JP2008058451A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device 1 lessening power consumption therefor by quickly dissolving dew condensation when dew condensation occurs in the image forming device 1 or quickly warming the inside of the image forming device for dew condensation prevention. <P>SOLUTION: The image forming device 1 has: a fixing device 20 for heating paper form P so that the toner images formed on the paper form P is fused and fixed; a paper conveying passage 70 formed so as to convey the paper form P passing through the fixing device 20 to the paper form conveying upstream side of the fixing device 20 again; and a control means 90 for performing control passing the paper form P through the fixing device 20 for a plurality of times and circulating the paper form P in the image forming device 1. By the configuration, since the warmed paper form P is circulated in the image forming device 1, the inside of the image forming device 1 is quickly warmed and a dew condensation state is quickly dissolved. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus including a copying machine, a printer, a facsimile machine, and the like.

  In general, when an electrophotographic image forming apparatus is placed in a low temperature environment and the image forming apparatus has cooled down, the image forming apparatus is started and image formation is performed in a relatively short time. May cause condensation. For example, in winter, the image forming apparatus is turned off at the end of the company's business, and the image forming apparatus is activated and image formation is performed on the first morning of the next day.

  The reason why condensation occurs will be explained. First, in an electrophotographic image forming apparatus, the fixing device is quickly warmed (generally up to about 200 ° C.) so that it can be used as soon as possible after the image forming apparatus is started. The fixing device here is for heating the paper on which the toner image is placed and fusing and fixing the toner.

  If the fixing device is heated to a temperature at which fixing can be permitted by the heater, the image forming apparatus itself can be used. However, the portions other than the fixing device in the image forming apparatus are in a state of being completely cooled. When image formation is performed in this state, moisture contained in the paper evaporates when passing through the fixing device, but the moisture appears as condensation because it is cooled by a cold member that is not sufficiently warmed.

  Also, the cause of dew condensation is not only due to the relationship with the fixing device. In general, the interior of a room is heated in winter, but dew condensation also occurs when this warm and moist air enters the image forming apparatus using, for example, a cooling intake fan. Since the inside of the image forming apparatus remains cold, dew condensation occurs in the paper conveyance path, the image carrier, the developing device, and the like due to warm and humid air.

  The state in which condensation is likely to continue continues until the entire image forming apparatus is warmed and the temperature difference between the conveyed paper and the image forming apparatus becomes small.

  Due to the above-described causes, when condensation occurs in the image forming apparatus (particularly in the paper conveyance path), there is a problem that the paper conveyed in the image forming apparatus may get wet with water due to condensation. If the paper gets wet with water, the paper discharged after the image formation may wrinkle or the paper may wave. In addition, the quality of an image formed with water may affect the quality of the formed image. Furthermore, the paper may get jammed in the worst case because the paper gets wet.

  To solve the problem of condensation in this image forming apparatus, an invention as disclosed in Patent Document 1 has been proposed. That is, in the patent document, a fixing device, a heater for heating the fixing device, a heater operating circuit, a heater control temperature sensor, a target temperature setting relating to the temperature of the heater at the time of job, standby mode, low power mode, sleep mode Value storage means, heater control means for controlling the temperature of the heater so that the heater temperature becomes the target temperature in each mode, environmental temperature storage means for storing the temperature for determining whether or not the environment tends to condense, There has been proposed an image forming apparatus including a large number of elements such as an environmental temperature sensor and an environment determination unit for determining whether or not the environment is likely to condense (Patent Document 1, Claim 1, Claim 4, Paragraph 0014). .

With this configuration, the image forming apparatus determines whether the environment in which it is placed is likely to condense, and in environments where condensation is likely to occur, the heater is turned on / off in standby mode and low power mode during non-jobs. Control off to prevent condensation. On the other hand, the heater is turned off in the sleep mode. By controlling the heating of the fixing device, power saving is also achieved.
JP-A-2004-20591 (Claim 1, paragraph 0014)

  Thus, it is necessary to prevent problems that occur when condensation occurs in the image forming apparatus. Here, in the invention described in Patent Document 1, when the sleep mode is abnormally long and the image forming apparatus has cooled down, or when the image forming apparatus main body is turned off at the end of work, the image forming apparatus is turned on the next morning. In such a case, since the image forming apparatus is placed in a low temperature environment and the image forming apparatus is cooled down, the paper is wetted, the paper is wrinkled or wavy due to condensation that occurs when the image forming apparatus is activated. Cannot cope with problems such as paper jams.

