JP2009063738A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of suppressing the occurrence of curling, without uselessly extending the length of warm-up. <P>SOLUTION: The image forming apparatus includes a fixing device 20 which has a pressure roller 21 coming into press-contact with a fixing belt 25, to form a nip portion and a humidity sensor 41 detecting humidity in the apparatus, passes a transfer paper P carrying a toner image to be fixed through the nip portion and applies heat and pressure to the toner of the toner image, to fix the toner image on a record medium, when the transfer paper P passes through the nip potion, and a control section 40 controlling the fixing device 20. When the humidity in an apparatus main body is prescribed humidity or higher, the control section 40 warms up the fixing belt 25 started on the basis of a warm-up start command to prescribed temperature, then, executes additional warm-up for warming up the pressure roller 21 according to the information of the transfer paper P and a copying mode and then, permits image formation. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a printer, a copying machine, and a facsimile machine including a fixing device that fixes a toner image by applying heat and pressure.

  In the image forming apparatus, the transfer paper that has passed through the fixing device may be curled, resulting in a conveyance jam or stacking failure. In recent years, in order to shorten the warm-up time, the fixing member is made of a material / configuration having a small heat capacity, and the fixing member and the pressure member are used to quickly fix the state by supplying almost all electric power to the fixing member during the warm-up. And the temperature difference will increase. In the fixing device, the amount of water evaporation of the transfer paper differs between the front and back, and curling has occurred. As measures for eliminating the curl, there are a method of removing the formed curl and a method of suppressing the occurrence of curl itself.

JP 2005-99373 A

  Since the former of curling countermeasures is equipped with a decurling function such as a decurler in the apparatus, there is a problem that the configuration becomes complicated and the cost is increased. Further, as the latter of the curling countermeasure, as described in Patent Document 1, when the humidity at which curling is likely to occur is high, the warm-up time is extended to reduce the temperature difference between the fixing member and the pressure member, It has been proposed to suppress the occurrence of curling.

  However, curl does not always occur when the humidity is high, but occurs when several conditions are met in addition to the high humidity. Therefore, if the warm-up time is always extended when the humidity is high, the warm-up time shortened by various measures is restored.

  In view of the above-described conventional problems, an object of the present invention is to provide an image forming apparatus capable of suppressing the occurrence of curling without extending unnecessary warm-up.

  In order to achieve the above object, the present invention includes a fixing member heated by a heating unit, a pressure member that presses against the fixing member to form a nip portion, and a humidity detection unit that detects humidity in the apparatus. A recording medium carrying a toner image to be fixed in the nip portion in a direction in which the toner image contacts the surface of the fixing member, and heat and pressure are applied to the toner of the toner image when the recording medium passes through the recording medium. In addition, the image forming apparatus includes a fixing device that fixes the toner image on a recording medium and a control unit that controls the fixing device. When the humidity in the apparatus main body is equal to or higher than a predetermined humidity, the control unit The present invention proposes an image forming apparatus that is controlled so as not to execute the mode of the fixing device for turning off the printer.

  In order to achieve the above object, the present invention provides a fixing member heated by a heating means, a pressure member that presses against the fixing member to form a nip portion, and humidity detection that detects humidity in the apparatus. A recording medium carrying a toner image to be fixed at the nip portion in a direction in which the toner image contacts the surface of the fixing member, and the toner of the toner image is heated when the recording medium passes through the recording medium. And an image forming apparatus having a fixing device that fixes the toner image on a recording medium by applying pressure and a control unit that controls the fixing device. There is proposed an image forming apparatus characterized in that, when transfer sheets having the same size and different vertical and horizontal directions are set in a paper supply unit, image formation is performed by feeding transfer paper that is difficult to curl.

  Furthermore, in order to achieve the above object, the present invention provides a fixing member heated by a heating unit, a pressure member that presses against the fixing member to form a nip portion, and a humidity that detects humidity in the apparatus. A recording medium carrying a toner image to be fixed at the nip portion in a direction in which the toner image contacts the surface of the fixing member, and when the toner image passes through the recording medium, In an image forming apparatus having a fixing device for fixing the toner image on a recording medium by applying heat and pressure, and a control unit for controlling the fixing device, the control unit is configured such that the humidity in the apparatus main body is equal to or higher than a predetermined humidity. Then, after completing the warm-up that the surface of the fixing member that has been started based on the warm-up start command is heated to a predetermined temperature, the second warp that warms the pressure member depending on the information on the recording medium and the copy mode. After running up, it proposes an image forming apparatus characterized by comprising an image forming authorization.

