JP6274564B2 - Sheet conveying apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a paper feed unit used in an image forming apparatus such as a printer, a facsimile machine, and a copying machine, and an image forming apparatus including the sheet conveying apparatus.

Conventionally known methods for separating stacked sheets such as originals and recording paper at the time of feeding include a separation method using frictional force and a separation method using air suction.
However, in the method using the frictional force, since a rubber material or the like is used for the feeding roller, the frictional force changes due to changes over time such as wear, and the separability decreases. In addition, when separating the same type of sheets with different friction coefficients or different types of sheets with different friction coefficients at the same time, it is difficult to separate sheets from multiple sheets that cannot be separated from the stacked sheets. May occur. Furthermore, since the sheet is separated by applying pressure when the sheet is separated, wrinkles and streaks may occur on the sheet or may become dirty.

On the other hand, the separation method using air suction is a non-friction separation method that does not depend on the friction coefficient of the roller or the sheet, but requires an air suction blower and an air duct. Makes noise and unsuitable for use in offices.
In view of this, an electrostatic attraction separation method has been proposed, which is a type of non-friction separation method, in which an electric field is formed on an adsorption belt, and this is brought into contact with a sheet for adsorption and separation.

  As described in Patent Document 1, Patent Document 2, and the like, an electrostatic adsorption separation type sheet conveyance device uses an endless adsorption belt wound around a plurality of rollers and provided with an alternating charge to a sheet position. In this method, the uppermost sheet is adsorbed to the adsorption belt by being swung or moved in parallel, and the uppermost sheet is adsorbed to the adsorption belt, and then the adsorption belt is moved in a direction away from the stack of stacked sheets. The separation feeding device using the electrostatic adsorption separation method is excellent in that it does not cause wear, sheet pain, noise, and the like, and can achieve downsizing of the device.

  In the electrostatic adsorption separation type sheet conveying apparatus, various methods such as Patent Documents 2, 3, and 4 are disclosed as means for improving adsorption and separation.

  Various methods such as Patent Documents 5 and 6 have been proposed as means for moving the endless suction belt in the direction in which the endless suction belt is separated in the electrostatic suction separation type sheet conveying apparatus.

In an electrostatic adsorption separation type sheet conveying apparatus, the following flow is taken to adsorb, separate, and convey sheets.
(1) The suction belt moves and the uppermost sheet of the sheet bundle comes into contact with the suction belt.
(2) The uppermost sheet is sucked to the suction belt by waiting in a contact state for a predetermined time.
(3) The suction belt moves in a state where the uppermost sheet is sucked and held, and the suction belt and the sheet are separated to the transport position.
(4) The two stretching rollers that hold the suction belt are rotated to convey the sheet.
(5) When the sheet is continuously fed after the sheet conveyance, the process returns to (1).
For example, in the separation mechanism using the suction belt proposed in Patent Document 1, the uppermost sheet adsorbed on the suction belt by the “up and down movement of the suction belt” in (3) and (4) in the series of operations. Separation is ensured by separating from the sheet bundle.

  In the case of a paper feeding device including a paper feeding cassette as a sheet material storage unit having a capacity of 500 sheets or more, it is conceivable that the bottom plate of the paper feeding cassette is made of metal in order to ensure strength. The configuration of the member that is in contact with the bottom plate may constitute a state of being electrically connected to the ground (that is, grounding).

  However, in the case of an electrostatic adsorption separation type sheet conveying apparatus, when the contact and adsorption to the sheet by the adsorption belt, the adsorption belt is caused by a potential difference between the charged adsorption belt and a ground plate made of a metal member and grounded. An electric field is formed between the base plate and the bottom plate. This electric field causes polarization in the sheet between the suction belt and the bottom plate, and the sheets are brought into close contact with each other by electrostatic force. It may occur that the adhesion between the sheets exceeds a value assumed in design. If the adhesion between the sheets is high, there is a risk of non-feeding due to the fact that the uppermost sheet cannot be lifted by the suction belt, or multiple feeds that are attracted and transported by the suction belt while the sheets are in close contact. there were.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a sheet conveying apparatus capable of suppressing a conveyance failure such as sheet non-feeding, in which the bottom plate of the sheet material container is made of metal. An image forming apparatus is provided.

