JP2020126124A - Image forming apparatus - Google Patents

Abstract

To reduce sticking of sheets loaded on an ejection tray and improve consistency of the sheets, in both a single-sided print mode and double-sided print mode.SOLUTION: An image forming apparatus comprises: an ejection roller pair; a reverse roller pair; and a cooling fan. After the end of printing on a single side in a single-sided print mode, or after the end of printing on both sides in a double-sided print mode, the ejection roller pair ejects a sheet passing through a fixing device through a first ejection port. After the end of printing on a single side in the double-sided print mode, the reverse roller pair temporarily causes the sheet passing through the fixing device to project to the outside from a second ejection port, and subsequently return the sheet to the inside of the apparatus. The cooling fan blows air to any one of the sheet that is being ejected from the first ejection port, the sheet that is ejected onto an ejection tray, and the sheet that is projected to the outside from the second ejection port. The first ejection port is located between the ejection tray and the second ejection port, and the cooling fan is located between the first ejection port and the second ejection port.SELECTED DRAWING: Figure 3

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, and a composite machine using the electrophotographic method.

In an image forming apparatus using an electrophotographic method, toner is applied to an electrostatic latent image formed on an image carrier such as a photoconductor drum to form a toner image. Then, after the formed toner image is transferred to a sheet such as paper, the fixing device fixes the toner image on the sheet.

By the way, the sheet immediately after fixing has a considerably high temperature. When the sheets that have not been sufficiently cooled after fixing are discharged to the discharge tray and stacked, the stacked sheets stick to each other due to re-fusion of the toner. Therefore, a configuration for cooling the sheet after fixing has been conventionally proposed.

For example, in Patent Document 1, an image forming apparatus capable of single-sided printing and double-sided printing is provided with a cooling duct for blowing air onto a sheet. This cooling duct is located above the reversing discharge port through which the sheet is discharged from the pair of reversing rollers by a predetermined size during double-sided printing, that is, on the opposite side of the discharge tray from the reversing discharge port. doing. It should be noted that a sheet discharge port for discharging a sheet after completion of single-sided printing or after completion of double-sided printing is located between the discharge tray and the reversing discharge port. In this configuration, the cooling duct (1) the sheet protruding from the reversing discharge port to the outside before the reversing of the reversing roller pair, and (2) the discharging process of discharging the sheet from the sheet discharging port toward the discharging tray by the discharging roller pair. It is possible to cool each sheet by blowing air onto each of the sheets (3) and (3) the discharged sheets loaded from the sheet discharge port and stacked on the discharge tray.

JP, 2010-256781, A

However, as in Patent Document 1, in the configuration in which the sheet discharge port is located between the discharge tray and the reversing discharge port and the cooling duct is located on the side opposite to the discharge tray with respect to the reversing discharge port, cooling is performed. The distance between the cooling duct and the seat of (2) is longer than the distance between the duct and the seat of (1), and the distance between the cooling duct and the seat of (3) is further longer. Therefore, in order to sufficiently cool the three patterns of sheets by blowing air, it is necessary to adjust the amount of air blown to each sheet, and for example, it is necessary to increase the amount of air blown for the sheets farther from the cooling duct. When the amount of blown air is increased, the sheet cooling effect can be obtained, but on the other hand, the sheets stacked on the discharge tray are likely to be disturbed, which may deteriorate the sheet alignment (stacking property).

In view of the above problems, the present invention uses a small air flow rate for each of the sheet protruding outward by the reversing roller pair, the sheet being discharged by the discharge roller pair, and the discharged sheet stacked on the discharge tray. Air can be blown to cool each sheet, which reduces sticking between sheets, whether they are printed in single-sided printing mode or double-sided printing mode and stacked on the output tray. At the same time, it is an object of the present invention to provide an image forming apparatus capable of improving the matching of sheets.

