JP2010256781A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that can more efficiently suppress a temperature increase of ejected sheets of paper, and can more reliably prevent sheets of paper from clinging to each other during both side printing. <P>SOLUTION: In the image forming apparatus, a cooling duct 25 blows air against not only sheets of paper 11 stacked on a paper ejection tray 20 but also a sheet of paper 11 being conveyed while being inverted by an inverting roller 22, and thereby cools the sheets of paper 11. Accordingly, even when both side printing is performed, the temperature increase of the ejected paper 11 can be efficiently suppressed and sheets of paper can be reliably prevented from clinging to each other. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine or a facsimile.

  2. Description of the Related Art Conventionally, in an image forming apparatus, a configuration has been proposed in which a sheet on a sheet discharge tray is cooled by a cooling fan in order to prevent sheets discharged from being attached to each other (see Patent Documents 1 and 2).

  Incidentally, there has been a demand for measures for cooling the paper more efficiently when performing double-sided printing in which the paper temperature is likely to rise in the image forming apparatus.

JP 2003-223093 A JP 2007-264416 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that can more efficiently suppress the temperature rise of discharged sheets and more reliably prevent sticking between sheets during duplex printing.

In order to solve the above-described problem, an image forming apparatus according to the present invention includes a discharge roller that discharges a sheet on which an image is formed,
A reversing roller which is disposed above the paper discharge roller and discharges paper having an image formed on one side by a predetermined amount by forward rotation and then reversely rotates to re-transport the paper into the apparatus; ,
A movable guide that selectively forms a first transport path for transporting the paper to the paper discharge roller and a second transport path for transporting the paper to the reverse roller;
A paper discharge tray for stacking sheets discharged from the paper discharge roller when printing on one or both sides is completed;
The sheet is disposed above the sheet discharged from the reverse roller by the predetermined size and above the sheet discharge tray, and is discharged from the sheet stacked on the sheet discharge tray and from the reverse roller and protrudes. And an air blowing section for blowing air onto the sheet.

  According to the image forming apparatus of the present invention, the air blowing unit can cool the paper being reversely conveyed by blowing air to the paper being reversely conveyed which is ejected from the reversing roller and protrudes. In addition, the air blowing unit can cool the stacked sheets by blowing air onto the sheets stacked on the discharge tray. The air blowing unit can cool the paper being discharged by blowing air onto the paper being discharged by the paper discharge roller. Further, the reversing paper cooled by the air blown from the air blowing section is re-conveyed into the apparatus, so that the temperature rise in the apparatus can also be suppressed. In addition, it is desirable that the air blowing unit is disposed so as to blow air substantially at the center in the width direction orthogonal to the sheet conveyance direction to improve the cooling efficiency.

In the image forming apparatus according to an embodiment, the air blowing unit is
Air is blown substantially perpendicularly to the surface of the paper stacked on the paper discharge tray and the surface of the paper ejected from the reversing roller.

  According to the image forming apparatus of this embodiment, the air blowing unit blows air substantially perpendicularly to the surface of the paper, so that the paper can be efficiently cooled and the paper is not displaced by the blown air. Can be suppressed.

  In the image forming apparatus according to the embodiment, the reversing roller is disposed on the downstream side of the sheet conveyance with respect to the sheet discharge roller and disposed on the upper side with respect to the sheet discharge roller.

  According to the image forming apparatus of this embodiment, since the reversing roller and the paper discharge roller are displaced in the sheet conveyance direction, the height of the apparatus can be suppressed.

  In the image forming apparatus according to the embodiment, when the sheet is conveyed by the reversing roller in the duplex printing mode, the air is blown out substantially perpendicularly to the surface of the sheet ejected from the reversing roller. On the other hand, when the sheet is not conveyed by the reversing roller in the duplex printing mode and in the single-sided printing mode, the air blowing is performed so that air is blown toward the portion of the sheet discharge tray immediately below the sheet discharge roller. The air blowing direction control part which controls the air blowing direction of a part is provided.

  According to the image forming apparatus of this embodiment, the air blowing portion is disposed in a portion of the paper discharge tray directly below the paper discharge roller except when the paper is conveyed by the reverse roller. Blow out the air. Thereby, the cooling efficiency of the paper stacked on the paper discharge tray can be improved.

