JP2018049115A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device that can reliably cool sheets being carried immediately after fixation.SOLUTION: On a fixed carriage route 27, a sheet heated and fixed by a fixing device 19 is carried. On a two-face carriage route 32, the sheet carried on the fixed carriage route 27 is reversed, and is further carried in a different direction from the fixed carriage route 27. Discharge ports 22a and 22b, constituting an example of blowing means, blows air to the sheet carried on the fixed carriage route 27 via a blown area RA formed penetrating the two-face carriage route 32. A controller 110 so controls sheet carriage on at least one of the fixed carriage route 27 and the two-face carriage route 32 as to blow air from the discharge ports 22a and 22b to the sheet carried on the two-face carriage route 32 when the sheet carried on the fixed carriage route 27 is not located in the blown area RA.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image forming apparatus that forms an image on a sheet by heat fixing.

  There is an image forming apparatus for fixing an image by heating a sheet at a high temperature. In Japanese Patent Laid-Open No. 2004-228867, a sheet that is imaged on the first surface while being conveyed upward by a conveyance path and heated by a fixing unit is reversed and conveyed downward by another conveyance path, and again in the first conveyance path. An image forming apparatus is shown in which an image is formed on the second surface and heated by a fixing unit. In such an image forming apparatus that heats and fixes a sheet at a high temperature, the fixing unit that heats and fixes the sheet at a high temperature serves as a heat source, and the temperature inside the apparatus that accommodates the image forming unit that is vulnerable to the high temperature rises.

  For this reason, in patent document 1, the through-air passage which penetrates the conveyance path which conveys a sheet | seat below is provided. Then, depending on the temperature of the image forming unit, the sheet guided downward is stopped immediately before the through air passage to open the air passage through the through air passage, and the outside air sucked by the air fan is passed through the through air passage. The image forming unit is cooled by blowing air through the air.

JP 2012-242671 A

  In such an image forming apparatus that heats and fixes a sheet at a high temperature, besides the above-described temperature rise in the apparatus, the curling of the sheet caused by moisture evaporation due to heating is a problem. In order to prevent this curling, it is necessary to cool the sheet immediately after fixing.

  However, Patent Document 1 aims at cooling an image forming portion that is vulnerable to high temperatures, and does not consider cooling of a sheet immediately after being conveyed. For this reason, in the cooling mechanism of Patent Document 1, even if the sheet guided downward is stopped immediately before the through air path and blown, the wind is applied to the sheet conveyed on the downstream conveyance path of the fixing unit. However, the sheet conveyed immediately after fixing cannot be reliably cooled to prevent curling.

  An object of the present invention is to provide an image forming apparatus capable of reliably cooling a sheet conveyed immediately after fixing.

  In the image forming apparatus of the present invention, the first conveyance path in which the sheet heated and fixed by the fixing unit is conveyed, and the sheet conveyed in the first conveyance path are reversed, and the direction is different from the first conveyance path. A second conveying path through which the sheet is conveyed, a blowing means for blowing air to the sheet conveyed through the first conveying path through a through air path formed through the second conveying path, and the penetration At least one of the first transport path and the second transport path so that the blower blows air to a sheet transported through the first transport path when a sheet transported through the second transport path is not positioned in the air path. And a control means for controlling one sheet conveyance.

  According to the present invention, the sheet conveyed immediately after fixing can be reliably cooled.

2 is an explanatory diagram of a configuration of a printer. FIG. It is a perspective view of the appearance of a sheet cooling unit. It is explanatory drawing of arrangement | positioning of the fan of a sheet | seat cooling part. It is explanatory drawing of the spray area | region of a sheet | seat cooling part. It is explanatory drawing of a structure of a sheet conveyance mechanism. It is a block diagram of a control system of the sheet transport mechanism. 6 is a first half of a flowchart of sheet conveyance control according to the first embodiment. 6 is a second half of a flowchart of sheet conveyance control according to the first embodiment. FIG. 10 is an explanatory diagram of conveyance control when forming a first sheet image of a first sheet. (A) is when the first sheet is cooled, and (b) is before the first sheet is reversed. It is explanatory drawing of the conveyance control which sends the 1st sheet | seat into a double-sided conveyance path. (A) is when the first sheet is reversed, and (b) is when the second sheet is fed. It is explanatory drawing of the conveyance control which sends a 2nd sheet | seat to a double-sided conveyance path. (A) is when the second sheet is cooled, and (b) is when the first sheet is discharged. FIG. 10 is an explanatory diagram of conveyance control when a first image is formed on a third sheet. FIG. 6 is an explanatory diagram of a partition wall in a second embodiment. (A) is a perspective view, (b) is a front view corresponding to a part of FIG.

  Embodiments of the present invention will be described in detail with reference to the drawings.

<Embodiment 1>
(Printer)
FIG. 1 is an explanatory diagram of the configuration of the printer. As shown in FIG. 1, a printer 1, which is an example of an image forming apparatus, is an electrophotographic monochrome copying machine in which an image reading device 25 is disposed on an upper part of an apparatus main body 10. The apparatus main body 10 forms an image on the sheet P based on image information sent from an external computer or image information of a document captured by the image reading device 25.

