet bundle 1, the drive transmission from the swing motor 30 to the pinion gear 15 is stopped by the torque limiter 33, and the suction separation unit 110. Stops swinging. As a result, contact between the suction belt 2 and the upper surface of the sheet bundle 1 with an unnecessarily large contact force can be suppressed, and damage to the suction separation unit 110 and the pinion gear 15 and deformation of the sheets of the sheet bundle 1 can be prevented. Can be suppressed.

  Here, in continuous feeding, the topmost sheet of the sheet bundle 1 stacked on the bottom plate 7 of the sheet feeding cassette 11 is fed while turning up the sheet by the suction belt 2 one by one. Therefore, each time a sheet is fed, the height of the sheet bundle 1 is lowered by one sheet, and the sheet height of the sheet bundle 1 is slightly changed. When the sheet stacking height of the sheet bundle 1 is lowered by several sheets and becomes below a certain fixed height, the bottom plate 7 can be raised to keep the sheet stacking height constant. At this time, if the position of the suction belt 2 with respect to the uppermost sheet of the sheet bundle 1 is set together when the bottom plate 7 is raised to a position where the uppermost sheet is the highest, the sheet height of the sheet bundle is set. When the change is minute, the suction belt 2 and the uppermost sheet are not in good surface contact with each other, and the contact force between the two becomes small, which may cause a feeding failure.

  The suction separation unit 110 is swung to the load torque limit value to bring the suction belt 2 into contact with the uppermost sheet of the sheet bundle 1, so that even if the sheet stacking height of the sheet bundle changes slightly, the suction belt 2 The height of the lower surface of the belt and the uppermost sheet of the sheet bundle 1 can be made substantially equal so that they can be brought into good surface contact with each other, and the contact force between the suction belt 2 and the uppermost sheet can be ensured with a constant magnitude. it can. Further, by adopting a configuration in which the limit value of the load torque of the adsorption separation unit 110 can be varied, the surface contact force can be arbitrarily set.

[Configuration example 2]
FIG. 13 is a schematic diagram of a sheet conveying apparatus according to Configuration Example 2.
In the present configuration example, a plurality of transmission paths for transmitting different predetermined torques to the bracket 12 of the adsorption / separation unit 110 are provided, and the pinion gear 15 includes a swing motor 30 via a clutch 34 and a torque limiter 33. Torque can be transmitted by the swing motor 31 via the clutch 36 and the torque limiter 35.

  In this configuration example, the torque limiter 33 and the torque limiter 35 have different torque limits, and the load torque threshold set in the torque limiter 33 is higher than the load torque threshold set in the torque limiter 35. It has become. The upper limit of the load torque applied to the bracket 12 of the adsorption separation unit 110 can be arbitrarily switched by switching between the clutch 34 and the clutch 36.

An example of switching between the clutch 34 and the clutch 36 is shown below.
For example, when the clutch 34 is turned on and the clutch 36 is turned off, the load torque is increased. When the clutch 34 is turned off and the clutch 36 is turned on, the load torque is reduced. The former is separated from the adsorption separation unit 110 than the latter. The upper limit of the load torque applied to the bracket 12 becomes higher.

[Configuration example 3]
FIG. 14 is a schematic view of the sheet conveying apparatus according to Configuration Example 3 as viewed from above. FIG. 15 is a perspective view of the urging support portion 112 and the guide groove 125.

  In this configuration example, there is a mechanism in which the other biasing support portion moves in conjunction with the movement of one biasing support portion. As described in the configuration example 1, when the biasing support portion 112 moves between the position A illustrated in FIG. 9A and the position B illustrated in FIG. The urging support part 124 can move between the position A and the position B in conjunction with the movement of the support part 112.

  The urging support portion 112 and the urging support portion 124 are slidably provided along the guide groove 125, and the urging support portion 112 and a rack gear 126 provided on each of the urging support portions 124 are provided. ing. A pinion gear 127 is rotatably held. At this time, the rack gear 126 and the pinion gear 127 are engaged, and the urging support portion 112 and the urging support portion 124 are connected. Further, a stopper support portion 128 is formed on the urging support portion 112. A stopper 129 is provided on the stopper support 128 so as to be rotatable at a constant angle. A serrated stopper claw 130 is formed below the stopper 129. Further, an engaging portion 131 is formed to face the stopper claw 130. At this time, the stopper 129 rotates by being urged by the compression spring 132, the stopper claw 130 and the engaging portion 131 are engaged, and the urging support portion 112 is fixed.

  In such a configuration, the urging support portion 112 and the urging support portion 124 are interlocked with each other, slide in contrast with the central axis in the paper feed conveyance direction X, and are fixed by the stopper 129. Therefore, the urging support part 112 and the urging support part 124 are movable between the position A and the position B. In this way, the biasing support portion 112 and the biasing support portion 124 can be moved between the position A and the position B by interlocking the biasing support portion 112 and the biasing support portion 124. The workability can be improved as compared with the case where the individual parts are moved individually.