  Further, in the invention described in Patent Document 1, the temperature of the fixing device is set to a certain level or higher by the heat from the heater, and the temperature in the image forming apparatus is increased to prevent condensation. However, this method simply keeps the fixing device warm and waits for the heat to be gradually transferred through the image forming apparatus. Once condensation occurs, there is a problem that the condensation cannot be resolved.

  Furthermore, the invention described in Patent Document 1 has a problem that the power of the image forming apparatus main body needs to be turned on in order to perform the control. Thus, a certain amount of power continues to be consumed even at night when no image forming apparatus is used. That is, there are various modes such as a sleep mode in which heating of the fixing device is turned off. However, in order to perform control, at least a part related to temperature control of the fixing device must continue to consume power.

  The present invention has been made in view of the above-mentioned problems of the prior art. When condensation occurs in the image forming apparatus, the condensation can be quickly eliminated, and the inside of the image forming apparatus can be prevented to prevent condensation. An object of the present invention is to provide an image forming apparatus that can be quickly warmed up and consumes less power.

  In order to achieve the above object, an image forming apparatus according to claim 1 is provided with a fixing device that heats a sheet and a sheet that has passed through the fixing apparatus in order to melt and fix a toner image formed on the sheet. By using the sheet conveyance path formed to be conveyed to the upstream side of the sheet conveyance of the fixing device and the sheet conveyance path, the sheet is passed through the fixing device a plurality of times, and the sheet is passed through the image forming apparatus. And control means for carrying out control for patrol.

  According to a second aspect of the present invention, in the first aspect of the present invention, an operation unit is provided that allows a user to command the control.

  According to the first aspect of the present invention, since the warmed paper circulates in the image forming apparatus, the heater of the fixing device is simply kept warmed, and compared with the case where the heat waits for the heat to be transmitted through the image forming apparatus. Thus, the inside of the image forming apparatus is quickly warmed. Therefore, even if condensation occurs, the state is quickly eliminated. Further, if the condensation according to the present invention is performed when condensation is likely to occur, the inside of the image forming apparatus can be quickly warmed up, so that condensation can be prevented quickly. Further, since it is not necessary to continuously turn on the image forming apparatus to prevent condensation, an image forming apparatus that consumes less power is provided.

  According to the second aspect of the invention, since the user instructs the control to rotate the paper only when condensation occurs or is likely to occur, the control is performed to rotate the paper only when necessary. The paper is not circulated wastefully. In addition, it is not necessary to employ a complicated configuration in which members such as a control device and a sensor are arranged such as automatic heater control of the fixing device and detection of a dew condensation state in the image forming apparatus.

  Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. In the description of the present embodiment, an example in which a copier is used as the image forming apparatus 1 and the paper P is circulated in the copier is described. However, each element such as configuration and arrangement described in this embodiment does not limit the scope of the invention and is merely an illustrative example.

  First, the outline of the image forming apparatus 1 in the embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic front sectional view showing a schematic configuration of an internal structure of an image forming apparatus 1 according to an embodiment of the present invention.

  As shown in FIG. 1, various apparatuses are built in a box-shaped apparatus main body 1 ', and a plurality of documents placed on the upper part thereof can be automatically and continuously sent. The apparatus 10 is mounted.

  In the apparatus main body 1 ′ of the image forming apparatus 1 according to the present embodiment, the fixing device 20, the paper feed trays 30, 31, 32, 33, the image forming unit 40, the operation unit 50, the image reading unit 60, and paper conveyance A path 70 and the like are provided. On the other hand, a manual feed tray 81 is provided on the right side of FIG. 1 and a discharge tray 82 is provided on the left side of the apparatus main body 1 ′.

  First, as shown in FIG. 1, the fixing device 20 in the present embodiment includes two rollers, a heating roller 21 and a pressure roller 22. The heating roller 21 includes, for example, a heater 23 connected to a power source in a cylindrical cored bar made of metal having excellent thermal conductivity, and an elastic layer is formed on the outer periphery of the cored bar. On the other hand, the pressure roller 22 has an elastic layer formed on the outer periphery of the cored bar, and a heater 23 may be incorporated in the cored bar as an auxiliary. Further, the heating roller 21 and the pressure roller 22 are provided with a film made of, for example, a fluororesin, and the releasability is enhanced.