The present invention is effective when the second warm-up is continued until the temperature of the pressure member reaches a predetermined temperature.
Furthermore, the present invention is effective when the second warm-up is executed for a preset time.

  Furthermore, the present invention is effective when the second warm-up setting time is longer as the humidity in the apparatus main body is higher.

  According to the present invention, the warm-up is extended only when the conditions under which curling is likely to occur, and the warm-up is extended so that the curling is unlikely to occur when even one condition with which curling is likely to occur is missing. By not, good operability and cost reduction can be achieved.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic cross-sectional view of an image forming apparatus having an image forming device 2 and a fixing device 20 arranged in the image forming apparatus main body 1. The image forming apparatus 2 shown in FIG. 1 has first to fourth image carriers 3Y, 3C, 3M, and 3K configured as drum-shaped photosensitive members, and a yellow toner image is formed on each of the image carriers. Then, a cyan toner image, a magenta toner image, and a black toner image are formed. An intermediate transfer belt 4 is disposed opposite to the first to fourth image carriers 3Y to 3K, and this intermediate transfer belt 4 is wound around support rollers 5, 6, 7, and 8 and is driven to rotate in the direction of the arrow. Is done.

  The first image carrier 3Y is driven to rotate clockwise in FIG. 1. At this time, the image carrier 3Y is charged to a predetermined polarity by the charging roller 9, and then emitted from the laser writing unit 10 to the charged surface. A light-modulated laser beam is irradiated. As a result, an electrostatic latent image is formed on the image carrier 3Y, and the electrostatic latent image is visualized as a yellow toner image by the developing device 11.

  A primary transfer roller 12 is disposed on the side opposite to the image carrier 3Y with the intermediate transfer belt 4 interposed therebetween, and a transfer voltage is applied to the primary transfer roller 12 so that the toner image on the image carrier 3Y is changed to an arrow. Primary transfer is performed on the intermediate transfer belt 4 traveling in the direction. The residual transfer toner adhering to the image carrier 3Y after the toner image transfer is removed by the cleaning device 13. In exactly the same manner, a cyan toner image, a magenta toner image, and a black toner image are formed on the second to fourth image carriers 3C, 3M, and 3K shown in FIG. 1, respectively, and these toner images are converted into yellow toner images. The toner images are transferred onto the intermediate transfer belt 4 and transferred to the primary transfer, and a toner image is formed on the intermediate transfer belt 4.

  On the other hand, as shown in FIG. 1, in the lower part of the image forming apparatus main body 11, a paper feed cassette 14 containing a recording medium made of, for example, transfer paper P and a paper feed device having a paper feed roller 15 are arranged. The uppermost transfer paper P is fed in the direction of the arrow by the rotation of the paper feed roller 15. The fed transfer paper P is fed by a registration roller pair 16 between the portion of the intermediate transfer belt 4 wound around the support roller 5 and the secondary transfer roller 17 disposed on the support roller 5 at a predetermined timing. Sent. At this time, a predetermined transfer voltage is applied to the secondary transfer roller 17, whereby the superimposed toner image on the intermediate transfer belt 4 is secondarily transferred to the transfer paper P.

  The transfer paper P onto which the toner image has been secondarily transferred is further conveyed upward and passes through the fixing device 20, and at this time, the toner image on the transfer paper is fixed by the action of heat and pressure. The transfer paper P that has passed through the fixing device 20 is discharged to the paper discharge unit 18 at the top of the image forming apparatus main body 1. Further, the transfer residual toner adhering to the intermediate transfer belt 4 after the toner image transfer is removed by the cleaning device 19.

  FIG. 2 is an enlarged front view of the fixing device 20 shown in FIG. 1 and 2 includes a pressure roller 21, a fixing roller 22, a tension roller 23, and a heating roller 24. The fixing roller 22, the tension roller 23, and the heating roller 24 include Is wrapped around an endless fixing belt 25. As described above, the fixing belt 25 of the fixing device of this example is wound around the three support rollers 22, 23, and 24. The number of the support rollers can be appropriately selected. In short, the fixing belt 25 may be wound around the fixing roller 22 and at least one other supporting roller.

  Heaters 30 and 31 as heating means are provided inside the heating roller 24 and the pressure roller 21, respectively, and the pressure roller 21 and the fixing belt 25 are heated by the heaters 30 and 31. At this time, contact type thermistors 26 and 27 are provided as temperature detecting means around the heating roller 24 and the pressure roller 21, respectively, and the pressure roller 21 and the fixing belt 25 are connected to the toner image based on the detected temperature of the thermistor. At a temperature suitable for fixing. Note that a thermopile may be used as the temperature detection means instead of the thermistor.

