JP2012020845A - Sheet delivery device, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet delivery device capable of preventing the sticking of a sheet with another sheet on a delivery tray and the increase of inside temperature, and to provide an image forming apparatus.SOLUTION: The sheet delivery device includes: a delivery roller pair 33 for delivering the sheet S with a thermally fixed toner image; a delivery tray 24 for loading the sheet S delivered by the delivery roller pair 33; a vent 35 provided between the delivery roller pair 33 and the delivery tray 24; a turning member 40, which is turned upward by the sheet S delivered from the delivery roller pair 33, for changing the direction of wind from the vent 35; a switchback roller 31, which is arranged above the turning member 40, for exposing part of the sheet S with the thermally fixed toner image outside the device, and then for drawing the sheet S into the device by reverse rotation; and a turning member 60 for turning upward the turning member 40, while being interlocked with the conveyance of the sheet S when exposing part of the sheet S by the switchback roller 31.

Description

  The present invention relates to a sheet discharging apparatus and an image forming apparatus for discharging a sheet on which an image has been formed to a discharge tray, and more particularly to an apparatus capable of cooling a discharged sheet.

  Conventionally, in an image forming apparatus such as a copying machine or a printer, a so-called electrophotographic system in which a toner image formed in an image forming unit is transferred to a sheet, and the transferred sheet is heated to fix the toner image on the sheet. Some have adopted In such an image forming apparatus, in recent years, there has been an increasing demand for high-speed image forming processing, and at the same time, a sheet heated for fixing a toner image is discharged without being sufficiently cooled and stacked in a state where heat is accumulated. There was a phenomenon of sticking each other.

  On the other hand, conventionally, as shown in FIG. 5A, in order to cool the sheet efficiently, air from the blower fan 33 is sent from the blower port 35 in the direction of arrow A when the sheet is discharged to the discharge tray 24. There are some which cool the lower surface of the sheet S. Further, when the sheet is not discharged, the sheet is cooled in the direction indicated by the arrow B on the upper surface of the sheet S stacked on the discharge tray 24 as shown in FIG. 5B to cool the sheet. (See Patent Document 1).

JP 2006-256707 A

  However, with the further increase in speed in recent image forming apparatuses, the following problems have arisen. In the above conventional example, since the sheet being conveyed at the time of reverse conveyance cannot be cooled (FIG. 5C), the sheet is stacked on the discharge tray due to an increase in the amount of stored heat during reverse conveyance accompanying the increase in speed. There is a risk that the attached sheets will stick to each other.

  Further, there is a problem that the in-machine temperature of the image forming apparatus rises when the sheet after reverse conveyance is conveyed again into the image forming apparatus without being cooled.

  The present invention has been made in order to solve the above-described problems of the prior art, and an object of the present invention is to prevent the sheets on which the images are formed from sticking to each other on the discharge tray, and at the same time, ascend in the apparatus. An object of the present invention is to provide a high-quality image forming apparatus that suppresses temperature.

  In order to achieve the above object, the present invention provides a discharge roller pair for discharging a sheet on which a toner image is fixed by heat, a stacking unit for stacking a sheet discharged by the discharge roller pair, the discharge roller pair, A blowing port provided between the stacking units, a changing unit having a rotation center above the discharge roller pair and rotating to change the direction of the air from the blowing port, and provided above the changing unit. A part of the sheet on which the toner image is fixed is exposed to the outside of the apparatus, and then reversely rotated to pull the sheet into the apparatus, and the sheet is conveyed to the outside by the switchback roller pair. Interlocking means for rotating the changing means upward in conjunction with the control means.

  As described above, according to the invention of the present application, it is possible to suppress sticking of sheets to each other on the discharge tray and increase in the in-machine temperature.

1 is a cross-sectional view illustrating an image forming apparatus including a sheet discharge device according to an embodiment of the present invention. It is sectional drawing explaining the said sheet | seat discharge apparatus. It is a perspective view explaining the said sheet discharge apparatus. It is a fragmentary sectional view explaining the said sheet discharge apparatus. It is a fragmentary sectional view explaining the conventional sheet discharge apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing an overall configuration of a full-color laser beam printer 100 which is an aspect of an image forming apparatus.