  In the image forming apparatus according to the embodiment, when printing in the single-sided printing mode, the air blowing amount of the air blowing unit is reduced or compared with the case of printing in the double-sided printing mode. An air blowing amount control unit that stops air blowing is provided.

  According to the image forming apparatus of this embodiment, in the single-sided printing mode in which tacking due to sticking of toner on the paper does not occur, the air blowing amount by the air blowing unit is reduced or the air blowing is stopped. Can be reduced.

  In the image forming apparatus according to the embodiment, during the reversing operation in which the sheet is conveyed by the reversing roller in the duplex printing mode, during the non-reversing operation in which the sheet is not conveyed by the reversing roller in the duplex printing mode. In comparison, an air blowing amount control unit that reduces the amount of air blown from the air blowing unit or stops air blowing by the air blowing unit is provided.

  According to the image forming apparatus of this embodiment, during the paper reversing operation that is easily affected by disturbance, the amount of air blown out from the air blowing portion is reduced, so that the positional deviation of the paper during reversal is prevented and the paper flutters. Noise can be prevented.

In the image forming apparatus according to the embodiment, a print instruction number identifying unit that recognizes the print instruction number;
When the number of print instructions recognized by the print instruction number identification unit is less than a predetermined number, the amount of air blown from the air blowing unit is smaller than when the number of print instructions is equal to or more than the predetermined number. An air blowing amount control unit that reduces or stops air blowing by the air blowing unit is provided.

  According to the image forming apparatus of this embodiment, since the temperature rise is small when the number of printed sheets is small, the power consumption can be reduced by reducing the amount of air blown from the air blowing unit or stopping the blowing of air. .

Further, in the image forming apparatus according to an embodiment, a temperature detection unit that detects a temperature of the paper stacked on the paper discharge tray or a temperature of the paper discharge tray;
When the temperature detected by the temperature detector is lower than a predetermined temperature, the amount of air blown from the air outlet is smaller than when the temperature detected by the temperature detector is equal to or higher than the predetermined temperature. An air blowing amount control unit that reduces or stops air blowing by the air blowing unit is provided.

  According to the image forming apparatus of this embodiment, when the temperature of the paper discharge tray detected by the temperature detection unit or the temperature of the paper stacked on the paper discharge tray is low, the amount of air blown from the air blowing unit is reduced. Since air blowing is stopped, power consumption can be reduced.

  According to the image forming apparatus of the present invention, the air blowing unit blows and cools not only the paper stacked on the paper discharge tray but also the paper being reversely conveyed, so that the paper is discharged even when performing duplex printing. Therefore, it is possible to efficiently suppress the temperature rise of the paper sheets and reliably prevent the paper sheets from sticking to each other.

1 is a diagram illustrating a configuration of a first embodiment of an image forming apparatus according to the present invention. It is a figure which shows the structure of the paper discharge part of the said 1st Embodiment. It is a control block diagram of the first embodiment and the second embodiment. It is a figure which shows the mode of the wind direction control at the time of inversion of the said 2nd Embodiment. It is a figure which shows the mode of the wind direction control at the time of the non-inversion of the said 2nd Embodiment. It is a flowchart of the wind direction control operation | movement of the said 2nd Embodiment. It is a flowchart of the inversion control in the said wind direction control operation | movement. It is a flowchart of the air volume control operation | movement in the said 1st, 2nd embodiment. It is a flowchart of inversion control in the air volume control operation.

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

(First embodiment)
FIG. 1 shows the configuration of an image forming apparatus according to the first embodiment of the present invention. This image forming apparatus supplies a sheet feeding cassette 13, a sheet feeding roller 14 for pulling out the sheet 11 from the sheet feeding cassette 13, and a sheet 11 pulled out by the sheet feeding roller 14 between the intermediate transfer belt 16 and the transfer roller 17. The conveyance roller 15 is provided.

  The intermediate transfer belt 16, the photoreceptor 9, an exposure device (not shown), and the like constitute an image forming unit 12. A toner image is transferred from the photoreceptor 9 to the intermediate transfer belt 16, and the toner image is transferred from the intermediate transfer belt 16 to the paper 11 by the transfer roller 17. The sheet 11 on which the toner image is transferred is heated while being pressed by the fixing roller 18 to fix the toner image. The paper 11 on which the toner image has been fixed is guided to a first transport path F1 formed by a movable guide 21 at the raised position shown in FIG. 20 is discharged. The paper discharged from the paper discharge roller 19 is the paper 11 on which single-sided printing is instructed and single-sided printing is completed, and the paper 11 on which double-sided printing is instructed and double-sided printing is completed.

