Image Forming Apparatus

The present invention claims priority under 35 U.S.C. § 119 to Japanese Application No. 2024-074425 filed on May 1, 2024, the entire contents of which being incorporated herein by reference.

The present invention relates to an image forming apparatus.

Conventionally, to prevent sheets from sticking to each other, an image forming apparatus has been proposed in which a charge adjustment device (static eliminator) capable of applying charges that repel each other is disposed immediately after an image forming section (e.g., see Japanese Unexamined Patent Publication No. 2016-157011).

Furthermore, a static eliminator has been proposed that includes discharge electrodes disposed in a non-contact manner with respect to a sheet and that is capable of applying an appropriate voltage corresponding to a sheet conveyance speed (see, for example, Japanese Unexamined Patent Publication No. 2021-111527).

However, when the sheet is subjected to the charge elimination processing by the apparatus described in Japanese Unexamined Patent Publication No. 2016-157011 or Japanese Unexamined Patent Publication No. 2021-111527, is further passed through a non-sheet stacking device for subjecting the sheet to post-processing and is stacked on a sheet stacking device, the sheet is re-charged by peeling discharge from a roller and friction with a sheet passing guide surface at the time of passing through the non-sheet stacking device. Therefore, the charge amount of the sheet conveyed to the sheet stacking device located on the downstream side in the sheet conveyance direction relative to the non-sheet stacking device becomes high (see). Furthermore, when the sheet recharged by the non-sheet stacking device is superimposed on the upper surface of the sheets stacked on the sheet stacking tray of the sheet stacking device, the residual charge of the stacked sheets is cumulatively increased, so that stacking unevenness (stacking shift) of the sheets occurs.

An object of the present invention is to suppress uneven stacking of sheets in a sheet stacking device located on the downstream side of a non-sheet stacking device in the sheet conveyance direction.

To achieve at least one of the abovementioned objects, according to an aspect of the present invention, an image forming apparatus reflecting one aspect of the present invention is an image forming apparatus comprising:

According to an aspect of the present invention, an image forming apparatus reflecting one aspect of the present invention is an image forming apparatus comprising:

Hereinafter, one or more embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the disclosed embodiments.

is a diagram illustrating an example of an overall configuration of an image forming apparatusaccording to the present embodiment. As illustrated in, the image forming apparatusis configured by arrangement of a sheet feed device, an image forming apparatus main body, a non-sheet stacking device (non-sheet stacker)A, a non-sheet stacking device (non-sheet stacker)B, a non-sheet stacking device (non-sheet stacker)C, a sheet stacking device (sheet stacker)D, and a sheet stacking device (sheet stacker)E in this order from upstream in a sheet conveyance direction. That is, the image forming apparatusis configured such that the non-sheet stacking devicesA toC are arranged adjacent to the image forming apparatus main bodyon the downstream side in the sheet conveyance direction and the plurality of sheet stacking devicesD and the sheet stacking deviceE are arranged further downstream.

The non-sheet stacking deviceA, the non-sheet stacking deviceB, the non-sheet stacking deviceC, the sheet stacking deviceD, and the sheet stacking deviceE are post-processing devices that process a sheet on which an image has been formed by the image forming apparatus main body. In the present embodiment, the image forming apparatusincluding three non-sheet stacking devices on the downstream side of the image forming apparatus main bodyin the sheet conveyance direction and two sheet stacking devices on the further downstream side of the three non-sheet stacking devices will be described as an example, but the numbers of the non-sheet stacking devices and the sheet stacking devices are not particularly limited.

Note that in the following description, the non-sheet stacking devicesA toC and the sheet stacking devicesD toE are referred to as the post-processing deviceswhen they are not distinguished from each other.

In addition, in the image forming apparatusof the present embodiment, as illustrated in, a discharging device (discharger)is disposed adjacent to the sheet stacking deviceD or at least one of the sheet stacking devicesE on the upstream side in the sheet conveyance direction.