  As a moving mechanism between the urging support portion 112 and the urging support portion 124, in addition to a moving mechanism manually operated by the user, a separate driving means is provided, and the user can operate the urging support portion 112 and the urging support portion by an operation panel. By instructing the switching of the position 124, the urging support part 112 and the urging support part 124 can be moved by the driving means. As the driving means, the biasing support portion 112 is not provided with the stopper support portion 128, the stopper 129, the stopper claw 130, and the engaging portion 131, and the pinion gear 127 is rotated by a drive source, and the biasing support portion 112 and A configuration in which the urging support portion 124 is slid along the guide groove 125 is exemplified.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
(Aspect A)
It has an adsorption belt such as an adsorption belt 2 that is arranged opposite to the upper surface of the sheet bundle such as the sheet bundle 1 and is rotatably stretched by a plurality of stretching rollers, and the support shaft 14 is upstream of the adsorption belt in the sheet conveying direction. An adsorption separation unit such as an adsorption separation unit 110 that is swingably supported by a support member such as an electrode, a charging means such as an electrode member 3 for charging the surface of the adsorption belt, and an uppermost sheet such as the uppermost sheet 1a of the sheet bundle. Support member so that the suction belt reciprocates between the suction position where the sheet is brought into contact with the suction belt and sucked and the transport position farther from the sheet bundle than the suction position where the uppermost sheet sucked by the suction belt is transported In a sheet conveying apparatus such as a sheet conveying apparatus 200 provided with an oscillating means such as an oscillating mechanism 120 that oscillates the adsorption / separation unit with respect to Upon contact with the uppermost sheet, it has a swing stop means such as a torque limiter 33 of a predetermined or more load is to stop the swing adsorptive separation unit according to according the rocking means to adsorptive separation unit. According to this, as described in the above embodiment, it is possible to prevent the adsorption failure, the adsorption separation unit from being damaged, or the uppermost sheet from being deformed.
(Aspect B)
In (Aspect A), the swinging unit is attached to a first drive transmission unit such as a rack gear unit 13 provided at a downstream end of the adsorption / separation unit in the sheet conveyance direction and a first drive attached to the apparatus main body. The second drive transmission unit such as the pinion gear 15 that meshes with the transmission unit, and a drive source such as a swing motor 30 that drives the second drive transmission unit, and the second drive transmission unit is driven by the drive source to drive the first drive. The adsorption / separation unit is swung by meshing between the transmission unit and the second drive transmission unit. According to this, when the adsorption / separation unit swings, the downstream end of the adsorption / separation unit is supported by the meshing between the first drive transmission unit and the second drive transmission unit. Thus, when the adsorption / separation unit is swung, the upstream side in the sheet conveyance direction of the adsorption / separation unit is supported by the support member, the downstream side in the sheet conveyance direction is supported by the rocking means, and the adsorption / separation unit is supported at both ends. Therefore, the vibration of the adsorption / separation unit can be suppressed as compared with the configuration in which the adsorption / separation unit is cantilevered.
(Aspect C)
In (Aspect B), the first drive transmission unit is a rack gear such as a rack gear unit 13, the second drive transmission unit is a pinion gear such as a pinion gear 15, and the swing stop means transmits a driving force of a certain level or more. The torque limiter 33 or the like is a torque limiter such as the torque limiter 33, and the drive source and the pinion gear are connected via the torque limiter. According to this, as described in the above embodiment, when the adsorption separation unit is overloaded, the drive transmission from the drive source to the pinion gear is stopped by the torque limiter, and the oscillation of the adsorption separation unit can be stopped. it can.
(Aspect D)
(Aspect C) includes a plurality of torque limiters such as a torque limiter 33 and a torque limiter 35 in which different torque limits are set, and is driven from the drive source to the pinion gear via any of the plurality of torque limiters. Transmit power. According to this, as described in the above embodiment, the load torque applied to the bracket 12 of the adsorption separation unit 110 can be arbitrarily switched.
(Aspect E)
In (Aspect A), (Aspect B), (Aspect C) or (Aspect D), when the suction belt and the uppermost sheet are brought into contact with each other, the urging force is adsorbed in a direction in which the adsorption belt is separated from the uppermost sheet. A biasing member such as biasing support portions 12 and 24 to be applied to the belt is provided, and switching means for switching whether the suction belt is biased or not biased by the biasing member. According to this, as described in the above embodiment, finer adjustment of the surface contact force generated between the suction belt 2 and the uppermost sheet 1a can be performed.
(Aspect F)
In (Espect E), a pair of the biasing members facing each other with the suction belt sandwiched in the axial direction is provided, and each biasing member is between a position where the suction belt is biased and a position where the suction belt is not biased. It is movable and has interlocking means for moving the other biasing member in conjunction with the movement of one of the biasing members. According to this, as explained about the above-mentioned embodiment, a pair of energizing members can be moved in conjunction, and workability can be improved.
(Aspect G)
An image forming apparatus comprising: an image forming unit that forms an image on a sheet; and a sheet conveying unit that separates the uppermost sheet from the stacked sheet bundle and conveys the sheet to the image forming unit. (Aspect A), (Aspect B), (Aspect C), (Aspect D), (Aspect E) or (Aspect F) sheet conveying apparatus was used. According to this, as described in the above-described embodiment, it is possible to suppress the adsorption failure, the adsorption separation unit from being damaged, or the uppermost sheet from being deformed, and good image formation can be performed.

DESCRIPTION OF SYMBOLS 1 Sheet bundle 1a Top sheet 1b 2nd sheet 2 Adsorption belt 3 Electrode member 4 Charging power supply 5 Downstream tension roller 5a Shaft 6 Upstream tension roller 6a Shaft 7 Bottom plate 8 Support member 9 Conveying roller pair 10 Guide member 11 Paper feed cassette 12 Bracket 12a Long hole 13 Rack gear portion 14 Support shaft 15 Pinion gear 16 Rotating shaft 17 Belt drive shaft 20 Housing 21 Spring 22 Bearing 23 Rib 24 Drive motor 25 Pulley 26a Pulley 26b Pulley 27 Pulley 28 Drive timing belt 29 Drive timing belt DESCRIPTION OF SYMBOLS 30 Oscillation motor 31 Oscillation motor 32 Driven gear 33 Torque limiter 34 Clutch 35 Torque limiter 36 Clutch 40 Sheet detection means 41 Lower end 42 Shaft 43 Transmission type optical sensor 43a Light receiving part 43b Light emitting part 4 Filler 50 Image forming unit 51 Conveying path 52 Paper feeding unit 53 Registration roller 54 Transfer device 55 Fixing device 56 Paper discharge roller pair 57 Paper discharge tray 58 Document reading unit 59 Automatic document conveyance device 59a Document tray 61 Photoconductor 62 Charging device 63 Laser Light 64 Developing device 65 Photoconductor cleaning device 70 Reinforcing member 80 Belt drive shaft support member 81 Compression spring 100 Copier 103 Electrode member 110 Adsorption / separation unit 112 Biasing support portion 120 Swing mechanism 124 Biasing support portion 125 Guide groove 126 Rack gear 127 Pinion gear 128 Stopper support portion 129 Stopper 130 Stopper claw 131 Engagement portion 132 Compression spring 200 Sheet conveying device 230 Drive mechanism

Japanese Patent Laid-Open No. 2003-237862

Claims (7)

Adsorption separation that has an adsorption belt that is arranged opposite to the upper surface of the sheet bundle and is rotatably supported by a plurality of tension rollers, and is supported by a support member so as to be swingable upstream of the adsorption belt in the sheet conveying direction. Unit,
Charging means for charging the surface of the adsorption belt;
The adsorption position between the adsorption position where the uppermost sheet of the sheet bundle is brought into contact with the adsorption belt and adsorbed and the conveyance position farther from the sheet bundle than the adsorption position where the uppermost sheet adsorbed on the adsorption belt is conveyed In a sheet conveying apparatus provided with a swinging means for swinging the adsorption separation unit with the support member as a fulcrum so that the belt reciprocates,
And a swing stopping means for stopping swinging of the adsorption / separation unit by the swinging means when a load exceeding a predetermined level is applied to the suction / separation unit when the suction belt and the uppermost sheet are in contact with each other. Sheet transport device. In the sheet conveying apparatus according to claim 1,
The swinging means includes a first drive transmission unit provided at a downstream end of the adsorption / separation unit in the sheet conveyance direction, a second drive transmission unit attached to the apparatus main body and meshing with the first drive transmission unit. A drive source for driving the second drive transmission unit, and driving the second drive transmission unit by the drive source, and engaging the first drive transmission unit with the second drive transmission unit A sheet conveying device characterized by swinging a separation unit. In the sheet conveying apparatus according to claim 2,
The first drive transmission unit is a rack gear, the second drive transmission unit is a pinion gear, and the swing stop means is a torque limiter that limits transmission of a driving force above a certain level.
The sheet conveying apparatus, wherein the drive source and the pinion gear are connected via the torque limiter. In the sheet conveying apparatus according to claim 3,
A sheet conveying apparatus comprising a plurality of torque limiters set with different torque limits, and transmitting a driving force from the driving source to the pinion gear via any of the plurality of torque limiters. In the sheet conveying apparatus according to claim 1, 2, 3, or 4,
A biasing member that applies a biasing force to the suction belt in a direction in which the suction belt separates from the uppermost sheet when the suction belt and the uppermost sheet are in contact with each other;
A sheet conveying apparatus comprising switching means for switching between energizing or not energizing the suction belt by the energizing member. In the sheet conveying apparatus according to claim 5,
A pair of urging members facing each other with the suction belt sandwiched in the axial direction is provided, and each urging member is movable between a position where the suction belt is urged and a position where the suction belt is not urged,
A sheet conveying apparatus comprising interlocking means for moving the other urging member in conjunction with movement of one of the urging members. Image forming means for forming an image on a sheet;
In an image forming apparatus comprising: a sheet conveying unit that separates the uppermost sheet from the stacked sheet bundle and conveys the sheet to the image forming unit;
An image forming apparatus using the sheet conveying device according to claim 1, as the sheet conveying unit.

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