  On the other hand, when printing on both sides of the paper 11 is not completed when the double-side printing is instructed, the movable guide 21 is rotated in the clockwise direction in FIG. 1 about the rotation shaft 21A. Thus, the second transport path F2 to the reverse roller 22 is formed. In this case, the paper 11 is guided by the movable guide 21 at the lowered position and conveyed from the fixing roller 18 to the reversing roller 22. The reversing roller 22 discharges the paper 11 on which the image is formed on one side by a predetermined size and then reversely rotates to re-transport the paper 11 into the apparatus and transport it to the duplex printing unit 23. The sheet 11 conveyed from the conveying roller 15 to the transfer roller 17 through the double-sided printing unit 23 is transferred with the toner image from the intermediate transfer belt 16 on the other side, and further heated while being pressed by the fixing roller 18. As a result, the toner image is fixed. As a result, the paper 11 on which images are formed on both sides is discharged from the paper discharge roller 19 to the paper discharge tray 20 and stacked.

  As shown in the control block diagram of FIG. 3, the image forming apparatus of this embodiment includes a CPU 27 that forms a control unit. The CPU 27 issues a sheet conveyance instruction to the paper feed roller 14, the conveyance roller 15, the intermediate transfer belt 16, the transfer roller 17, the fixing roller 18, the paper discharge roller 19, and the reverse roller 22. Further, the CPU 27 issues a primary transfer instruction to the intermediate transfer belt 16, a secondary transfer instruction to the transfer roller 17, and a fixing instruction to the fixing roller 18. Further, the CPU 27 issues an image forming instruction to the image forming unit 12 and a conveyance path switching instruction to the movable guide 21.

  In the image forming apparatus of this embodiment, the paper discharge port 5 for discharging the paper 11 from the paper discharge roller 19 and the paper discharge port 6 for discharging the paper 11 from the reverse roller 22 are provided. Have. As a result, the paper 11 printed on the first side and the paper 11 printed on the second side can be smoothly passed to improve productivity during double-sided printing.

  On the other hand, in general, when the printing speed of the image forming apparatus and the productivity of double-sided printing increase, paper with a high temperature after fixing is successively stacked on the paper discharge tray, which is also affected by the weight of the overlapped paper. The toner before adhering to the adjacent paper surface tends to stick. There is also a tendency that so-called tacking, in which the toner is peeled off and the image is lost when the attached sheets are peeled off, is likely to occur.

  Therefore, the image forming apparatus of this embodiment includes a cooling duct 25 as an air blowing portion attached to the main body 10 in order to prevent the tacking. The cooling duct 25 is disposed above the paper discharge tray 20 and above the paper 11 that is discharged from the reverse roller 22 by a predetermined size. The cooling duct 25 blows out cooling air generated by the rotation of the cooling fan 24 that has received a sheet cooling instruction from the CPU 27 in FIG. As shown in FIG. 2, the cooling duct 25 blows cooling air in the direction indicated by the arrow X and blows cooling air on the paper 11 stacked on the paper discharge tray 20 to cool the stacked paper 11. Further, the cooling duct 25 blows cooling air in the direction indicated by the arrow X, and blows cooling air to the paper 11 ejected from the reversing roller 22 so as to cool the paper 11 during reverse conveyance. Furthermore, the reversal of the cooled paper 11 that has been turned over is carried back into the main body 10 so that the temperature rise in the main body 10 can be suppressed.

  The cooling duct 25 is preferably disposed so as to blow air substantially at the center in the width direction orthogonal to the conveyance direction of the paper 11 to improve the cooling efficiency. The cooling duct 25 preferably blows cooling air substantially perpendicularly to the surface of the paper 11 loaded on the paper discharge tray 20. By blowing the cooling air substantially perpendicularly to the surface of the stacked paper 11, the paper 11 can be efficiently cooled and the displacement of the paper 11 due to the blown cooling air can be suppressed. That is, if the cooling air is applied obliquely to the stacked paper, the paper is likely to be displaced.

  In this embodiment, the reversing roller 22 is disposed downstream of the paper discharge roller 19 in the conveyance of the paper 11 and is disposed above the paper discharge roller 19. 19 is displaced in the conveyance direction of the paper 11, so that the height of the main body 10 can be suppressed.

