JP2006330398A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent deterioration in function of an image reading part or sticking between pieces of paper in a paper ejecting part by preventing rising of temperature in the paper ejecting part even in continuous image formation without the occurrence of deterioration in image quality and deterioration in stacking property of the paper in the paper ejecting part. <P>SOLUTION: The image forming apparatus is provided with a blower fan 64 in a close proximity with an ejecting opening 63 on a backside of the paper ejecting part 60. The blower fan 64 sucks in air from the front surface side of an image forming apparatus 1 and exhausts it to the back surface side of the image forming apparatus 1, and forms an air flow path in the paper ejecting part 60 which is approximately in parallel to a surface of paper to be ejected from the ejecting opening 63 and also orthogonal to the paper ejecting direction. A control part 70 activates the blower fan 64 only while the paper to be ejected is held by paper ejecting rollers 61. The paper to be ejected is not air-blown in an unstable state after being separated from the paper ejecting rollers 61 until the paper is placed on a paper ejecting tray 62 and the storing position on the paper ejecting tray 62 is not disturbed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that performs electrophotographic image formation on paper, and stacks and stores the image-formed paper in a paper discharge unit during continuous image formation.

  The structure of an image forming apparatus tends to be complicated due to the multi-functionality and high speed of the apparatus. On the other hand, there is a strong demand for downsizing in order to easily operate an operation unit and handle a document. For this reason, some recent image forming apparatuses employ a so-called front access system in which an image forming unit and a discharge unit are arranged between a lowermost sheet feeding unit and an uppermost document reading unit (scanner). .

  An image forming unit that performs electrophotographic image formation includes a fixing unit that heats toner transferred onto a sheet to a melting temperature and fixes the toner on the surface of the sheet. The paper discharge unit stores and stacks high-temperature sheets that have passed through the fixing unit. The fixing unit for heating the toner to the melting temperature and the paper discharge unit for storing the paper heated by the fixing unit are arranged below the document reading unit.

  For this reason, the heat generated in the fixing unit and the heat accumulated in the paper discharge unit warm the original reading unit located above them. A solid-state imaging device (CCD) is disposed in the document reading unit, and the temperature of the CCD may exceed the endurance temperature range.

  In particular, during continuous image formation, a plurality of sheets sequentially passing through the fixing unit are stacked and stored in the paper discharge unit. Each of a plurality of sheets stacked and stored in the paper discharge unit has toner adhered to it. Since almost no air flows between each of the stacked sheets, the heat in the toner applied when passing through the fixing unit continues to accumulate.

  For this reason, the image reading unit located above the paper discharge unit is also warmed by the heat of a plurality of sheets stored in the paper discharge unit, and the temperature of the CCD is likely to exceed the durable temperature range.

  Also, during continuous image formation, the toner adhering to each sheet is not sufficiently fixed, and a plurality of sheets are stacked and stored in the paper discharge unit, so that the toner adheres to other sheets adjacent vertically, Not only does the image quality deteriorate, but the sheets may be adhered to each other in a state where they cannot be separated from each other by the toner.

In view of this, some conventional image forming apparatuses include a cooling device that blows outside air onto a sheet that has passed through the fixing unit and before being discharged to the sheet discharge unit (see, for example, Patent Document 1 or 2). .)
Japanese Patent Laid-Open No. 11-30891 JP 2004-109356 A

  However, in the configurations disclosed in Patent Documents 1 and 2, outside air is blown against the paper located between the fixing unit and the paper discharge roller inside the apparatus, so that the toner melted on the paper rapidly To be cooled. For this reason, there is a problem that the smoothness of the surface of the toner is lost due to an abrupt temperature change and image quality is deteriorated.

  Further, while the sheet passes through the fixing unit and is discharged to the sheet discharge tray by the sheet discharge roller, air is continuously blown against the sheet. For this reason, the paper is affected by the blown air when the leading end is nipped by the discharge roller and when the trailing end is separated from the discharge roller and falls onto the discharge tray. Errors are likely to occur in the nipping position and the discharge position on the discharge tray. As a result, a plurality of sheets cannot be stacked and stored on the sheet discharge tray in a state in which the positions of the sheets are aligned during continuous image formation, and there is a problem in that the sheet stackability of the sheet discharge unit is deteriorated.

  An object of the present invention is to appropriately control the position and timing at which air is blown to the paper discharged to the paper discharge unit, thereby preventing image quality deterioration and deterioration of paper stacking property in the paper discharge unit. Another object of the present invention is to provide an image forming apparatus that can prevent a temperature rise in a paper discharge unit even during continuous image formation, and can prevent a decrease in function in an image reading unit and adhesion of sheets in a paper discharge unit.

  As means for solving the above problems, an image reading apparatus of the present invention has the following configuration.

(1) A fixing unit that heats the toner transferred onto the sheet to a melting temperature, and a sheet that has passed through the fixing unit on the downstream side of the fixing unit in the sheet conveyance path from the discharge port positioned further downstream. An image forming unit having a paper discharge roller for discharging toward the
A paper discharge tray for stacking and storing the image-formed paper discharged from the discharge port on the upper surface;
A blowing means for blowing air to the paper being discharged from the discharge port toward the discharge tray;
And control means for controlling the operation of the air blowing means in accordance with whether or not the paper that has passed through the fixing unit has passed through the paper discharge roller.

  In this configuration, while the sheet heated when passing through the fixing unit is discharged from the discharge port to the discharge tray, the discharge port and the discharge port are determined depending on whether or not the sheet is held between the discharge rollers. The operating state of the air blowing means that blows air to the paper discharge tray changes. Therefore, if the discharge direction does not change due to air blowing because the paper being discharged is sandwiched between the paper discharge rollers, the air is blown to the paper by the blowing means, and the paper being discharged is not pinched by the paper discharge rollers. When the position in the direction orthogonal to the discharge direction is changed by blowing air, it is possible to prevent blowing by the blowing means.

(2) The control means starts the operation of the air blowing means after the front end of one sheet that has passed through the fixing unit passes through the paper discharge roller, and before the rear end passes through the paper discharge roller. Control which stops operation | movement of the said ventilation means is performed.

  In this configuration, air is blown to the paper by the air blowing means while the paper being discharged is held between the paper discharge rollers, and air is blown by the air blowing means while the paper being discharged is not held between the paper discharge rollers. Is not done. Therefore, the paper being discharged is cooled by receiving air while the position in the direction orthogonal to the discharge direction is defined by the paper discharge roller, and the position in the direction orthogonal to the discharge direction is defined away from the paper discharge roller. In the state where it is not done, it does not receive ventilation.

(3) The control unit performs the control at the time of continuous image formation in which image formation is continuously performed on a plurality of sheets conveyed with a predetermined gap between the sheet conveyance paths. And

  In this configuration, during continuous image formation in which a plurality of sheets are continuously discharged with a predetermined gap between each other, the air blowing unit keeps the sheet being discharged between the discharge rollers. While the paper is blown and the paper being discharged is not sandwiched between the paper discharge rollers, the blower does not blow. Therefore, each of the plurality of sheets discharged continuously is cooled by receiving air while the position in the direction orthogonal to the discharge direction is defined by the discharge roller, and separated from the discharge roller in the discharge direction. In a state where the position in the direction orthogonal to the direction is not defined, no air is received.

(4) The control unit may change a time from the start of operation of the air blowing unit to the stop of operation according to the size in the discharge direction of the sheet discharged from the discharge port.

  In this configuration, the sheet discharged from the discharge port is blown over a time corresponding to the size in the sheet discharge direction. Therefore, even when the size in the paper discharge direction changes variously, the air is blown without excess or deficiency.

(5) When the control unit continuously performs a plurality of jobs each including an image forming process on a single sheet or a plurality of sheets with a time interval between the jobs, The air blowing means is operated.

  In this configuration, the blowing unit operates also between each of a plurality of jobs that are continuously performed with a time interval. Therefore, air is blown to the paper stacked on the paper discharge tray while the paper is not discharged from the discharge port.

(6) The discharge roller is a reversing roller that rotates in the reverse direction with the rear end of the image-formed paper sandwiched on one side during image formation on both sides of the paper.
The control means is characterized in that the air flow rate during the double-sided image formation is increased as compared with the single-sided image formation in which an image is formed on only one side of the paper.

  In this configuration, when forming a double-sided image in which images are formed on both sides of a sheet, a larger amount of air is blown than when forming a single-sided image in which an image is formed only on one side of the sheet. Therefore, the paper on which the image is formed on the first surface when the double-sided image is formed is formed with an image on the second side after receiving a larger amount of air than when the single-sided image is formed.

(7) The air blowing unit blows air between the discharge port and the discharge tray in a direction substantially parallel to the sheet surface with respect to the paper being discharged and perpendicular to the discharge direction from the discharge port. It is characterized by that.

  In this configuration, air is blown in a direction substantially parallel to the sheet surface and perpendicular to the sheet discharge direction with respect to the sheet being discharged from the discharge port to the discharge tray. Accordingly, air is blown in the front-rear direction of the apparatus with respect to the sheet discharged in the left-right direction of the apparatus.

  According to the present invention, the following effects can be obtained.

(1) Disturbing the paper discharge position in the paper discharge tray by blowing air to the paper by the blowing means only when the discharge direction does not change due to air blowing because the paper being discharged is sandwiched between the paper discharge rollers. The paper can be cooled without any problems. As a result, it is possible to prevent the temperature rise of the paper discharge unit even during continuous image formation without causing degradation of image quality and deterioration of the stacking property of the paper in the paper discharge unit. In addition, it is possible to prevent the sheets from being bonded to each other in the paper discharge unit.

(2) The paper discharged to the paper discharge tray can be cooled by blowing only while the position in the direction orthogonal to the discharge direction is defined by being sandwiched between the paper discharge rollers. As a result, it is possible to prevent the temperature rise of the paper discharge unit even during continuous image formation without causing degradation of image quality and deterioration of the stacking property of the paper in the paper discharge unit. In addition, it is possible to prevent the sheets from being bonded to each other in the paper discharge unit.

(3) Each of a plurality of continuously discharged sheets can be cooled by blowing only while the position in the direction orthogonal to the discharge direction is defined by the discharge roller. As a result, air is not blown to the paper in a state where the position in the direction orthogonal to the discharge direction is not defined apart from the discharge roller, and a plurality of sheets are stacked and stored at the aligned positions on the discharge tray. can do.

(4) By blowing air over a time corresponding to the size in the paper discharge direction with respect to the paper discharged from the discharge port, even if the size in the paper discharge direction changes variously, it depends on the heat capacity of the paper The air can be blown without excess or deficiency, and the paper can be reliably cooled regardless of its size.

(5) While the sheet is not discharged from the discharge port, the temperature of the discharge unit can be further lowered by blowing air on the sheet stacked on the discharge tray.

(6) At the time of double-sided image formation, a larger amount of air is blown to the paper on which the image is formed on the first side than at the time of single-sided image formation, so that the temperature of the paper at the time of image formation on the second side It can be closer to the temperature during image formation. As a result, the image forming state on both sides of the paper can be made uniform.

(7) Blowing means provided on the back of the apparatus even when the paper discharged in the left-right direction of the apparatus can be blown in the front-rear direction of the apparatus and the paper discharge unit is open to the front of the apparatus Thus, it is possible to reliably blow air to the paper being discharged.

  Hereinafter, an image forming apparatus according to the best embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a front sectional view showing a schematic configuration of an image forming apparatus including an image reading apparatus according to an embodiment of the present invention. The image forming apparatus 1 has a copying function for forming at least an image read from a document on a sheet (including a recording medium such as an OHP).

  The image forming apparatus 1 includes a document reading unit 10, a paper feeding unit 20, an image forming unit 30, a paper discharge unit 60, an operation panel unit (not shown), and the like. The document reading unit 10 is disposed on the upper part of the apparatus main body, and includes a document table 11A, a sheet reading table 11B, an automatic document feeder 12, and a reading unit 13.

  The document table 11 </ b> A and the sheet reading table 11 </ b> B are provided on the upper part of the housing 19 in which the reading unit 13 is disposed so as to face the automatic document feeder 12 and are made of transparent glass. The automatic document feeder 12 conveys the sheet-like documents stored on the document placing tray 12A one by one onto the sheet reading table 11B by the rotation of the feeding roller 14.

  The automatic document feeder 12 is disposed above the document table 11A and the sheet reading table 11B, and functions as a document cover that selectively opens and closes the upper surfaces of the document table 11A and the sheet reading table 11B.

  The reading unit 13 includes mirror bases 13A and 13B, a lens 13C, and a solid-state imaging block (hereinafter referred to as CCD) 13D. The mirror base 13A is mounted with the light source lamp and the first mirror and reciprocates in the horizontal direction. The mirror base 13B is mounted with the second mirror and the third mirror and moves in the same direction at half the speed of the mirror base 13A. The lens 13 </ b> C forms an image on the CCD 13 </ b> D of the reflected light that is emitted from the light source lamp and reflected by the image surface of the document and then distributed through the first to third mirrors.

  In the fixed reading mode in which the image of the document placed on the document table 11A is read, the mirror base 13A moves forward in the arrow Y direction from the left end of the document table 11A to a position facing at least the entire surface of the document. During this time, the CCD 13D reads an image line by line in the main scanning direction from the document placed on the document table 11A. The reading unit 13 that has reached the end of the document or the end of the document table 11A moves backward in the direction of the arrow Y '.

  In the sheet reading mode for reading an image of a sheet-like document conveyed from the document placing tray 12A of the automatic document feeder 12 to the sheet reading table 11B, the mirror base 13A is arranged on the sheet reading table 11B as shown in FIG. It stops at a position facing the bottom. The sheet-like document that has passed through the sheet reading table 11B is discharged onto the discharge tray 12B.

  The CCD 13D receives reflected light from the light source lamp mounted on the mirror base 13A on the image surface of the original through the first to third mirrors and the lens 13C that are traversed by the mirror bases 13A and 13B. An electrical signal corresponding to the amount of received light is output. This electrical signal is converted into digital data as image data, subjected to predetermined image processing, and supplied to the image forming unit 30.

  The paper feed unit 20 is disposed at the lower part of the main body of the image forming apparatus 1 and includes a paper feed tray 21, a manual feed tray 22, a paper feed roller 23, a separating member 24, and the like. The paper feed tray 21 and the manual feed tray 22 place paper to be fed to the paper transport path P during image formation. The paper feed roller 23 rotates to carry the paper stored in the paper feed tray 21 one by one.

  The image forming unit 30 is disposed on the manual feed tray 22 side below the document reading unit 10, and includes a laser scanning unit (hereinafter referred to as LSU) 37, a photosensitive drum 31, and a fixing device 36. A charger 32, a developing device 33, a transfer device 34, and a cleaning unit 35 are arranged in this order along the arrow A direction that is the rotation direction of the photosensitive drum 31.

  The photosensitive drum 31 rotates in the direction of arrow A during image formation. During this time, a predetermined charge is uniformly applied to the surface of the photosensitive drum 31 by the charger 32, and then irradiated with image light modulated by image data from the LSU 37, and an electrostatic latent image due to photoconductive action is generated. It is formed. Next, toner is supplied from the developing device 33 to the surface of the photosensitive drum 31, and the electrostatic latent image is visualized as a toner image.

  On the downstream side of the paper feed roller 23 in the paper transport path P, there is provided a registration roller 51 that determines the timing at which the paper should be transported between the photoconductive drum 31 and the transfer device 34 in accordance with the rotation of the photoconductive drum 31. It has been. The sheet fed prior to the rotation of the photosensitive drum 31 is guided between the photosensitive drum 31 and the transfer device 34 by the registration roller 51 in synchronization with the rotation of the photosensitive drum 31. The toner image carried on the surface of the photosensitive drum 31 is transferred onto the surface of the paper by the transfer device 34. The surface of the photosensitive drum 31 that has completed this transfer process faces the cleaning unit 35, and the residual toner is removed, and the surface is repeatedly used for forming a toner image.

  The fixing device 36 includes a heating roller 38 and a pressure roller 39. The sheet on which the toner image is transferred is heated and pressed when passing between the heating roller 38 and the pressure roller 39. The heating roller 38 is heated to a temperature at which the toner can be melted. When the paper passes between the heating roller 38 and the pressure roller 39, the toner image is melted and fixed on the surface of the paper.

  The paper discharge unit 60 is disposed between the document reading unit 10 and the paper supply unit 20 in the vertical direction, and includes a paper discharge roller 61, a paper discharge tray 62, and the like. The paper discharge roller 61 is disposed inside the discharge port 63, and discharges the paper transported on the paper transport path P and passed through the fixing device 36 to the paper discharge tray 62.

  The paper discharge roller 61 is rotatable in both forward and reverse directions, and discharges the paper while sandwiching the paper conveyed on the paper conveyance path P when the double-sided image is formed on both sides of the paper. The sheet rotates in the direction opposite to the rotation direction and conveys the sheet to the sheet conveyance path P ′. The sheet conveyance path P ′ joins the sheet conveyance path P at a position downstream of the fixing device 36 in the sheet conveyance path P and at a position upstream of the registration roller 51. The paper discharge tray 62 stacks and stores the image-formed paper discharged from the discharge port 63 via the paper discharge roller 61.

  A paper discharge sensor 65 is provided in the vicinity of the paper discharge roller 61 on the upstream side of the paper discharge roller 61 in the paper transport path P. The paper discharge sensor 65 detects paper that has been transported through the paper transport path P on the upstream side of the paper discharge roller 61.

  The paper discharge unit 60 is open to the front side and the left side of the image forming apparatus 1, and the back side and the right side are closed. In the paper discharge unit 60, the paper discharge tray 62 is movable up and down according to the amount of paper stored. The paper discharge tray 62 is located at the height position shown in FIG. 1 in a state where no paper is stored, and descends from the position shown in FIG. 1 as the paper storage amount increases.

  A blower fan 64 is provided on the back surface of the paper discharge unit 60 in the vicinity of the discharge port 63. The blower fan 64 is a blower unit of the present invention and sucks air on the front side of the image forming apparatus 1 and discharges it to the back side of the image forming apparatus 1. Therefore, the blower fan 64 forms a blower path inside the paper discharge unit 60 in a direction substantially parallel to the paper surface of the paper discharged from the discharge port 63 and orthogonal to the paper discharge direction.

  The arrangement position of the blower fan 64 is not limited to the position shown in FIG. 1, and can be placed at an arbitrary position in the paper discharge unit 60 on the condition that sufficient air can be blown to the paper being discharged. Can be arranged.

  FIG. 2 is a block diagram illustrating a configuration of a main part of the control unit of the image forming apparatus 1. The control unit 70 of the image forming apparatus 1 is configured by connecting input / output devices such as a motor driver 74, a paper discharge sensor 65, and a clutch driver 76 to a CPU 71 including a ROM 72 and a RAM 73. The control part 70 is a control means of this invention. The input / output devices include load devices (not shown) such as motors and clutches provided in the document reading unit 10, the paper feeding unit 20, and the image forming unit 30, as well as key switches and displays of an operation panel (not shown).

  The CPU 71 controls each input / output device according to a program written in the ROM 72 in advance, and writes data input / output during this period in a predetermined memory area of the RAM 73. The paper discharge sensor 65 outputs a signal corresponding to the presence or absence of paper in the vicinity of the paper discharge roller 61 to the CPU 71.

  The CPU 71 supplies drive data to the motor driver 74 based on the detection signal of the paper discharge sensor 65. The motor driver 74 drives the blower motor 81 that supplies rotation to the fan of the blower fan 64 based on the drive data supplied from the CPU 71. Note that the CPU 71 changes drive data supplied to the motor driver 74 according to image forming conditions such as whether double-sided image formation or single-sided image formation is performed. For example, the CPU 71 can supply drive data to the motor driver 74 for rotating the blower motor 81 at a higher speed during double-sided image formation than during single-sided image formation.

  Further, the CPU 71 supplies switching data to the clutch driver 76 based on the detection signal of the paper discharge sensor 65 during double-sided image formation. The clutch driver 76 is included in the load device of the image forming unit 30 and operates a clutch 82 that selectively switches the rotation direction of the paper discharge roller 61 to the normal rotation direction or the reverse rotation direction based on the switching data supplied from the CPU 71. Let

  3 and 4 are flowcharts showing a part of the processing procedure of the control unit 70. FIG. The CPU 71 of the control unit 70 is on standby for a start key operation on the operation panel (S1). When the start key is operated to start the image forming job, the CPU 71 reads an image of the document via the document reading unit 10, feeds the sheet from the sheet feeding unit 20, and the image in the image forming unit 30. The formation process is started (S2).

  The CPU 71 determines whether it is a single-sided image forming process or a double-sided image forming process (S3). During the single-sided image forming process, the blower motor 81 is driven when a predetermined time T1 elapses after the paper discharge sensor 65 detects the paper ( S4, S5, S6). The predetermined time T1 is a time required from the time when the paper discharge sensor 65 detects the paper until the paper is completely held between the paper discharge rollers 61.

  The CPU 71 stops driving the blower motor 81 when the paper discharge sensor 65 no longer detects paper (S7, S8), and determines whether or not the next image forming process is included in the job being executed (S7, S8). S9). If the job being executed includes the next image forming process, the CPU 71 returns to the process of S2 (S9 → S2).

  Note that a job refers to a group of image forming processes for forming an image of a single or a plurality of originals on a single or a plurality of sheets. While the previous job is being executed, the image forming apparatus 1 receives a job to be executed next, and in principle, executes the jobs in the received order.

  If the job being executed does not include the next image forming process, the CPU 71 determines whether there is a next job waiting (S10). If there is no next job, the CPU 71 returns to the standby state for the start key operation (S10 → S1).

  When there is a next job, the CPU 71 drives the blower motor 81 after the predetermined time T2 has elapsed (S11, S12). The predetermined time T2 is a sufficient time until the paper is completely discharged onto the paper discharge tray 62 after the paper discharge sensor 65 no longer detects the paper.

  The CPU 71 continues to drive the blower motor 81 until the start timing of the next job (S12, S13). When the start timing of the next job comes, the drive of the blower motor 81 is stopped and the image forming process is started (S14 → S2).

  During the double-sided image forming process, the CPU 71 determines whether or not it is during the image forming process for the first side of the paper (S21), and when the paper discharge sensor 65 detects the paper during the image forming process for the first side. When the predetermined time T1 elapses, the blower motor 81 is driven (S22 to S24). As described above, the predetermined time T1 is a time required from when the paper discharge sensor 65 detects a paper to when the paper is completely held between the paper discharge rollers 61.

  The CPU 71 drives the clutch 82 via the clutch driver 76 and reverses the paper discharge roller 61 when a predetermined time T3 has elapsed since the paper discharge sensor 65 detected the paper (S25, S26). This predetermined time T3 is from the time when the leading edge of the paper to be discharged is detected by the paper discharge sensor 65, and the trailing edge of the paper is downstream of the fixing device 36 in the paper conveyance path P and the paper conveyance path P and the paper conveyance. This is a sufficient time to pass through the joining position with the path P ′.

  As a result, the image-formed sheet on the first surface is conveyed between the photosensitive drum 31 and the transfer unit 34 with the front and back surfaces reversed, via the sheet conveyance path P ′. During this time, the blower fan 64 can be driven or stopped.

  However, the CPU 71 drives the blower motor 81 and continues blowing by the blower fan 64 at least while the sheet is held between the discharge rollers 61. For this reason, air blown by the blower fan 64 is performed while the paper reciprocates outside the discharge port 63 due to normal rotation and reverse rotation of the paper discharge roller 61, and the paper is sufficiently cooled. As a result, the temperature of the image-formed paper on the first side becomes substantially the same as that at the time of image formation on the first side when image formation is performed on the second side, and the image formation state on the front and back sides of the paper Can be made constant. Further, by making the rotation speed of the blower motor 81 at the time of double-sided image formation faster than at the time of single-sided image formation, the temperature of the image-formed paper on the first side is set to the temperature before the image formation on the second side is performed. It can be lowered more sufficiently.

  Note that the CPU 71 detects that the rear end of the sheet conveyed in the direction opposite to the discharge direction by the reverse discharge roller 61 passes the discharge sensor 65 and the discharge sensor 65 no longer detects the sheet. The driving of the clutch 82 is stopped, and the paper discharge roller 61 is rotated forward.

  When the image forming process is performed on the second surface of the paper whose front and back sides are reversed (S2), the CPU 71 waits for the paper discharge sensor 65 to detect the paper through the processes of S3 and S21 (S27). When a predetermined time T1 has elapsed since the paper sensor 65 detected the paper, the blower motor 81 is driven (S28, S29). As described above, the predetermined time T1 is a time required from when the paper discharge sensor 65 detects a paper to when the paper is completely held between the paper discharge rollers 61.

  The CPU 71 stops driving the blower motor 81 when the paper discharge sensor 65 no longer detects paper (S30, S31), and determines whether or not the next image forming process is included in the job being executed (S30, S31). S32). If the job being executed includes the next image forming process, the CPU 71 returns to the process of S2.

  If the job being executed does not include the next image forming process, the CPU 71 determines whether or not there is a next job waiting (S33). If there is no next job, the CPU 71 returns to the standby state for the start key operation.

  When there is a next job, the CPU 71 drives the blower motor 81 after the predetermined time T2 has elapsed (S34, S35). As described above, the predetermined time T2 is a sufficient time from when the paper discharge sensor 65 no longer detects paper to when the paper is completely discharged onto the paper discharge tray 62.

  The CPU 71 continues to drive the blower motor 81 until the start timing of the next job (S35, S36). When the start timing of the next job comes, the drive of the blower motor 81 is stopped and the image forming process is started (S37 → S2).

  With the above processing, the CPU 71 blows air on the paper by the blower fan 64 and passes through the fixing device 36 only while the paper to be discharged to the paper discharge tray 62 is held between the paper discharge rollers 61. Encourage heat dissipation of the heat received. The paper to be discharged to the paper discharge tray 62 receives air blown from the blower fan 64 in an unstable state until it is not pinched by the paper discharge roller 61 and is then placed on the paper discharge tray 62. Absent. For this reason, the sheet after the image forming process can be reliably cooled without disturbing the storage position on the discharge tray 62.

  In addition, when a plurality of jobs are continuously executed at predetermined time intervals, the blower fan 64 blows air while the image forming process is paused between the jobs by the processes of S34 to S37. Done. For this reason, air is blown to the paper on which the image is formed in the previous job stored in the paper discharge tray 62, and the paper discharge unit 60 becomes hot due to preheating of the paper discharged to the paper discharge tray 62. There is nothing.

  Accordingly, it is possible to prevent the plurality of sheets stacked and stored in the sheet discharge tray 62 from being bonded to each other by the toner softened by the preheating. In addition, it is possible to prevent the document reading unit 10 disposed above the paper discharge unit 60 from exceeding the operating temperature of the device such as the CCD 13D and to continue normal document reading processing. However, the processing of S34 to S37 can be omitted on condition that the sheet is sufficiently cooled when discharged onto the discharge tray 62.

  Through the processes of S4 to S8 and S27 to S31, after a predetermined time T1 has elapsed from when the leading edge of the paper reaches the paper discharge sensor 65, until the trailing edge of the paper passes the paper discharge sensor 65, Blowing by the blower fan 64 is performed. For this reason, when the paper size in the transport direction fluctuates, air is blown by the blower fan 64 for a time corresponding to the paper size. However, the blowing time by the blower fan 64 is set in advance for each paper size in the transport direction, and the CPU 71 determines the blown time by the blower fan 64 according to the paper size included in the image forming processing conditions. Good.

1 is a front sectional view showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention. 2 is a block diagram illustrating a configuration of a main part of a control unit of the image forming apparatus. FIG. It is a flowchart which shows the process sequence at the time of the single-sided image formation of the said control part. It is a flowchart which shows the process sequence at the time of the double-sided image formation of the said control part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Image reading part 20 Paper feeding part 30 Image forming part 60 Paper discharge part 61 Paper discharge roller 62 Paper discharge tray 63 Paper discharge port 64 Blower fan 65 Paper discharge sensor 70 Control part

Claims (7)

A fixing unit that heats the toner transferred onto the sheet to a melting temperature, and a sheet that has passed through the fixing unit on the downstream side of the fixing unit in the sheet conveyance path is discharged sideways from a discharge port positioned further downstream. An image forming unit provided with a paper discharge roller,
A paper discharge tray for stacking and storing the image-formed paper discharged from the discharge port on the upper surface;
A blowing means for blowing air to the paper being discharged from the discharge port toward the discharge tray;
An image forming apparatus comprising: a control unit that controls an operation of the blowing unit according to whether or not the sheet that has passed through the fixing unit has passed through the sheet discharge roller.   The control unit starts the operation of the blowing unit after the front end of one sheet that has passed through the fixing unit has passed the discharge roller, and the blowing unit before the rear end passes the discharge roller. The image forming apparatus according to claim 1, wherein control for stopping the operation is performed.   The control unit performs the control at the time of continuous image formation in which image formation is continuously performed on a plurality of sheets conveyed with a predetermined gap between the sheet conveyance paths. Item 3. The image forming apparatus according to Item 2.   3. The image forming apparatus according to claim 2, wherein the control unit changes a time period from the start of operation of the air blowing unit to the stop of operation according to a size in a discharge direction of the sheet discharged from the discharge port. .   When the control means performs a plurality of jobs, each of which includes an image forming process for a single sheet or a plurality of sheets, with a time interval between the jobs, the blower means is used between the jobs. The image forming apparatus according to claim 2, wherein the image forming apparatus is operated. The discharge roller is a reversing roller that rotates in the reverse direction with the rear end of the image-formed paper sandwiched on one side at the time of double-sided image formation for forming images on both sides of the paper,
3. The image forming apparatus according to claim 2, wherein the control unit increases an air flow rate at the time of the double-sided image formation as compared with a single-sided image formation in which an image is formed on only one side of a sheet.   The blowing means blows air between the discharge port and the discharge tray in a direction substantially parallel to a sheet surface and perpendicular to a discharge direction from the discharge port with respect to a sheet being discharged. The image forming apparatus according to claim 1.

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