To achieve the above object, the first configuration of the present invention includes an image forming unit that forms a toner image on a sheet in a single-sided printing mode or a double-sided printing mode, and a fixing device that fixes the toner image. In the image forming apparatus, after the single-sided printing in the single-sided printing mode in the image forming unit or the double-sided printing in the double-sided printing mode is completed, the sheet that has passed through the fixing device is discharged through the first discharge port. A pair of discharge rollers for discharging through the sheet, a discharge tray for receiving the sheet discharged through the first discharge port, and a passage through the fixing device after completion of single-sided printing in the double-sided printing mode in the image forming unit The sheet thus ejected once from the second discharge port to the outside, and then returned to the inside of the machine to form a toner image on the opposite surface of the image forming section, and the discharge roller pair. A sheet that is being discharged from the first discharge port while being nipped, a discharged sheet that has been discharged onto the discharge tray from the first discharge port, and the second sheet while being nipped by the reversing roller pair. And a cooling fan that blows air toward either of the sheets protruding from the discharge port to the outside. The first discharge port is located between the discharge tray and the second discharge port, and the cooling fan is located between the first discharge port and the second discharge port. There is.

According to the first configuration of the present invention, since the cooling fan is located between the first discharge port and the second discharge port, the distance between the sheet being discharged and the cooling fan, and the second It is possible to keep a short distance between the sheet protruding from the discharge port of the sheet and the cooling fan. Further, the distance between the discharged sheets and the cooling fan can be maintained at a shorter distance as compared with, for example, the case where the cooling fan is located on the side opposite to the discharge tray with respect to the second discharge port. Therefore, the cooling fan can efficiently cool all the three patterns of sheets, and a sufficient cooling effect can be obtained even with a small air flow rate. As a result, even if the sheets printed in either the single-sided printing mode or the double-sided printing mode are stacked on the discharge tray, it is possible to reduce the sticking of the sheets due to the re-fusing of the toner and to reduce the air flow rate. It is possible to reduce the disturbance of the sheets stacked on the discharge tray and improve the sheet alignment (stackability).

FIG. 1 is a perspective view showing an external configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a cross-sectional view schematically showing a schematic configuration of the image forming apparatus. FIG. 3 is a block diagram showing a schematic configuration of a main part of the image forming apparatus. 6 is a flowchart showing a flow of operations relating to sheet cooling in a single-sided printing mode. FIG. 3 is a cross-sectional view schematically showing how a sheet is discharged from a first discharge port of the image forming apparatus. FIG. 6 is a cross-sectional view schematically showing a state where the sheet is discharged onto a discharge tray. 7 is a flowchart showing a flow of operations relating to sheet cooling in a double-sided printing mode. FIG. 6 is a cross-sectional view schematically showing a state in which a sheet is projected to the outside from a second discharge port of the image forming apparatus. FIG. 3 is a cross-sectional view schematically showing a configuration example of a cooling fan included in the image forming apparatus.

[Schematic configuration of image forming apparatus]
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing an external configuration of an image forming apparatus 100 according to an embodiment of the present invention, and FIG. 2 is a sectional view schematically showing a schematic configuration of the image forming apparatus 100. The image forming apparatus 100 is, for example, a in-body discharge type tandem color copier. The image forming apparatus 100 roughly includes a main body housing 40 and an upper housing 41 arranged above the main body housing 40.

An image reading unit 42 is provided in the upper housing 41. The image reading unit 42 includes a scanner lamp that illuminates the original during copying, a scanning optical system that includes a mirror that changes the optical path of the reflected light from the original, and a condenser lens that collects and forms an image of the reflected light from the original. , And a CCD sensor or the like (not shown) that converts the formed image light into an electric signal, and reads a document image and converts it into image data.

When the originals are read one by one by the image reading unit 42, the original conveying device 43 located above the image reading unit 42 is opened, and the originals are placed on the contact glass provided on the upper surface of the upper housing 41. When the document reading unit 42 automatically reads the document bundle, the document bundle is placed on the paper feed tray of the document feeder 43 in the closed state, so that the document bundles are fed one by one. It is automatically fed onto the contact glass.