The sheet feed devicecontains sheets and feeds the sheets to the image forming apparatus main bodyunder the control of the image forming apparatus main body. Note that a base material of the sheet used in the image forming apparatusis not particularly limited, and may be a film made of resin, or may be paper such as plain paper containing paper pulp as a main component and high-quality paper.

The image forming apparatus main bodyincludes a controller, an image forming section, a fixing section, a sheet conveyance section, and the like. The image forming apparatus main bodyforms an image on the sheet fed from the sheet feed deviceby an electrophotographic method, and outputs the sheet on which the image has been formed to the non-sheet stacking deviceA. A discharging sectionis provided on a downstream side of the fixing section in the housing of the image forming apparatus main body. The discharging sectiondischarges the image-formed sheet conveyed from the fixing section. The discharging sectionmay discharge the sheet by contacting the sheet or may discharge the sheet in a non-contact state.

The non-sheet stacking devicesA toC are post-processing devices having a function of performing processing other than stacking of sheets, such as punching, folding, binding, and bookbinding, on the sheets output from the image forming apparatus main body.

The sheet stacking devicesD toE are post-processing devices exclusively for sheet stacking, which stack the sheet that has passed through the non-sheet stacking devicesA toC.

The discharging deviceis a non-contact ion type static eliminator (ionizer). The discharging devicegenerates positive and negative ions and sends the ions to the conveyed sheet to discharge the sheet. As a method of generating ions in the non-contact ion type discharging device, there are a corona discharge method, a plasma method, a soft X-ray method, and the like, and the discharging devicemay generate ions by any method. In addition, in the present embodiment, the voltage application method to the electrode needle of the discharging deviceis an AC (alternating current) method but may be any of a DC (direct current) method, a pulse AC method, a pulse DC method, and a high-frequency AC method. In addition, in the discharging device, as a method of sending the generated ions to the sheet, there are a radiation type, a windless type, an air type, a gun type, and the like, and any of them may be used. In addition, the discharging deviceis not limited to a non-contact ion type and may be a discharging device that discharges static electricity from a sheet by an electric line of force radiation method.

Here, as illustrated on the left side of, when the discharging deviceis discharged, a spark occurs to the exterior metal plate of the adjacent post-processing device, and the capability of eliminating static electricity from the sheet is attenuated. Therefore, as shown on the right side of, the periphery of the discharging deviceis preferably covered with the covermade of an insulator. Thus, attenuation of the discharging capability can be suppressed. Here, a reference sign P inandindicates a sheet.

In addition, as shown on the left side of, in the discharging device, when discharge occurs when a sheet does not pass, spark may occur to the grounding surfaceof the sheet metal. Therefore, as shown in the right side of, it is preferable that the lower side of the sheet path is closed by a guide platemade of an insulator. Thus, a spark to the ground surfacecan be prevented. Here, a dotted line inindicates a sheet path.

The discharging deviceis unitized and can be inserted between the post-processing devicesof the image forming apparatusfrom the front so as to be easily attached and detached. The term “between the post-processing devices” means between non-sheet stacking devices, between a non-sheet stacking device and a sheet stacking device, or between sheet stacking devices.is a diagram illustrating a state in which the discharging deviceis mounted between two post-processing devices.is a diagram illustrating a state in which a discharging deviceis attached between two post-processing deviceswhen viewed from above.is an enlarged view of a portion indicated by a rectanglein.is a diagram illustrating a lock mechanism that fixes the discharging devicebetween the two post-processing devices.is an enlarged view of a portion indicated by a rectanglein.

As illustrated in, pinsfor connection to another device are provided at two upper and lower positions on a back side of a side surfaceon a downstream side of each post-processing device. On a far side of the side surfaceon the upstream side of each post-processing device, members having pin holesfor connection with other apparatuses in two places, upper and lower, are provided. In a state where the two post-processing devicesare connected, the pinsof the post-processing deviceon the upstream side and the pin holesof the post-processing deviceon the downstream side are engaged with each other in two upper and lower places indicated by dotted-line rectangles in(STin). The pinsand the pin holesare connectors for connecting other devices to the post-processing device.