  The image forming unit 180 forms a toner image on the photosensitive drum 18 and transfers the toner image to a sheet passing through the transfer unit NP. In the image forming unit 180, a charging roller 33, an exposure device 34, a developing device 35, a transfer roller 17, and a drum cleaning device 181 are disposed around the photosensitive drum 18. The photosensitive drum 18 has a photosensitive layer on the peripheral surface of a metal cylinder. The charging roller 33 is applied with an oscillating voltage obtained by superimposing an AC voltage on a DC voltage, and charges the photosensitive drum 18 to a uniform potential.

  The exposure device 34 generates a laser beam L by driving a semiconductor laser with an image signal obtained by ON-OFF modulating a scanning line signal obtained by developing image data. The exposure device 34 scans and exposes the photosensitive drum 18 with the laser beam L to form an electrostatic latent image.

  The developing device 35 carries a developer on a developing roller and transports the developer to a portion facing the photosensitive drum 18 to develop the electrostatic latent image on the photosensitive drum 18 into a toner image. The transfer roller 17 is applied with a DC voltage and transfers the toner image on the photosensitive drum 18 to a sheet passing through the transfer portion NP.

  A paper feeding unit 11 is disposed at the lower part of the apparatus main body 10. The cassette 11a of the paper supply unit 11 is detachable from the apparatus main body 10 in a direction perpendicular to the paper surface, and sheets P cut to a prescribed size are stored in a stacked form.

  The pickup roller 12 feeds the sheet P from the cassette 11 a and feeds it to the separation unit 13. The separation unit 13 forms a nip with a conveying roller 13a that is rotationally driven in the sheet conveying direction and a retard roller 13b that is rotationally driven in the opposite direction to the sheet conveying direction and is driven to rotate by the conveying roller 13a. The separation unit 13 separates the multi-feed sheets and feeds only the uppermost sheet P of the cassette 11 a to the registration roller 16.

  In a stopped state, the registration roller 16 abuts the leading edge of the sheet P against the roller nip to correct the skew of the sheet P, and then starts to rotate in synchronization with the toner image on the photosensitive drum 18 to transfer the sheet P to the transfer unit NP. Send it in. The sheet P on which the toner image is transferred by the transfer unit NP is conveyed to the fixing device 19 and the image is fixed on the surface. The sheet P on which the image is fixed is conveyed to the first carry-out unit 23 and is discharged and stacked on the discharge tray 24 through the first carry-out unit 23.

(Fixing device)
The fixing device 19 is a so-called on-demand type fixing device that rises quickly. The fixing device 19 receives the sheet P on which the toner image is transferred in the image forming unit 180 from below. The fixing device 19 fixes the image on the sheet by melting and solidifying the toner image on the sheet P to be nipped and conveyed by the high heat supplied from the fixing unit 20a and the pressing force of the pressure roller 20b. .

  In the fixing unit 20a, a fixing belt 20e is rotatably fitted on a support portion 20d supported by a non-rotating beam member penetrating in the axial direction. A heater is fixed to the side of the support portion 20d that contacts the fixing belt 20e. In the heater, the applied voltage is ON / OFF controlled so that the temperature of the support portion 20d is maintained at a predetermined temperature. The pressure roller 20b is configured by providing an elastic layer around the shaft member, and both ends are spring-biased by a pressure mechanism (not shown) so as to contact the fixing unit 20a with a predetermined pressure.

(Duplex printing mode)
The printer 1 can execute a duplex printing mode in which images are formed on both sides of a sheet. In the duplex printing mode, the front and rear ends of the sheet P on which the image is fixed on the first surface (front surface) by the fixing device 19 are reversed by the reversing unit 26 and fed to the transfer unit NP, and the second surface (back surface) Also, the toner image is transferred and the image is fixed by the fixing device 19.

  The sheet P on which the image is formed on the first surface is stopped in a state where the rear end portion is sandwiched between the reversing units 26, folded back by reversing the sheet conveying direction of the reversing units 26, and sent to the duplex conveying path 32. It is. The reversing tray 48 has a tray surface substantially straight above the discharge tray 24, and supports the sheet P to be reversed stacked on the tray surface.

  The sheet P on which the image is formed on the first surface is transferred by the reversing unit 26 so that the trailing edge of the sheet P is changed to the leading edge by the reversing operation and conveyed on the duplex conveying path 32, and the toner image on the first surface is transferred Is fed again to the registration roller 16 in a reverse state. The registration roller 16 corrects the skew of the sheet P, feeds the sheet P to the transfer unit NP in synchronization with the toner image on the photosensitive drum 18, and transfers the toner image to the second surface of the sheet P. The sheet P to which the toner image has been transferred is conveyed to the fixing device 19 and the image on the second surface is also fixed, and then discharged to the discharge tray 24 by the first carry-out unit 23.

(Jam generation in duplex printing mode)
If the sheet P is curled when the sheet on which the image is fixed is reversed by the reversing unit 26 and sent to the duplex conveying path 32, it interferes with a member in the duplex conveying path 32 or a member in the sheet feeding conveying path 14. As a result, jamming is likely to occur. In particular, if the trailing edge of the sheet P conveyed on the fixing conveyance path 27 is curled, the leading edge of the reversing sheet P is warped after being folded by the reversing unit 26, and easily collides with a guide or the like during conveyance. .

  Therefore, the printer 1 reduces the curl by providing the sheet cooling unit 40 and cooling the sheet P at an early stage after the heat fixing. As shown in FIG. 1, the sheet cooling unit 40 blows air as indicated by an arrow E with respect to the sheet P that passes through the blowing area RA of the fixing conveyance path 27 through the duplex conveyance path 32. The intake fan 21 draws outside air from the outside air port 36 to the intake duct 22 and blows it out from the discharge ports 22 a and 22 b toward the fixing conveyance path 27.