The main body housing 40 is composed of a lower housing 40 a and a connecting housing 40 b located above the lower housing 40 a along the right side portion of FIG. 2 and connected to the upper housing 41. The connection housing 40b is provided with an operation panel 44 (see FIG. 1) that receives a setting input by the user. Note that the items of the setting input by the user include, for example, the number of copies, single-sided printing, double-sided printing, enlargement/reduction, print density, and the like. Further, the connection housing 40b constitutes a sheet discharging section 31 for discharging the printed sheet S on the discharging tray 22 located at the bottom of the in-body discharging space 30. As the sheet S, generally used copy sheets, postcards, envelopes, transparent films and the like can be used.

The image forming units Pa to Pd, the exposure device 5, the paper feed cassette 16, and the like are arranged in the lower housing 40a. In the lower housing 40a, the four image forming portions Pa, Pb, Pc and Pd are arranged in this order (from the left side in FIG. 2) along the running direction of the intermediate transfer belt 8. The intermediate transfer belt 8 runs counterclockwise in FIG. 2 by a driving unit (not shown). These image forming portions Pa to Pd are provided corresponding to images of four different colors (cyan, magenta, yellow and black), and cyan, magenta, and Yellow and black images are sequentially formed.

Photosensitive drums 1a, 1b, 1c and 1d carrying a visible image (toner image) of each color are arranged in these image forming portions Pa to Pd, and the above-mentioned intermediate transfer belt 8 is used for each image. It is provided adjacent to the forming portions Pa to Pd. The toner images formed on these photosensitive drums 1a to 1d are sequentially primary-transferred and superposed on the intermediate transfer belt 8 which moves while contacting the photosensitive drums 1a to 1d, and then the secondary transfer roller. Secondary transfer is performed on the sheet S by the action of 9. The sheet S to which the toner image is secondarily transferred is discharged onto, for example, the discharge tray 22 after the toner image is fixed by the fixing device 15. An image forming process is performed on each of the photoconductor drums 1a to 1d while rotating the photoconductor drums 1a to 1d in the clockwise direction in FIG.

The sheet S to which the toner image is transferred is housed in a paper feed cassette 16 below the main body of the image forming apparatus 100, and will be described later as a secondary transfer roller 9 via a paper feed roller 12 and a registration roller pair 13. The intermediate transfer belt 8 is conveyed to the nip portion with the drive roller 11. A sheet made of a dielectric resin is used for the intermediate transfer belt 8, and a seamless (seamless) belt is mainly used. Further, on the downstream side of the secondary transfer roller 9, a blade-shaped belt cleaner 17 for removing toner and the like remaining on the surface of the intermediate transfer belt 8 is arranged.

Next, the image forming units Pa to Pd will be described. Chargers 2a, 2b, 2c and 2d for charging the photosensitive drums 1a to 1d and image information on the photosensitive drums 1a to 1d are provided around and below the rotatably arranged photosensitive drums 1a to 1d. Of the developing device 3a, 3b, 3c and 3d for forming a toner image on the photosensitive drums 1a to 1d, and the developer (toner) remaining on the photosensitive drums 1a to 1d. Cleaning units 7a, 7b, 7c and 7d are provided.

When performing a copy operation, the image reading unit 42 reads an image of a document and converts it into image data. Then, the surfaces of the photosensitive drums 1a to 1d are uniformly charged by the chargers 2a to 2d, and then the exposure device 5 irradiates the photosensitive drums 1a to 1d with light according to the image data. To form an electrostatic latent image. The developing devices 3a to 3d are filled with a predetermined amount of a developer (for example, a two-component developer) containing toners of cyan, magenta, yellow, and black. In addition, when the ratio of the toner in the developer filled in each of the developing devices 3a to 3d is less than the specified value due to the formation of the toner image, the toner is supplied from the toner containers 4a to 4d to each of the developing devices 3a to 3d. It The toner in the developer is supplied onto the photoconductor drums 1a to 1d by the developing devices 3a to 3d and electrostatically adheres to each other, so that a toner image corresponding to the electrostatic latent image is formed.

