JP2017171492A - Sheet conveyance apparatus and image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet conveyance apparatus capable of stably conveying a sheet with a configuration adopting an electrostatic attraction supply system, and an image formation apparatus.SOLUTION: After a sheet S is electrostatically attracted to a supply belt 6, the sheet S is conveyed to the downstream side of a conveying direction by rotating the supply belt 6. When the sheet S electrostatically attracted to the supply belt 6 is conveyed to a downstream end of the conveying direction in a planar portion 23 of the supply belt 6, the sheet S is peeled off from the supply belt 6 in order from a leading end. On the downstream side of the sheet S in the conveying direction with respect to a support part, a conveyance belt 8 rotated when the sheet S is conveyed is disposed. A planar portion 33 of the conveyance belt 8 extends to a position beyond a portion of the supply belt 6, which is in contact with a roller 22, to the upstream side of the conveyance direction.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a sheet conveying apparatus that conveys a sheet and an image forming apparatus including the sheet conveying apparatus.

  For example, an image forming apparatus such as a printer or a copying machine is provided with a sheet conveying device that conveys a sheet such as paper. The sheet is conveyed on the conveyance path by the sheet conveyance device. While the sheet is conveyed, an image is formed on the sheet by an image forming unit provided in the middle of the conveyance path.

  As a method for supplying a sheet to a conveyance path, an electrostatic adsorption supply method is known in which conveyance is started by adsorbing a sheet to an adsorption belt by electrostatic force. In the configuration adopting this electrostatic suction supply system, the suction belt is provided above the sheet material storage portion for storing the sheets in a stacked state so as to be able to be raised and lowered by swinging. At the start of sheet conveyance, the bottom plate that supports the sheet is raised in the sheet material container, and the suction belt is lowered, so that the suction belt and the uppermost sheet on the bottom plate come into contact with each other. A charging voltage is applied from the electrode member to the suction belt in a state where the suction belt and the uppermost sheet are in contact with each other. As a result, the uppermost sheet is electrostatically attracted to the attracting belt. Thereafter, the suction belt starts to run.

  A pair of conveyance rollers is provided on the downstream side in the sheet conveyance direction with respect to the suction belt. As the suction belt travels, the sheet adsorbed on the suction belt is separated from the suction belt in order from the front end and is conveyed toward the conveyance roller. When the leading edge of the sheet enters between the conveyance rollers, a conveyance force is applied to the sheet from the conveyance rollers.

JP 2014-223971 A

  However, in the configuration employing the electrostatic suction supply method, the position of the leading edge of the sheet separated from the suction belt is difficult to be determined. For this reason, there is a possibility that the leading edge of the sheet may be bent when the leading edge of the sheet does not enter between the conveying rollers well and the leading edge of the sheet contacts the peripheral surface of the conveying roller.

  An object of the present invention is to provide a sheet conveying apparatus and an image forming apparatus that can stably convey a sheet in a configuration employing an electrostatic attraction supply system.

  In order to achieve the above object, according to this configuration, the sheet conveying apparatus according to the present invention supports the sheet to be conveyed by the support surface of the support portion. A first endless belt is disposed at a position facing the support surface with a space therebetween. The first endless belt is charged by the charging unit. The sheet is electrostatically attracted to the first endless belt by the charging of the first endless belt. Further, when the sheet is conveyed, the first endless belt is rotated. The sheet is conveyed by rotating the first endless belt in a state where the sheet is adsorbed to the first endless belt.

  When the sheet electrostatically attracted to the first endless belt is conveyed to the downstream end of the first endless belt in the conveying direction, the sheet is peeled off from the first endless belt in order from the front end. A second endless belt that is rotated when the sheet is conveyed is disposed downstream of the support unit in the sheet conveying direction. At least a part of the second endless belt is opposed to the first endless belt from the lower side in the direction orthogonal to the support surface. Therefore, even if the leading edge of the sheet peeled off from the first endless belt is out of order, the leading edge is satisfactorily landed on the second endless belt. Therefore, the sheet can be stably conveyed.

  The present invention can be realized not only in the form of a sheet conveying apparatus, but also in the form of an image forming apparatus provided with a sheet conveying apparatus, for example.

  According to the present invention, a sheet can be stably conveyed in a configuration employing an electrostatic adsorption supply system.