(Second embodiment)
Next explained is an image forming apparatus according to the second embodiment of the invention. In the image forming apparatus according to the second embodiment, as shown in FIGS. 4A and 4B, a wind direction changing plate 35 that changes the direction of the cooling air blown from the cooling duct 25 is attached to the cooling duct 25. The second embodiment is different from the first embodiment in that the wind direction changing plate 35 is provided. Therefore, in the second embodiment, the operation of the wind direction changing plate 35 will be mainly described.

  This wind direction changing plate 35 is controlled to a horizontal posture by the CPU 27 as shown in FIG. 4A when the reversing roller 22 is transporting the paper 11 in the duplex printing mode. The posture control of the wind direction changing plate 35 is performed by driving a solenoid (not shown) or the like and rotating the wind direction changing plate 35 as an example. As a result, as shown by the arrow 41 in FIG. 4A, the cooling duct 25 discharges the cooling air by a predetermined dimension from the reversing roller 22 and the cooling air blows out substantially perpendicularly to the surface of the paper 11 protruding, and the paper being reversed. 11 is cooled efficiently. On the other hand, when the reversing roller 22 is not transporting the paper 11 in the double-sided printing mode and in the single-sided printing mode, the wind direction changing plate 35 is discharged from the paper discharge tray 20 by the CPU 27 as shown in FIG. 4B. The vertical posture is controlled so as to point to the portion 20 </ b> A immediately below the paper roller 19. As a result, the cooling duct 25 blows cooling air toward the portion 20A of the paper discharge tray 20 directly below the paper discharge roller 19 as indicated by the arrow 42 in FIG. 4B. Therefore, the cooling efficiency of the paper 11 stacked on the paper discharge tray 20 can be improved.

  Next, the attitude | position control operation | movement of the wind direction change board 35 by CPU27 is demonstrated with reference to the flowchart shown to FIG. 5A and FIG. 5B.

  In step S1, the number n of prints is set to 1, and the process proceeds to step S2 to issue a print instruction. In the next step S3, the wind direction changing plate 35 is controlled to the vertical posture of FIG. 4B. Next, in step S4, it is determined whether or not the printing mode identified by the printing mode identification unit 31 is the duplex printing mode. If it is determined that the printing mode is the duplex printing mode, the process proceeds to step S5 and is not the duplex printing mode. If it judges, it will progress to step S14. In step S14, the first side of the nth sheet is printed, and in step S15, the discharge roller 19 is rotated forward. Next, in step S16, it is determined whether or not there is an (n + 1) th sheet to be printed. If it is determined that there is a sheet to be printed, in step S17, (n + 1) is set to n and the process returns to step S14. If it is determined that there is no next sheet to be printed, this operation is terminated.

  On the other hand, in step S5, since it is a double-sided printing mode, the second side (back side) of the nth sheet 11 is printed, and the process proceeds to step S6 to perform reversal control. In this step S5, the 2 × nth page is printed on the back surface of the nth sheet 11. For example, when n = 1, the reversal control is performed after printing the second page on the first sheet.

  In this reversal control, in step S31 of the flowchart of FIG. 5B, the movable guide 21 is moved to the lowered position to form a conveyance path to the reversing roller 22, the reversing roller 22 is rotated forward in step S32, and the wind direction changing plate is step S33. 35 is controlled to the horizontal posture shown in FIG. 4A. As a result, the cooling duct 25 efficiently cools the paper 11 being reversed by blowing cooling air substantially perpendicularly to the surface of the paper 11 being reversed by the reversing roller 22. Next, the process proceeds to step S <b> 34, where the reversing roller 22 is reversed and the paper 11 is conveyed again into the main body 10. In step S35, the movable guide 21 is set to the raised position. Then, after the sheet 11 is re-conveyed by the reversing roller 22, the air direction changing plate 35 is controlled to the vertical posture shown in FIG. 4B in step S36. Therefore, when the paper 11 is not conveyed by the reversing roller 22, the cooling duct 25 blows cooling air toward the portion 20 </ b> A of the paper discharge tray 20 directly below the paper discharge roller 19 to the paper discharge tray 20. The stacked paper 11 is efficiently cooled. The wind direction changing plate 35 and steps S3 and S33, S36 constitute an air blowing direction control unit.