Then, by applying a predetermined transfer voltage to the primary transfer rollers 6a to 6d, the yellow, cyan, magenta, and black toner images on the photoconductor drums 1a to 1d are primarily transferred onto the intermediate transfer belt 8. These four-color images are formed in a predetermined positional relationship that is predetermined for forming a predetermined full-color image. After that, the toner and the like remaining on the surfaces of the photosensitive drums 1a to 1d are removed by the cleaning units 7a to 7d in preparation for the subsequent formation of a new electrostatic latent image.

The intermediate transfer belt 8 is stretched over a tension roller 10 on the upstream side and a drive roller 11 on the downstream side. When the intermediate transfer belt 8 starts rotating counterclockwise with the rotation of the drive roller 11 by the drive motor (not shown), the sheet S is adjacent to the drive roller 11 from the registration roller pair 13 at a predetermined timing. Then, the full color image on the intermediate transfer belt 8 is transferred onto the sheet S by being conveyed to a nip portion (secondary transfer nip portion) with the secondary transfer roller 9 provided. The sheet S to which the toner image is transferred passes through the sheet transport path 14 and is transported to the fixing device 15.

The sheet S conveyed to the fixing device 15 is heated and pressed by the fixing roller pair 15a. As a result, the toner image is fixed on the surface of the sheet S, and a predetermined full-color image is formed. When the single-sided printing mode in which printing is performed on only one side of the sheet S is set, the sheet S is guided to the first transport path 19 by the branching portion 18, and the first discharge port 21 is guided by the discharge roller pair 20. It is discharged onto the discharge tray 22 via the.

On the other hand, when the double-sided printing mode in which printing is performed on both sides of the sheet S is set, the sheet S that has passed the fixing device 15 is guided to the second transport path 23 by the branch portion 18. Then, a part of the sheet S is once made to project from the second discharge port 25 to the outside of the connection housing 40b, that is, the in-body discharge space 30 by the forward rotation of the pair of reversing rollers 24. Thereafter, the reversing roller pair 24 is reversed to switch back the sheet S, the sheet S is guided to the reversing conveyance path 26, and the printing surface is reversed. It is re-conveyed to the next transfer nip portion. Then, the next image formed on the intermediate transfer belt 8 is transferred by the secondary transfer roller 9 to the surface of the sheet S on which the image is not formed (the surface opposite to the printing surface). Then, the sheet S is conveyed to the fixing device 15 and the toner image is fixed thereon, and then passes through the first conveyance path 19 and is ejected onto the ejection tray 22 by the ejection roller pair 20.

Here, the sheet discharging unit 31 has a cooling fan 50. The cooling fan 50 includes (A) a sheet S that is being discharged toward the discharge tray 22 from the first discharge port 21 while being nipped by the pair of discharge rollers 20 and (B) a discharge tray from the first discharge port 21. The blown air is directed toward either the discharged sheet S discharged onto the sheet 22 or the sheet S protruding outward from the second discharge port 25 while being nipped by the (C) reversing roller pair 24. Such a cooling fan 50 is composed of, for example, an axial flow fan 50a.

Here, in the present embodiment, the positional relationship among the first discharge port 21, the second discharge port 25, the discharge tray 22, and the cooling fan 50 is as follows. That is, the first discharge port 21 is located between the discharge tray 22 and the second discharge port 25 in the direction perpendicular to the installation surface of the image forming apparatus 100 (vertical direction). The cooling fan 50 is located between the first outlet 21 and the second outlet 25. That is, the discharge tray 22, the first discharge port 21, the cooling fan 50, and the second discharge port 25 are located in this order from the bottom to the top.

Further, FIG. 3 is a block diagram showing a schematic configuration of a main part of the image forming apparatus 100 of this embodiment. The image forming apparatus 100 of this embodiment further includes a fan control unit 51. The fan control unit 51 is a controller that controls the cooling fan 50 described above, and includes a drive unit 52 and a main control unit 53. The drive unit 52 is a drive mechanism that rotates the cooling fan 50, and is configured to include, for example, a motor and a gear.