1 is a schematic sectional view showing a configuration of a printer provided with a sheet conveying apparatus according to an embodiment of the present invention. It is the illustration side view which looked at the supply tray and the supply belt from the downstream of the conveyance direction. It is the illustration top view which looked at the supply tray from upper direction. FIG. 2 is a block diagram illustrating an electrical configuration of a printer. 6 is a flowchart illustrating a flow of processing for sheet conveyance control. FIG. 3 is a schematic sectional view (No. 1) showing a conveyance state of a sheet. FIG. 6 is a schematic cross-sectional view (part 2) illustrating a conveyance state of a sheet. It is an illustration sectional view showing the composition provided with the lift mechanism. 6 is a flowchart illustrating a flow of processing for sheet conveyance control that can be employed in a configuration in which a lift mechanism is provided. It is an illustration side view showing other examples of composition for making the interval between a supply tray and a supply belt smaller than both sides in the central part of the width direction. FIG. 6 is an illustrative cross-sectional view showing an example of a configuration for making an interval between a supply tray and a supply belt smaller on the downstream side in the transport direction than on the upstream side.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<Schematic configuration of printer>
A printer 1 shown in FIG. 1 includes a sheet conveying device 2 that conveys a sheet S. In the printer 1, the sheet S is conveyed in one direction (hereinafter referred to as “conveying direction”, which coincides with the direction from the left side to the right side in FIG. 1) by the sheet conveying device 2. Then, an image is formed on one surface of the sheet S during the conveyance of the sheet S by the sheet conveying apparatus 2. The image-formed sheet S is discharged from the main body 3 to a discharge tray 4 extending to the outside. The sheets S discharged to the discharge tray 4 are supported on the discharge tray 4 in a stacked state.

  The sheet conveying apparatus 2 includes a supply tray 5 (an example of a support unit), a supply belt 6 (an example of an endless belt), a charging roller 7 (an example of a charging unit), and a conveyance belt 8.

  The supply tray 5 is configured to be detachable with respect to the main body 3 by insertion and removal in a direction along the transport direction. Of course, the supply tray 5 may be fixed to the main body 3. The following description is based on the state in which the supply tray 5 is mounted on the main body 3, and the “vertical direction” is defined in a state in which the main body 3 is installed on a horizontal plane. Here, the vertical direction is the same as the vertical direction in FIG.

  The supply tray 5 is provided with a substantially rectangular plate-like support member 11 (an example of a plate-like member). The support member 11 is provided so that both surfaces thereof face up and down. The upper surface of the support member 11 is formed as a support surface 12 that can be supported in a state where the sheets S are stacked, on a plane extending in the transport direction and the width direction orthogonal to the transport direction. The support surface 12 has a size (area) larger than the maximum size of the sheet S that can be conveyed by the sheet conveying apparatus 2, for example, A4 size. The support member 11 is made of an insulating member such as glass.

  A lifting member 13 is provided on the support surface 12. The lifting member 13 is disposed at the downstream end of the support surface 12 in the transport direction and at the center in the width direction. The lifting member 13 has an arcuate shape when viewed from the width direction, and has a substantially rectangular shape when viewed from the transport direction and from above, as shown in FIGS. The lifting member 13 is made of an insulating resin.

  The sheet S before image formation is supported on the support surface 12 so that the downstream end in the transport direction rides on the lifting member 13. As a result, the sheet S is supported in a state where the downstream end in the transport direction and the center in the width direction (hereinafter referred to as “downstream center”) are lifted from the support surface 12 by the lifting member 13. Supported by Here, the central portion in the width direction refers to the middle region when the sheet S is divided into three equal parts in the width direction, and the downstream side in the conveyance direction refers to the downstream side when the sheet S is divided into two equal parts in the conveyance direction. Indicates the area. The lifting member 13 does not need to lift all of the downstream central portion, and may be lifted at least partially. When a plurality of sheets S are supported on the support surface 12, the plurality of sheets S are supported on the support surface 12 in a stacked state.