  Next, the process proceeds to step S7 in FIG. 5A to determine whether there is an (n + 1) th sheet to be printed. When it is determined that there is an (n + 1) th sheet, the process proceeds to step S8. When it is determined that there is no n + 1) th sheet, the process proceeds to step S18. In this step S18, the toner image from the intermediate transfer belt 16 is transferred to the first surface (front surface) of the nth sheet 11 conveyed from the conveying roller 15 to the transfer roller 17 through the duplex printing unit 23, Further, the toner image is fixed by being heated while being pressed by the fixing roller 18. That is, in step S18, the (2n-1) th page is printed on the surface of the nth sheet 11. For example, when n = 1, the first page is printed on the first sheet.

  Next, in step S19, the paper discharge roller 19 is rotated forward to discharge the double-side printed paper 11 to the paper discharge tray 20, and the operation is terminated.

  On the other hand, in step S8, printing is performed on the second side of the (n + 1) th sheet. That is, in step S8, the 2 (n + 1) th page is printed on the back surface of the (n + 1) th sheet. For example, when n = 1, the fourth page is printed on the second sheet. Next, the process proceeds to step S9, and the inversion control is performed on the (n + 1) th sheet according to the flowchart of FIG. 5B described above.

  Next, in step S10, the toner image from the intermediate transfer belt 16 is transferred to the first sheet 11 of the nth sheet 11 conveyed from the conveyance roller 15 to the transfer roller 17 through the duplex printing unit 23, and further, The toner image is fixed by being heated while being pressed by the fixing roller 18. That is, in step S10, the (2n-1) th page is printed on the surface of the nth sheet. For example, when n = 1, the first page is printed on the first sheet.

  In step S11, the paper discharge roller 19 is rotated forward. In step S12, it is determined whether or not there is an (n + 2) th sheet to be printed. If it is determined that there is an (n + 2) th sheet, the process proceeds to step S13 and (n + 2) sheets are printed. If it is determined that there is no eye paper, the process proceeds to step S20. In step S13, (n + 1) is set to n, and the process returns to step S8.

  On the other hand, in step S20, printing is performed on the first side (front side) of the (n + 1) th sheet. In step S20, the {2 (n + 1) -1} page is printed on the surface of the (n + 1) th sheet. For example, when n = 1, the third page is printed on the second sheet. In step S21, the paper discharge roller 19 is rotated forward to discharge the (n + 1) th sheet, and the operation is terminated.

  As described above, in this embodiment, when the reversing roller 22 is reversing the paper 11 in the double-sided printing mode, the wind direction changing plate 35 is set to the horizontal posture of FIG. Cooling air is blown to efficiently cool the paper 11 being reversed. On the other hand, when the reversing roller 22 is not transporting the paper 11 and in the single-sided printing mode, the air direction changing plate 35 is set to the vertical posture of FIG. 4B and the cooling duct 25 is directly below the discharge roller 19 in the discharge tray 20. The cooling air is blown out toward the portion 20 </ b> A so that the cooling efficiency of the paper 11 loaded on the paper discharge tray 20 can be improved.

  In the present embodiment, as described above, in the case of double-sided printing, after the back side (second side) is printed first, reverse conveyance is performed to print the front side (first side). Further, in order to improve productivity, after printing the second side of the first sheet, the second sheet is fed from the paper feed cassette 13 during the period when the first sheet passes through the reverse path. A two-sheet circulation system for feeding paper is used.

  Next, the operation in which the CPU 27 controls the rotational speed of the cooling fan 24 to control the amount of air blown from the cooling duct 25 will be described with reference to the flowcharts shown in FIGS. 6A and 6B. Steps S53, S55, S60, S62, S64, S83, and S86 of this flowchart constitute an air blowing amount control unit.

  In step S51, the number n of prints is set to 1, and the process proceeds to step S52 to issue a print instruction. In the next step S53, the cooling fan 24 is rotated at full speed to maximize the amount of cooling air blown from the cooling duct 25. . Next, the process proceeds to step S54, where it is determined whether or not the print mode identified by the print mode identifying unit 31 is the double-sided print mode. If it is determined that the print mode is the double-sided print mode, the process proceeds to step S55 and is not the double-sided print mode. If it judges, it will progress to step S64. In step S64, the rotational speed of the cooling fan 24 is decreased to reduce the amount of cooling air blown out by the cooling duct 25. As an example, the air volume of the cooling fan 24 in step S64 is set to 50% of the maximum blowing amount.