The main control unit 53 is composed of, for example, a central processing unit (CPU), and controls the drive unit 52 based on the print mode (single-sided print mode, double-sided print mode) set on the operation panel 44. Then, the cooling fan 50 is rotated. In addition, the main control unit 53 switches the branching unit 18 according to the set print mode (switches the sheet transport path between the first transport path 19 and the second transport path 23) and the like of the image forming apparatus 100. It also controls the operation of each part.

[Cooling fan rotation control (single-sided printing mode)]
Next, an example of rotation control of the cooling fan 50 will be described. FIG. 4 is a flowchart showing the flow of operations relating to the cooling of the sheet S in the single-sided printing mode. When the single-sided printing mode is set on the operation panel 44 and the start button for instructing the start of printing is pressed by the user (S1), the fan controller 51 (main controller 53) is ejected from the fixing device 15. The branch portion 18 is driven so that the sheet is guided to the first transport path 19 (S2). After that, the sheet S is fed to the image forming units Pa to Pd, the toner images of the respective colors are formed in the image forming units Pa to Pd, and the toner images are transferred onto the sheet S by the method described above. .. As a result, a color toner image is carried on one side of the sheet S (S3). The toner image on the sheet S is fixed by the fixing device 15 (S4).

On the other hand, the fan control unit 51 rotates the axial fan 50a serving as the cooling fan 50 in one direction to blow air downward from the axial fan 50a (S5). In FIG. 4, after the toner image is fixed in S4, the air blowing in S5 is performed. However, the air blowing in S5 may be performed before the sheet S is ejected from the first ejection port 21, and the fixing is performed. The latter is not limited. For example, immediately after the start button is pressed in S1, the downward flow of air may be started by rotating the axial fan 50a.

The sheet S having the toner image fixed by the fixing device 15 is conveyed through the first conveying path 19 and is ejected from the first ejection port 21 by the ejection roller pair 20 as shown in FIG. 5 (S6). At this time, since the air is blown downward by the axial fan 50a, the downward air from the axial fan 50a is applied to the sheet S that is being ejected from the first ejection port 21 toward the ejection tray 22. Hit As a result, the sheet S whose temperature has risen due to the passage of the fixing device 15 is cooled. Since the sheet S being discharged is nipped by the pair of discharge rollers 20, the posture of the sheet S is unlikely to be disturbed even if the sheet S is exposed to wind.

Then, the sheet S lands on the discharge tray 22 as shown in FIG. 6 (S7). The discharged sheet S that has landed on the discharge tray 22 is blown downward by the axial flow fan 50a, so that the sheet S is continuously cooled.

If the sheet S after the nip formed by the discharge roller pair 20 is released is hit by air, the posture of the sheet S may be disturbed and the integrity of the sheets S stacked on the discharge tray 22 may be affected. .. Therefore, after the nip formed by the pair of discharge rollers 20 is released, the blow of air by the axial fan 50a may be temporarily stopped or the blown amount may be reduced for a predetermined time until the sheet S lands on the discharge tray 22. At this time, for example, the fan control unit 51 (for example, the main control unit 53) determines the time when the nip of the discharge roller pair 20 is released based on the elapsed time from the drive time of the branch unit 18 in S2. You can That is, the fan control unit 51 has a function as a time counting unit (timer) that measures the elapsed time, determines the time when the nip of the discharge roller pair 20 is released, and then the axial flow for a predetermined time. The air blowing by the fan 50a can be temporarily stopped or the air blowing amount can be reduced.

Next, the fan control unit 51 determines whether or not the next page has been printed (S8). If the next page has not been printed, the air blow by the axial fan 50a is stopped after a predetermined time has elapsed (S9). , A series of processing ends. On the other hand, if the next page is printed in S8, the process returns to S3 and the subsequent operations are repeated.