  The supply belt 6 is disposed above the lifting member 13 with a gap, for example, 3 to 9 mm, from the lifting member 13. The supply belt 6 is formed in an endless shape and is wound around two rollers 21 and 22. The two rollers 21 and 22 are arranged at an interval in the transport direction so that the rotation axis extends in the width direction and the supply belt 6 is stretched. The lower ends of the peripheral surfaces of the rollers 21 and 22 are arranged at the same position (height) in the vertical direction. Thereby, the supply belt 6 has a planar portion 23 extending in the transport direction and the width direction between the lower ends of the two rollers 21 and 22. The roller 22 on the downstream side in the transport direction of the two rollers 21 and 22 is disposed on the downstream side of the downstream end of the support member 11 in the transport direction. Further, as shown in FIG. 2, the supply belt 6 has a larger dimension in the width direction than the maximum sheet S that can be conveyed. Therefore, at least the downstream end in the transport direction of the sheet S supported by the support surface 12 faces the planar portion 23 of the supply belt 6 in the vertical direction over the entire width in the width direction. The supply belt 6 is made of a conductive member, for example, nylon made of a conductive agent.

  As shown in FIG. 1, the charging roller 7 is disposed at substantially the same position as the lifting member 13 in the conveyance direction inside the supply belt 6. The circumferential surface of the charging roller 7 is in contact with the inner surface of the planar portion 23 of the supply belt 6, and is driven to rotate as the supply belt 6 rotates (movement of the planar portion 23). A negative charging voltage, for example, 1.3 kV, is applied to the charging roller 7 from the charging voltage application circuit 43 (see FIG. 4). By applying the charging voltage, the planar portion 23 of the supply belt 6 is negatively charged. Further, the roller 22 supporting the supply belt 6 also functions as a static elimination roller connected (grounded) to the ground, and the portion of the supply belt 6 that contacts the roller 22 is grounded via the roller 22. To eliminate static electricity.

  The conveyor belt 8 is made of rubber, for example. The conveyance belt 8 is disposed on the downstream side in the conveyance direction with respect to the supply tray 5 (support member 11). The conveyor belt 8 is formed in an endless shape and is wound around two rollers 31 and 32. One roller 31 is arranged below the roller 22 supporting the supply belt 6 so that the rotation axis extends in the width direction and the rotation axis is positioned upstream of the rotation axis of the roller 22 in the transport direction. Has been. The other roller 32 is arranged in the vicinity of the discharge tray 4 so that the rotation axis extends in the width direction. The upper ends of the peripheral surfaces of the rollers 31 and 32 are arranged at the same position (height) in the vertical direction. Thereby, the conveyance belt 8 has a planar portion 33 extending in the conveyance direction and the width direction between the upper ends of the two rollers 31 and 32. The end of the planar portion 33 on the upstream side in the conveyance direction is opposed to the planar portion 23 of the supply belt 6 with an interval in the vertical direction from the lower side. The interval is designed in the range of 10 mm or more and 30 mm or less, for example.

  An inkjet image forming unit 9 is provided above the transport belt 8, for example. In the ink jet system, an image is formed on the sheet S by directly ejecting fine droplets of ink onto the sheet S conveyed by the conveyance belt 8.

<Electrical configuration of printer>
As shown in FIG. 4, the printer 1 includes a transport motor 41 that generates rotational driving force for the supply belt 6 and the transport belt 8, a motor drive circuit 42 for driving the transport motor 41, and a charging roller 7. A charging voltage application circuit 43 for applying a charging voltage is provided.

  The driving force of the transport motor 41 is transmitted to one of the rollers 21 and 22 that support the supply belt 6 via the electromagnetic clutch 44. In a state where the electromagnetic clutch 44 is on, the driving force of the transport motor 41 is transmitted to one of the rollers 21 and 22, and the rollers 21 and 22 and the supply belt 6 rotate. When the electromagnetic clutch 44 is turned off, transmission of the driving force from the transport motor 41 to one of the rollers 21 and 22 is interrupted.

  Further, the driving force of the transport motor 41 is transmitted to one of the rollers 31 and 32 that support the transport belt 8 via the electromagnetic clutch 45. When the electromagnetic clutch 45 is turned on, the driving force of the transport motor 41 is transmitted to one of the rollers 31 and 32, and the rollers 31 and 32 and the transport belt 8 rotate. In the state where the electromagnetic clutch 45 is turned off, transmission of the driving force from the transport motor 41 to one of the rollers 31 and 32 is interrupted.

  The printer 1 further includes an application specific integrated circuit (ASIC) 51, a ROM 52, and a RAM 53. The ASIC 51 includes a CPU 54 (an example of a control unit).

  A communication interface 61 is connected to the ASIC 51. The communication interface 61 is an interface for communication with an external device such as a PC (personal computer) connected to a LAN (Local Area Network). The communication method may be a wireless communication method or a wired communication method. Image data received from the external device via the communication interface 61 is input to the ASIC 51.

  Further, a charge amount sensor 62 and an optical sensor 63 are connected to the ASIC 51.

  The charge amount sensor 62 detects the charge amount of the planar portion 23 of the supply belt 6 and outputs a detection signal corresponding to the charge amount. The CPU 54 of the ASIC 51 can detect the charge amount of the planar portion 23 of the supply belt 6 from the detection signal of the charge amount sensor 62.

  The optical sensor 63 is a CIS (Contact Image Sensor), and as shown in FIG. 1, the optical sensor 63 is upstream of the image forming unit 9 in the conveyance direction, and is moved up and down from the upper side to the planar portion 33 of the conveyance belt 8. It arrange | positions in the position which opposes a direction, and is extended in the width direction. The CPU 54 of the ASIC 51 can detect from the detection signal of the optical sensor 63 that the sheet S has reached the detection position of the optical sensor 63 (a position facing the optical sensor 63 in the vertical direction in the planar portion 33).

  The CPU 54 controls the image forming unit 9, the motor drive circuit 42, the charging voltage application circuit 43, and the electromagnetic clutches 44 and 45 by executing programs for various processes, and the sheet S by the sheet conveying device 2. And the image forming operation by the image forming unit 9 are controlled.

  The ROM 52 stores programs executed by the CPU 54 and various data.

  The RAM 53 is used as a work area when the CPU 54 executes a program.

<Sheet conveyance control>
In order to convey one sheet S from the supply tray 5, the processing shown in FIG. 5 is executed by the CPU 54 of the ASIC 51.

  In this process, the CPU 54 controls the charging voltage application circuit 43 to start application of the charging voltage from the charging voltage application circuit 43 to the charging roller 7 (S1).

  In a state where the charging voltage is not applied to the charging roller 7, the sheet S supported on the support surface 12 of the support member 11 is separated from the supply belt 6 as shown in FIG. 6A (a).

  When the charging voltage is applied to the charging roller 7 and the planar portion 23 of the supply belt 6 is negatively charged, as shown in FIG. 6A (b), the downstream end of the uppermost sheet S in the conveying direction. Is electrostatically attracted to the planar portion 23. Specifically, as shown in FIG. 2, since the lifting member 13 is provided on the support surface 12, the vertical distance (shortest distance) between the lifting member 13 and the planar portion 23 of the supply belt 6. Is shorter than the vertical distance (shortest distance) between the support surface 12 and the planar portion 23. Therefore, when the planar portion 23 is charged, the downstream central portion of the uppermost sheet S is electrostatically attracted to the planar portion 23 in the first region 71 between the lifting member 13 and the planar portion 23. Thereafter, the sheet S is electrostatically attracted to the planar portion 23 in the second regions 72 on both sides in the width direction with respect to the first region 71. As a result, as shown in FIG. 6A (b), the downstream end of the uppermost sheet S in the transport direction is electrostatically adsorbed to the planar portion 23.

  After starting the application of the charging voltage to the charging roller 7, the CPU 54 determines whether or not the sheet S is electrostatically attracted to the planar portion 23 of the supply belt 6 (S2). When the sheet S is electrostatically attracted to the planar portion 23, the charge escapes from the planar portion 23 to the sheet S, so that the charge amount of the planar portion 23 changes. The CPU 54 refers to the detection signal of the charge amount sensor 62 to determine whether or not the charge amount of the planar portion 23 has changed by a predetermined value or more, and when the charge amount has changed by a predetermined value or more, the sheet S is 23 is determined to be electrostatically attracted.

  When the sheet S is not electrostatically attracted to the planar portion 23 (S2: NO), the CPU 54 determines whether or not a first predetermined time has elapsed from the start of applying the charging voltage (S3).

  When the first predetermined time has not elapsed since the start of application of the charging voltage (S3: NO), the CPU 54 determines again whether or not the sheet S is electrostatically attracted to the planar portion 23 (S2).

  When the sheet S is electrostatically adsorbed to the planar portion 23 of the supply belt 6 from the start of applying the charging voltage to the charging roller 7 until the first predetermined time elapses (S2: YES), the CPU 54 The drive circuit 42 is controlled to drive the transport motor 41. Thereafter, the CPU 54 turns on the electromagnetic clutches 44 and 45. When the electromagnetic clutch 44 is turned on, the supply belt 6 starts to rotate (S4). Further, when the electromagnetic clutch 45 is turned on, the conveyance belt 8 starts to rotate. The supply belt 6 and the conveyance belt 8 rotate at the same moving speed.

  As the supply belt 6 starts to rotate, as shown in FIG. 6A (c), the sheet S electrostatically attracted to the planar portion 23 is conveyed downstream in the conveying direction.

  As the conveyance of the sheet S proceeds, the leading edge of the sheet S reaches the downstream end of the planar portion 23 in the conveyance direction. Since the portion of the supply belt 6 that contacts the roller 22 is neutralized, when the sheet S is further conveyed, as shown in FIG. 6B (d), the sheet S is moved from the leading edge as the sheet S is conveyed. It peels from the supply belt 6 in order. The end of the planar portion 33 of the transport belt 8 on the upstream side in the transport direction faces the planar portion 23 of the supply belt 6 from below. Therefore, the leading edge of the sheet S peeled off from the supply belt 6 is landed on the planar portion 33 of the conveyance belt 8.

  When the entire sheet S is peeled off from the supply belt 6, the entire sheet S is transferred to the planar portion 33 of the conveyance belt 8 as shown in FIG. 6B (e). Thereafter, the sheet S is conveyed downstream in the conveying direction by the rotation of the conveying belt 8.

  After starting the rotation of the supply belt 6, the CPU 54 determines from the detection signal of the optical sensor 63 whether the trailing edge of the sheet S has reached the detection position of the optical sensor 63, that is, whether the trailing edge of the sheet S has been detected. Is determined (S5).

  When the trailing edge of the sheet S has not reached the detection position of the optical sensor 63 (S5: NO), the CPU 54 determines whether or not a second predetermined time has elapsed from the start of rotation of the supply belt 6 (S6). .

  When the second predetermined time has not elapsed since the start of rotation of the supply belt 6 (S6: NO), the CPU 54 determines again whether or not the trailing edge of the sheet S has reached the detection position of the optical sensor 63 (S5). ).

  If the trailing edge of the sheet S reaches the detection position of the optical sensor 63 before the second predetermined time elapses after the rotation of the supply belt 6 starts (S5: YES), the CPU 54 turns off the electromagnetic clutch 44. To do. When the electromagnetic clutch 44 is turned off, the supply belt 6 stops (S7).

  Further, the CPU 54 controls the charging voltage application circuit 43 to stop the application of the charging voltage from the charging voltage application circuit 43 to the charging roller 7 (S8). Thereafter, the processing shown in FIG. 5 ends.

  On the other hand, when the sheet S is not electrostatically attracted to the planar portion 23 of the supply belt 6 and the first predetermined time has elapsed from the start of application of the charging voltage to the charging roller 7 (S3: YES), the CPU 54 The conveying device 2 is stopped by error (S9), and the processing shown in FIG. When the error is stopped, the application of the charging voltage to the charging roller 7 is stopped.

  Even when the second predetermined time has elapsed from the start of rotation of the supply belt 6 without the trailing edge of the sheet S reaching the detection position of the optical sensor 63 (S6: YES), the CPU 54 moves the sheet conveying device 2 over. The error is stopped (S9), and the process shown in FIG. 5 is terminated. Due to the error stop, the application of the charging voltage to the charging roller 7 is stopped and the supply belt 6 is stopped.

<Effect>
As described above, the sheet S to be conveyed is supported by the support surface 12 of the supply tray 5 (support member 11). A supply belt 6 is disposed at a position facing the support surface 12 with a gap. The supply belt 6 is charged by a charging voltage applied via the charging roller 7 and is rotated when the sheet S is conveyed.

  Between the supply tray 5 and the supply belt 6, the 1st area | region 71 with the relatively short space | interval (shortest distance) and the 2nd area | region 72 with comparatively long have arisen. Therefore, when the supply belt 6 is charged, first, the sheet S can be partially electrostatically adsorbed to the supply belt 6 in the width direction in the first region 71 where the interval between the supply tray 5 and the supply belt 6 is short. Thereafter, the sheet S is electrostatically attracted to the supply belt 6 in the second region 72 where the interval between the supply tray 5 and the supply belt 6 is long. Thereby, even if the supply belt 6 and the sheet S are spaced apart, the sheet S can be electrostatically adsorbed to the supply belt 6.

  Therefore, when the conveyance of the sheet S is started, there is no mechanical operation for bringing the supply belt 6 into contact with the sheet S, and generation of sound due to the contact between the supply belt 6 and the sheet S can be suppressed.

  When the gap between the supply tray 5 and the supply belt 6 is substantially uniform in the width direction, both side portions in the width direction of the downstream center portion of the sheet S are electrostatically attracted to the supply belt 6 before the downstream center portion, The downstream central portion where the weight of the sheet S is concentrated is difficult to lift. In the sheet conveying apparatus 2, the first region 71 is a central region in the width direction, and the second region 72 is a region on both sides in the width direction with respect to the first region 71. Therefore, the supply belt 6 is electrostatically attracted to the supply belt 6 in order from the downstream central portion of the sheet S toward the both sides in the width direction due to charging. As a result, the downstream end of the sheet S in the transport direction can be electrostatically attracted to the supply belt 6 over the entire width in the width direction. In addition, since the sheet S is electrostatically attracted to the supply belt 6 in order from the downstream central portion, the sheet S is less likely to wrinkle. Further, in the configuration in which the sheet S is positioned on the support surface 12 with the center reference in the width direction, the sheet S is displaced in the width direction by electrostatic adsorption from the downstream center portion of the sheet S to the supply belt 6. Can be suppressed.

  Further, the supply tray 5 and the supply belt 6 are provided in the first region 71 in the central portion in the width direction while suppressing an increase in cost by a simple structure in which the lifting member 13 is disposed in the central portion in the width direction on the support surface 12. The distance between the supply tray 5 and the supply belt 6 can be long in the second regions 72 on both sides in the width direction.

  Furthermore, an insulating member is used as the material of the support member 11 that provides the support surface 12, and the support surface 12 has a size larger than the maximum size of the sheet S that can be conveyed. When electrostatically attracting to the sheet 6, the sheet S is easily peeled off from the support surface 12. Therefore, the sheet S can be more electrostatically adsorbed to the supply belt 6.

  Further, the sheet S is electrostatically attracted to the supply belt 6 in a state where the supply belt 6 is stopped. Therefore, when the sheet S is electrostatically attracted to the supply belt 6, the frictional force due to the friction with the other sheet S or the support surface 12 does not act on the sheet S. Therefore, it is possible to suppress the sheet S from being once electrostatically attracted to the supply belt 6 and then peeled off, and the sheet S can be favorably electrostatically attracted to the supply belt 6.

  After the sheet S is electrostatically attracted to the supply belt 6, the supply belt 6 rotates to convey the sheet S to the downstream side in the conveyance direction. When the sheet S electrostatically attracted to the supply belt 6 is conveyed to the downstream end in the conveyance direction in the planar portion 23 of the supply belt 6, the sheet S is peeled from the supply belt 6 in order from the front end. A conveyance belt 8 that is rotated when the sheet S is conveyed is disposed downstream of the support unit in the conveyance direction of the sheet S. At least a part of the conveyor belt 8 faces the supply belt 6 in the vertical direction from below. Specifically, the planar portion 33 of the conveyance belt 8 extends to a position where the portion of the supply belt 6 that contacts the roller 22 extends to the upstream side in the conveyance direction. Therefore, even if the leading edge of the sheet S peeled off from the supply belt 6 is out of order, the leading edge is satisfactorily landed on the planar portion 33 of the conveying belt 8. Therefore, the sheet S can be stably conveyed.