As illustrated in, fixing metal fittingsare provided at two positions, upper and lower, on the near side of a side surfaceon the downstream side of each post-processing device. Fixing bracketsare provided at two positions, upper and lower, on a near side of a side surfaceon an upstream side of each post-processing device. The fixing bracketis provided with a pin hole, a screw hole, and a screw hole. The fixing bracketis provided with a pin hole, a screw hole, and a screw hole. In a state where the two post-processing devicesare connected, the pin hole, the screw hole, and the screw holeof the fixing metal fittingand the pin hole, the screw hole, and the screw holeof the fixing metal fittingare overlapped with each other, and the locking metal fittingis attached (STin).

Further, as shown in, pin receiversare provided at two upper and lower positions indicated by rectangles of chain lines inon the inner side of the side surfaceon the upstream side of the discharging device. On the side surfaceon the downstream side of the discharging device, pinsare provided at two upper and lower positions indicated by rectangles of chain lines in. The pin receiverand the pinare connecting members connected to a connector of the post-processing device.

When the discharging deviceis mounted between the two post-processing devices, as shown in, the user releases the connection between the two post-processing devices, moves the post-processing deviceon the downstream side by about 50 mm, and inserts and mounts the discharging deviceinto the vacant space from the front side (front surface) in the arrow direction.

To be specific, first, the user removes the lock fittingsattached to the near side of the connecting portion of the two post-processing devices(STto STin). Next, the user releases the engagement between the pinof the post-processing deviceon the upstream side and the pin receiverof the post-processing deviceon the downstream side and moves the post-processing deviceon the downstream side by about 50 mm (step Sto Sinand step Sin). Next, the user inserts the discharging devicebetween the two post-processing devices(STin), engages the pinof the upstream post-processing devicewith the pin receiverof the discharging device, and engages the pin receiverof the downstream post-processing devicewith the pinof the discharging device(STin). Next, the user inserts the pinand the pinof the lock fittinginto the pin holeof the fixing fittingand the pin holeof the fixing fitting, respectively (STin), and screws the lock fitting(step S).

After the insertion of the discharging device, when a user attaches a front cover, the attachment of the discharging deviceis completed.

In the image forming apparatusof the present embodiment, the discharging deviceis disposed adjacent to at least one sheet stacking device on the upstream side in the sheet conveyance direction. Further, the discharging deviceis unitized, and is configured to be insertable (connectable) between the post-processing devices. Therefore, in the image forming apparatus, it is possible to easily replace the discharging devicebetween the post-processing devicesaccording to the needs of the user.

Hereinafter, effects of the image forming apparatusconfigured as described above will be described.

is a graph illustrating a change in the charge amount on a single sheet during sheet passing in a conventional image forming apparatus not including a discharging device. The charge amount (V) is measured at the discharge port of each device constituting the image forming apparatus and is an average value of 30 sheets. Note that the horizontal axis of the graph starts from the right according to the arrangement order when the image forming apparatus is viewed from the front. The same applies toand. As illustrated in, the charge amount on the sheet fed by the sheet feed deviceincreases due to triboelectric charging as the conveyance length increases, but the charge amount on the sheet temporarily decreases due to discharging by the discharging sectionof the image forming apparatus main body. However, thereafter, the charge amount on the sheet increased due to triboelectric charging as the conveyance length increased, and the final charge amount on the sheet in the sheet stacking deviceE became −2251V.

In the non-sheet stacking devicesA toC, the sheets do not contact each other unlike the sheet stacking deviceD and the sheet stacking deviceE, and thus the electrostatic problem is unlikely to occur. However, in the sheet stacking deviceD and the sheet stacking deviceE, since electric charge is accumulated due to stacking of sheets, an electrostatic problem such as uneven stacking of sheets occurs.

is a graph illustrating a change in the charge amount on a single sheet during sheet passing in the image forming apparatus() in which the discharging deviceis disposed adjacent to the sheet stacking deviceD on the upstream side in the sheet conveyance direction. The charge amount (V) is measured at the discharge port of each device constituting the image forming apparatus and is an average value of 30 sheets. As illustrated in, the sheet fed by the sheet feed devicehas an increased charge amount due to triboelectric charging as the sheet is conveyed farther, but the charge amount on the sheet temporarily decreases due to the discharging by the discharging sectionof the image forming apparatus main body. Thereafter, the charge amount on the sheet increases again as the sheet passes through the non-sheet stacking deviceA to the non-sheet stacking deviceC, but since the discharging deviceis arranged immediately before the sheet stacking deviceD, the charge amount on the sheet conveyed to the sheet stacking deviceD is almost zero. Thereafter, the charge amount of the sheet increased by passing through the sheet stacking deviceD and the sheet stacking deviceE, but the final charge amount of the sheet in the sheet stacking deviceE became −576V. This is about ¼ of the charge amount in the sheet stacking deviceE of the conventional image forming apparatus illustrated in.

is a graph of changes in the charge amount on a single sheet during sheet passing in the image forming apparatus() in which discharging deviceis disposed adjacent to each of the sheet stacking deviceD and the sheet stacking deviceE each on the upstream side in the sheet conveyance direction. The charge amount (V) is measured at the discharge port of each device constituting the image forming apparatus and is an average value of 30 sheets. As illustrated in, the sheet fed by the sheet feed devicehas an increased charge amount due to triboelectric charging as the sheet is conveyed farther, but the charge amount on the sheet temporarily decreases due to the discharging by the discharging sectionof the image forming apparatus main body. Thereafter, the charge amount on the sheet increases again as the sheet passes through the non-sheet stacking deviceA to the non-sheet stacking deviceC, but the charge amount on the sheet to be conveyed to the sheet stacking deviceD is almost zero because the discharging deviceis arranged immediately before the sheet stacking deviceD. Thereafter, the charge amount on the sheet increased as the sheet passed through the sheet stacking deviceD, but since the discharging devicewas also arranged immediately before the sheet stacking deviceE, the charge amount on the sheet conveyed to the sheet stacking deviceE became almost zero, and the final charge amount on the sheet at the sheet stacking deviceE became −152V.

is a graph illustrating a change in accumulated charge amount when one to one hundred sheets are stacked in the sheet stacking deviceE of each of the image forming apparatuses whose charge amount changes are illustrated into. The conventional image forming apparatus corresponding tois defined as pattern 1. The image forming apparatus() corresponding tois defined as pattern 2. The image forming apparatus() corresponding tois referred to as pattern 3. Note that a measuring device having a measurement range of +20 kV was used for measuring the charge amount. As illustrated in, as the sheets are stacked, the accumulated charges are self-discharged to the sheet stacking tray side, so that the charge amount converges to the charge amount of about 50 sheets. The amount of stacking shift of sheets is within the requirement until the charge amount reaches −10 kV but is outside the requirement when the charge amount exceeds −10 kV. That is, when the charge amount exceeds −10 kV, uneven stacking of sheets occurs.

As illustrated in, in the conventional image forming apparatus of pattern 1, the accumulated charge amount exceeds-10 kV on and after the third stacked sheet, and the uneven stacking of sheets occurs. On the other hand, in the image forming apparatusof the pattern 2 and the pattern 3, the accumulated charge amount does not exceed −10 kV even on the hundredth sheet, and the occurrence of the stacking unevenness of the sheets is suppressed.