  These rollers are pressed to form a nip. Then, when the paper P to which the toner has been transferred by the image forming unit 40 described later passes through this nip, the toner and the paper P are pressurized and heated, and the toner is fixed to the paper P. The heating roller 21 and the pressure roller 22 in the fixing device 20 are rotationally driven at a predetermined process speed by a driving device (not shown). One may follow the other. Further, instead of the fixing device 20 having such a configuration, a belt-type fixing device using a fixing belt may be employed.

  In this embodiment, as shown in FIG. 1, a total of four paper feeding trays are provided, which correspond to the paper feeding trays 30, 31, 32, and 33. Each of the paper feed trays 30, 31, 32, and 33 stores paper P having various predetermined sizes such as A size and B size. Each paper feed tray 30, 31, 32, 33 is provided with a pickup roller 34. The pickup roller 34 is rotationally driven in a counterclockwise direction in FIG. 1 by a driving device (not shown). Then, the paper P in contact with the pickup roller 34 is sent out toward the paper transport path 70 one by one.

  Next, the image forming unit 40 includes a photosensitive drum 41 as an image carrier, a charger 42, an exposure device 43, a developing device 44, a cleaning member 45, a transfer roller 46, and the like.

  Therefore, each part constituting the image forming unit 40 will be described. First, the photosensitive drum 41 has a photoconductive layer made of an amorphous silicon photosensitive member or an OPC photosensitive member on the outer peripheral surface of the drum, and is driven at a predetermined rotational speed by a driving device (not shown). It is rotationally driven in the direction.

  The charger 42 is provided on the upper portion of the photosensitive drum 41 and uniformly charges the surface of the photosensitive drum 41 to a predetermined potential. The exposure device 43 is provided above the photosensitive drum 41 and the developing device 44, and forms image data to be formed read by the image reading unit 60 and an image input from a computer connected to the image forming device 1. In response to pixel signals such as characters, the surface of the photosensitive drum 41 is scanned and exposed, and an electrostatic latent image based on image information is formed on the surface of the photosensitive drum 41 charged by the charger 42.

  The developing device 44 is provided on a side portion of the photosensitive drum 41 and plays a role of supplying toner to the photosensitive drum 41 on which the electrostatic latent image is formed and developing the electrostatic latent image as a toner image. The cleaning member 45 is provided on the left side of the photosensitive drum 41 as viewed from the front, and removes and collects transfer residual toner on the surface of the photosensitive drum 41. For example, a drum cleaning roller or a cleaning blade in which an elastic body is formed on the blade. FIG. 1 shows a drum cleaning roller.

  The transfer roller 46 is provided immediately below the photosensitive drum 41, and is formed, for example, by winding a conductive material around the outer periphery of an aluminum shaft. The transfer roller 46 forms a nip with the photosensitive drum 41. When the paper P passes through the nip, a transfer current having a polarity opposite to that of the photosensitive drum 41 is passed through the transfer roller 46, and the toner image on the photosensitive drum 41 is transferred to the paper P. The transfer roller 46 is driven to rotate counterclockwise at a predetermined process speed by a driving device (not shown).

  Here, an image forming operation in the image forming unit 40 will be described. First, the photosensitive drum 41 is charged to a predetermined polarity and potential by the charger 42. Next, laser light controlled based on image data to be formed is irradiated from the exposure device 43 toward the photosensitive drum 41, and an electrostatic latent image based on the image data is formed on the surface of the photosensitive drum 41. . Next, the toner is ejected from the developing device 44, and the toner image is developed from the electrostatic latent image. Next, the toner image is transferred onto the paper P at the nip portion between the transfer roller 46 and the photosensitive drum 41. Thereafter, the toner image on the paper P is heated and fixed by the heating roller 21 and the pressure roller 22 by the fixing device 20 described above. The paper P discharged from the fixing device 20 is discharged out of the apparatus by the conveying means. After the toner image is transferred, the toner remaining on the surface of the photosensitive drum 41 is removed from the photosensitive drum 41 by the drum cleaning member 45 to prepare for the next image formation.

  In FIG. 1, only one image forming unit 40 is provided. However, in the color-compatible image forming apparatus 1, the image forming units 40 may be arranged in parallel by the number of toners of each color. Alternatively, a so-called rotary system in which the developing devices 44 for the respective colors are housed in one rotary, and the rotary is rotated to sequentially face the photosensitive drum 41 so as to face the photosensitive drum 41 may be adopted.

  The operation unit 50 is provided above the image forming apparatus 1. In this embodiment, the operation unit 50 includes a liquid crystal display unit 51, an LED 52, a numeric keypad 53, a start button 54, a stop / clear button 555, a reset button 56, and the like. (See FIG. 3). The user inputs to the operation unit 50 and operates the image forming apparatus 1 such as using the number of copies to be printed or a desired function (double-sided printing function or the like) of the image forming apparatus 1. Details of the operation unit 50 will be described later.

  The image reading unit 60 reads a document to be copied. It comprises a contact glass 61 provided at the uppermost part of the apparatus main body 1 'and an optical system unit 62 provided at the lower part thereof. The contact glass 61 includes a contact glass 61a for reading a document sent from the automatic document feeder 10, and a contact glass 61b for a user to place the document by opening and closing the automatic document feeder 10 upward. It is made up of. The optical system unit 62 irradiates light on the original passing through or placed on the contact glasses 61 a and 61 b, and the reflected light passes through a lens or the like in the optical system unit 62 to be charged by a CCD (Charge Coupled). The document that has been input and read in (Device) is converted into data.

  In the paper transport path 70, the paper P picked up from the paper feed trays 30, 31, 32, 33 passes through the image forming unit 40 and the fixing device 20 and is formed on the side surface of the image forming apparatus 1. It is formed so as to be discharged to the discharge tray 82. Further, the paper transport path 70 in the image forming apparatus 1 of the present embodiment includes a circuit 72 so that the paper P that has passed through the fixing device 20 can be transported and circulated again to the upstream side of the paper transport of the fixing device 20. . More specifically, the paper P that has passed through the fixing device 20 is transported to the upstream side of the paper transport of the image forming unit 40. For example, the sheet conveyance path 70 through which the sheet P can be circulated can be seen by the image forming apparatus 1 having a duplex printing function. The selection of whether to discharge the paper P as it is to the discharge tray 82 or to make a circulation is made by a switching guide 73 provided between the discharge unit 71 and the downstream side of the fixing device 20 in the conveyance direction of the paper P. Done. In FIG. 1, a plurality of circles shown along the paper conveyance path 70 indicate a conveyance roller pair 74. The conveyance roller pair 74 is moved in a predetermined direction by a driving device (not shown). It is driven to rotate so as to convey the paper P.

  A duplex printing tray 75 is provided in the middle of the circuit 72 for circulating the paper P. When performing duplex printing, the paper P is switched back on the duplex printing tray 75. Specifically, the paper P guided to the circuit 72 by the switching guide 73 is provided in the vicinity of one side end portion of the duplex printing tray 75 and is driven to rotate forward and backward by a driving device (not shown). It is pushed onto the duplex printing tray 75 by a possible switchback roller pair 76. However, the switchback roller pair 76 does not completely push the paper P onto the double-sided printing tray 75 but rotates reversely around the rear end of the paper P. When the paper P is pulled out from the double-sided printing tray 75 by this reverse rotation, the paper P is reversed from the original and conveyed toward the image forming unit 40. Note that if the conveyance roller pair 74 provided in the discharge unit 71 is a copier capable of reverse rotation, the discharge unit 71 may be switched back.

  On the other hand, the configuration provided outside the apparatus main body 1 ′ will be described. The manual feed tray 81 is configured to be able to place the paper P, and the pickup roller 34 is provided in the same manner as the paper feed trays 30 to 33. ing. The paper P placed on the manual feed tray 81 can be fed to the upstream side of the image forming unit 40 in the paper conveyance direction. The discharge tray 82 is for receiving the image-formed paper P discharged from a discharge portion 71 provided at the end of the paper conveyance path 70.

  Next, an outline of the control means 90 according to the embodiment of the present invention will be described. FIG. 2 is a block diagram for explaining an embodiment of the control means 90 according to the embodiment of the present invention.

  Note that when the image forming apparatus 1 is used, the image forming apparatus 1 is controlled in various ways, so that the control unit 90 of the entire image forming apparatus 1 is complicated. Therefore, the control unit 90 will be described with respect to parts necessary for the implementation of the present invention. That is, the control unit 90 according to the embodiment of the present invention constitutes a part of all the control units 90 related to the image forming apparatus 1.

  The control unit 90 includes a CPU 91 (Central Processing Unit) as a central processing unit, a ROM 92 (Read Only Memory) that is a read-only storage unit, a RAM 93 (Random Access Memory) that is a readable / writable storage unit, and a temporary image. At least a plurality of I / Fs 96 (interfaces) connected to each device are provided in order to control each device in the image forming apparatus 1 and receive an input in order to control each device in the image forming apparatus 1 and the temporary storage unit 94 that stores data and the like. Yes. Further, the control means 90 can be appropriately arranged inside the apparatus main body 1 ′.

  The ROM 92 stores a control program for the image forming apparatus 1 and data that is not changed during use of the image forming apparatus 1 such as numerical values necessary for control. The RAM 93 stores necessary data generated during the control of the image forming apparatus 1 and data temporarily required for the control of the image forming apparatus 1.

  The counter 95 is used to count the number. For example, when performing the patrol control of the paper P according to the embodiment of the present invention, the counter 95 is used to count the number of patrols. Even if the counter 95 is not provided separately, the number of times may be counted by software, for example, stored in the RAM 93.

  The control unit 90 transmits a control signal from the CPU 91 to the respective units and apparatuses in the image forming apparatus 1 through the I / F 96. In addition, a signal indicating the state and an input signal are transmitted from each part or device to the CPU 91 through the I / F 96. For example, the operation unit 50, the fixing device 20, the heater 23 in the fixing device 20, the image forming unit 40, each conveyance roller pair 74, and the paper feed tray 30 are the parts and devices controlled by the control unit 90 in the present embodiment. , 31, 32, 33 (pickup roller 34), switching guide 73, and the like. The contents of the patrol control of the paper P in this embodiment will be described later.

  Next, the operation unit 50 provided in the image forming apparatus 1 according to the embodiment of the present invention will be specifically described. FIG. 3 is an explanatory diagram illustrating an example of the operation unit 50 according to the embodiment of the present invention.

  As shown in FIG. 3, the operation part 50 which concerns on embodiment of this invention gives a panel-like thing as an example. The operation unit 50 includes a liquid crystal display unit 51, LEDs 52 indicating various states, a numeric keypad 53, a start button 54, a stop / clear button 55, a reset button 56, and the like.

  The liquid crystal display unit 51 displays the state of the image forming apparatus 1, displays the image forming status and the number of copies, and can be used as a touch panel to perform various settings such as functions such as double-sided printing and black-and-white reversal, magnification setting, and density setting. It has become. The numeric keypad 53 is used to set the number of copies to be printed and to input the other party's number when the image forming apparatus 1 also has a FAX function. The start button 54 is used by the user to instruct to start image formation, and the stop / clear button 55 is used to stop image formation. The reset button 56 is used, for example, when setting various settings of the image forming apparatus 1 to a default state. That is, the user operates and inputs the operation unit 50 to perform various settings of the image forming apparatus 1 and execute various functions such as image formation.

  As shown in FIG. 3, a display such as “dew condensation prevention mode” or “recovery mode” can be displayed on the liquid crystal display unit 51 as a part of each function of the image forming apparatus 1. This is for selecting the control for circulating the paper P according to the present invention.

  Next, based on FIGS. 1 to 3, the control / operation for circulating the paper P in the image forming apparatus 1 will be described. The conveyance direction of the paper P is indicated by an arrow in FIG.

  First, in order to perform the patrol control of the paper P according to the embodiment of the present invention, the user can select and input the “condensation prevention mode” or the “recovery mode” with the operation unit 50 (see FIG. 3). As a result, the user issues a command for patrol control of the paper P, so that control is performed so that the paper P is circulated only when necessary, and the paper P is not circulated unnecessarily. Here, the “condensation prevention mode” is intended to prevent a problem caused by paper becoming wet by selecting this mode in advance when condensation is likely to occur, thereby heating the inside of the image forming apparatus 1. . The “recovery mode” is for recovering the situation when condensation actually occurs and the paper P gets wet. Note that it is also possible to provide a difference in the number of circulations of the paper P between the “condensation prevention mode” and the “recovery mode”.