[Cooling fan rotation control (double-sided printing mode)]
Next, the rotation control of the cooling fan 50 when the double-sided printing mode is set will be described. FIG. 7 is a flowchart showing the flow of operations relating to the cooling of the sheet S in the double-sided printing mode. When the double-sided printing mode is set on the operation panel 44 and the start button for instructing to start printing is pressed by the user (S11), the fan controller 51 (main controller 53) is ejected from the fixing device 15. The branch portion 18 is driven so that the sheet is guided to the second transport path 23 (S12). After that, the sheet S is fed to the image forming units Pa to Pd, the toner images of the respective colors are formed in the image forming units Pa to Pd, and the toner images are transferred onto the sheet S by the method described above. .. As a result, a color toner image is carried on one side of the sheet S (S13). The toner image on the sheet S is fixed by the fixing device 15 (S14).

On the other hand, the fan control unit 51 rotates the axial fan 50a in the direction opposite to the one direction (opposite to the rotating direction in S5), and blows the axial fan 50a upward (S15). In FIG. 7, after the toner image is fixed in S14, the air blowing in S15 is performed, but the air blowing in S15 may be performed until the sheet S projects from the second discharge port 25, and after the fixing. Is not limited. For example, immediately after the start button is pressed in S11, the axial fan 50a may be rotated to start blowing air upward.

The sheet S on which the toner image is fixed by the fixing device 15 is conveyed through the second conveying path 23, and as shown in FIG. 8, the sheet S is projected from the second discharge port 25 to the outside by the forward rotation of the pair of reversing rollers 24. (S16). At this time, since the air is blown upward by the axial fan 50a, the upward wind from the axial fan 50a hits the sheet S protruding from the second outlet 25. As a result, the sheet S whose temperature has risen due to the passage of the fixing device 15 is cooled. Here, in the sheet S protruding from the second discharge port 25, when the surface facing the discharge tray 22 (the surface on the axial fan 50a side) is the print surface on which the toner image is formed, the above-mentioned printing is performed. Since the wind from the axial fan 50a directly hits the surface, the temperature of the printing surface (especially toner) can be efficiently lowered. Since the sheet S is nipped by the reversing roller pair 24, the posture of the sheet S is unlikely to be disturbed even when the sheet S is hit by upward wind.

After that, when the reversing roller pair 24 is reversed and the sheet S is returned to the inside of the machine (S17), the fan control unit 51 switches the branching unit 18 to a position for guiding the sheet S from the fixing device 15 to the first transport path 19. Position (S18). The sheet S returned to the inside of the machine is guided to the image forming units Pa to Pd via the reverse conveyance path 26, and a toner image of each color is formed on each of the surfaces opposite to the previously printed surface and each toner image. Is transferred onto the sheet S. As a result, a color toner image is carried on the opposite surface of the sheet S (S19). The toner image is fixed by the fixing device 15 (S20).

On the other hand, the fan control unit 51 rotates the axial fan 50a in the one direction (the same direction as the rotation direction in S5) to blow the axial fan 50a downward (S21). That is, the blowing direction of the axial fan 50a is switched from upward to downward. In FIG. 7, air is blown in S21 after the toner image is fixed in S20. However, the air blow in S21 may be performed before the sheet S is ejected from the first ejection port 21, and the fixing is performed. The latter is not limited. For example, the rotation of the axial fan 50a may be reversed after a predetermined time has elapsed after the pair of reversing rollers 24 has been reversed, and air may be blown downward.

The sheet S having the toner image fixed by the fixing device 15 is conveyed through the first conveying path 19 and is discharged from the first discharge port 21 by the discharge roller pair 20 as in FIG. 5 (S22). At this time, since the air is blown downward by the axial fan 50a, the downward air from the axial fan 50a is applied to the sheet S that is being ejected from the first ejection port 21 toward the ejection tray 22. Hit As a result, the sheet S whose temperature has risen due to the passage of the fixing device 15 is cooled. After that, the sheet S lands on the discharge tray 22 as in FIG. 6 (S23). The discharged sheet S that has landed on the discharge tray 22 is blown downward by the axial flow fan 50a, so that the sheet S is continuously cooled.

Next, the fan control unit 51 determines whether or not the next page has been printed (S24). If the next page has not been printed, the blow by the axial fan 50a is stopped after a predetermined time has elapsed (S25). , A series of processing ends. On the other hand, if the next page is printed in S24, the process returns to S12 and the subsequent operations are repeated.

〔effect〕
As described above, in the image forming apparatus 100 of this embodiment, the first discharge port 21 is located between the discharge tray 22 and the second discharge port 25, and the cooling fan 50 is the first discharge port. 21 and the second discharge port 25. Thus, the distance between the sheet S that is being discharged from the first discharge port 21 and the cooling fan 50 and the distance between the sheet S that protrudes from the second discharge port 25 and the cooling fan 50 are both kept at short distances. You can Further, as for the distance between the sheet S already discharged on the discharge tray 22 and the cooling fan 50, as compared with the case where the cooling fan 50 is positioned on the opposite side of the second discharge port 25 from the discharge tray 22, for example. , Can be kept at a short distance. Therefore, all the three patterns of the sheet S can be efficiently cooled, and a sufficient cooling effect can be obtained even with a small air flow rate. As a result, even if the sheets S printed in either the single-sided printing mode or the double-sided printing mode are stacked on the discharge tray 22, it is possible to reduce the sticking of the sheets due to the re-fusing of the toner and to reduce the air flow rate. Due to the decrease, the disturbance of the sheets S stacked on the discharge tray 22 can be reduced, and the consistency (stacking property) of the sheets S can be improved.

The cooling fan 50 is composed of an axial fan 50a. In the configuration using the axial fan 50a, as described above, the blowing direction can be switched between the upward direction and the downward direction by switching the rotation direction. Therefore, the air flow direction can be appropriately switched by the single axial fan 50a to cool the three patterns of the sheet S. That is, the three patterns of the sheet S can be cooled by controlling the rotation of the single axial fan 50a.

Further, the fan control unit 51 blows air toward the sheet S that is being discharged from the first discharge port 21 and the sheet S that has been discharged onto the discharge tray 22, and when the sheet protruding from the second discharge port 25 to the outside. The rotation direction of the axial fan 50a is switched between when the air is blown to S and the air blowing direction is switched. The discharge tray 22, the first discharge port 21, the cooling fan 50 (axial flow fan 50a), and the second discharge port 25 are arranged in this order along one direction (here, from bottom to top). The sheet S being discharged and the discharged sheet S are located on the same side (for example, the lower side) as viewed from the axial fan 50a, and the sheet S protruding from the second discharge port 25 to the outside is the axial fan. It is located on the side opposite to the discharge tray 22 (for example, on the upper side) when viewed from 50 a. Therefore, by switching the rotation direction of the axial fan 50a and switching the air blowing direction as described above, the sheet S in the process of being discharged and the discharged sheet S in the same direction (for example, downward) from the axial fan 50a. It is possible to reliably cool the sheet by blowing air, and it is possible to reliably cool the sheet protruding from the second outlet 25 to the outside by blowing air in the opposite direction (for example, upward) from the axial fan 50a.

In the case where the surface of the sheet S protruding from the second discharge port 25 to the outside is the printing surface on which the toner image is formed, the cooling fan 50 causes the sheet S to face the sheet S. The air is blown to the printed surface. In this case, since the printing surface is cooled efficiently, when the sheet S is returned to the inside of the machine by the reversing roller pair 24, the toner is re-fused to the roller or the like which is being conveyed in the machine and the roller or the like is removed. The situation of getting dirty can be reduced. This also leads to avoiding deterioration of the image quality of the image printed on the sheet S. Therefore, in the so-called face-down mode in which the sheet S is conveyed with the printing surface facing downward, in the double-sided printing mode, the sheet S protruding from the second discharge port 25 is cooled by the upward air flow by the cooling fan 50. The configuration of the embodiment becomes more effective.

[Other configurations of cooling fan]
FIG. 9 is a sectional view schematically showing another configuration of the cooling fan 50. As shown in the figure, the cooling fan 50 may include a first sirocco fan 50b and a second sirocco fan 50c. The first sirocco fan 50b blows (downward) from the first discharge port 21 toward the sheet S that is being discharged or the sheet S that has been discharged onto the discharge tray 22. The second sirocco fan 50c blows air (upward) toward the sheet S protruding from the second outlet 25.

As described above, in the configuration in which the cooling fan 50 includes the first sirocco fan 50b and the second sirocco fan 50c, the fan control unit 51 drives the first sirocco fan 50b and the second sirocco fan 50c to blow air. Switching control is performed according to the sheet S to be printed. That is, when the air is sent to the sheet S that is being discharged or the sheet S that has been discharged, the fan control unit 51 drives the first sirocco fan 50b and stops the driving of the second sirocco fan 50c. On the other hand, when the air is blown to the sheet S protruding from the second discharge port 25, the fan control unit 51 drives the second sirocco fan 50c and stops the driving of the first sirocco fan 50b.

In this way, by switching the driving of the first sirocco fan 50b and the second sirocco fan 50c in accordance with the sheet S to be blown, it is possible to cool any of the sheets S of the above three patterns. Therefore, it is not necessary to control the rotation direction as in the case of using the axial flow fan 50a, and simple control for simply switching the driving of the first sirocco fan 50b and the second sirocco fan 50c enables the sheet S of the above-described three patterns. Can be cooled.

In the present embodiment, the configuration and control for cooling the sheet in the color copying machine have been described. It is possible to apply to the image forming apparatus.

The present invention can be applied to an image forming apparatus such as a color copying machine.

15 Fixing Device 20 Ejection Roller Pair 21 First Ejection Port 22 Ejection Tray 24 Reverse Roller Pair 25 Second Ejection Port 50 Cooling Fan 50a Axial Fan 50b First Sirocco Fan 50c Second Sirocco Fan 51 Fan Control Unit 100 Image forming apparatus Pa to Pd Image forming unit S sheet

Claims (5)

An image forming unit that forms a toner image on a sheet in the single-sided printing mode or the double-sided printing mode,
An image forming apparatus comprising a fixing device for fixing the toner image,
A pair of discharge rollers that discharges the sheet that has passed through the fixing device through the first discharge port after the single-sided printing in the single-sided printing mode in the image forming unit or the double-sided printing in the double-sided printing mode is completed. When,
A discharge tray for receiving the sheet discharged through the first discharge port,
After completion of single-sided printing in the double-sided printing mode in the image forming section, the sheet that has passed through the fixing device is temporarily projected to the outside from the second discharge port, and then to the surface on the opposite side in the image forming section. Pair of reversing rollers returned to the machine to form the toner image of
A sheet in the process of being discharged from the first discharge port while being nipped by the discharge roller pair, a discharged sheet discharged onto the discharge tray from the first discharge port, and a nip by the reversing roller pair. Meanwhile, a sheet protruding from the second discharge port to the outside, and a cooling fan that blows air toward either of the sheets,
The first discharge port is located between the discharge tray and the second discharge port,
The image forming apparatus, wherein the cooling fan is located between the first discharge port and the second discharge port. The image forming apparatus according to claim 1, wherein the cooling fan is an axial fan. Further comprising a fan control unit for controlling the cooling fan,
The fan control unit switches the rotation direction of the axial fan between when the sheet is being discharged and when the sheet is already discharged and when the sheet is projected to the outside from the second discharge port. The image forming apparatus according to claim 2, wherein the air blowing direction is switched. Further comprising a fan control unit for controlling the cooling fan,
The cooling fan is
A first sirocco fan for blowing air toward the sheet in the middle of discharging or the discharged sheet;
A second sirocco fan for blowing air toward the sheet protruding from the second outlet,
The image forming apparatus according to claim 1, wherein the fan control unit switches driving of the first sirocco fan and the second sirocco fan in accordance with a sheet to be blown. In the sheet protruding outward from the second discharge port, the surface facing the discharge tray is a printing surface on which the toner image is formed,
The image forming apparatus according to claim 1, wherein the cooling fan blows air to the printing surface of the sheet.

Images