(Sheet cooling part)
FIG. 2 is a perspective view of the appearance of the sheet cooling unit. FIG. 3 is an explanatory view of the arrangement of the fans in the seat cooling unit. FIG. 4 is an explanatory diagram of the spray region of the sheet cooling unit. As illustrated in FIG. 1, the intake fan 21, the intake duct 22, and the discharge ports 22 a and 22 b, which are an example of the blowing unit, are blown areas RA that are an example of a through-air path formed through the double-sided conveyance path 32. Then, the air is blown to the sheet conveyed through the fixing conveyance path 27. The spray area RA is disposed adjacent to the fixing device 19 on the downstream side in the sheet conveying direction. The intake fan 21, the intake duct 22, and the discharge ports 22 a and 22 b are disposed between the exterior member of the image forming apparatus main body and the double-sided conveyance path 32.

  As shown in FIG. 2, the intake duct 22 and the intake fan 21 are disposed in the center of the double-sided conveyance path 32 in the sheet width direction orthogonal to the sheet conveyance direction. Exhaust ducts 29a and 29b are arranged with the intake duct 22 sandwiched in the seat width direction. As a result, a duct having a height that is a full distance between the housing side wall of the apparatus main body 10 and the double-sided conveyance path 32 is provided, and a relatively large-diameter fan can be accommodated. In FIG. 1, the intake duct 22 and the exhaust ducts 29a and 29b are overlapped for convenience of illustration, but in actuality, as shown in FIG. 2, they are arranged adjacent to each other in the seat width direction. .

  The intake duct 22 has a hollow shape, and an intake fan 21 is fitted therein. In the intake duct 22, discharge ports 22a and 22b are formed. The intake duct 22 divides the air flow in the width direction of the double-sided conveyance path 32 and blows it out from the discharge ports 22 a and 22 b arranged at the end portions in the width direction of the double-sided conveyance path 32, as indicated by broken lines. The air discharged from the discharge ports 22a and 22b of the intake duct 22 is blown to the non-printing surface side of the sheet P immediately after being discharged in the horizontal direction and discharged from the fixing device 19.

  As shown in FIG. 1, the exhaust ducts 29a and 29b and the exhaust fans 31a and 31b, which are examples of suction means, spray on the downstream side in the transport direction of the fixing transport path 27 from the position where the discharge ports 22a and 22b blow air. Air in area RA is sucked. As shown in FIG. 2, the exhaust ducts 29a and 29b are disposed on both sides in the width direction of the double-sided conveyance path 32 corresponding to the discharge ports 22a and 22b. The exhaust ducts 29a and 29b suck the air in the double-sided conveyance path 32 and guide it upward, and discharge it to the outside of the apparatus main body 10 through the exhaust ports 30a and 30b. The intake duct 22 and the exhaust ducts 29a and 29b form an inner wall surface of a double-sided conveyance path 32 that is curved along the sheet conveyance direction. The intake duct 22 and the exhaust ducts 29a and 29b are arranged along the sheet conveyance direction so as to have a gentle curve, and form a part of the guide surface of the sheet conveyed through the double-sided conveyance path 32. .

  In FIG. 3, the exhaust fans 31 a and 31 b are shown with the exhaust ducts 29 a and 29 b removed, and the intake fan 21 is shown with the intake duct 22 removed. As shown in FIG. 3, the intake fan 21 disposed in the center is disposed adjacent to the outer wall of the apparatus main body 10 so as to suck airflow from the outside air port 36 in the horizontal direction. The exhaust fans 31a and 31b arranged on the left and right sides of the intake fan 21 stand in the horizontal direction from the housing side wall of the apparatus main body 10 so as to suck air from below and guide the air upward and blow out the airflow in the horizontal direction. Raised.

  The exhaust fans 31 a and 31 b exhaust the air in the apparatus main body 10 that has been sucked in from the outside by the intake fan 21 to the outside of the apparatus main body 10. The air whose temperature has increased by being blown onto the sheet P conveyed through the fixing conveyance path 27 is discharged to the outside of the apparatus main body 10 through the exhaust ducts (29a, 29b: FIG. 2) into which the exhaust fans 31a, 31b are respectively fitted. The

  As shown in FIG. 4, the discharge ports 22 a and 22 b and the exhaust fans 31 a and 31 b are disposed on both sides of the fixing conveyance path 27 in the sheet width direction. The discharge ports 22a and 22b are arranged at the end of the printable range 28 for the A4 size laterally fed sheet P. The discharge ports 22a and 22b send air toward the end in the longitudinal direction of the A4 size laterally fed sheet, respectively. The printable range 28 is 297 mm, and can correspond to A4 size horizontal feed (297 mm × 210 mm) or A3 size vertical feed (297 mm × 420 mm). When the intake fan (21: FIG. 3) provided in the intake duct 22 rotates, air is taken in from the outside air port (36: FIG. 3), and air is discharged from the discharge ports 22a, 22b of the intake duct 22.

  The air discharged from the discharge ports 22a and 22b of the intake duct 22 is sucked by the exhaust fans 31a and 31b after cooling the rear end portion of the sheet from the non-printing surface side, and the exhaust ducts (29a and 29b: FIG. 2). Then, the air is exhausted to the outside of the apparatus main body 10. The wind speed of the discharge ports 22a and 22b of the intake duct 22 is higher than the suction speed of the exhaust fans 31a and 31b.

(Sheet transport mechanism)
FIG. 5 is an explanatory diagram of the configuration of the sheet conveying mechanism. As shown in FIG. 1, each roller of the sheet conveying mechanism of the apparatus main body 10 has an opposing roller. However, FIG. 5 shows only one roller. As shown in FIG. 5, the fixing conveyance path 27, which is an example of a first conveyance path, conveys a sheet heated and fixed by a fixing device 19, which is an example of a fixing unit. In the double-sided conveyance path 32, which is an example of the second conveyance path, the sheet conveyed through the fixing conveyance path 27 is reversed, and the sheet is conveyed in a direction different from the fixing conveyance path 27. As shown in FIG. 1, the double-sided conveyance path 32 is disposed between the fixing conveyance path 27 and the exterior member of the image forming apparatus main body, and conveys a sheet for forming an image on both sides. The reversing unit 26, which is an example of a reversing conveyance unit, places the sheet on the reversing tray 48 and stops it, then reverses the sheet and conveys the sheet to the duplex conveyance path 32.

  A conveyance roller 45 on the upstream side and a conveyance roller 46 on the downstream side of the fixing conveyance path 27 respectively hold the sheet at an interval in the sheet conveyance direction. Between the conveyance roller 45 and the conveyance roller 46, a spray area RA that is cooled by blowing air by the sheet cooling unit 40 is set. The intake fan 21 blows air onto a seat that passes through the blowing area RA. The sheet in the fixing conveyance path 27 is conveyed to the conveyance rollers 45, 46, 46 and is delivered to the second carry-out / reversing unit 26. The sheet on the double-sided conveyance path 32 is conveyed to the conveyance rollers 43, 44, and 49, and stops at the leading edge against the registration roller 16.

(Blower interference by sheet)
As shown in FIG. 5, in the single-sided printing mode, the sheet P to which the toner image has been transferred by the transfer unit NP and heated by the fixing device 19 is cooled in the spray area RA of the fixing conveyance path 27, and then the first The paper is discharged from the carry-out unit 23 to a discharge tray (24: FIG. 1). In this case, the cooling of the subsequent sheet P that passes through the spray area RA of the fixing conveyance path 27 is not hindered by the preceding sheet P that passes through the duplex conveyance path 32.

  However, in the duplex printing mode, at the timing when the preceding sheet passes through the duplex conveyance path 32, cooling of the subsequent sheet passing through the spray area RA of the fixing conveyance path 27 may be hindered. In the printer (1: FIG. 1), the fixing conveyance path 27 and the double-side conveyance path 32 are arranged adjacent to each other. Then, the sheet cooling unit 40 penetrates the double-sided conveyance path 32 and blows air to the blowing area RA of the fixing conveyance path 27. For this reason, if there is a preceding sheet at a position overlapping the spray area RA in the double-sided conveyance path 32, the subsequent sheet passing through the fixing conveyance path 27 is not sufficiently cooled, and it is difficult to reduce curl. . As a result, the curl of the subsequent sheet passing through the spray area RA of the fixing conveyance path 27 tends to increase.

  Therefore, in the first embodiment, in the double-sided printing mode, the fixing conveyance path 27 and the double-sided conveyance path 32 are controlled so that the timing at which the sheet P passes through the spray area RA is shifted. The sheet is conveyed so that the sheet conveyed through the fixing conveyance path 27 passes through the blowing area RA when the sheet is not conveyed through the double-sided conveyance path 32 of the blowing area RA through which the discharge ports 22a and 22b blow air. Transport is controlled.

(Sheet conveyance control)
FIG. 6 is a block diagram of a control system of the sheet conveying mechanism. As shown in FIG. 6 with reference to FIG. 5, in the control unit 110, the program and data recorded in the ROM 112 are held in the RAM 113, and the CPU 111 performs necessary calculations and controls, whereby each of the apparatus main bodies 10. The unit and the sheet transport mechanism 50 are operated in an integrated manner. The CPU 111, which is an example of a control unit, performs fixing conveyance so that the discharge ports 22 a and 22 b blow air to the sheet conveyed through the fixing conveyance path 27 when the sheet conveyed through the duplex conveyance path 32 is not positioned in the spray area RA. The sheet conveyance of at least one of the path 27 and the duplex conveyance path 32 is controlled. Therefore, the sheet conveyed through the fixing conveyance path 27 can be cooled without being affected by the sheet conveyed through the duplex conveyance path 32.

  Specifically, the sheet conveying timing of the conveying means such as the registration roller 16 is controlled so that the succeeding sheet passes the blowing area RA of the fixing conveying path 27 after the preceding sheet has passed the blowing area RA of the duplex conveying path 32. To control. Here, it is desirable that the entire succeeding sheet pass through the spray area RA, but since the limit on the transport timing of the preceding sheet becomes large, the effect of curl is the greatest if not cooled, and the leading edge is changed after inversion. The sheet conveyance may be controlled so that at least the rear end side of the succeeding sheet passes.

  The control unit 110 controls the discharge ports 22a and 22b to blow air to at least the rear end side of the sheet conveyed through the fixing conveyance path 27 when the sheet conveyed through the duplex conveyance path 32 is not positioned in the spray area RA. To do. The control unit 110 controls the discharge ports 22a and 22b to blow at least the rear end side of the sheet conveyed through the fixing conveyance path 27 before or after the sheet conveyed through the duplex conveyance path 32 passes through the spray area RA. To do. For this reason, it is possible to suppress the curling of the front end side of the sheet in the double-sided conveyance path 32 that is a great hindrance to sheet conveyance after being reversed by the reversing unit 26.

  Incidentally, the reversing unit 26, which is an example of a bent conveyance path, forms a bent portion for conveying the sheet on the upstream side of the spray area RA of the double-sided conveyance path 32. When the sheet is stopped at the bent portion, the sheet is bent with cooling, and a wrinkle is generated. Therefore, the control unit 110 conveys the sheet conveyed on the double-sided conveyance path 32 at a stretch without stopping between the reversing unit 26 and the spray area RA.

(Control of Embodiment 1)
FIG. 7 is the first half of a flowchart of sheet conveyance control in the first embodiment. FIG. 8 is the latter half of the flowchart of the sheet conveyance control in the first embodiment. FIG. 9 is an explanatory diagram of the conveyance control during the first surface printing of the first sheet. FIG. 10 is an explanatory diagram of conveyance control for feeding the first sheet into the double-sided conveyance path. FIG. 11 is an explanatory diagram of conveyance control for feeding the second sheet to the duplex conveyance path. FIG. 12 is an explanatory diagram of the conveyance control during the first image formation of the third sheet. In FIG. 9, (a) is when the first sheet is cooled, and (b) is before the first sheet is reversed. In FIG. 10, (a) is after the first sheet is reversed, and (b) is when the second sheet is being fed. In FIG. 11, (a) is when the second sheet is cooled, and (b) is when the first sheet is discharged. 9 to 12 illustrate the control when there are three sheets P. FIG. 9 to 12, the sheet P is A4 size lateral feed.

  The sheet conveyance control in the first embodiment will be described with reference to the flowcharts of FIGS. As shown in FIG. 9A, the CPU 111 starts feeding the first sheet P1 (S31). After the first sheet P1 turns on the registration sensor 53 (YES in S32), the CPU 111 starts the rotation of the registration roller 16 after the image formation preparation is completed (S33). The CPU 111 stops the rotation of the registration roller 16 (S35) after the trailing edge of the sheet P1 passes through the registration roller 16 and the registration sensor 53 is turned off (YES in S34). Then, the feeding of the second sheet P2 is started, and the registration roller 16 is made to wait (S36).

  The CPU 111 conveys the sheet P1 to the transfer unit NP, transfers the toner image, heats it with the fixing device 19, and conveys it to the reversing unit 26. The sheet P1 that has passed through the fixing device 19 crosses the spray area RA of the fixing conveyance path 27 at a constant speed and is cooled from the non-printing surface side by the sheet cooling unit 40.

  As shown in FIG. 9B, when the sheet P1 turns on the reverse sensor 57 and a predetermined time has elapsed (YES in S37), the CPU 111 reaches a position where the sheet P1 protruding from the reverse unit 26 can be reversed. The reverse roller (41: FIG. 5) of the reverse unit 26 is temporarily stopped and the reverse rotation is started (S38). The CPU 111 operates the conveyance rollers 43, 49, 44 to send the sheet P1 to the double-side conveyance path 32 and convey it (S39).

  When a predetermined time has elapsed after the trailing edge of the sheet P1 turns off the reverse sensor 57 (YES in S40), the CPU 111 starts the rotation of the registration roller 16 (S41) and feeds the sheet P2 to the transfer unit NP. As shown in FIG. 10B, the rotation start timing of the registration roller 16 is such that the leading edge of the second sheet P2 reaches the spraying area RA at the timing when the trailing edge of the sheet P1 comes out of the spraying area RA. Is set to That is, the CPU 111 controls the timing at which the sheet is conveyed from the reversing unit 26 to the double-sided conveyance path 32, so that the sheet conveyed by the double-sided conveyance path 32 and the sheet conveyed by the fixing conveyance path 27 reach the spray area RA. Is passed through the spray area RA. When the registration sensor 53 is turned off and a predetermined time has elapsed (YES in S42), the CPU 111 stops the rotation of the registration roller 16 (S43).

  The CPU 111 reduces the sheet conveying speed of the duplex conveying path 32 at the timing when the trailing edge of the sheet P1 passes through the spray area RA, and after the second sheet P2 passes through the registration roller 16 and the registration roller 16 stops. Control is performed so that the first sheet P1 reaches the registration roller 16 (S44). On the other hand, when the CPU 111 determines that the sheet P1 cannot pass through the spraying area RA until the leading edge of the sheet P2 reaches the spraying area RA based on the size of the sheet being conveyed, The rotational speeds of 49 and 44 are increased, and adjustment is performed so that the rear end of the sheet P1 passes through the spray area RA until the leading edge of the second sheet P2 reaches the spray area RA (S39). That is, the CPU 111 controls the sheet conveyance speed of the duplex conveyance path 32.

  As shown in FIG. 11A, after the sheet P1 passes through the spray area RA of the double-sided conveyance path 32, the second sheet P2 passes through the fixing device 19, and the spray area RA of the fixing conveyance path 27 is kept constant. Pass at speed. Thereby, the sheet P2 is cooled from the non-printing surface side without being blocked by the sheet P1. After the second sheet P2 has passed through the registration roller 16 (YES in S43), the CPU 111 stops the registration roller 16 (S44), and then causes the first sheet P1 to reach the registration roller 16. The image formation on the second side is waited (S45). In this standby state, the rear end of the sheet P1 is located at a position lower than the spray area RA, so that the sheet P1 does not hinder the cooling of the sheet P2.

  The CPU 111 feeds the sheet P2 cooled in the spray area RA to the reversing unit 26. Further, the rotation of the registration roller 16 is started in accordance with the timing of the toner image on the photosensitive drum 18 (S46), and the transfer of the toner image to the second surface of the sheet P1 is started. When the sheet P1 passes through the registration roller 16 (YES in S47), the registration roller 16 is stopped (S48). The CPU 111 starts feeding the third sheet P2 and waits at the registration roller 16 (S49).

  As shown in FIG. 11B, the CPU 111 sends the preceding sheet P1 having the toner image transferred to the second surface to the fixing device 19, passes through the spray area RA, cools from the non-printing surface side, and continues as it is. It discharges through the first carry-out unit 23 (S50). Further, when a predetermined time has elapsed after the sheet P2 cooled in the spray area RA is fed to the reversing unit 26 and the reversing sensor 57 is turned on (YES in S51), the CPU 111 protrudes from the reversing unit 26. Is determined to have reached a reversible position, the reversing roller 41 of the reversing unit 26 is temporarily stopped, and then reverse rotation is started (S52).

  The CPU 111 adjusts the speeds of the transport rollers 43, 49, and 44 so that the leading edge of the sheet P1 reaches the spray area RA after the trailing edge of the sheet P2 passes through the spray area RA (S53). Accordingly, the sheet P2 passes through the spraying area RA before the sheet P1 passes through the spraying area RA, and thus does not hinder the cooling of the sheet P1.

  When a predetermined time has elapsed after the trailing edge of the sheet P2 turns off the reverse sensor 57 (YES in S54), the CPU 111 determines the timing of the toner image on the photosensitive drum 18 as shown in FIG. 12 with reference to FIG. At the same time, the rotation of the registration roller 16 is started (S55). Then, the transfer of the toner image onto the first surface of the third sheet P3 is started. After the sheet P3 has passed the registration sensor 53 (YES in S56), the CPU 111 stops the rotation of the registration roller 16 (S57). The CPU 111 controls the sheet conveyance speed of the duplex conveyance path 32 so that the sheet P2 reaches the registration roller 16 after the registration roller 16 is stopped (S58). Then, the second sheet P2 is put on standby by the registration roller 16 (S59).

  As described above, the CPU 111 controls the reverse rotation timing (S52) of the reversing unit 26 and the rotation of the transport rollers 43, 49, and 44 (S53). As a result, as shown in FIG. 12, the toner image is transferred to the first surface, and the sheet P2 passes through the spray area RA before the third sheet P3 heated by the fixing device 19 reaches the spray area RA. Therefore, the cooling of the sheet P3 is not hindered.

  The CPU 111 starts the rotation of the registration roller 16 (S60), and after the sheet P2 has passed the registration sensor 53 (YES in S61), stops the rotation of the registration roller 16 (S62). The CPU 111 transfers the toner image onto the second surface of the second sheet P2, sends the sheet P2 onto which the toner image has been transferred, to the fixing device 19, passes through the spray area RA, and cools from the non-printing surface side. As it is, it is discharged through the first carry-out unit 23 (S63).

  As shown in FIG. 12, the sheet P3 is fed to the reversing unit 26, and the reversing sensor 57 is turned on. When the reversing sensor 57 is turned on and a predetermined time has elapsed (YES in S64), the CPU 111 determines that the sheet P3 protruding from the reversing unit 26 has reached a reversible position, and temporarily turns the reversing roller 41 of the reversing unit 26 on. After stopping, reverse rotation is started (S65). The CPU 111 adjusts the speeds of the transport rollers 43, 49, and 44 so that the leading edge of the sheet P3 reaches the spraying area RA after the trailing edge of the sheet P2 passes through the spraying area RA (S66). Since the sheet P3 passes through the spray area RA after the sheet P2 passes through the spray area RA, cooling of the sheet P2 is not hindered.

  The CPU 111 operates the conveyance rollers 43, 49, and 44 to convey the sheet P3 to the registration roller 16 (S66), and waits for image formation on the second surface of the sheet P3 (S67). When a predetermined time elapses after the trailing edge of the sheet P3 turns off the reverse sensor 57 (YES in S68), the CPU 111 starts rotating the registration roller 16 and toner on the second surface of the third sheet P3. Image transfer is started (S69). When the sheet P3 passes the registration roller 16 (YES in S70), the CPU 111 stops the registration roller 16 (S71). The CPU 111 sends the sheet P3 having the toner image transferred to the second surface thereof to the fixing device 19 and discharges it through the first carry-out unit 23 (S72).

(Effect of Embodiment 1)
In the first embodiment, at least the rear end side of the sheet conveyed on the fixing conveyance path 27 when the sheet is not located in the area where the discharge ports 22a and 22b of the double-side conveyance path 32 blow air and penetrates the blowing area RA. The sheet conveyance is controlled so as to pass. For this reason, it is possible to reliably remove the curl of the sheet without being blocked by the sheet of the duplex conveying path 32. The curling of the sheet after fixing can be suppressed or reduced without arranging a plurality of sensors in the double-sided conveyance path 32 and executing complicated conveyance control.