  Also, the occurrence of condensation depends on factors such as the temperature in the area where the image forming apparatus 1 is used and the installation location. Therefore, for example, when condensation frequently occurs, it is possible to set a timer in the “condensation prevention mode”, or when the frequency of condensation occurrence is not high, the “condensation prevention mode” is omitted and the “recovery mode” is omitted. Or only can be selected.

  When the user inputs to the operation unit 50 so as to circulate the paper P in the image forming apparatus 1 to eliminate / prevent condensation, the input signal is transmitted to the CPU 91 through the I / F 96, and the CPU 91 receives the paper P The cyclic control program is read from the ROM 92 to the RAM 93 and activated (see FIG. 2). Thereafter, the program instructs to perform the following operation, and the control unit 90 issues a control signal to output the fixing device 20, the heater 23 in the fixing device 20, the image forming unit 40, and the sheet conveyance. Each conveyance roller pair 74, paper feed trays 30, 31, 32, 33 (pickup roller 34), switching guide 73, and the like in the path 70 are controlled to perform the following operations.

  First, in order to perform the control of the present invention, since the paper P for circulating the paper transport path 70 is required, any one of the paper feed trays 30, 31, 32, and 33 is operated. Then, the paper P is fed into the paper conveyance path 70. Note that the paper P circulated in the image forming apparatus 1 in order to eliminate or prevent dew condensation is basically unusable thereafter, such as wrinkles, undulations, and stains. Therefore, for example, unnecessary paper P such as miscopy paper may be placed on the manual feed tray 81, and the paper P may be sent from the manual feed tray 81 to the paper transport path 70 (see FIG. 1).

  The sheet P sent to the upstream portion of the sheet conveyance path 70 first passes through the image forming unit 40. Here, since the sheet P is merely for eliminating or preventing condensation, the image forming unit 40 basically does not perform image forming operations such as development. However, since the paper P needs to be transported, in the present embodiment, the photosensitive drum 41 and the transfer roller 46 need to be rotated.

  Next, the paper P that has passed through the image forming unit 40 passes through the fixing device 20. Since the fixing device 20 is heated by the heater 23 in the device, heat is applied to the paper P, and the paper P is warmed. Then, the heated paper P is conveyed so as to circulate in the image forming apparatus 1, whereby the inside of the image forming apparatus 1 is heated. It should be noted that the sheet P does not pass through the fixing device 20 because the sheet P is not sufficiently heated even when the image forming apparatus 1 passes the sheet P in a state where the fixing device 20 is not yet sufficiently warmed immediately after the power is turned on. The fixing device 20 is controlled so that it is heated sufficiently.

  Then, the sheet P warmed after passing through the fixing device 20 is conveyed by the switching guide 73 while warming the sheet conveyance path 70 in the direction of the circuit 72 (see FIG. 1). Here, the switchback roller pair 76 may or may not switch the paper P. This is because the sheet P is not transported to the circuit 72 for performing double-sided printing.

  Thereafter, the paper P is transported while warming the circuit 72 and is transported to the upstream side of the image forming unit 40. The sheet P is conveyed toward the image forming unit 40 as it is to warm the image forming unit 40. The paper P that has passed through the image forming unit 40 is again passed through the fixing device 20 and warmed again. Then, the paper P that has passed through the fixing device 20 and has been warmed again is conveyed by the switching guide 73 toward the circuit 72 again. Thereafter, the paper P finally circulates in the image forming apparatus 1 a predetermined number of times, is guided in the direction of the discharge unit 71 by the switching guide 73, and is discharged from the discharge unit 71 to the discharge tray 82. It should be noted that the number of circulations of the paper P may be counted by detecting that the paper P has passed through a switch provided at any location on the paper conveyance path 70 or by providing a sensor. .

  In this way, if the warmed paper P is circulated in the image forming apparatus 1 a plurality of times, the heater 23 in the fixing device 20 is continuously warmed so that the heat is gradually transmitted. The entire image forming apparatus 1 can be warmed much earlier. That is, since the inside of the image forming apparatus 1 is rapidly warmed, dew condensation that has occurred in the image forming apparatus 1 can be quickly eliminated or prevented.

