JP2011158810A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that does not generate a waiting time and does not reduce the productivity when the recording material and glossiness are changed. <P>SOLUTION: This image forming apparatus includes a fixing belt and nip forming roller. When the recording material and glossiness are changed, the winding length to the nip forming roller of the fixing belt is changed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus for forming an image by an electrophotographic process, and more particularly to improvement of a fixing device in the image forming apparatus.

  For fixing an image formed by an electrophotographic process, a heat fixing device for heating and fusing toner is often used.

  When an image is thermally fixed on a recording material such as paper, the optimum fixing conditions change if the thickness, type, etc. of the recording material are different. For this purpose, for example, Patent Document 1 discloses a technique for changing fixing conditions such as a fixing temperature and a recording material conveyance speed in accordance with the type of recording material.

  In addition, when forming a photographic image or the like, an image is formed by appropriately selecting the glossiness. In the electrophotographic process, the glossiness is changed by changing the melting degree of the toner. . Therefore, even when the glossiness is changed, the fixing temperature and the recording material conveyance speed are changed to change the amount of heat applied to the recording material, thereby changing the melting degree of the toner.

Japanese Patent Laid-Open No. 2003-91110

  When changing the fixing temperature according to the thickness and type of the recording material or according to the setting of the mode for specifying the glossiness, there is a waiting time from when the change is set to when image formation becomes possible There's a problem. That is, when a fixing member such as a fixing roller or a fixing belt is set to a certain level of temperature, it takes time to change the fixing member to another level of temperature.

  Further, when the recording material conveyance speed is changed according to the thickness and type of the recording material or according to the setting of the mode for specifying the glossiness, the process speed of the entire image forming apparatus, that is, the photosensitivity at which an image is formed. Since the rotation speed of the body drum and the conveyance speed of the recording material from paper feeding to paper ejection are changed, the productivity of image formation, that is, the number of images formed per unit time changes. For example, in image formation on thick paper, the recording material conveyance speed in the fixing device is reduced, but this reduces the productivity of image formation.

  The present invention solves such a problem, enables image formation on various thicknesses and types of recording materials without causing waiting time and without changing productivity, or various glossiness. It is an object of the present invention to provide a fixing device and an image forming apparatus that can form an image of the same degree.

  The object is achieved by the following invention.

1. A first roller;
A second roller disposed downstream of the first roller in the recording material conveyance direction;
An endless fixing belt stretched between the first roller and the second roller;
A nip forming roller that contacts the fixing belt and forms a fixing nip from a position where the fixing belt is in contact with the second roller to a position where the fixing belt is separated from the second roller;
A winding length adjusting unit that adjusts a winding length that is a range in which the fixing belt and the nip forming roller are in contact with each other to adjust a nip width of the fixing nip;
A fixing device.

2. The fixing device according to 1;
An image forming apparatus comprising: a control unit that controls the winding length adjusting unit so as to change the winding length according to information corresponding to an adjustment amount of the winding length.

  3. 3. The image forming apparatus according to item 2, wherein the information corresponding to the adjustment amount of the winding length is information relating to the thickness or type of the recording material.

  4). 3. The image forming apparatus according to 2, wherein the information corresponding to the adjustment amount of the winding length is information relating to the glossiness of the image after fixing.

  5. 2. The fixing device according to 1, wherein the winding length adjusting unit includes a moving unit that moves the first roller.

  6). A pressing member disposed between the first roller and the second roller and pressing the fixing belt against the nip forming roller; and the winding length adjusting means moves the pressing member and the pressing member. The fixing device according to 1 above, further comprising a moving unit.

  7). The fixing device according to 1, 5, or 6, wherein the second roller separates a recording material.

  In the present invention, by changing the winding length of the fixing belt around the nip forming roller, it is possible to change the thickness and type of the recording material or change the glossiness. As a result, an image forming apparatus capable of forming an image without changing waiting time and changing the productivity of image formation even when the recording material is changed or the glossiness setting is changed is realized. Is done.

1 is a diagram illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a diagram illustrating an example of a fixing device according to an embodiment of the present invention. FIG. 3 is a diagram illustrating a layer configuration of a fixing belt. It is a block diagram of a control system. It is another example of the fixing device according to the embodiment of the present invention.