In order to achieve the above object, the invention of claim 1 is provided with a suction belt which is disposed opposite to the upper surface of the stacked sheet bundle and sucks the uppermost sheet of the sheet bundle, and the uppermost sheet of the sheet bundle is The suction belt can be reciprocated between a suction position to be suctioned by the suction belt and a transport position that is farther from the sheet bundle than the suction position for transporting the uppermost sheet sucked by the suction belt. In a sheet conveying apparatus comprising an electrostatic adsorption separation type adsorption separation unit and a sheet material accommodation unit for stacking and accommodating the sheet bundle, the sheet material accommodation unit comprises a bottom plate made of a metal member, When the uppermost sheet is attracted to the adsorption belt, the bottom plate is configured not to be electrically connected to the ground.

  According to the present invention, the bottom plate of the sheet material accommodating portion is made of metal, and conveyance failure such as sheet non-feeding can be suppressed.

1 is a schematic configuration diagram of a copier according to an embodiment. FIG. 3 is a perspective view of a sheet conveying device in a paper feeding unit of the copier. The schematic block diagram of the sheet conveying apparatus. The schematic block diagram of the adsorption | suction separation unit of the sheet conveying apparatus. The schematic block diagram of the drive mechanism of the adsorption belt of the adsorption separation unit. The perspective view of the principal part structure of the adsorption separation unit. The perspective view of the modification of the adsorption separation unit. The schematic block diagram of the other modification of the adsorption separation unit. The perspective view of the modification. Explanatory drawing of the sheet conveyance operation | movement using the sheet conveyance apparatus. FIG. 3 is a schematic configuration diagram illustrating a characteristic point of a sheet feeding cassette of the sheet conveying apparatus. FIG. 10 is a diagram illustrating a modification of feature points of the sheet cassette. Operation | movement explanatory drawing of the modification.

  Hereinafter, an embodiment in which the present invention is applied to a copying machine which is an electrophotographic image forming apparatus will be described.

FIG. 1 is a schematic configuration diagram of a 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. The original reading unit 58 for reading the original conveyed on the contact glass by the recording medium and the recording material sheet (sheet) fed from the paper feeding unit 52, an image is obtained based on the original image read by the original reading unit 58. And an image forming unit 50 as image forming means for forming. 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. 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. The sheet feeding unit 52 is provided with a sheet conveying device 200.

  In the image forming unit 50, first, the surface of the photoconductor 61 is uniformly charged by the charging device 62 as the photoconductor 61 rotates. 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 and conveys the sheets one by one, and stops against the registration roller 53. 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.

  2 is a perspective view illustrating a schematic configuration of the sheet conveying apparatus 200 in the sheet feeding unit 52, FIG. 3 is a schematic configuration diagram illustrating the sheet conveying apparatus 200, and FIG. 4 illustrates an adsorption unit and a separating unit. FIG. 3 is a diagram illustrating a main configuration of an adsorption separation unit 110.

  As shown in FIG. 2, the sheet conveying apparatus 200 includes a sheet detection unit 40 that detects that the uppermost sheet 1 a of the sheet bundle 1 has reached a predetermined position, and a sheet material that stacks and stores a plurality of sheets. A sheet feeding cassette 11 serving as a storage unit, an adsorption / separation unit 110, an oscillation mechanism 120 serving as an oscillation unit for oscillating the adsorption / separation unit 110, a drive mechanism 130 for moving the adsorption belt 2 endlessly, and the like are provided.

  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 reached a predetermined position, and the rotation of the support member 8 is stopped.

  As shown in FIG. 3, the paper feed cassette 11 has a bottom plate 7 on which a plurality of stacked sheet bundles 1 are stacked. A support member 8 that supports the bottom plate 7 is rotatably attached between the bottom portion 11 a of the paper feed cassette 11 and the bottom plate 7. Details of the paper feed cassette 11 will be described later.