<Overall configuration of image forming apparatus>
In FIG. 1, the image forming apparatus 100 includes four photosensitive drums 1a, 1b, 1c, and 1d along a sheet conveyance path extending in the vertical direction. Each of the photosensitive drums 1a to 1d is rotationally driven counterclockwise in FIG. 1 by a driving unit (not shown). Around each of the photosensitive drums 1a to 1d, a charging roller 2a to 2d that uniformly charges the surface of the corresponding photosensitive drum, and a laser beam irradiated to the photosensitive drum charged based on image information are electrostatically charged. Scanner units 3a to 3d for forming latent images are provided. Further, developing devices 4a to 4d that develop the electrostatic latent image on the photosensitive drum as a toner image, a transfer unit 5 that superimposes the toner images on the photosensitive drums 1a to 1d and transfers them onto the sheet S, and the photosensitive after transfer. Cleaning devices 6a to 6d for removing toner remaining on the surface of the body drum are disposed.

  The scanner unit 3 is disposed in the horizontal direction of the photosensitive drum 1, and laser light corresponding to an image signal is directed from a laser diode (not shown) toward polygon mirrors 9a to 9d that are rotated at high speed by a scanner motor (not shown). Irradiated. The laser beams applied to the polygon mirrors 9a to 9d are scanned onto the surfaces of the photosensitive drums 1a to 1d through slits 32a to 32d provided in a partition wall that separates the process cartridges 7a to 7d and the scanner unit 3 described later.

  The developing devices 4a to 4d are constituted by developing units that respectively store yellow, magenta, cyan, and black toners. A transfer belt 11 is disposed so as to face all the photosensitive drums 1a to 1d and to rotate so as to be in contact therewith. The transfer belt 11 rotates and moves by electrostatically attracting the sheet S to the outer peripheral surface in order to bring the sheet S into contact with the photosensitive drums 1a to 1d. Thus, the sheet S is conveyed by the transfer belt 11 to a transfer position between the photosensitive drums 1a to 1d and the corresponding transfer rollers 12a to 12d, and a toner image on the photosensitive drum is transferred at each transfer position. The photosensitive drums 1a to 1d, the developing devices 4a to 4d, the transfer unit 5 and the like described above constitute an image forming unit.

  The paper feed unit 16 feeds and conveys the sheet S from the paper feed cassette 17 in which a plurality of sheets S are stored toward the image forming unit. The sheet S is fed and conveyed one by one by the pickup roller 18, and the leading edge of the sheet S is temporarily stopped at the nip portion of the registration roller pair 19 to form a loop, thereby performing skew feeding. Detection means 51 for detecting the attributes (thickness, size, paper type, etc.) of the sheet S is installed in front of the nip portion of the registration roller pair 19. When the sheet S is stopped by the registration roller pair 19, the sheet S is detected. Detect attributes. In addition, a detection unit 50 for detecting the ambient temperature of the environment in which the image forming apparatus main body is installed is installed above the sheet feeding unit 16.

  In this way, the sheets S separated and fed one by one from the paper feed cassette 17 synchronize the rotation of the transfer belt 11 and the image writing position by the scanner unit 3, and then transfer from the registration roller pair 19 to the transfer belt 11. Paper is being fed. The sheet S on which the color toner images are sequentially transferred while being transferred by the transfer belt 11 is then heated and pressed by the heating roller 21 and the pressure roller 22 of the fixing device 20 to fix the toner image. .

  As the image forming operation in the image forming unit described above, an image forming process reflecting the detection result of the attribute of the sheet S and the environmental temperature by the detecting means 50 and 51 is selected.

  First, the process cartridges 7a to 7d including the photosensitive drums 1a to 1d, the developing devices 4a to 4d, and the cleaning devices 6a to 6d are sequentially driven in accordance with the printing timing, and the photosensitive drums 1a to 1d are driven according to the driving. Are driven to rotate counterclockwise. Then, the scanner units 3a to 3d corresponding to the process cartridges 7a to 7d are sequentially driven. By this driving, the charging rollers 2a to 2d apply a uniform charge to the peripheral surface of the photosensitive drum 1, and the scanner units 3a to 3d expose the peripheral surfaces of the photosensitive drums 1a to 1d according to image signals. Then, electrostatic latent images are formed on the peripheral surfaces of the photosensitive drums 1a to 1d. The developing rollers in the developing devices 4a to 4d move the toner to the low potential portion of the electrostatic latent image to form (develop) the toner images on the peripheral surfaces of the photosensitive drums 1a to 1d.