Hereinafter, the present invention will be described based on an embodiment of the present invention, but the present invention is not limited to the embodiment.
<Image forming apparatus>
FIG. 1 is a diagram showing an overall configuration of an image forming apparatus according to an embodiment of the present invention.

  The image forming apparatus includes an image forming apparatus main body GH and an image reading apparatus YP. The image forming apparatus main body GH is called a tandem type color image forming apparatus, and includes a plurality of image forming units 10Y, 10M, 10C, and 10K, and an intermediate transfer belt 6 that is an endless belt-like intermediate transfer body. The unit 60, the transfer device 70, the paper feeding / conveying means, the fixing device 80, and the paper discharge device 90 are included.

  An image reading device YP comprising an automatic document feeder 201 and a document image scanning exposure device 202 is installed on the upper part of the image forming apparatus main body GH. The document d placed on the document table of the automatic document feeder 201 is transported by a transport unit, and an image on one or both sides of the document is scanned and exposed by the optical system of the document image scanning exposure device 202, and the line image sensor CCD is scanned. Is read.

  The signal formed by photoelectric conversion by the line image sensor CCD is subjected to analog processing, A / D conversion, shading correction, image compression processing, and the like in the image processing unit, and then exposure means 3Y, 3M, 3C, 3K. Sent to.

  The image forming unit 10Y that forms a yellow (Y) image includes a photosensitive drum 1Y, a charging unit 2Y, an exposure unit 3Y, a developing device 4Y, and a cleaning unit 8Y disposed around the photosensitive drum 1Y. . The image forming unit 10M that forms a magenta (M) color image includes a photosensitive drum 1M, and a charging unit 2M, an exposing unit 3M, a developing device 4M, and a cleaning unit 8M disposed around the photosensitive drum 1M. . The image forming unit 10C that forms a cyan (C) color image includes a photosensitive drum 1C, and charging means 2C, exposure means 3C, developing device 4C, and cleaning means 8C disposed around the photosensitive drum 1C. . The image forming unit 10K that forms a black (Bk) image includes a photosensitive drum 1K, and charging means 2K, exposure means 3K, developing device 4K, and cleaning means 8K disposed around the photosensitive drum 1K. . The charging unit 2Y and the exposure unit 3Y, the charging unit 2M and the exposure unit 3M, the charging unit 2C and the exposure device 3C, and the charging unit 2K and the exposure device 3K constitute a latent image forming unit.

  The intermediate transfer belt 6 is wound around a plurality of rollers and is rotatably supported.

  The fixing device 80 includes an entrance roller 83, a separation roller 84, and a nip forming roller 85. The fixing device 80 conveys the recording material P carrying an unfixed image, and fixes the unfixed toner image on the recording material P in the course of conveyance.

  The images of the respective colors formed in the image forming units 10Y, 10M, 10C, and 10K are sequentially superimposed and transferred onto the rotating intermediate transfer belt 6 by the transfer means 7Y, 7M, 7C, and 7K (primary transfer). An image obtained by combining the color images is formed. The recording material P accommodated in the paper feeding cassette 20 is fed by the paper feeding means 21 and is conveyed to the transfer device 70 through the paper feeding rollers 22A, 22B, 22C, 22D, the registration rollers 23, etc. A color image is transferred onto P (secondary transfer). The recording material P to which the color image has been transferred is heated in the fixing device 80, and the color image on the recording material P is fixed. Thereafter, the paper is sandwiched between a paper discharge roller 91 of the paper discharge device 90 and a corrugation roller 92 which is a pinch roller and is placed on the paper discharge tray 25 outside the apparatus.

On the other hand, after the color image is transferred to the recording material P by the transfer device 70, the residual toner is removed by the cleaning means 8A from the intermediate transfer belt 6 from which the recording material P is separated by curvature.
[Fixing device]
<Embodiment 1>
A fixing device according to Embodiment 1 of the present invention will be described with reference to FIGS.