  In step S65, printing is performed on the first surface of the nth sheet, and in step S66, the discharge roller 19 is rotated forward. Next, in step S67, it is determined whether or not there is a (n + 1) th sheet to be printed. If it is determined that there is a sheet to be printed, in step S68, (n + 1) is set to n and the process returns to step S65. If it is determined that there is no next sheet to be printed, this operation is terminated.

  On the other hand, in step S55, the rotational speed of the cooling fan 24 is decreased to reduce the amount of cooling air blown out by the cooling duct 25. As an example, the air volume of the cooling fan 24 in step S55 is set to 90% of the maximum blowing amount. In step S56, the second side (back side) of the nth sheet 11 is printed. In step S57, reversal control is performed.

  In this reversal control, in step S81 in the flowchart of FIG. 6B, the movable guide 21 is moved down to form a transport path to the reversing roller 22, and in step S82, the reversing roller 22 is rotated forward, and in step S83, the cooling fan 24 is rotated. The rotational speed of the cooling air is reduced to reduce the amount of cooling air blown out by the cooling duct 25. As an example, the air volume of the cooling fan 24 in step S83 is set to 70% of the maximum blowing amount.

  Next, proceeding to step S84, the reversing roller 22 is rotated in the reverse direction so that the paper 11 is conveyed again into the main body 10. In step S85, the movable guide 21 is moved to the raised position, and then in step S86, the cooling fan 24 is rotated at full speed. The amount of cooling air blown from the cooling duct 25 is maximized.

  Next, the process proceeds to step S58 in FIG. 6A to determine whether there is an (n + 1) th sheet to be printed. When it is determined that there is an (n + 1) th sheet, the process proceeds to step S59. When it is determined that there is no n + 1) th sheet, the process proceeds to step S69. In step S69, the toner image from the intermediate transfer belt 16 is transferred to the first sheet (front surface) of the nth sheet 11 conveyed from the conveying roller 15 to the transfer roller 17 through the duplex printing unit 23, Further, the toner image is fixed by being heated while being pressed by the fixing roller 18. As a result, printing is performed on the first surface (front surface) of the nth sheet 11, and the sheet 11 printed on both sides is discharged to the sheet discharge tray 20 by rotating the sheet discharge roller 19 in step S70. Exit.

  On the other hand, in step S59, the temperature of the paper 11 stacked on the paper discharge tray 20 is detected by a detection signal from the paper temperature detection unit 33, and it is determined whether or not this temperature is 50 ° C. or higher. If it judges, it will progress to step S60, and if it judges that it is less than 50 degreeC, it will progress to step S61. In step S60, the cooling fan 24 is rotated at full speed to maximize the amount of cooling air blown from the cooling duct 25. On the other hand, in step S61, it is determined whether n is 20 or more. If it is determined that n is 20 or more, the process proceeds to step S62. If n is determined to be less than 20, the process proceeds to step S63. This step S61 constitutes the print instruction number identifying unit 32.

  In step S62, the cooling fan 24 is rotated at full speed to maximize the amount of cooling air blown from the cooling duct 25. On the other hand, in step S63, after printing on the second side (back side) of the (n + 1) th sheet, the process proceeds to step S71, and the inversion control is performed on the (n + 1) th sheet according to the flowchart of FIG. 6B described above. . In step S72, the n-th sheet 11 transported from the transport roller 15 to the transfer roller 17 through the duplex printing unit 23 has a toner image from the intermediate transfer belt 16 on the first surface (front surface). The toner image is fixed by being heated while being pressed by the fixing roller 18. As a result, printing is performed on the first surface (front surface) of the nth sheet. In step S73, the paper discharge roller 19 is rotated forward. In step S74, it is determined whether or not there is an (n + 2) th sheet to be printed. If it is determined that there is an (n + 2) th sheet, the process proceeds to step S75 and (n + 2) sheets are printed. If it is determined that there is no eye paper, the process proceeds to step S76. In step S75, (n + 1) is set to n, and the process returns to step S59. On the other hand, in step S76, printing is performed on the first side (front side) of the (n + 1) th sheet, and the process proceeds to step S77 where the paper discharge roller 19 is rotated forward to discharge the (n + 1) th sheet 11. Paper and finish this operation.