  In the first embodiment, at least the rear end portion that is changed to the front end by reversal of the sheet P that passes through the spray region RA can be reliably cooled. For this reason, the warp of the sheet P folded by the reversing unit 26 can be small. As a result, it is possible to suppress the occurrence of jamming during sheet conveyance, jamming, or winding around the photosensitive drum 18 caused by the leading edge of the sheet P interfering with the inlet of the double-sided conveyance path 32 or members in the double-sided conveyance path 32.

  In the first embodiment, the sheet conveyance is controlled so that the trailing end side of the sheet following the preceding sheet passes through the blowing area RA after the preceding sheet has passed through the area through which air passes toward the blowing area RA. For this reason, even when the sheet size is large, it is difficult for the reversing unit 26 to collide with the preceding sheet and the succeeding sheet following the preceding sheet.

  In the first embodiment, the interval between the sheet conveyed to the double-sided conveyance path 32 and the sheet conveyed to the double-sided conveyance path 32 subsequent to the sheet are separated from the sheet not conveyed to the double-sided conveyance path 32 and the sheet following the sheet. It is larger than the interval. For this reason, it is possible to execute the duplex printing mode without increasing complicated control just by increasing the sheet interval (paper interval).

  In the first embodiment, the spray area RA is set at a position adjacent to the fixing device 19 in the fixing conveyance path 27, and the air discharged from the discharge ports 22 a and 22 b is applied to the sheet P immediately after being discharged from the fixing device 19. Spray. For this reason, the curl of the sheet can be removed at an early stage of the cooling process of the sheet on which the image is fixed.

  In the first embodiment, air is blown onto the non-printing surface of the sheet stretched linearly by the conveying rollers 45 and 46. For this reason, even if the sheet is easily curled, the toner image can be solidified in a straight line to prevent the curling from occurring.

  In the first embodiment, the discharge ports 22a and 22b and the exhaust fans 31a and 31b are arranged on both sides of the fixing conveyance path 27 in the sheet width direction. The sheet cooling unit 40 blows and cools both ends of the sheet in the sheet width direction from the non-printing surface side. For this reason, both sides in the sheet width direction in which curling is likely to occur can be intensively cooled to remove curl with a small air volume.

  In the first embodiment, air is blown to the blowing area RA of the fixing conveyance path 27 through the double-sided conveyance path 32, and at the same time, air is sucked from the blowing area RA through the double-sided conveyance path 32. Therefore, the air on the sprayed sheet surface is removed to efficiently cool the sheet, and the curl can be removed with a small air volume.

  In the first embodiment, the discharge ports 22a and 22b of the intake duct 22 and the exhaust ports 30a and 30b of the exhaust ducts 29a and 29b are disposed adjacent to each other. For this reason, the air in the printer 1 can be efficiently exhausted outside the apparatus.

  In the first embodiment, air is sucked on the downstream side in the sheet conveyance direction of the fixing conveyance path 27 rather than the discharge ports 22a and 22b blowing air. For this reason, the air of the sheet surface sprayed using sheet conveyance can be removed, the sheet can be efficiently cooled, and the curl can be removed with a small air volume.

<Embodiment 2>
In the second embodiment, partition walls 37a and 37b are provided between the discharge ports 22a and 22b and the exhaust fans 31a and 31b in the first embodiment. Since the configuration other than this is the same as that of the first embodiment, only differences from the first embodiment will be described with reference to FIGS. 1 to 11.

(Partition wall)
FIG. 13 is an explanatory diagram of a partition in the second embodiment. In FIG. 13, (a) is a perspective view of the duct, and (b) is an explanatory view corresponding to a part of FIG.

  As shown in FIG. 12A, in the second embodiment, a partition wall 37a is provided so as to partition the discharge port 22a and the exhaust fan 31a, and the discharge port 22b and the exhaust fan 31b are partitioned. A partition wall 37b is provided.

  As shown in FIG. 12B, the partition walls 37a and 37b are formed of a thin resin sheet of an elastic material, and are pushed by the sheet conveyed through the double-sided conveyance path 32 and deformed as indicated by a broken line, Does not interfere with sheet transport. The partition walls 37a and 37b block the flow of air flowing directly from the discharge ports 22a and 22b to the exhaust fans 31a and 31b. The partition walls 37a and 37b prevent the air blown from the discharge ports 22a and 22b from being exhausted through the exhaust fans 31a and 31b before cooling the sheet P transported through the fixing transport path 27.

<Other embodiments>
The image forming apparatus of the present invention is not limited to the specific components, part forms, and actual dimensions in the first embodiment. Another embodiment in which a part or all of the configuration of the first embodiment is replaced with an equivalent member is also possible. The configuration and numerical values described in the first embodiment are appropriately changed depending on the configuration of the image forming apparatus and various conditions. For example, the fixing device 19 may be a heating roller method in which a sheet is heated by a fixing roller and a pressure roller instead of a so-called on-demand method in which an image surface is heated via an endless belt by a heat source such as a ceramic heater. Good.

  Here, in the apparatus for cooling the image forming unit of Patent Document 1, the preceding sheet is stopped immediately before the penetrating air path so that the conveyed sheet becomes an obstacle to cooling of the image forming unit whose temperature has been increased. It is preventing. However, the conveyance path in the area for forming the through air path for cooling the conveyance path downstream of the fixing unit in order to cool the sheet immediately after fixing has a bent portion to reduce the size of the image forming apparatus main body. Once the preceding sheet is stopped at such a curved path just before the through-air path, the sheet that has been fixed and is still at a high temperature curls with a curled flaw, which causes jams and poor loading. May occur. For this reason, the CPU as the control means does not stop the sheet until it passes through the through air passage, together with the control for conveying the through air passage so that the sheet conveyed through the second conveyance passage is not closed. By controlling so as to convey, it is possible to prevent the occurrence of bending curl.

  In the first embodiment, control is performed so that the preceding sheet passes through the spraying area RA of the fixing conveyance path 27 after the preceding sheet passes through the spraying area RA of the double-sided conveyance path 32. However, the present invention is not limited to this. Even if the sheet conveyance timing is controlled so that the subsequent sheet passes through the blowing area RA of the fixing conveyance path 27 and then passes through the blowing area RA of the double-sided conveyance path 32 after the subsequent sheet passes through the blowing area RA of the fixing conveyance path 27. Good.

  In the first embodiment, one intake fan 21 is provided, and two exhaust fans 31 a and 31 b are arranged with the intake fan 21 interposed therebetween. However, the number and arrangement of fans may be changed if a cycle of air that is cooled by blowing and exhausted by suction is possible.

  In the first embodiment, the reverse conveyance speed of the sheet is implemented by constant speed control. However, in order to blow air to the trailing edge of the sheet, the sheet reversal timing or stop at the reversing position, acceleration / deceleration of the conveyance speed in the conveyance path, and the conveyance speed during re-conveyance to the registration roller 15 are variable. It is also possible to do.

  In the first embodiment, the rotational speeds of the intake fan 21 and the exhaust fans 31a and 31b are made constant. However, the rotational speeds of the intake fan 21 and the exhaust fans 31a and 31b may be increased only while the rear end region of the seat P passes. The rotational speeds of the intake fan 21 and the exhaust fans 31a and 31b may be changed according to the fixing temperature and the sheet type. The flow of air discharged from the discharge ports 22a and 22b may be set by a method of changing the mounting angle of the intake fan 21, not by the method of deflecting and guiding the air in the intake duct 22.

  In Embodiment 1, ventilation and suction were performed using a duct and a fan. However, blowing may be performed by a compressor and an air pipe, and suction may be performed by a compressor and an ejector pump.

1: printer (image forming apparatus), 10: apparatus main body, 11: paper feeding unit, 14: paper feeding conveyance path, 16: registration roller (first conveyance path), 18: photosensitive drum (first conveyance path), 19 : Fixing device (first conveying path, fixing means), 20a: fixing belt unit, 20b: pressure roller, 21: intake fan (air blowing means), 22: air intake duct (air blowing means), 22a, 22b: discharge port ( (Blowing means), 23: first carry-out unit, 24: discharge tray, 26: second carry-out / reversing unit (second conveyance path, bent conveyance path, reverse conveyance means), 27: fixing conveyance path (first conveyance path) 28: Printable range, 29a, 29b: Exhaust duct (suction means), 31a, 31b: Exhaust fan (suction means), 32: Double-sided conveyance path (second conveyance path), 40: Sheet cooling section, 50: Sheet Transport mechanism, 110: control unit (control Means), 111: CPU (control means), 112: ROM, 113: RAM, RA: spray area, P: Sheet

Claims (8)

A first conveyance path through which a sheet heated and fixed by a fixing unit is conveyed;
A second conveyance path in which the sheet conveyed in the first conveyance path is reversed and the sheet is conveyed in a direction different from the first conveyance path;
Blower means for blowing air to the sheet conveyed through the first conveyance path through a through air path formed through the second conveyance path;
The first conveying path and the second conveying path so that the blower blows air to the sheet conveyed through the first conveying path when the sheet conveyed through the second conveying path is not positioned in the through air path. Control means for controlling at least one of the sheet conveyance,
An image forming apparatus. The control means is configured such that when the sheet conveyed through the second conveyance path is not positioned in the through air path, the blowing means blows air to at least the rear end side of the sheet conveyed through the first conveyance path. Control the transport,
The image forming apparatus according to claim 1. The second transport path has a bent transport path having a bent portion on the upstream side of the through-air path,
The control means controls the sheet conveyed through the second conveyance path to convey the sheet from the bent conveyance path to the through air path without stopping.
The image forming apparatus according to claim 1, wherein: The control means is configured so that the blowing means blows at least the rear end side of the sheet conveyed through the first conveyance path before or after the sheet conveyed through the second conveyance path passes through the through air passage. Control,
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The second conveyance path is a double-side conveyance path through which a sheet for forming an image on both sides is conveyed, and is disposed between the first conveyance path and an exterior member of the image forming apparatus main body.
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. A reverse conveying means for conveying the sheet to the second conveying path by inverting the sheet after being placed on the tray and stopping;
The control means controls the timing of conveying the sheet from the reverse conveying means to the second conveying path;
The image forming apparatus according to claim 1, wherein the image forming apparatus includes: The control means controls a sheet conveying speed of the second conveying path;
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. A suction means for sucking air on the downstream side in the transport direction of the first transport path from a position where the air blower blows air;
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

Images