The charged sheets cause a problem such as sticking due to contact between the stopped sheets and contact with a guide plate. On the other hand, such a problem is unlikely to occur during sheet passing. That is, it is considered that a problem such as the sticking of the sheet is unlikely to occur in the non-sheet stacking devicesA toC, but a problem such as the sticking of the sheet occurs in the sheet stacking devicesD toE. Therefore, it is necessary that the sheets be discharged before the sheet stacking deviceD orE where the sheets contact each other. In addition, in the sheet stacking devicesD andE, accumulation of residual charges of the sheets occurs, and therefore, it is preferable that the residual charges are made close to 0 V before the sheet stacking deviceD orE. In the image forming apparatusof the present embodiment, the discharging deviceis disposed adjacent to at least one of the sheet stacking devicesD orE on the upstream side in the sheet conveyance direction. Therefore, as illustrated inand, the residual charge can be brought close to 0 V before the sheet stacking device. Thus, as illustrated in, even if the accumulation of residual charges occurs in the sheet stacking deviceD orE, the accumulation can be suppressed to a low level, so that the occurrence of uneven stacking of sheets can be suppressed. As described above, in the image forming apparatusof the present embodiment, by arranging the discharging deviceadjacent to the sheet stacking deviceD or at least one of the sheet stacking devicesE on the upstream side in the sheet conveyance direction, it is possible to perform efficient discharging in terms of costs and performances.

In addition, as in the past, in a case of a configuration in which the discharging section is disposed in each device (unit) configuring the image forming apparatus, since an inner configuration is greatly different in each unit, it has been difficult to replace the discharging device. On the other hand, in the image forming apparatusof the present embodiment, the discharging deviceis configured to be detachable between the two post-processing devices. Therefore, a user can easily replace the discharging devicewith another one anywhere between the post-processing devices. In addition, conventionally, the discharging members have been provided everywhere in the image forming apparatus (including the inside of the post-processing device), but in the image forming apparatusof the present embodiment, efficient discharging can be performed, and therefore, there is an advantage that they become unnecessary.

Note that in a case where the non-sheet stacking deviceA to the non-sheet stacking deviceC are the post-processing devicesincluding a stacker of sheets, for example, in a case of a case binding apparatus, a saddle stitch apparatus, a multi-folding apparatus, or the like, it is preferable to arrange the discharging deviceadjacent to these apparatuses on the upstream side in the sheet conveyance direction thereof. Thus, it is possible to suppress the occurrence of bundle displacement or the like due to the generation of static electricity when sheets are stacked on the stacker.

In addition, the sheet printed on both sides in the image forming apparatus main bodyhas a large charge amount on both sides. Therefore, as shown in, it is preferable that the discharging deviceis arranged on each of the upper side and the lower side of the sheet path. Thus, the charge amount on both sides of the sheet can be suppressed, and the occurrence of uneven stacking of sheets can be more effectively suppressed.

As described above, the image forming apparatusincludes the non-sheet stacking devicesA toC adjacent to the downstream side of the image forming apparatus main bodyin the sheet conveyance direction to perform post-processing on the sheet output from the image forming apparatus main body, and further includes the sheet stacking deviceD and the sheet stacking deviceE on the downstream side of the non-sheet stacking devicesA toC in the sheet conveyance direction. In the image forming apparatus, a discharging deviceis arranged adjacent to at least the sheet stacking deviceD on the upstream side in the sheet conveyance direction.

Therefore, it is possible to efficiently suppress the occurrence of uneven stacking of sheets in the sheet stacking device located on the downstream side of the non-sheet stacking device in the sheet conveyance direction. In particular, by adopting a configuration in which the discharging device is provided adjacent to each of the plurality of sheet stacking devices on the upstream side in the sheet conveyance direction, it is possible to efficiently suppress the occurrence of uneven stacking of sheets in the sheet stacking devices.

The above-described embodiment is a preferred example of the present invention and not intended to limit the present invention.

Although embodiments of the present invention have been described and shown in detail, the disclosed embodiments are made for purposes of illustration and example only and not limitation. The scope of the present invention should be interpreted by terms of the appended claims.

The entire disclosure of Japanese Patent Application No. 2024-074425, filed on May 1, 2024, including description, claims, drawings and abstract is incorporated herein by reference.