  Thus, in this embodiment, in the single-sided printing mode in which tacking due to toner sticking to the paper does not occur, the number of cooling air blown from the cooling duct 25 is reduced by reducing the rotational speed of the cooling fan 24. , Can reduce power consumption.

  Note that the tacking is caused by sticking of toner on adjacent paper and occurs in the double-sided printing mode. Therefore, in the single-sided printing mode, the cooling fan 24 does not necessarily have to be activated. The cooling fan 24 is activated as a measure against water vapor in the printing mode. That is, the paper 11 is heated suddenly by the fixing roller 18, and the moisture contained in the paper 11 rises as water vapor, and steam may rise from the main body 10 like white smoke. In order to prevent the user from misidentifying this as a fire, the cooling fan 24 is operated to scatter steam. However, at this time, if the airflow of the cooling fan 24 in the single-sided printing mode is the same as the airflow of the cooling fan 24 in the double-sided printing mode, the water vapor is drastically cooled in the vicinity of the paper discharge roller 19, causing condensation. It is desirable to make the air volume of the cooling fan 24 in the single-sided printing mode smaller than the air volume of the cooling fan 24 in the double-sided printing mode. Instead of reducing the air volume of the cooling fan 24, the air volume of the cooling air blown out by the cooling duct 25 may be reduced by reducing the opening area of the air outlet of the cooling duct 25. Of course, when priority is given to reducing power consumption, the cooling fan 24 may be stopped in the single-sided printing mode.

  Further, during the reversing operation in which the paper 11 is conveyed by the reversing roller 22 in the double-sided printing mode, compared with the non-reversing operation in which the paper 11 is not conveyed by the reversing roller 22 in the double-sided printing mode, the cooling duct 25 Reduce cooling air flow rate. As a result, during the paper reversing operation that is easily affected by disturbance, the amount of cooling air blown off can be reduced to prevent positional deviation of the paper 11 being reversed and to prevent noise caused by flapping of the paper 11. That is, as illustrated in FIG. 2, since the paper 11 being reversed by the reversing roller 22 is approaching the cooling duct 25, in order to cool the paper 11 stacked on the paper discharge tray 20 on the paper 11 being reversed. If the air volume is blown, the paper 11 may be displaced from the reversing roller 22 and the print image may be skewed. Further, if a strong wind is applied to the paper 11 that is held only by the reversing roller 22 and has a free end, the paper 11 may flutter and cause noise. In the case of a printing speed and a fixing temperature at which tacking does not occur even if the paper 11 being reversed is not cooled, the cooling fan 24 may be controlled to stop while the paper is reversed by the reverse roller 22.

  Further, when the number of prints for one job increases, a large amount of paper 11 is stacked on the paper discharge tray 20 at a time, so there is no heat escape and the temperature of the paper 11 on the paper discharge tray 20 rises rapidly. Further, as the number of stacked sheets on the sheet discharge tray 20 increases, the toner is more easily stuck with the weight of the stacked sheets 11.

  Therefore, in this embodiment, when a print instruction for a predetermined number of sheets (for example, 20 sheets) or more is made in one job, the air flow of the cooling fan 24 is maximized, while the print instruction in one job is made. When the number is less than the specified number, the air volume control for reducing the air volume of the cooling fan 24 is performed. As a result, power consumption can be suppressed while securing the cooling capacity when the paper temperature rises and the toner becomes easy to stick. In the case where the number of printed sheets is small and the printing speed and fixing temperature are such that tacking does not occur even if the paper 11 is not cooled, the cooling fan 24 is stopped during the reversal of the paper by the reversing roller 22. Also good.

  In addition, when the paper that has been printed in the previous job remains on the paper discharge tray 20, or when the paper stacked on the paper discharge tray 20 is removed during one job, the paper on the paper discharge tray 20 Therefore, it is difficult for the print number identifying unit 32 to recognize the number of sheets actually stacked.

  Therefore, in this embodiment, when the temperature at which the paper temperature detection unit 33 detects the temperature of the paper 11 on the paper discharge tray 20 and the temperature of the paper discharge tray 20 itself is equal to or higher than a specified temperature (for example, 50 ° C.) The air volume of the cooling fan 24 is set to the maximum value. On the other hand, when the detected temperature is less than the specified value and the number of printed sheets is less than the specified number, the air consumption of the cooling fan 24 can be reduced to reduce power consumption. In the case where the number of printed sheets is small and the printing speed and fixing temperature are such that tacking does not occur even if the paper 11 is not cooled, the cooling fan 24 is stopped instead of decreasing the air volume of the cooling fan 24. It is good also as control. Note that the air volume control operation of the cooling fan 24 described in the flowcharts of FIGS. 6A and 6B in the second embodiment may be employed in the first embodiment described above.