  The sheet S fed from the sheet feeding unit 16 is pressed against the outer periphery of the transfer belt 11 so as to be sandwiched between the electrostatic adsorption roller 15 and the transfer belt 11. In this state, a voltage is applied between the transfer belt 11 and the electrostatic attraction roller 15 to induce a charge on the dielectric sheet S and the dielectric layer of the transfer belt 11, and the sheet S is transferred to the transfer belt 11. It is comprised so that electrostatic adsorption may be carried out to the outer periphery of. As a result, the sheet S is stably adsorbed to the transfer belt 11 and conveyed to the transfer position corresponding to the most downstream photosensitive drum 1d.

  While the sheet S is conveyed in this manner, the toner images on the photosensitive drums 1a to 1d are sequentially transferred by the electric field formed between the photosensitive drums 1a to 1d and the transfer rollers 12a to 12d. . The sheet S on which the toner images of four colors are transferred is carried into the fixing device 20, and the toner image is heat-fixed by the heating roller 21 and the pressure roller 22 of the fixing device 20, and then loaded by the discharge roller pair 30. To the discharge tray 24.

  When performing duplex printing, after the toner image is thermally fixed on the sheet S by the fixing device 20, the sheet conveying path is switched by the switching member 29 to convey the sheet S to the reverse conveying path 25, and the switchback roller pair 31 performs sheet feeding. A part of the tip end side of S is conveyed so as to be exposed to the outside of the image forming apparatus. When the trailing edge of the sheet S is conveyed to the vicinity of the nip of the switchback roller pair 31, the switchback roller pair 31 is stopped, reversed, and conveyed again to the refeed conveyance path 36 in the image forming apparatus. The sheet S conveyed to the refeed conveyance path 36 is conveyed by the conveyance roller pairs 26, 27, and 28 to the registration roller pair 19 through the U-turn portion at the lower part of the apparatus, and is transferred to the transfer unit 5 while performing skew feeding. Repaid. Thereafter, as in the case of single-sided printing, the sheet S on which the toner image is transferred by the transfer unit 5 is conveyed to the fixing device 20 and discharged to the discharge tray 24 after fixing.

<Sheet cooling configuration and sheet cooling method in sheet discharge device>
FIG. 2 is a drawing showing the sheet discharge configuration of the sheet discharge apparatus according to the present invention, and shows the configuration around the discharge section in the image forming apparatus of FIG. The image forming apparatus according to the present embodiment is configured such that the sheet S conveyed to the discharge tray 24 and the reverse conveyance path 25 is cooled by the blower and conveyed. Here, a sheet cooling configuration and a sheet cooling method during sheet discharge will be described with reference to FIGS.

  As shown in FIG. 2, a conveyance roller pair 23 and a discharge roller pair 30 are provided in the conveyance direction of the sheet S by the heating roller 21 and the pressure roller 22 of the fixing device 20. A reverse conveyance path 25 for reverse conveyance is provided downstream in the conveyance direction of the conveyance roller pair 23, and a switchback roller pair 31 that can rotate forward and reverse is disposed further downstream of the reverse conveyance path 25. Further, a blower fan 33 as a blower is disposed below the discharge tray 24, and a blower port 35 that is a blowout port for air blown by the blower fan 33 is formed below the discharge roller pair 30.

  The air blown from the blower fan 33 is guided from the blower port 35 to the outside of the apparatus through the air passage 34. In the vicinity of the air blowing port 35, a rotating member 40, which is a changing means for changing the direction of the air blown by the blower fan 33, is provided. The rotating member 40 is configured with a rotation center 40c above the discharge roller pair 30 and an area larger than the opening area of the air blowing port 35, and is a sheet holder as a guide portion disposed so as to cover the air blowing port 35. A contact portion 40a is provided. The rotating member 40 also functions as a full load detection unit that detects whether or not the sheets S stacked on the discharge tray 24 are full.