  Further, the roller 22 is grounded, so that the portion of the supply belt 6 that contacts the roller 22 is neutralized. Therefore, when the sheet S is transported to the downstream end in the transport direction in the planar portion 23, the electrostatic adsorption force is released, so that the sheet S can be favorably peeled from the supply belt 6.

  Further, since the supply belt 6 and the conveyance belt 8 rotate at the same moving speed, when the leading edge of the sheet S lands on the planar portion 33 of the conveyance belt 8, a force in a direction in which the sheet S is pulled or pushed back. Application to the sheet S from the conveyance belt 8 can be suppressed. Therefore, the sheet S can be transferred favorably on the planar portion 33 of the conveyance belt 8.

  The distance between the planar portion 23 of the supply belt 6 and the planar portion 33 of the conveying belt 8 is designed within a range of 10 mm or more and 30 mm or less. As a result, the leading edge of the sheet S can be satisfactorily landed on the planar portion 33 of the conveyance belt 8, and the conveyance belt 8 can be suppressed from being affected by the charging of the supply belt 6.

  When the conveyance belt 8 is made of rubber, it is possible to further suppress the conveyance belt 8 from being affected by the charging of the supply belt 6. Further, it is possible to suppress the position of the sheet S from being shifted on the planar portion 33 of the transport belt 8, and the sheet S can be transported stably.

<Modification>
As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented with another form.

  For example, as shown in phantom lines in FIG. 1, the second charging roller 81 is provided on the upstream side in the transport direction with respect to the charging roller 7 in a state of contacting the inner surface of the supply belt 6. Also good. Then, a negative charging voltage may be applied to the second charging roller 81. In this case, it is preferable that a charging voltage lower than the charging voltage applied to the charging roller 7 is applied to the second charging roller 81. Thereby, the downstream side in the conveyance direction of the sheet S can be adsorbed to the planar portion 23 of the supply belt 6 before the upstream side.

  As shown in FIG. 7, a lift mechanism 82 that lifts and lowers the support member 11 in the vertical direction is provided. When the sheet S is not electrostatically attracted to the supply belt 6 after the supply belt 6 starts to be charged, the lift mechanism 82 is provided. Thus, the support member 11 may be lifted up, and the sheet S may be brought close to the planar portion 23 of the supply belt 6.

  In this case, as shown in FIG. 8, steps S11 and S12 may be added to the processing shown in FIG. In the process shown in FIG. 8, when the sheet S is not electrostatically attracted to the planar portion 23 of the supply belt 6 and the first predetermined time has elapsed since the start of application of the charging voltage to the charging roller 7 (S3). : YES), the CPU 54 controls the lift mechanism 82 to lift up the support member 11 (S11). Accordingly, the sheet S approaches the planar portion 23 of the supply belt 6, and the sheet S is easily electrostatically attracted to the planar portion 23 of the supply belt 6. Thereafter, the CPU 54 determines whether or not the sheet S is electrostatically attracted to the planar portion 23 of the supply belt 6 (S12). When the sheet S is electrostatically attracted to the planar portion 23 of the supply belt 6 (S12: YES), the CPU 54 starts the rotation of the supply belt 6 (S4). On the other hand, when the sheet S is not electrostatically attracted to the planar portion 23 (S12: NO), the CPU 54 stops the error of the sheet conveying device 2 (S9) and ends the process shown in FIG.

  The rotation of the supply belt 6 may be started regardless of whether the sheet S is electrostatically attracted to the planar portion 23 of the supply belt 6. In this case, after the charging of the supply belt 6 starts, when the trailing edge of the sheet S does not reach the detection position of the optical sensor 63, the support member 11 is lifted up by the lift mechanism 82, and the sheet S becomes a flat surface of the supply belt 6. It may be approximated to the shaped part 23.

  Further, in the above-described embodiment, the configuration in which the lifting member 13 is disposed in the center portion in the width direction of the support surface 12 is taken up. However, the first region 71 in the center portion in the width direction is also illustrated by the configuration illustrated in FIG. Thus, the interval between the supply tray 5 and the supply belt 6 can be shortened, and the interval between the supply tray 5 and the supply belt 6 can be increased in the second regions 72 on both sides in the width direction. That is, the rollers 21 and 22 that support the supply belt 6 are formed in a crown shape in which the central portion in the width direction has a larger diameter than both ends, and the supply tray 5 can be formed in the first region 71 in the central portion in the width direction. Thus, it is possible to obtain a configuration in which the distance between the supply belt 6 and the supply belt 6 is short and the distance between the supply tray 5 and the supply belt 6 is long in the second regions 72 on both sides in the width direction.