DESCRIPTION OF SYMBOLS 10 Main body 11 Paper 12 Image forming part 13 Paper feed cassette 14 Paper feed roller 15 Conveyance roller 16 Intermediate transfer belt 17 Transfer roller 18 Fixing roller 19 Paper discharge roller 20 Paper discharge tray 21 Movable guide 22 Reverse roller 23 Double-sided printing unit 24 Cooling fan 25 Cooling duct 27 CPU
31 Print Mode Identification Unit 32 Printed Number Identification Unit 33 Paper Temperature Detection Unit 35 Wind Direction Change Plate

Claims (9)

A paper discharge roller for discharging the paper on which the image is formed;
A reversing roller which is disposed above the paper discharge roller and discharges paper having an image formed on one side by a predetermined amount by forward rotation and then reversely rotates to re-transport the paper into the apparatus; ,
A movable guide that selectively forms a first transport path for transporting the paper to the paper discharge roller and a second transport path for transporting the paper to the reverse roller;
A paper discharge tray for stacking sheets discharged from the paper discharge roller when printing on one or both sides is completed;
The sheet is disposed above the sheet discharged from the reverse roller by the predetermined size and above the sheet discharge tray, and is discharged from the sheet stacked on the sheet discharge tray and from the reverse roller and protrudes. An image forming apparatus comprising: an air blowing unit that blows air onto the sheet. The image forming apparatus according to claim 1.
The air blowing part is
An image forming apparatus, wherein the image forming apparatus is disposed so as to blow air at a position that is substantially the center in the width direction of the sheet. The image forming apparatus according to claim 1, wherein
The air blowing part is
An image forming apparatus, wherein air is blown substantially perpendicularly to a surface of a sheet stacked on the sheet discharge tray and a surface of a sheet discharged from the reversing roller and protruded. The image forming apparatus according to any one of claims 1 to 3,
2. The image forming apparatus according to claim 1, wherein the reversing roller is disposed downstream of the paper discharge roller in conveying the paper and is disposed above the paper discharge roller. The image forming apparatus according to claim 1,
When the paper is being conveyed by the reversing roller in the duplex printing mode, air is blown out substantially perpendicularly to the surface of the paper ejected from the reversing roller, while the paper is conveyed by the reversing roller in the duplex printing mode. In the single-sided printing mode, the air blowing direction for controlling the air blowing direction of the air blowing portion so as to blow air toward the portion immediately below the paper discharge roller in the paper discharge tray An image forming apparatus comprising a control unit. The image forming apparatus according to any one of claims 1 to 5,
When performing printing in the single-sided printing mode, compared to performing printing in the double-sided printing mode, the air blowing amount control unit that reduces the air blowing amount of the air blowing unit or stops the blowing of air by the air blowing unit An image forming apparatus comprising: The image forming apparatus according to any one of claims 1 to 6,
The amount of air blown from the air blowing unit during the reversing operation in which the paper is conveyed by the reversing roller in the duplex printing mode, compared to the non-reversing operation in which the paper is not conveyed by the reversing roller in the double-sided printing mode. An image forming apparatus, comprising: an air blowing amount control unit that reduces air flow or stops air blowing by the air blowing unit. The image forming apparatus according to any one of claims 1 to 7,
A print instruction number identification unit for recognizing the print instruction number;
When the number of print instructions recognized by the print instruction number identification unit is less than a predetermined number, the amount of air blown from the air blowing unit is smaller than when the number of print instructions is equal to or more than the predetermined number. An image forming apparatus comprising: an air blowing amount control unit that reduces or stops air blowing by the air blowing unit. The image forming apparatus according to any one of claims 1 to 8,
A temperature detector for detecting the temperature of the paper stacked on the paper discharge tray or the temperature of the paper discharge tray;
When the temperature detected by the temperature detector is lower than a predetermined temperature, the amount of air blown out from the air outlet is smaller than when the temperature detected by the temperature detector is equal to or higher than the predetermined temperature. An image forming apparatus comprising: an air blowing amount control unit that reduces or stops air blowing by the air blowing unit.

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