  Here, according to an experiment conducted by the inventor, after the image forming apparatus 1 is placed in a low temperature environment and is completely cooled, the image forming apparatus 1 is turned on and continuously fed onto the paper P by the image forming apparatus 1. When image formation is performed, it has been found that the dew condensation state is eliminated or prevented only by circulating the paper P about 10 times in the image forming apparatus 1. Therefore, if the sheet P is circulated using the number of times of at least 5 times or more and 20 times or less, more preferably at least 8 times or more and 15 times or less as a guide, the number of times is sufficient. In addition, since the cyclic control of the paper P is performed in a normal usable state after the power is turned on, it is necessary to keep the image forming apparatus 1 turned on and prevent condensation all night when the image forming apparatus 1 is not used. The power consumption is obviously reduced. Note that the number of times of circulation may be fixed, for example, 10 times, or the user may be able to input the number of times by input, or the changed number of times may be stored in a separate storage unit. You may make it leave.

  If the paper P patrol control according to the present invention is not performed, when the image forming apparatus is once placed in a low temperature environment and the cooled image forming apparatus is activated, at least 50 sheets to 100 sheets are continuously dewed. The inventor has also confirmed that this is likely to occur. Then, after the image forming apparatus 1 is activated, there is a possibility that the paper P after image formation may be wet, undulated or eventually jammed in the range where image formation is performed on about 100 sheets. Therefore, the present invention can clearly solve the problem caused by condensation.

  As described above, the image forming apparatus 1 according to the present embodiment includes the fixing device 20 that heats the paper P and the paper P that has passed through the fixing device 20 in order to melt and fix the toner image formed on the paper P. By using the sheet conveyance path 70 formed so as to be conveyed again upstream of the sheet conveyance of the fixing device 20 and the sheet conveyance path 70, the sheet P is passed through the fixing device 20 a plurality of times, and the sheet P is fed. The image forming apparatus 1 includes a control unit that performs a control to circulate in the image forming apparatus 1, so that the warmed paper P circulates in the image forming apparatus 1 and simply keeps the heater 23 of the fixing device 20 warm, and the heat is transferred to the image forming apparatus 1. The image forming apparatus 1 is warmed up more quickly than in the case where the information is transmitted to the inside. Therefore, even if condensation occurs, the state is quickly eliminated. In addition, if the control according to the present invention is performed when condensation is likely to occur, the inside of the image forming apparatus 1 can be rapidly warmed, so that condensation can be prevented quickly. Further, since it is not necessary to continuously turn on the image forming apparatus 1 to prevent condensation, the image forming apparatus 1 that consumes less power is provided.

  Further, if the operation unit 50 that can be instructed by the user is provided, the control is performed so that the paper P is circulated only when necessary as instructed by the user, and the paper P is circulated wastefully. Nothing will happen. In addition, it is not necessary to employ a complicated configuration in which members such as a control device and a sensor are arranged, such as automatically controlling the heater 23 of the fixing device 20 and detecting the dew condensation state in the image forming apparatus 1.

  Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the invention.

  In the above embodiment, the case of a copying machine has been described. However, the present invention can be applied to a printer having a double-sided printing function, for example.

  Further, after the image forming apparatus 1 is activated, the patrol control of the paper P may be automatically performed. However, since the paper P is used, it is necessary to enable the user to set the automatic control using the operation unit 50 or the like.

  The present invention can be used in an image forming apparatus 1 such as a copying machine or a printer.

1 is a schematic front sectional view showing a schematic configuration of an internal structure of an image forming apparatus 1 according to an embodiment of the present invention. It is a block diagram for demonstrating embodiment of the control means which concerns on embodiment of this invention. It is explanatory drawing which shows an example of the operation part which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 20 Fixing apparatus 23 Heater 50 Operation part 51 Liquid crystal display part 70 Paper conveyance path 72 Circuit 90 Control means

Claims (2)

A fixing device for heating the paper to melt and fix the toner image formed on the paper;
A paper transport path formed so that the paper that has passed through the fixing device is transported to the paper transport upstream side of the fixing device again;
Control means for controlling the paper to be passed through the fixing device a plurality of times by using the paper conveyance path and the paper to circulate in the image forming apparatus;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, further comprising an operation unit that allows a user to instruct the control.

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