  Furthermore, as shown in FIG. 10, the position of the charging roller 7 is shifted downward, and the charging roller 7 presses the supply belt 6 downward, whereby the distance between the supply tray 5 and the supply belt 6 is reached. May be smaller on the downstream side in the transport direction than on the upstream side. As a result, a stronger electrostatic force can be applied on the downstream side in the conveyance direction of the sheet S than on the upstream side, and the end on the downstream side in the conveyance direction of the sheet S can be electrostatically attracted to the supply belt 6 satisfactorily. it can.

  Also, the support member 11 is provided obliquely with respect to the transport direction, so that the interval between the supply tray 5 and the supply belt 6 can be made smaller on the downstream side in the transport direction than on the upstream side.

  In the above-described embodiment, the configuration in which the sheet conveying device 2 is provided in the printer 1 is taken up. However, the sheet conveying device according to the present invention conveys a sheet-like document to an image reading device that reads an image of the document. It can also be used as a device to perform.

  In addition, various design changes are possible within the scope of the matters described in the claims.

  Although the charging roller 7 is disposed at substantially the same position in the transport direction as the lifting member 13, for example, the charging roller 7 may be disposed at a position shifted to the downstream side in the transport direction with respect to the lifting member 13.

  Although the conveyance belt 8 has the planar portion 33 extending in the conveyance direction between the two rollers 31 and 32, the planar portion 33 may be inclined with respect to the conveyance direction.

  Further, even if the conveyor belt 8 is made of the same material as the supply belt 6, for example, nylon to which a conductive agent is added, it may be charged with a charge amount different from that of the outer periphery of the supply belt 6 and weaker than the supply belt 6. Good.

  The image forming unit 9 is not limited to the ink jet type but may be an electrophotographic type. In that case, a transfer roller or transfer charger for transferring the toner image onto the sheet S is provided inside the transport belt 8.

  Moreover, the case where CPU54 performed each process was demonstrated. However, the ASIC 51 may include a plurality of CPUs, and the plurality of CPUs may cooperate to execute each process.

DESCRIPTION OF SYMBOLS 1 Printer 2 Sheet conveying apparatus 5 Supply tray 6 Supply belt 7 Charging roller 8 Conveying belt 9 Image forming part 12 Support surface S sheet

Claims (7)

A sheet conveying apparatus that conveys a sheet using electrostatic force,
A support portion having a support surface for supporting the sheet;
A first endless belt disposed opposite to the support surface at a distance and rotating during conveyance of the sheet;
A charging unit for charging the first endless belt;
A sheet is transported downstream of the support portion in the sheet transport direction, and at least a part of the first endless belt is opposed to the first endless belt in a direction perpendicular to the support surface. And a second endless belt that rotates at times. The sheet conveying apparatus according to claim 1,
A static elimination roller disposed at a downstream end in the transport direction inside the first endless belt, contacting the inner peripheral surface of the first endless belt to support the first endless belt, and grounded Prepared,
The sheet conveying apparatus, wherein the second endless belt extends to a position where a contact portion between the first endless belt and the static elimination roller exceeds an upstream side in the conveying direction. The sheet conveying apparatus according to claim 1 or 2,
The sheet conveying apparatus, wherein the first endless belt and the second endless belt rotate at the same moving speed. The sheet conveying device according to any one of claims 1 to 3,
The distance between the first endless belt and the second endless belt in the direction orthogonal to the support surface is in the range of 10 mm to 30 mm. The sheet conveying device according to any one of claims 1 to 4,
The sheet conveying apparatus, wherein an outer peripheral surface of the second endless belt is grounded or charged with a different charge and a smaller charge amount than the outer peripheral surface of the first endless belt. A sheet conveying apparatus according to any one of claims 1 to 5,
The second endless belt is a sheet conveying apparatus made of rubber. A sheet conveying device according to any one of claims 1 to 6,
An image forming apparatus comprising: an image forming unit that is disposed to face a sheet conveyance surface of the second endless belt and forms an image on the sheet.

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