As shown in FIG. 4, 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 having a thickness of about 50 μm having a resistance of 10 ⁸ Ω · cm or more and a conductive layer having a resistance of 10 ⁶ Ω · cm or less formed by aluminum vapor deposition. It has a layer structure. By making the suction belt 2 have the two-layer structure as described above, the conductive layer can be used as a grounded counter electrode, and the charging member 3 serving as a charging means for applying a charge to the suction belt 2 is used as the suction belt 2. It can be provided anywhere as long as it is in contact with the surface layer. Further, a retaining rib 23 is provided on the inner side of both side edges of the suction belt 2 and is engaged with both side end surfaces of the rollers 5 and 6 to prevent the belt from shifting.

The downstream tension roller 5 is provided with a conductive rubber layer having a resistance value of 10 ⁶ Ωcm 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.

  As shown in FIG. 4, 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. 2 and 3, 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. 3, 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 elongated 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 to rotate even if the upstream tension roller 6 (the shaft thereof) moves in the elongated 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. Normally, even if the tension of the suction belt 2 is 5 N or less, the suction belt 2 can be rotationally driven and the sheet adsorbed on the suction belt 2 can be conveyed without slipping between the roller and the belt. When conveying a sheet with special conditions such as a sheet with high adhesion, 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. 5 is a schematic configuration diagram of a drive mechanism 130 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 24 a 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 peripheral surface of the suction belt 2.

  The driving force of the driving motor 24 is transmitted to the downstream tension roller 5 via 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.

  The drive mechanism 130 may be configured so that the drive force is transmitted from the drive motor 24 to the upstream tension roller 6, and the upstream tension roller 6 may be used as a drive roller for rotating the suction belt 2.

  As shown in FIGS. 2 and 3, a swing mechanism 120 serving as a swinging unit that swings the bracket 12 is provided on the downstream side of the sheet feeding unit 52 in the sheet conveyance 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. A driven gear 32 that meshes with a motor gear 31 fixed to the motor shaft 30 a of the swing motor 30 is provided at one end of the rotating shaft 16.

  Each pinion gear 15 provided corresponding to each bracket 12 is fixed to the rotation shaft 16 that is the same shaft member, and the rotation shaft 16 is rotated by the swing motor 30 to rotate each pinion gear 15. be able to. Thereby, the two pinion gears 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.

  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. Further, 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 110. be able to.

  In the swing mechanism 120 having such a configuration, 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, the one bracket 12 and the other bracket 12 can be integrally swung. Thus, the suction belt 2 held by each bracket 12 is prevented from being twisted when the bracket is swung, and the uppermost sheet 1a adsorbed to the suction belt 2 is prevented from being separated from the suction belt 2. Can do.

  As shown in FIG. 6, a roller-shaped charging member 3 as a charging unit for charging the surface of the suction belt 2 is in contact with the surface of the suction belt 2. The charging member 3 is rotatably provided in the adsorption separation unit 110, and the position with respect to the adsorption belt 2 is uniquely determined. The charging member 3 is connected to a charging power source 4 that generates alternating current.

  Although the roller-shaped charging member 3 is used as the charging means, a blade-shaped electrode member 103 as shown in FIG. 7 may be used. By making the electrode member 103 into a blade shape, it is possible to form a charge pattern having a smaller pitch width than the roller-shaped charging member 3. As a result, the adsorption force of the stacked sheet bundle to the uppermost sheet 1a increases rapidly, and the adsorption force acting on the second and subsequent sheets decreases more quickly. Therefore, it is advantageous in that the time required for the separation operation can be shortened. Further, the alternating charging interval can be easily reduced in pitch, and stable charging can be performed even if the suction belt 2 has a minute wave.

As the swing mechanism 120 that swings the adsorption separation unit 110, a configuration as shown in FIG. 8 or FIG. 9 may be adopted.
8 and 9, the swinging mechanism that swings the adsorption / separation unit 110 includes a bracket 112, a rotating gear 113, a rotating shaft 114, a rotating gear 115, a rotating motor 117, and the like.