  The fixing device 80 includes a heater 81, a fixing belt 82, an entry roller 83 as a first roller, a separation roller 84 as a second roller, a nip forming roller 85, an entry guide member 86, and an auxiliary heater 87. Have

  The recording material P guided by the entry guide member 86 and carried into the fixing device 80 is heated by the fixing belt 82 when passing through the fixing nip N. The toner image carried on the recording material P is heated by heating by the fixing belt 82, melted, and fixed on the recording material P.

  The radius of the separation roller 84 is set to such a small value that the recording material P is separated from the fixing belt 82 due to the rigidity of the recording material itself, and the recording material P is separated from the fixing belt 82 when leaving the fixing nip N. To do.

  The heater 81 heats the fixing belt 82 to the fixing temperature. The heater 81 is an induction heating element that generates heat when a high-frequency current is supplied to the coil and an induction current is generated in the resistor. For example, JP 2005-181938 A, JP 2005-228438 A, JP What is disclosed by 2006-3889 gazette etc. is used. An induction heating type fixing device using an induction heating element has an advantage of a short warm-up time. However, a halogen lamp, a resistance heating element, or the like can be used as the heater.

  As shown in FIG. 3, the fixing belt 82 is made of a base material 82a made of nickel, polyimide, etc., an elastic layer 82b made of silicon rubber, and further, PFA (perfluoroalkyl vinyl ether) or PTFE (polytetrafluoroethylene) or the like. It consists of an endless belt on which a releasable surface layer 82c made of fluororesin is formed.

  The entrance roller 83 as the first roller is made of a pipe made of aluminum alloy, carbon steel, stainless steel or the like. The separation roller 84 as the second roller has a base body 84a made of a pipe made of aluminum alloy, carbon steel, stainless steel or the like, and an elastic layer 84b made of silicon rubber formed thereon. As shown in the figure, the fixing belt 82 is moved in the conveyance direction of the recording material P, the entrance roller 83 is disposed on the upstream side in the recording material conveyance direction, and the separation roller 84 is disposed on the downstream side in the recording material conveyance direction. .

  The nip forming roller 85 is made of a base body 85a made of a pipe made of aluminum alloy, carbon steel, stainless steel or the like, an elastic layer 85b made of silicon rubber formed thereon, and a fluororesin such as PFA or PTFE formed thereon. A surface layer 85c is provided.

  The auxiliary heater 87 is a heater for maintaining the temperature of the fixing belt 82 heated by the heater 81, and includes a halogen lamp.

  When the recording material P is a standard paper or a thin paper having a thickness usually used for copying or printing, the entrance roller 83 is in the position of a solid line, but the recording material P is a thick paper thicker than the standard paper. In this case, the position is moved to the position indicated by the dotted line. Note that the heater 81 moves to the position of the dotted line in response to the movement of the entry roller 83, and the heating capability for the fixing belt 82 is maintained constant.

  The fixing nip N is formed in a range where the fixing belt 82 is in contact with the nip forming roller 85. When the entrance roller 83 is at the position of the solid line, the fixing nip N is formed between the point Na where the fixing belt 82 is in contact with the nip forming roller 85 and the point Nc. On the other hand, when the entrance roller 83 is at the position of the dotted line, the fixing nip N is formed between the point Nb where the fixing belt 82 is in contact with the nip forming roller 85 and the point Nc. As the entrance roller 83 moves downward from the position of the solid line to the position of the dotted line, the upstream end of the fixing nip N moves from the point Na to the point Nb and to the upstream side in the conveyance direction of the recording material P. That is, when the entry roller 83 moves from the solid line position to the dotted line position, the range in the recording material conveyance direction in which the fixing belt 82 contacts the nip forming roller 85 becomes long. The fixing nip N is formed in a range where the fixing belt 82 contacts the nip forming roller 85.

  At the point Nc, the fixing belt 82 is nipped by the separation roller 84 and the nip forming roller 85. That is, the fixing belt 82 is in contact with the separation roller 84 at the point Nc. On the other hand, at the points Na and Nb, the fixing belt 82 is separated from the separation roller 84 and is in contact with only the nip forming roller 85. As described above, the nip width is changed by changing the point where the fixing belt 82 is separated from the separation roller 84 and is in contact with the nip forming roller 85 from the point Na to the point Nb.