  When the sheet S is not discharged from the discharge roller pair 30, the rotating member 40 is at a home position in a state where it is hung down to a predetermined position by its own weight as shown in FIG. When the sheet S is discharged to the discharge tray 24 and the stacked sheet height becomes equal to or higher than a predetermined level, the rotating member 40 comes into contact with the uppermost surface of the stacked sheets. Further, when the rotating member 40 is rotated by a predetermined angle while being in contact with the top surface of the stacked sheets, it is detected that the sheets stacked on the discharge tray 24 have a predetermined stacking height, and are in a full state. It comes to judge.

  As shown in FIG. 2B, when the sheet S is discharged from the pair of discharge rollers 30, the leading end of the sheet S comes into contact with the sheet contact portion 40a, and the rotating member 40 is pushed up by the sheet S. Until the sheet passes through the discharge roller pair 30. Therefore, when the sheet S is being discharged to the discharge tray 24 by the discharge roller pair 30, the sheet contact portion 40a causes the air from the blower fan 33 to flow from the blower port 35 to the arrow A as shown in FIG. The lower surface (image forming surface) which is the first surface of the sheet S is cooled.

  When the trailing edge of the sheet S passes through the discharge roller pair 30 and is discharged to the discharge tray 24, the rotating member 40 rotates by its own weight and returns to the home position shown in FIG. This state is maintained until the sheet S is discharged. At this time, as shown in FIG. 2A, the direction of air from the air blowing port 35 is changed in the direction of arrow B by the rotating member 40, that is, the upper surface of the sheets S stacked on the discharge tray 24, that is, the sheet discharge. Sprayed onto a second surface (non-image forming surface) different from the time. Thereby, the upper surface of the sheet S stacked on the discharge tray 24 is cooled.

  The rotating member 40 according to the present embodiment is configured to be pushed up by the discharged sheet. However, since the force is also applied to the rotating member 40 in the direction pushed up by the air blown from the air blowing port 35, the discharged sheet is discharged. The burden of is reduced. Further, the rotating member 40 is provided with a spring (not shown) for canceling a moment that the rotating member 40 tries to rotate toward the home position by its own weight, and a force is applied upward. For this reason, even if the discharged sheet is thin paper, there is little risk of buckling due to the weight of the rotating member 40.

  Next, a sheet cooling configuration and a sheet cooling method when the sheet S is reversely conveyed by the switchback roller pair 31 will be described with reference to FIGS. 3 and 4.

  As shown in FIGS. 3A and 4A, the switchback roller pair 31 rotates in conjunction with the conveyance of the sheet S downstream in the conveyance direction when a part of the sheet is exposed outside the apparatus. A rotation member 60 is provided as interlocking means for rotating the member 40 upward. The rotation member 60 has a rotation center 60 c disposed above the conveyance path of the sheet S, and a sheet contact portion 60 a disposed in the conveyance path of the sheet S. The sheet abutting portion 60a is disposed so as to abut on the sheet S that passes when the sheet S is conveyed, and the sheet abutting portion 60a is pressed against the leading edge of the sheet S when the sheet is conveyed, so that the rotation member 60 is rotated about the rotation center 60c. From the base point, the sheet S is pushed up to the front end. In addition, the link member 60b disposed on the rotation member 60 outside the conveyance region in the width direction orthogonal to the sheet conveyance direction is also rotated around the rotation center 40c outside the conveyance region in the width direction. It is provided so as to be able to engage with the link portion 40b that can be arranged. As described above, the rotating member 40 according to the present embodiment is configured to be pushed up by the discharged sheet, but force is also applied to the sheet abutting portion 40a in the direction pushed up by the air blown from the air blowing port 35. Therefore, the burden on the discharged sheet is reduced. Further, the rotating member 40 is provided with a spring (not shown) that applies a force in a direction opposite to the weight of the rotating member 40 in order to cancel the moment that the rotating member 40 tries to rotate due to its own weight. As a result, the leading edge of the sheet S is configured not to buckle when the leading edge of the sheet S abuts against the sheet abutting portion 60a and pushes up the rotating member 60.