  A rotation shaft 114 is provided at a position parallel to the roller shafts of the downstream tension roller 5 and the upstream tension roller 6 and opposite to the feeding direction. Then, the adsorption separation unit 110 is swung up and down by brackets 112 that rotatably support both ends of the downstream tension roller 5 and the upstream tension roller 6. A rotation gear 113 that meshes with the rotation gear 115 provided on the motor shaft 116 of the rotation motor 117 is provided at one axial end side of the rotation shaft 114. Then, the bracket 112 is rotated in the vertical direction according to the rotational drive direction of the rotary motor 117.

The sheet conveying operation of the sheet conveying apparatus 200 is as follows.
As shown in FIG. 10A, 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 in the clockwise direction in the figure, and the adsorption separation unit 110 is rotated counterclockwise in the figure with the support shaft 14 as a fulcrum (sheet). Swing in a direction away from the bundle. 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. 10B, 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 charging member 3, and a pitch (pitch is determined) on the surface of the suction belt 2 according to the AC power source frequency and the circumferential speed of the suction belt 2. 5 to 15 mm is preferable, and an alternating charge pattern is formed. The power source 4 may be an alternating current or an alternating potential of high and low, and a rectangular wave, a sine wave or the like can be considered. 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, as shown in FIG. 10C, 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. Also, before and after this, the swing motor 30 is rotated in the reverse direction, the pinion gear 15 is rotated counterclockwise in the figure, and the adsorption separation unit 110 is rotated clockwise in the figure (the sheet bundle) with the support shaft 14 as a fulcrum. Rocks in a direction close to When the bottom plate 7 is raised and the suction separation unit 110 is lowered, the uppermost sheet 1a of the sheet bundle 1 comes into contact with the upstream tension roller 6 via the suction 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 hits the lower end 41 of the long hole 12a. 6 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 sheet detecting means 40 is the uppermost sheet 1a of the sheet bundle 1. Is detected, and the ascent of the bottom plate 7 is stopped. Further, when the adsorption separation unit 110 reaches the adsorption position, the rotation of the swing motor 30 is stopped. 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. 10D, when the rise of the bottom plate 7 is stopped and the lowering (swinging) of the adsorption separation unit 110 is stopped, 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. 10 (d), when the uppermost sheet 1 a is adsorbed to the adsorbing belt 2, the swing motor 30 is driven to rotate the pinion gear 15 clockwise to adsorb and separate unit 110. Is pivoted counterclockwise in the figure with 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 moves relative to the bracket 12 in the direction of the sheet bundle 1 without moving from the upper surface of the sheet bundle 1 due to its own weight. As a result, the suction belt 2 moves so as to swing around the rotation center of the upstream tension roller 6, and the 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 around 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 rotates 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 elongated hole 12a. In this way, when the suction separating unit 110 is further rotated from the state in which the upstream tension roller 6 is in contact with the lower end 41 of the elongated hole 12a, the upstream tension roller 6 also moves together with the bracket 12, and the upstream side The tension roller 6 is separated from the upper surface of the sheet bundle 1. As shown in FIG. 10E, when the suction 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, and the uppermost sheet 1 a sucked on the suction belt 2 is transported toward the transport 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 curvature separation and guided to the guide member 10. However, it moves toward the pair of transport rollers 9 (see FIG. 10E).

  The linear speeds of the conveyance roller pair 9 and the suction belt 2 are the same. When the conveyance roller pair 9 is intermittently driven at a timing, the drive motor 24 is driven so that the adsorption belt 2 is also intermittently driven. To control. Alternatively, the drive of the suction belt 2 may be controlled by providing an electromagnetic clutch in the drive mechanism 130 and controlling the electromagnetic clutch.

  The suction belt 2 may be charged by the length of the conveyance roller pair 9 from the sheet separation position of the suction belt 2, and thereafter, the suction belt 2 may be neutralized by the charging member 3. . Thus, after the sheet is conveyed to the conveying roller pair 9, the sheet is conveyed only by the conveying force of the conveying roller pair 9 without being affected by the suction belt 2. Further, by neutralizing the suction belt 2, it is possible to suppress the second sheet 1 b from being electrostatically attracted to the separated suction belt 2.

  An elongated hole 12 a is provided in the bracket 12, and the shaft 6 a of the upstream tension roller 6 is held in the elongated hole 12 a. The upstream tension roller 6 is downstream of the bracket 12 with respect to the bracket 12. When the suction separation unit 110 is in the feeding position, the upstream stretching roller 6 is set so that the inclination angle of the suction belt 2 with respect to the upper surface of the sheet bundle is a predetermined angle. Any structure may be used as long as the structure is supported.

The characteristic part of this embodiment is as follows.
FIG. 11 is a diagram illustrating a main configuration of the sheet feeding cassette 11 as a sheet material accommodation unit. In order to ensure strength, the bottom plate 7 and the support member 8 are made of metal members. Further, the bottom 11a, the front fence 11b, the back fence 11c, and the side fence (not shown) in the paper feed cassette 11 are configured by non-conductive members such as resin members, for example.

  A neutralization unit is provided for removing charges initially held before the sheet bundle 1 is set in the paper feed cassette 11. As the static eliminating means, a ground may be connected to the floor plate 7. In this case, when at least the uppermost sheet 1a is adsorbed to the adsorbing belt 2, in order to be able to intentionally disconnect the ground and the bottom plate 7, for example, it is electrically connected to an earth such as a switch. A switching unit that can switch between the connected state and the unconnected state, and a control unit that controls the switching timing of the switching unit by a paper feed signal.

  In this embodiment, when at least the uppermost sheet 1a is adsorbed to the adsorption belt 2, the bottom plate 7 is not electrically connected to the ground, and the uppermost sheet 1a is attached to the case where the bottom plate 7 is grounded. The potential difference between the adsorption belt 2 and the bottom plate 7 when adsorbed on the adsorption belt 2 can be reduced. Therefore, the magnitude of the electric field formed by the potential difference is also reduced, and the adhesion between sheets due to static electricity can be reduced. Thereby, conveyance failure, such as sheet non-feeding, can be suppressed.

In a winter environment or the like, the sheet bundle 1 is charged by static electricity before being set in the apparatus. However, the charge of the sheet bundle 1 can be released by removing the sheet by the charge removing means. It becomes. Thereby, it is possible to prevent an adverse effect on the image due to the accumulation of electric charges on the bottom plate 7.
[Modification 1]
FIG. 12 is a view showing a modified example of the switching means in the sheet feeding cassette 11 as the sheet material accommodating portion. In this modification, a ground member 150 connected to the ground is provided at the bottom 11a as the switching means.

  As shown in the description of the sheet conveying operation, the bottom plate 7 is normally waiting at the lowered position. Sheets are also set at this position. At this time, in order to prevent accumulation of static electricity on the metal member, the bottom plate 7 is in contact with the ground member 150 so that the bottom plate 7 is grounded as shown in FIG.

  On the other hand, when the paper feed signal is input, the bottom plate 7 waiting at the lowered position starts to rise. When the bottom plate 7 is lifted from the lowered position, the bottom plate 7 is not in contact with the ground member 150 as shown in FIG.

In the first modification, it is possible to easily switch between a state of being electrically connected to the ground and a state of being not connected without providing a separate control unit for controlling the switching timing of the switching means.
The present invention is not limited to the image forming apparatus of the present embodiment, and can be applied to, for example, an inkjet image forming apparatus.

What has been described above is an example, and the present invention has a specific effect for each of the following aspects.
(Aspect 1)
A suction position that is disposed opposite to the upper surface of the stacked sheet bundle 1 and sucks the uppermost sheet 1a of the sheet bundle 1 and sucks the uppermost sheet 1a of the sheet bundle 1 onto the suction belt 2. An adsorption separation unit configured such that the adsorption belt 2 can reciprocate between a conveyance position separated from the sheet bundle 1 rather than the adsorption position for conveying the uppermost sheet 1a adsorbed to the adsorption belt 2. 110 and a sheet feeding apparatus 11 as a sheet material storage unit for stacking and storing the sheet bundle 1, the sheet feeding unit 52 includes a bottom plate 7 made of a metal member, and at least When the uppermost sheet 1a is adsorbed to the adsorption belt 2, the bottom plate 7 is configured not to be electrically connected to the ground.
With this configuration, when the uppermost sheet 1a is adsorbed to the adsorption belt 2, the bottom plate 7 is not electrically connected to the ground, so that the uppermost sheet is compared with the case where the bottom plate 7 is grounded. The potential difference between the suction belt 2 in contact with 1a and the bottom plate 7 can be reduced. Therefore, the magnitude of the electric field formed by the potential difference is also reduced, and the adhesion between sheets due to static electricity can be reduced. Thereby, conveyance failure, such as sheet non-feeding, can be suppressed.

(Aspect 2)
In the sheet conveying apparatus according to the first aspect, a switching unit is provided so that the sheet feeding cassette 11 serving as the sheet material accommodation unit can be switched between a state where it is electrically connected to the ground and a state where it is not connected. By adopting such a configuration, in addition to the effect of the aspect 1, it becomes possible to release the charged charges by static electricity that the sheet bundle 1 has before being set in the apparatus. Thereby, it is possible to prevent an adverse effect on the image due to the accumulation of electric charges on the bottom plate 7.

(Aspect 3)
In the sheet conveying apparatus according to the second aspect, the switching unit includes a ground member 150 below the bottom plate, and the bottom plate 7 can be switched between contact and non-contact by the vertical movement of the bottom plate 7. It was.
By adopting such a configuration, in addition to the effect of the aspect 2, it is possible to easily switch between a state of being electrically connected to the ground and a state of being not connected without providing a special control means.

(Aspect 4)
An image forming unit such as an image forming unit 50 that forms an image on a sheet, and a sheet conveying unit 200 that separates the uppermost sheet 1b from the stacked sheet bundle 1 and conveys the uppermost sheet 1b to the image forming unit. The sheet conveying unit 200 includes the sheet conveying device according to the first aspect or the second aspect.
According to this, it is possible to perform image formation by performing good sheet conveyance.

1: Sheet bundle 1a: Top sheet 2: Adsorption belt 3, 103: Electrode member 4: Charging power source 5: Downstream tension roller 6: Upstream tension roller 7: Bottom plate 8: Support member 9: Conveying roller pair 10 : Guide member 11: Paper feed cassette 11a: Bottom part 11b: Front fence 11c: Back fence 12: Bracket 12a: Slot 13: Rack gear part 14: Support shaft 15: Pinion gear 16: Rotating shaft 20: Housing 21: Spring 22: Bearing 23: Stopping rib 24: Drive motor 30: Oscillating motor 40: Sheet detecting means 50: Image forming unit 52: Paper feeding unit 70: Reinforcement member 100: Copying machine 110: Suction separation unit 120: Oscillating mechanism 130 : Drive mechanism 150: Earth member 200: Sheet conveying device

JP-A-5-139548 JP 2010-37047 A Japanese Patent Laid-Open No. 2003-237862 JP 2004-26314 A JP 2003-237958 A JP 2010-126317 A

Claims (4)

A suction belt that is disposed opposite to the upper surface of the stacked sheet bundle and sucks the uppermost sheet of the sheet bundle, sucks the uppermost sheet of the sheet bundle to the suction belt, and sucks the suction belt to the suction belt. An electrostatic adsorption separation type adsorption separation unit configured such that the adsorption belt can reciprocate between a conveyance position separated from the sheet bundle rather than the adsorption position for conveying the uppermost sheet;
In a sheet conveying apparatus provided with a sheet material storage unit that stacks and stores the sheet bundle,
The sheet material accommodating portion includes a bottom plate made of a metal member,
A sheet conveying apparatus configured to prevent the bottom plate from being electrically connected to the ground when at least the uppermost sheet is adsorbed to the adsorption belt. In the sheet conveying apparatus according to claim 1,
A sheet conveying apparatus, comprising: a switching unit that enables switching between a state in which the sheet material accommodating portion is electrically connected to the ground and a state in which the sheet material accommodating portion is not connected to the ground. In the sheet conveying apparatus according to claim 2,
The sheet conveying apparatus, wherein the switching unit is configured to provide a grounding member below the bottom plate and to switch contact and non-contact between the bottom plate and the grounding member by vertical movement of the bottom plate. 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 uppermost sheet to the image forming unit;
An image forming apparatus comprising the sheet conveying device according to claim 1 as the sheet conveying unit.

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