  A range in which the fixing belt 82 contacts the nip forming roller 85, that is, a range in which the fixing nip N is formed is referred to as a winding length in the following. As the winding length changes, the amount of heat applied to the recording material P changes. In other words, the amount of heat applied to the recording material P is changed by changing the winding length without changing the temperature of the fixing belt 82 or changing the conveyance speed of the recording material P.

  When fixing a toner image on thick paper, a larger amount of heat is required than when fixing a toner image on standard paper, but the winding length of the fixing belt 82 around the nip forming roller 85 is changed as described above. As a result, the amount of heat applied to the recording material P changes, and good fixing to thick paper is performed.

  In the example shown in the figure, the entry roller 83 is moved between two points, the solid line position and the dotted line position, but it can be moved to three or more positions to correspond to various thicknesses of the recording material P. is there. Further, the winding length of the fixing belt 82 can be changed in accordance with the type of recording material such as coated paper or OHP sheet.

  As shown, the entry roller 83 moves, but the separation roller 84 does not move. As described above, since the positional relationship between the nip forming roller 85 and the separation roller 84 is unchanged when the entry roller 83 moves, the separation position of the recording material P from the fixing belt 82 is always constant. Thereby, the transportability of the recording material P in the fixing device 80 is not changed by adjusting the fixing performance due to the movement of the entry roller 83.

  Further, when the recording material P leaves the fixing device 80, there is a phenomenon called blistering in which irregularities are formed on the surface of the recording material due to a sudden release of water vapor from the recording material P, and the fixing property is adjusted. May cause blisters.

  In the illustrated embodiment, the separation roller 84 always presses the recording material P against the nip forming roller 85 with a constant pressure even when the winding length is changed. This prevents blisters even when the fixing property is changed by changing the winding length.

  The surface property of the image, that is, the glossiness is adjusted by adjusting the amount of heat applied to the recording material P in the fixing step.

  The glossiness can be adjusted by adjusting the winding length of the fixing belt 82 around the nip forming roller 85 as shown in the figure. That is, when an image with high glossiness such as a glossy image is formed, the entry roller 83 is moved to the dotted line position so that the winding length of the fixing belt 82 is increased.

  FIG. 4 is a block diagram of a control system that moves the entrance roller 83 in accordance with the thickness and type of the recording material or the glossiness of the image.

In the operation unit OP, information such as the thickness and type of the recording material is input by an operator's operation, and gloss is set by an operator's operation for setting the gloss level such as gloss finish. Similarly, recording material thickness, type information, and information indicating glossiness are input from an external device and input to the control unit CS via the communication unit TS. The control unit CS has an actual adjustment amount of the entry roller 83 corresponding to the input information, and the control unit CS obtains the adjustment amount based on the information from the operation unit OP or the communication unit TS, When the paper is switched with the thick paper or when the mode is switched between the normal mode and the gloss mode, the motor MT as the moving means is operated to move the entry roller 83 to change its position. Then, the winding length of the fixing belt 82 around the nip forming roller 85 is changed. In this way, the control unit CS controls the winding length adjusting means including the entrance roller 83 and the motor MT that moves the entrance roller 83, and changes the winding length of the fixing belt 82 with respect to the nip forming roller 85. Then, the control unit CS changes the winding length based on information from the operation unit OP and the communication unit TS that constitute the paper type information generation unit and the glossiness information generation unit, respectively.
<Embodiment 2>
FIG. 5 shows a fixing device 80 according to the second embodiment. In FIG. 5, the same components as those in FIG. In the second embodiment, a pressing roller 88 as a pressing member makes the fixing belt 82 contact the nip forming roller 85 between the entrance roller 83 and the separation roller 84.

  The pressing roller 88 constituting the winding length adjusting means is driven by the motor MT of FIG. 4 and moved from the solid line position to the dotted line position, thereby forming the upstream end of the fixing nip N from the point Na to the point Nb. By moving, the winding length of the fixing belt 82 around the nip forming roller 85 is changed, and the nip width of the fixing nip N is changed.

  89 is a tension roller.

  The embodiment described above is an example of a fixing device in which a heated fixing belt 82 heats and fixes a toner image, but the present invention is also applied to a fixing device that heats and fixes a toner image by a heating roller. It is possible.