  When a part of the leading end side of the sheet S is conveyed so as to be exposed to the outside by the forward rotation of the switchback roller pair 31, as shown in FIG. 4A, the sheet contact portion 60a of the rotating member 60 is Upon receiving a force in the E direction from the sheet S, the rotation member 60 rotates in the C direction about the rotation center 60c. At this time, the link portion 60b of the rotation member 60 applies a force in the W direction to the link portion 40b of the rotation member 40, and the rotation member 40 rotates in the D direction based on the rotation center 40c. 3 is in the position shown in FIG. 3C and FIG. 4B until it is reversed and conveyed into the apparatus.

  Therefore, when the sheet S is conveyed by the switchback roller pair 31 before and after reversal, the air from the blower fan 33 is sent from the blower port 35 through the arrow A as shown in FIGS. 3 (c) and 4 (b). The lower surface (image forming surface) that is the first surface of the sheet S is cooled.

  When the switchback roller pair 31 rotates in the reverse direction and the sheet S is conveyed to the reverse conveying path 25 and pulled into the apparatus, the rotating members 40 and 60 rotate by their own weight, return to the home position, and then the sheet. This state is maintained until S is discharged. At this time, as shown in FIG. 3A, the direction of the air from the air blowing port 35 is changed to the arrow B direction by the rotating member 40, and the upper surface of the sheet S discharged to the discharge tray 24, that is, when the sheet is discharged. And blown out to a different second surface (non-image forming surface). Thereby, the upper surface of the sheet S discharged to the discharge tray 24 is cooled.

  Further, the sheet S conveyed from the reversal conveyance path 25 to the image forming unit via the refeed conveyance path 36 is image-formed on the second surface, and when the sheet S is discharged to the discharge tray 24, the air from the blower fan 33 again. Is blown to the second surface from the blower port 35 and cooled.

  As described above, the sheet S is efficiently cooled by blowing air to different surfaces of the sheet S when the sheet is discharged and when the sheet is reversed and when the sheet is not discharged. For this reason, both sides of the discharged sheet S are effectively cooled even in a high-speed machine with a high image forming speed, and sticking of plastic films such as OHT sheets on the discharge tray is prevented. Further, it is possible to prevent the temperature rise in the apparatus due to the reverse transfer of the stored sheet S and the re-conveyance of the sheet S into the image forming apparatus.

S sheet 20 fixing device 25 reverse conveyance path 30 discharge roller pair 31 switchback roller pair 33 blower fan 35 blower port 40 rotating member (changing means)
60 Rotating member (interlocking means)

Claims (4)

A pair of discharge rollers for discharging the sheet on which the toner image is fixed by heat;
A stacking means for stacking sheets discharged by the discharge roller pair;
An air outlet provided between the discharge roller pair and the stacking means;
A changing means having a rotation center above the discharge roller pair and rotating to change the direction of the air from the air outlet;
A pair of switchback rollers provided above the changing means and exposing a part of the sheet on which the toner image is fixed to the outside of the apparatus, and then reversely rotating and pulling the sheet into the apparatus;
Interlocking means for rotating the changing means upward in conjunction with conveyance of the sheet to the outside of the apparatus by the switchback roller pair;
A sheet discharging apparatus comprising:   The changing means has a rotatable guide portion that guides air from the blower opening, and the interlocking means is engaged with the changing means by pressing a sheet conveyed from the switchback roller pair. The sheet discharging apparatus according to claim 1, wherein the guide unit is rotated so as to guide air to a lower surface of a sheet conveyed from the switchback roller pair.   The changing means is configured such that when the sheet is discharged by the discharge roller pair, it is blown to the lower surface of the sheet, and when the sheet is not discharged from the discharge means, the discharge roller pair is blown toward the stacking means. The sheet discharging apparatus according to claim 1, wherein the sheet discharging device is rotated upward by the sheet discharged from the sheet.   An image forming unit that forms a toner image on a sheet in an image forming unit, a fixing device that fixes the toner image on the sheet by heat, and a sheet discharge device according to any one of claims 1 to 3. An image forming apparatus comprising: