JP2007086337A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To ensure a fixing process without escaping heat from a fixing device so as to cope with a high speed printing process, and to sufficiently cool paper after fixing. <P>SOLUTION: In the fixing device, air curtain forming means 71 are disposed in the paper insertion port 393 and paper ejection port 394 of the fixing device 39, respectively and the air curtain forming means 71 are provided with circulation paths 713 by which air is blown from air blowing parts 711 disposed in the paper insertion port 393 and paper ejection port 394, air blown is recovered from air recovery parts 712 disposed in the paper insertion port 393 and paper exhaust port 394, and then the air is circulated to the air blowing parts 711. During the operation of the device, the air curtain forming means 71 disposed in the paper insertion port 393 stops air blowing during the passage of paper through the paper insertion port 393, and the air curtain generating means 71 disposed in the paper ejection port 394 decreases the blowing quantity of air during the passage of the paper through the paper ejection port. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fixing device in which unfixed developer on a sheet is melted and fixed by a fixing roller by passing the sheet after transfer between fixing rollers arranged in a fixing frame. The present invention relates to a fixing device that prevents heat in the fixing frame from escaping to the outside.

  In recent years, development of image forming apparatuses that perform high-speed printing processing has progressed. For example, the number of sheets to be printed on standard paper (A4 landscape transport) was 40-60 sheets / minute up to several years ago, but now the processing speed has increased to 100-120 sheets / minute.

  Usually, while the image forming apparatus is on standby, the fixing device is always ready to start printing, the surface temperature of the heating roller constituting the fixing device is controlled at approximately 160 to 200 ° C., and the pressure roller receives from the heating roller It is heated in the range of 100 to 150 ° C. in terms of heat. In order to realize high-speed printing processing, it is necessary to contribute to melting and fixing of the unfixed developer so as not to let this heat amount escape to the outside of the fixing device as much as possible.

On the other hand, the temperature of such a heating roller is very high as compared with the entire apparatus, and even if a heat-resistant member is arranged in the fixing device, the temperature of surrounding members is increased, which has an adverse effect on document reading and printing processes. There was a possibility. In order to prevent such an adverse effect, conventionally, a method of discharging air heated by the fixing unit to the outside of the apparatus using a blower fan has been widely used. Further, by forming a band-shaped air curtain through which gas flows from one side of the front and back of the apparatus main body between the heat generation space and the image formation space to the other side, the heat generation space to the image formation space is formed. An image forming apparatus (see, for example, Patent Document 1) devised to cut off the heat transfer has also been proposed.
JP 2003-295740 A

  According to the image forming apparatus described in Patent Document 1, the temperature inside the apparatus can be appropriately controlled. However, the air curtain is merely a partition between the heat generating space and the image forming space, and the heat exchanged air is basically exhausted to the outside. That is, the heat of the heat generating space, in particular, the heat generated from the fixing device is not devised so as not to escape from the inside of the fixing device. That is, it is not devised not to let the heat inside the fixing device escape to correspond to the recent high-speed printing processing.

  On the other hand, when such a high-speed printing process is performed, the paper that has passed through the fixing portion (heating, pressure roller pressing portion) controlled to the above temperature by the fixing device is warmed to a high temperature and discharged soon before it is sufficiently cooled. Since the paper is sequentially discharged to the section, the discharged paper is approximately 70 to 100 ° C. For this reason, when the developer on the paper is stacked before it is completely fixed, there is a problem that the upper and lower papers are bonded by the unfixed developer.

  The present invention was devised to solve such problems, and its purpose is to perform the fixing process reliably without releasing the heat inside the fixing device so as to sufficiently cope with the recent high-speed printing process, and to fix the fixing process. An object of the present invention is to provide a fixing device capable of high-speed printing processing by sufficiently cooling the subsequent sheet.

  In order to solve the above problems, the fixing device of the present invention melts and fixes the unfixed developer on the paper with the fixing roller by passing the paper after transfer between the fixing rollers arranged in the fixing frame. In the fixing device, the air curtain forming means for forming the air curtain is respectively arranged on the upstream side and the downstream side in the sheet conveying direction of the fixing frame. More specifically, the air curtain forming means is disposed at a paper insertion port and a paper discharge port of the fixing frame, respectively. Further, the air curtain forming means blows out air from an air blowing portion disposed at the paper insertion port and the paper discharge port, and collects air blown from an air recovery portion disposed at the paper insertion port and the paper discharge port. And it is set as the structure provided with the circulation path which circulates to the said air blowing part.

  As described above, the air curtain forming means is disposed at the paper insertion port and the paper discharge port of the fixing frame, respectively, and the air is circulated without being exhausted to the outside. The generated heat can be contained in the fixing device. As a result, the heat generated in the fixing device can be contributed to the fixing process without escaping to the outside, so that it is possible to sufficiently cope with the high-speed printing process.

  In addition, when the apparatus is in operation, the air curtain forming means disposed on the upstream side of the fixing frame in the sheet conveyance direction is configured to stop air blowing while the sheet passes through the sheet insertion port. That is, in the standby state during operation of the apparatus, the paper insertion opening is blocked by the air curtain, but when the printing process is performed and the paper passes through the paper insertion opening, the air blowing is stopped. This is because the developer on the paper passing through the paper insertion opening is in an unfixed state, and it is necessary to prevent the image due to the unfixed developer on the paper from being disturbed by the blowing of air.

  On the other hand, when the apparatus is in operation, the air curtain forming means arranged on the downstream side of the fixing frame in the sheet conveying direction is configured to reduce the amount of air blown while the sheet passes through the sheet discharge port. Here, the amount of air blown while the sheet is passing through the sheet discharge port is controlled to an air volume that does not hinder the conveyance of the sheet and has a cooling effect. In other words, the air curtain forming means arranged on the downstream side of the fixing frame in the sheet conveying direction releases the heat inside the fixing apparatus to the outside by blocking the sheet discharge port with the air curtain in the standby state during operation of the apparatus. On the other hand, during the printing process, by reducing the amount of air blown out, the operation is performed to cool the passing paper while preventing the heat inside the fixing device from escaping to the outside.

  According to the fixing device of the present invention, the air curtain forming means is disposed at the paper insertion port and the paper discharge port of the fixing frame, respectively, and the air is circulated without being exhausted to the outside. Since the heat generated can be contributed to the fixing process without escaping to the outside, the high-speed printing process can be sufficiently handled. In addition, the air curtain forming means arranged on the upstream side in the paper conveyance direction is configured to stop the air blowing while the paper is passing through the paper insertion opening, so that unfixed development on the paper passing through the paper insertion opening is performed. It is possible to prevent the image of the agent from being disturbed. In addition, the air curtain forming means arranged on the downstream side in the paper transport direction is configured to reduce the amount of air blown while the paper is passing through the paper discharge port, so that the heat inside the fixing device can be released to the outside. In this way, it is possible to reliably cool the passing paper while preventing it.

  Embodiments of the present invention will be described below with reference to the drawings. In this embodiment, a case where the fixing device of the present invention is applied to a digital copying machine as an image forming machine will be described.

-Description of the overall configuration of the digital copying machine 1-
FIG. 1 schematically shows the internal configuration of a digital copying machine 1 according to this embodiment. As shown in FIG. 1, the digital copying machine 1 includes a scanner unit 2, an image forming unit 3 that forms an image on a recording sheet P as a recording medium, and a sheet transport unit that transports the recording sheet P to the image forming unit 3. A mechanism 4 is provided. Hereinafter, each part will be described.

<Description of Scanner Unit 2>
The scanner unit 2 includes a document placing table 21 made of transparent glass and the like, and a double-sided automatic document feeder (RADF; Reversing Automatic Document Feeder) 22 that feeds a document onto the document placing table 21. This is a part for creating image data by reading an image of the document on the document table 21.

  The RADF 22 includes an automatic paper feed tray 22a for automatically feeding a plurality of set originals one by one onto the original placement table 21. Further, the RADF 22 can cause the scanner unit 23 described later to read one side or both sides of the document according to the user's selection. Specifically, a transport path for transporting a document on the automatic paper feed tray 22a onto the document placement table 21 and a reversing path for reversing the document so that the scanner unit 23 can read both sides of the document are provided. When only one side of the document is read, only the transport path is used. On the other hand, when both sides of the document are read, the document transported on the document table 21 via the transport path is reversed on the reverse path. It is conveyed again onto the document table 21. For this reason, each path is provided with a transport path switching means and a sensor group (both not shown) for recognizing the transport position of the document. The configuration of the RADF 22 is well known in the art and will not be described in detail.

  In addition, the scanner unit 2 includes a scanner unit 23 for reading an image of a document conveyed on the document placing table 21. The scanner unit 23 includes a lamp reflector assembly 24, a plurality of reflection mirrors 25a, 25b, and 25c, an optical lens body 26, and a photoelectric conversion element (CCD) 27.

  The lamp reflector assembly 24 irradiates light on the document placed on the document placement table 21. Each reflecting mirror 25a, 25b, 25c reflects the reflected light from the document once in the left direction in the drawing as shown by the two-dot chain line in FIG. 1, and then reflects it downward, and then the optical lens body. The light is reflected in the right direction in the figure so as to go to H.26.

  As a document image reading operation, when a document is placed on the document placement table 21, the first scanning unit 23 a composed of the lamp reflector assembly 24 and the reflection mirror 25 a scans along the document placement table 21 in the horizontal direction. Irradiate the entire document with light. At this time, the second scanning unit 23b composed of the reflection mirrors 25b and 25c moves in the same direction at a predetermined speed (half the speed relative to the first scanning unit 23a) with respect to the first scanning unit 23a. The light reflected by the reflecting mirrors 25a, 25b, and 25c and passed through the optical lens body 26 is imaged on the photoelectric conversion element 27, and the reflected light is converted into an electric signal (original image data) in the photoelectric conversion element 27. It has been converted to. The image data obtained in this way is transmitted to the control unit (image processing unit) 3A, where various processing is performed, and then temporarily stored in the memory of the control unit 3A. Then, the image data in the memory is read and used for the image forming operation by the image forming unit 3.

<Description of Image Forming Unit 3>
The image forming unit 3 includes a laser writing unit 31 and an electrophotographic process unit 32 as a light beam scanning device. The laser writing unit 31 irradiates the surface of the photosensitive drum 33 of the electrophotographic process unit 32 with laser light based on the document image data converted by the photoelectric conversion element 27. Specifically, the laser writing unit 31 includes a semiconductor laser light source that irradiates a laser beam corresponding to the image data, a polygon mirror that deflects the laser beam at an equal angular velocity, and the laser beam deflected at the equal angular velocity is a photosensitive drum. 33 has an f-θ lens or the like that corrects so as to scan at a constant speed. Details of these will be described later.

  The photosensitive drum 33 rotates in the direction indicated by the arrow in FIG. 1, and the laser beam from the laser writing unit 31 is reflected and irradiated by the folding mirror 31a, whereby an electrostatic latent image is formed on the surface thereof. It is like that.

  The electrophotographic process unit 32 includes a charger 34, a developing unit 35, a transfer unit 36, a static eliminator 37, a peeling unit, a cleaning unit 38, and a fixing device 39 arranged around the photosensitive drum 33. Yes. The charger 34 charges the surface of the photosensitive drum 33 before the electrostatic latent image is formed to a predetermined potential. The developing unit 35 develops the electrostatic latent image formed on the surface of the photosensitive drum 33 into a visible image with toner as an image forming material. The transfer device 36 transfers the toner image formed on the surface of the photosensitive drum 33 onto the recording paper P. The static eliminator 37 neutralizes the recording paper P after the toner image has been transferred so that the recording paper P can be easily peeled off from the photosensitive drum 33. The cleaning device 38 is configured to remove toner remaining on the surface of the photosensitive drum 33 after toner transfer. The fixing device 39 fixes the toner image transferred to the recording paper P onto the recording paper P by heating.

  Thus, when an image is formed on the recording paper P, the surface of the photosensitive drum 33 is charged to a predetermined potential by the charger 34, and the laser writing unit 31 emits laser light based on the image data to the photosensitive drum 33. An electrostatic latent image is formed by irradiating the surface. Thereafter, the developing device 35 develops a visible image with toner on the surface of the photosensitive drum 33, and the toner image is transferred to the recording paper P fed from the paper transport mechanism 4 by the transfer device 36. Thereafter, the recording paper P is heated by the fixing device 39 to fix the toner image. On the other hand, the toner remaining on the surface of the photosensitive drum 33 is removed by the cleaning device 38. Thereby, one cycle of the image forming operation (printing operation) on the recording paper P is completed. By repeating this cycle, it is possible to continuously form images on a plurality of recording sheets P, P,.

<Description of the paper transport mechanism 4>
The paper transport mechanism 4 includes recordings stored in first, second, and third paper feed cassettes 41, 42, and 43, a manual feed tray 44, and a large-capacity paper feed cassette 61 that can accommodate a plurality of paper types. The paper P, P,... Are conveyed one by one to cause image formation by the image forming unit 3 and the recording paper P on which the image has been formed is discharged to the paper discharge tray 51. Since the digital copying machine 1 is intended to perform high-speed printing processing, the first, second, and third paper feed cassettes 41, 42, and 43 each store 500 to 1500 standard size recording sheets. It has a possible configuration.

  In addition, the paper transport mechanism 4 includes a duplex copying unit 45 that once collects the recording paper P with an image formed on one side and then causes the image forming unit 3 to form an image on the other side. The duplex copying unit 45 can be replaced with a normal paper cassette so that the number of paper cassettes mounted can be increased.

  Each of the paper feed cassettes 41, 42, 43 contains recording papers P, P,... Having different sizes, and the recording paper P from the paper feed cassette containing the recording paper P of the size desired by the user. Are sequentially taken out one by one and conveyed to the image forming unit 3 through the conveyance path 40.

  The transport path 40 of the paper transport mechanism 4 includes a main transport path 46 and a switchback transport path 47.

  The main conveyance path 46 is branched at one end (upstream end in the recording sheet conveyance direction) and faces the discharge side of each of the paper feed cassettes 41, 42, 43, the manual feed tray 44 and the large capacity paper feed cassette 61. At the same time, the other end (downstream end side in the recording paper conveyance direction) faces the post-processing device 50 including the paper discharge tray 51 via the transfer device 36 and the fixing device 39. The post-processing device 50 incorporates a mechanism capable of post-processing such as stapling processing, and a mechanism for raising and lowering the paper discharge tray 51 to switch the paper discharge tray 51 for discharging the recording paper P. Is incorporated.

  One end (upper end in the figure) of the switchback conveyance path 47 is connected to the main conveyance path 46 on the downstream side (left side in the figure) with respect to the position where the fixing device 39 is disposed, and an intermediate part (in the vertical direction in the figure). The central portion is branched into first and second branch paths 47A and 47B. The first branch passage 47A extends vertically downward. On the other hand, one end of the second branch path 47B faces the carry-in side of the duplex copying unit 45.

  First and second branching claws 47a and 47b are provided at the connecting portion between the main transport path 46 and the switchback transport path 47 and at the branch portion of the switchback transport path 47, respectively.

  The first branching claw 47a closes the switchback conveyance path 47, and the second position closes the discharge side of the main conveyance path 46 and connects the main conveyance path 46 and the switchback conveyance path 47. It can freely rotate around the horizontal axis. When the first branching claw 47a is in the first position, the recording paper P that has passed through the image forming unit 3 is discharged to the discharge tray 51 as it is. On the other hand, when the first branching claw 47 a is in the second position, the recording paper P that has passed through the image forming unit 3 is supplied to the switchback conveyance path 47.

  The second branch claw 47b opens the first branch path 47A of the switchback transport path 47 and closes the second branch path 47B, and opens the second branch path 47B and opens the first branch path 47A. It can be freely rotated around the horizontal axis between the closed second position. When the second branch claw 47b is in the first position, the recording paper P transported to the switchback transport path 47 is guided to the first branch path 47A and transported to its lower end position. Thereafter, when the second branching claw 47b is in the second position and the conveyance direction of the recording paper P is reversed, the recording paper P is conveyed to the second branching path 47B through the branching portion and supplied to the duplex copying unit 45. It has come to be. That is, when the recording paper P is supplied to the duplex copying unit 45 through the first branch path 47A and the second branch path 47B, the recording paper P is turned upside down when the recording paper P is supplied to the image forming unit 3. The image can be formed on the back surface of the recording paper P.

  As a result, when single-sided copying is performed by the copying machine 1, the first branching claw 47a is in the first position, and is taken out from each of the paper cassettes 41, 42, 43, the manual feed tray 44, or the large-capacity paper feeding cassette 61. After the recording paper P has been image-formed by the image forming unit 3, it is discharged as it is to the paper discharge tray 51.

  On the other hand, when double-sided copying is performed, first, the first branch claw 47a is in the second position and the second claw 47b is in the first position. As a result, the recording paper P taken out from each of the paper cassettes 41, 42, 43, the manual feed tray 44 or the large-capacity paper feed cassette 61 and formed on one side by the image forming unit 3 It is led to the branch path 47A. Thereafter, the second branching claw 47b is in the second position, the conveyance direction of the recording paper P is reversed, and the recording paper P is supplied from the second branch path 47B to the duplex copying unit 45 through the branching portion. When image formation is performed on the other side of the recording paper P, the first branching claw 47a is in the first position, and the recording paper P taken out from the double-sided copying unit 45 is image-formed by the image forming unit 3 and discharged. The paper is discharged to the tray 51.

  A pickup roller 48 is disposed at the upstream end of the main conveyance path 46 (a portion facing the discharge side of the paper feed cassettes 41, 42, 43, the manual feed tray 44, the duplex copying unit 45, and the large capacity paper feed cassette 61). ing. Further, on the downstream side of each pickup roller 48, a plurality of paper feed rollers 49 for feeding the taken recording paper P to the main transport path 46 are disposed. By the rotation of the pickup roller 48 and the paper feed roller 49, the recording paper P stored in the paper feed cassettes 41, 42, 43, the manual feed tray 44, the duplex copying unit 45 and the large capacity paper feed cassette 61 is selectively 1. Paper can be fed to the main conveyance path 46 sheet by sheet.

  The above is the description of the overall configuration of the digital copying machine 1.

-Description of the fixing device 39 according to the present invention-
FIG. 2 shows the structure of the fixing device 39.
The fixing device 39 includes a fixing unit 390 that houses a heating roller 391 and a pressure roller 392. The fixing unit 390 includes an upper fixing frame 390a that accommodates the heating roller 391 and a lower fixing frame 390b that accommodates the pressure roller 392, and a sheet between the upper fixing frame 390a and the lower fixing frame 390b. In the conveyance path (the path from the right side to the left side in FIG. 2), the paper insertion slot 393 is upstream in the paper conveyance direction X (right side in FIG. 2), and the downstream side in the paper conveyance direction X (left side in FIG. 2). Paper discharge ports 394 are respectively formed. That is, the fixing device 39 is closed by the upper fixing frame 390a and the lower fixing frame 390b except for the paper insertion port 393 and the paper discharging port 394, and the heating roller is provided in the upper fixing frame 390a and the lower fixing frame 390b. 391 and the pressure roller 392 are arranged to face each other in a state of contact. Further, the heating roller 391 and the pressure roller 392 are rotatably supported by the respective frames 390a and 390b via bearings (not shown).

  Further, a sheet peeling claw 395, a roller surface temperature detection member (thermistor) 396, and a roller surface cleaning member 397 are disposed on the outer peripheral portion of the heating roller 391.

  On the other hand, the pressure roller 392 is provided with a pressure member (not shown) capable of pressing the pressure roller 392 with a predetermined pressure amount against the heating roller 391 at both ends of the roller. Further, a paper peeling claw 398 and a roller surface cleaning member 399 are disposed on the outer peripheral portion of the pressure roller 392 in the same manner as the outer peripheral portion of the heating roller.

  In such a fixing device 39, unfixed developer on the recording paper is melted by the surface temperature of the heating roller 391 and the pressing force at the pressing portion 600 (fixing nip portion) between the heating roller 391 and the pressure roller 392. And fixing on the recording paper.

  In the fixing device 39 having such a configuration, in the present embodiment, the air curtain forming means 71 for forming an air curtain is arranged on the upstream side and the downstream side in the sheet conveying direction of the fixing device 39, respectively. That is, as shown in FIG. 2, the air curtain forming means 71 is disposed at the paper insertion port 393 and the paper discharge port 394 of the fixing frames 390a and 390b, respectively.

  The air curtain forming means 71 includes an air blowing portion 711 disposed on the upper side of the paper insertion port 393 and the paper discharge port 394, and an air recovery portion 712 disposed on the lower side of the paper insertion port 393 and the paper discharge port 394. And a circulation path (circulation duct) 713 that circulates the air collected from the air collection unit 712 to the air blowing unit 711. The circulation path 713 includes a blowing fan 714 ( 3) is arranged, and a collecting fan 715 (see FIG. 3) is arranged in the vicinity of the air collecting unit 712. If necessary, one or more suction fans (not shown) may be arranged in the circulation path 713 between the blowout fan 714 and the recovery fan 715.

  As shown in FIG. 3, the air blowing portion 711 and the air recovery portion 712 are formed in a horizontally long shape so as to cover the entire paper insertion port 393 and the paper discharge port 394 formed in a horizontally long shape. As a result, the paper insertion port 393 and the paper discharge port 394 are completely blocked by the air curtain blown from the air blowing portion 711. Further, as shown in FIG. 3, the circulation path 713 first extends in the horizontal direction so as not to cross the sheet conveyance path, and then extends in the up-down direction so that the air blowing part 711 and the air recovery part 712 are connected. It has a structure that connects.

  In the air curtain forming means 71 having such a configuration, the control unit 3A performs air blowing control during operation (standby) of the multifunction machine and printing processing.

  Next, air blowing control by the air curtain forming means 71 having the above configuration will be described with reference to a flowchart shown in FIG. 4 and a diagram showing a heat transfer state inside the fixing device shown in FIG. FIG. 6 shows a heat transfer (diffusion) state in the fixing device when the air curtain forming means 71 is not provided, and will be referred to as appropriate in the following description.

  In the state where the power supply of the multifunction machine itself is not turned on, the fixing device 39 is naturally also in the off state, and the air curtain forming means 71 is also in the off state.

  On the other hand, when the power source of the multifunction device is turned on, the multifunction device enters an operating state, and the fixing device 39 also warms up (preheats), and then shifts to a standby state for accepting a print request (step S1). At this time, the control unit 3A drives and controls the air curtain forming unit 71 to blow out a predetermined amount of compressed air from the air blowing unit 711, collect the air blown out from the air collecting unit 712, and air through the circulation path 713. By circulating to the blowout part 711, an air curtain is formed at the paper insertion port 393 and the paper discharge port 394.

  FIG. 5A shows the state at this time, that is, the internal state of the fixing device 39 in the standby state of the multifunction peripheral. A predetermined pressure of air is blown out from the air blowing portion 711 by the air curtain forming means 71, and the paper insertion port 393 and the paper discharge port 394 are completely blocked from the outside by the air curtain. Therefore, the heat in the fixing device 39 convects inside the device as indicated by the thick arrows in the figure and does not leak out to the outside of the device. Thereby, since the effect of keeping the inside of the fixing device 39 is obtained, the time for heating the heating roller 392 can be shortened, and the energy saving effect of the copying machine itself can also be obtained. Incidentally, when there is no air curtain forming means 71, as shown in FIG. 6A, the heat generated inside the apparatus leaks out from the paper insertion port 393 and the paper discharge port 394.

  When a print request is accepted in this state (Yes in Step S1), the control unit 3A displays a message for prompting input of print conditions on a display unit (not shown) (Step S3), and input of print conditions. Whether or not is completed is monitored (step S2). When the input of printing conditions is completed (Yes in step S2), it is confirmed whether or not an air curtain is formed by the air curtain forming means 71 (step S4). When starting the printing process from the standby state, the air curtain should have been formed (Yes in step S4), but a printing request was made immediately after the MFP itself was started up. In some cases, the air curtain forming means 71 may not be driven yet. Therefore, in that case (that is, when it is determined No in step S4), the control unit 3A drives and controls the air curtain forming means 71 to form an air curtain (step S5).

  Thereafter, the control unit 3A executes an initial operation (initialization process) of the multifunction peripheral (step S6), and monitors whether the initial operation is completed (step S7). When the initial operation is completed, the printing process is started (step S8).

  FIG. 5B shows the internal state of the fixing device 39 immediately after the start of the printing process, that is, in a state where processing such as the transfer process is being performed and the recording paper has not yet reached the fixing process (fixing device 39). ing. This state is the same as the standby state shown in FIG. Incidentally, when there is no air curtain forming means 71, as shown in FIG. 6B, the heat generated inside the apparatus leaks out from the paper insertion port 393 and the paper discharge port 394.

  In this state, the control unit 3A monitors whether or not the leading edge of the recording paper has passed the transfer process (step S9). When the leading edge of the recording sheet passes the transfer process (when it is determined Yes in step S9), the driving of the air curtain forming means 71 disposed on the sheet insertion port 393 side is stopped, and the air blowing unit 711 The air blowing is stopped (step S10). Further, the air curtain forming means 71 arranged on the paper discharge port 394 side is driven and controlled to reduce the amount of air blown from the air blowing portion 711 (step S11). That is, the amount of air blown out is controlled so as not to obstruct the conveyance of the recording paper and to have a cooling effect. FIG. 5C shows the state at this time.

  That is, when the printing process is performed and the recording paper passes through the paper insertion opening 393, the blowing of air on the paper insertion opening 393 side is stopped. Thereby, it is possible to prevent the image due to the unfixed developer on the recording paper from being disturbed by the blowing of air. On the other hand, on the paper discharge port 394 side, by reducing the amount of air blown out, it is possible to cool the recording paper that has completed the fixing process while preventing the heat inside the fixing device 39 from escaping to the outside. Incidentally, when there is no air curtain forming means 71, as shown in FIG. 6C, the heat generated inside the apparatus leaks not only from the paper insertion port 393 but also from the paper discharge port 394. It will be.

  Thereafter, the control unit 3A checks whether or not the trailing edge of the recording paper has passed the fixing process (step S12), and if the trailing edge of the recording paper has passed the fixing process (Yes is determined in step S12). Then, the air curtain forming means 71 on the paper insertion port 393 side is again driven and controlled to start blowing compressed air from the air blowing portion 711 to form an air curtain (step S13). On the other hand, the air curtain forming unit 71 on the paper discharge port 394 side maintains a state in which the amount of air blown from the air blowing unit 711 is reduced until one print job is completed.

  The control unit 3A repeats the processes in steps S8 to S13 until one print job is completed (until No is determined in step S14). When one print job is completed, the printer returns to the standby state again. Incidentally, the state of the air curtain forming means 71 at this time is the state shown in FIG.

  The above is summarized as follows. Since the air curtain forming means 71 arranged on the paper insertion opening 393 side is naturally turned off when the power of the multifunction machine is turned off, the air curtain forming means 71 is also turned off. In the standby state waiting for a print request when the printer is turned on, the air curtain forming means 71 is in a driving state, and compressed air is blown from the air blowing portion 711 to form an air curtain. When there is a print request, on / off control of the air blowing is performed in accordance with the passage of the recording paper. On the other hand, since the air curtain forming means 71 arranged on the paper discharge port 394 side is naturally in the off state when the power of the multi-function peripheral is turned off, the air curtain forming means 71 is also in the off-state. When the power supply is turned on, in the standby state waiting for a print request, the air curtain forming means 71 is in a driving state, and compressed air is blown out from the air blowing portion 711 to form an air curtain. When there is a print request, the air blowing amount switching (large / small) control is performed in accordance with the passage of the recording paper. That is, switching control of the air blowing amount is performed so that the recording paper is large (that is, the same as the standby state waiting for a print request) and small when the recording paper is passing. Yes.

1 is a cross-sectional view illustrating an outline of an internal configuration of a digital copying machine according to the present invention. It is sectional drawing which shows the structure of a fixing device and an air curtain formation means. It is a side view which shows arrangement | positioning of a fixing device and an air curtain formation means. It is a flowchart which shows the air blowing control process by an air curtain formation means. FIG. 7 is an explanatory diagram showing a heat transfer state inside the fixing device of the air blowing control itself by the air curtain forming means. It is explanatory drawing which shows the diffusion state of the heat from a fixing device when there is no air curtain formation means.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Digital copier 2 Scanner part 3 Image forming part 4 Paper conveyance mechanism 39 Fixing device 390 Fixing unit 390a Upper fixing frame 390b Lower fixing frame 391 Heating roller 392 Pressure roller 393 Paper insertion port 394 Paper discharge port 395,398 Paper peeling claw 396 Roller surface temperature detection member 397, 399 Roller surface cleaning member 71 Air curtain forming means 711 Air blowing part 712 Air recovery part 713 Circulation path (circulation duct)
714 Fan for blowout 715 Fan for collection P Recording paper

Claims (6)

In the fixing device that melts and fixes the unfixed developer on the paper by the fixing roller by passing the paper after transfer between the fixing rollers arranged in the fixing frame,
An air curtain forming means for forming an air curtain is arranged on the upstream side and the downstream side of the fixing frame in the sheet conveying direction, respectively.   The fixing device according to claim 1, wherein the air curtain forming unit is disposed at a paper insertion port and a paper discharge port of the fixing frame.   The air curtain forming means blows out air from an air blowing portion disposed at the paper insertion port and the paper discharge port, and collects air blown from an air recovery portion disposed at the paper insertion port and the paper discharge port. The fixing device according to claim 2, further comprising a circulation path that circulates in the air blowing portion.   The air curtain forming means disposed upstream of the fixing frame in the sheet conveying direction during operation of the apparatus stops air blowing while the sheet passes through the sheet insertion port. Item 4. The fixing device according to Item 3.   The air curtain forming means disposed downstream of the fixing frame in the sheet conveyance direction during operation of the apparatus reduces the amount of air blown out while the sheet is passing through the sheet discharge port. The fixing device according to claim 3.   The fixing device according to claim 5, wherein the amount of air blown while the sheet is passing through the sheet discharge port is controlled to an air volume that does not impede conveyance of the sheet and has a cooling effect.

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