  The pressure roller 21 is rotationally driven in the direction shown in FIG. 2, whereby the fixing belt 25 is driven in the direction of the arrow, and accordingly, the fixing roller 22 and the heating roller 24 are counterclockwise in FIG. Followed rotation. At this time, as described above, the transfer paper P carrying the toner image secondarily transferred from the intermediate transfer belt 4 shown in FIG. 1 is guided to the entrance guide 29A and the nip between the pressure roller 21 and the fixing belt 25 is reached. The toner image comes into contact with the surface of the fixing belt 25. As a result, heat and pressure are applied to the toner image carried on the transfer paper P, the toner of the toner image is melted, and the toner image is fixed on the transfer paper P. Reference numeral 28 denotes a separation plate for preventing the transfer paper P from being wrapped around the fixing belt 25, and 29B denotes an exit guide for the transfer paper P.

  By the way, as described above, the transfer paper P that has passed through the fixing device 20 may be curled to cause a conveyance jam or a stacking failure. Therefore, the present inventor considered the conditions under which curls are formed. As a result, it was found that there are several conditions that are likely to cause curling, and curling occurs when all of these conditions are met. The condition is firstly humidity. When the humidity is high, for example, when the humidity detected by the humidity sensor 41 provided in the apparatus main body is 60% or more, secondly, the fixing belt 25 and the pressure roller 21. When the temperature difference is large, the third recording medium used is plain paper.

  Therefore, curling is difficult if one of these conditions is missing, but it is not rare that the three conditions are satisfied, but it is necessary to take measures against curling. The curl countermeasure is controlled according to the flow of FIGS. 4 to 6 using the control device of FIG.

  In FIG. 4, when the temperature of the fixing belt 25 is lower than the fixable temperature when the power is turned on or a print command is issued, the control unit 40 issues a warm-up start request (step 1). Then, the heater 30 is turned on (step 2) and checked, and the warm-up is performed until the temperature of the fixing belt 25 reaches the fixable temperature (step 3).

  Thus, when the print request in step 4 is received when the warm-up is completed, it is determined whether the humidity in step 5 is 60% or higher. If the humidity does not reach 60%, curling may occur. Is very small, printing is immediately permitted in step 9 and printing is executed. If the humidity is 60% or higher in step 5, it is determined whether the transfer paper P in step 6 is plain paper. If the transfer paper P is not plain paper, the possibility of curling is very small, so that the printing is immediately permitted in step 9 and printing is executed. Further, when the transfer paper P is plain paper, there is a high possibility of curling, so the heater 30 is turned on while rotating the fixing roller as an additional warm-up (step 7). This additional warm-up is performed until the pressure roller 21 reaches a certain temperature (step 8), and when the pressure roller 21 reaches that temperature, the temperature difference from the fixing belt 25 becomes a difference in which curling is unlikely to occur. It is assumed that the print job is permitted in step 9 and printing is executed.

  As described above, according to the present invention, when the warm-up is completed, it is determined whether or not the curl is likely to be generated, and the additional warm-up is executed only when the curl is likely to occur. Cost reduction and improved operability. Note that curl is more likely to occur as the humidity increases. Therefore, the set temperature of the pressure roller that completes the additional warm-up can be varied according to the humidity level, and the additional warm-up time can be increased as the humidity increases. desirable.

By the way, if the conditions for easily curling can be further narrowed down, useless warm-up can be further reduced.
Therefore, when the conditions for easy curling were inferred from experiments, for example, even plain paper has a tendency to curl easily depending on the gap and paper feeding direction. It turned out to be difficult. In addition, when the paper size is a standard size such as A4 size, ordinary plain paper is likely to curl in the transverse paper conveyed in the short direction and difficult to curl when conveyed in the longitudinal direction. I understood.

This condition is shown in the flowchart of FIG. 5 in which step 6 of the flowchart of FIG. 4 is changed.
In FIG. 5, step 6 is added to determine whether or not the sheet is in landscape mode (step 6A) and to determine whether it is a single-sided mode (step 6B). With this configuration, even when the additional warm-up is performed, it is not necessary to perform the additional warm-up in the case of longitudinal paper feeding or in the duplex mode.

  As described above, it is difficult to curl in the sheet passing direction of the transfer paper. Therefore, when transfer paper of the same size but different direction is set in the paper feeding unit, curling is performed even if conditions for easy curling are met. The use of transfer paper in a direction that is difficult to curl can suppress curling. FIG. 6 is a flowchart showing an example of such control.

  In FIG. 6, if there is a print request for A4 size horizontal paper in step 1, it is determined whether the conditions for easy curling are met (step 2). A sheet is printed (step 3). When the curling conditions are met, a search is made for the presence of A4 size longitudinal paper on another tray (step 4), and it is determined whether or not it is set (step 5). When the sheet is set, image processing (step 6) rotated by 90 ° is performed, and then printing is performed on the transfer paper of A4 size longitudinal paper (step 7). In step 5, when an A4 size longitudinal paper transfer sheet is not set, an additional warm-up in step 8 is performed to eliminate one condition that is likely to curl, and then an A4 size paper is printed in step 3. .

Thus, the occurrence of curling can be suppressed by skillfully utilizing the paper passing direction in which the transfer paper is difficult to curl.
Further, since the curl is generated when the humidity in the apparatus is high, when the humidity is higher than a predetermined value, for example, 60%, the main body power is turned off so as not to increase the temperature difference between the fixing belt 25 and the pressure roller 21. Control not to enter the mode or sleep mode. In this way, in the standby state when the humidity is high, by not entering the off mode or the sleep mode, the pressure roller 21 is supported in a state where the temperature is high to some extent, so that curling can be suppressed.

  Further, as shown in FIG. 7, when it is recognized that the humidity is high, that is, when it is recognized that the humidity is 60% or more, the fixing set temperature is lowered by a predetermined temperature. For example, by lowering the fixing set temperature 160 ° C. by a predetermined temperature 10 ° C. to 150 ° C., the temperature difference between the fixing belt 25 and the pressure roller 21 can be reduced and curling can be suppressed.

It is a schematic sectional drawing which shows an example of an image forming apparatus. 1 is a configuration diagram illustrating a fixing device according to the present invention. 2 is a block diagram of a control device that controls the fixing device. FIG. It is a flowchart which shows an example of control by the control part of FIG. It is a flowchart which shows another example of control by the control part of FIG. It is a flowchart which shows another example of control by the control part of FIG. It is a flowchart which shows the example of control in another embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 20 Fixing device 21 Pressure roller 22 Fixing roller 24 Heating roller 25 Fixing belt 26, 27 Heater 30, 31 Thermistor 40 Control part 41 Humidity sensor

Claims (6)

A fixing member that is heated by a heating unit; a pressure member that presses against the fixing member to form a nip portion; and a humidity detection unit that detects humidity in the apparatus main body, and should be fixed to the nip portion. A recording medium carrying a toner image is passed in such a direction that the toner image comes into contact with the surface of the fixing member, and heat and pressure are applied to the toner of the toner image during the passage to fix the toner image to the recording medium. In an image forming apparatus having a fixing device for controlling and a control unit for controlling the fixing device,
The image forming apparatus according to claim 1, wherein the control unit performs control so as not to execute the mode of the fixing device for turning off the main body power when the humidity in the apparatus main body is equal to or higher than a predetermined humidity. A fixing member that is heated by a heating unit; a pressure member that presses against the fixing member to form a nip portion; and a humidity detection unit that detects humidity in the apparatus body, and should be fixed to the nip portion. A recording medium carrying a toner image is passed in such a direction that the toner image comes into contact with the surface of the fixing member, and heat and pressure are applied to the toner of the toner image during the passage to fix the toner image to the recording medium. In an image forming apparatus having a fixing device for controlling and a control unit for controlling the fixing device,
When the humidity inside the main body of the apparatus is equal to or higher than the predetermined humidity, the control unit feeds a transfer sheet that is difficult to curl when a transfer sheet having the same size and different vertical and horizontal directions is set in the paper supply unit. An image forming apparatus. A fixing member that is heated by a heating unit; a pressure member that presses against the fixing member to form a nip portion; and a humidity detection unit that detects humidity in the apparatus body, and should be fixed to the nip portion. A recording medium carrying a toner image is passed in such a direction that the toner image comes into contact with the surface of the fixing member, and heat and pressure are applied to the toner of the toner image during the passage to fix the toner image to the recording medium. In an image forming apparatus having a fixing device for controlling and a control unit for controlling the fixing device,
When the humidity inside the apparatus main body is equal to or higher than a predetermined humidity, the control unit completes the warm-up that starts the surface of the fixing member to a predetermined temperature based on a warm-up start command, and then uses the information on the recording medium and the copy mode. The image forming apparatus is characterized in that after the second warm-up for warming the pressure member is performed, image formation is permitted.   4. The image forming apparatus according to claim 3, wherein the second warm-up is continued until the temperature of the pressure member reaches a predetermined temperature.   4. The image forming apparatus according to claim 3, wherein the second warm-up is executed for a preset time.   6. The image forming apparatus according to claim 5, wherein the second warm-up setting time is longer as the humidity in the apparatus main body is higher.

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