  In such a fixing device, a fixing belt is brought into contact with a heating roller heated by a heater to form a fixing nip. The recording material passing through the fixing nip is heated by a heating roller and fixed. By changing the winding length of the fixing belt around the heating roller as the nip forming roller, the amount of heat applied to the recording material is changed, and the fixing property is adjusted.

  The information for adjusting the winding length is not limited to the above, and may be changed according to environmental changes (temperature, humidity) during use of the image forming apparatus or processing during image formation. Good. Further, if necessary, a service person or the like may be able to directly input the adjustment amount.

  The fixing device shown in FIG. 2 having the following configuration was used.

Heater 81: Dielectric exothermic heater Fixing belt 82: Endless belt made of electroformed Ni and having a 200 μm thick silicon rubber layer (rubber hardness 20 °) formed on a 40 μm thick base material, and a PFA layer formed thereon. : Hard roller with an outer diameter of φ30 made of aluminum alloy Separation roller 84: Roller with an outer diameter of 35φ with a 2 mm thick silicon rubber layer (rubber hardness 50 °) formed on a base made of aluminum alloy Nip forming roller: From aluminum alloy A roller with an outer diameter of 45φ having a 1.5 mm-thick silicon rubber layer (rubber hardness 50 °) formed on the substrate and a PFA layer formed thereon Auxiliary heater 87: halogen heater Recording material conveyance speed: 300 mm / sec
The winding length was changed when switching between standard paper and cardboard, and when switching between normal mode and gloss mode.

  In the following comparative examples, the fixing device shown in FIG. 2 was used, and the fixing property was adjusted by changing the fixing temperature or the conveying speed without changing the winding length.

Comparative Example 1
By changing the fixing temperature, fixing in standard paper fixing, thick paper fixing, normal mode, and gloss mode was performed.

Comparative Example 2
By changing the recording material conveyance speed, fixing in standard paper fixing, thick paper fixing, normal mode, and gloss mode was performed.

  Table 1 shows the waiting time and productivity in Examples and Comparative Examples 1 and 2. In Table 1, a display represented by an arrow such as “standard paper → thick paper” indicates that the image forming process is switched from the image forming process for the standard paper to the image forming mode for the thick paper. The waiting time is a waiting time from the switching operation until fixing is possible.

  In Comparative Example 1, there was a waiting time when the recording material was changed and when the mode was changed.

  In Comparative Example 2, productivity decreased when switching from standard paper to thick paper and when switching from normal mode to gloss mode.

  On the other hand, in the example, no waiting time occurred at the time of the switching, and productivity was not lowered.

80 Fixing Device 81 Heater 82 Fixing Belt 83 Incoming Roller 84 Separating Roller 85 Nip Forming Roller CS Control Unit OP Operation Unit TS Communication Unit

Claims (7)

A first roller;
A second roller disposed downstream of the first roller in the recording material conveyance direction;
An endless fixing belt stretched between the first roller and the second roller;
A nip forming roller that contacts the fixing belt and forms a fixing nip from a position where the fixing belt is in contact with the second roller to a position where the fixing belt is separated from the second roller;
A winding length adjusting unit that adjusts a winding length that is a range in which the fixing belt and the nip forming roller are in contact with each other to adjust a nip width of the fixing nip;
A fixing device. A fixing device according to claim 1;
An image forming apparatus comprising: a control unit that controls the winding length adjusting unit so as to change the winding length according to information corresponding to an adjustment amount of the winding length.   The image forming apparatus according to claim 2, wherein the information corresponding to the adjustment amount of the winding length is information related to a thickness or a type of the recording material.   The image forming apparatus according to claim 2, wherein the information corresponding to the adjustment amount of the winding length is information relating to the glossiness of the image after fixing.   The fixing device according to claim 1, wherein the winding length adjusting unit includes a moving unit that moves the first roller.   A pressing member disposed between the first roller and the second roller and pressing the fixing belt against the nip forming roller; and the winding length adjusting means moves the pressing member and the pressing member. The fixing device according to claim 1, further comprising a moving unit.   The fixing device according to claim 1, wherein the second roller separates a recording material.

Images