JP2010049178A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems wherein a small-diameter peeling roller is arranged in a nip outlet in order to improve the peelability, but there is patterning where a belt deforms into the shape of the roller during stopping, bending stress of repetition in a peeling roller section is high, and lifetime of the belt reduces. <P>SOLUTION: An image forming apparatus includes a rigidity detecting means for detecting the rigidity of paper, an image pattern recognizing means for recognizing an image to be recorded on the paper, and a determining means for determining movement of the peeling roller based on signals from the rigidity detecting means and the image pattern recognizing means. The peeling roller is moved so that the paper discharging direction of the nip formed by a pressurizing roller and a backup roller in response to a signal from the determining means substantially matches with the belt surface to the peeling roller. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus that heats and fixes toner onto a sheet using toner.

  An electrophotographic image forming apparatus forms a latent image on a photosensitive member by laser scanning, attaches toner to the latent image by a developing unit, transfers the toner image to an intermediate transfer belt by a first transfer unit, The second transfer unit transfers the toner image from the intermediate transfer belt to the paper, and the fixing device melts and fixes the toner on the paper with heat and pressure.

  In the fixing device, a backup roller is pressed against a heated roller or belt to form a nip portion that sandwiches the paper, and pressure and heat are applied to the toner on the paper while the paper is conveyed.

Japanese Patent No. 3155804

  Here, when the paper is thin and has low rigidity, the paper may be wound around a roller or a belt due to the adhesion force of the melted toner. Patent Document 1 describes that one of the rollers that stretch the belt is constituted by a small-diameter peeling roller.

  For example, when the surface of a toner layer of two or more colors is formed near the leading edge of the paper and is close to the full width of the paper, the paper becomes very easy to wind when the paper thickness is about 0.07 mm. In order to stably peel even such an image and paper thickness, the diameter of the peeling roller is desirably 10 mm or less.

  However, when the belt is wound around such a small-diameter roller, the belt is curled while the apparatus is stopped, and as a result, uneven glossiness of the image occurs in the next fixing operation. In addition, since the bending stress increases with a small radius of curvature, the life of the belt also decreases.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus having a long-life fixing device that does not wind a sheet.

  In order to achieve the above object, the present invention includes a latent image forming unit that forms a latent image on a photoconductor, a developing unit that forms a toner image by attaching toner to the latent image, and a toner image on the photoconductor. An intermediate transfer belt to which the toner image is transferred, a first transfer means for transferring the toner image on the photosensitive member to the intermediate transfer belt, a paper transport means for transporting paper, and a toner image on the intermediate transfer belt as paper. The present invention is intended for an electrophotographic image forming apparatus having a second transfer means for transferring the toner image on the paper and a fixing device for fusing and fixing the toner image on the paper.

According to the first means of the present invention, the fixing device is stretched between a heating roller, a pressure roller whose surface is an elastic body, a tension roller, and the heating roller, the pressure roller, and the tension roller. A fixing belt, a backup roller pressed against the pressure roller via the fixing belt, a peeling roller movable along the outer periphery of the pressure roller and having a smaller diameter than the pressure roller, and the peeling A moving means for moving the roller in the paper conveyance direction at the nip portion exit of the pressure roller and the backup roller,
Rigidity detection means for detecting the rigidity of the paper, image pattern recognition means for recognizing an image recorded on the previous paper, and judgment for determining the movement of the peeling roller from signals of the rigidity detection means and the image pattern recognition means Means and
The separation roller is moved in accordance with a signal from the determination means so that the sheet discharge direction of the nip portion and the surface of the fixing belt up to the separation roller substantially coincide with each other. .

  The second means of the present invention is characterized in that, in the first means, a peeling claw that can be retracted in accordance with the movement of the peeling roller is provided in the vicinity of the exit of the nip portion of the pressure roller and the backup roller. It is.

  According to a third means of the present invention, in the first or second means, the peeling roller is hollow and cooled by a gas or a liquid.

  The present invention is configured as described above, and can provide an image forming apparatus having a long-life fixing device without winding a sheet.

  The first means is configured as described above, and if the toner image of two or more colors is not formed as a wide solid image, the paper is thin and does not wind even if the rigidity is low. The image is recognized by, the result is judged by the judging means, and the peeling roller is not used. Further, if the paper is thick and has high rigidity, even if a toner image of two or more colors is formed on almost the entire surface near the leading edge of the paper, it will not be wound. Therefore, the result of the rigidity detection means is judged by the judgment means, and the peeling roller Is not used. By reducing the frequency of using a small-diameter peeling roller in this way, it is possible to extend the life of the belt.

  On the other hand, by moving the peeling roller to a position where the paper discharge direction of the nip formed by the backup roller and the belt surface to the peeling roller coincide with each other, when the peeling roller is retracted and when using the peeling roller, The same transport path can be used without changing the transport direction.

  In the second means, a peeling claw that can be retracted according to the movement of the peeling roller is provided near the exit of the nip portion of the pressure roller and the backup roller.

  Even if the paper is thin and has low rigidity, and a toner image of two or more colors is formed in almost the full width, it is possible to peel off the paper with a peeling claw if there is sufficient margin from the leading edge of the paper to the image (for example, 5 mm or more). is there. If the image pattern recognition means recognizes that this margin (or a line image or character with a print density that can be considered to be a margin) is a sufficient distance from the leading edge of the paper, the judgment means does not move the peeling roller, but the peeling roller moves. Peel off the paper using the nail. If the margin is insufficient and the paper rigidity is low, a peeling roller is used, in which case the peeling claw is retracted.

  Since the frequency of using the peeling roller is further reduced, the life of the belt can be further improved.

  In the third means, the peeling roller is cooled by gas or liquid. By cooling the peeling roller, the peelability is improved, and it is possible to use thin paper with lower rigidity. Further, it is possible to give gloss to the image by peeling off the toner after cooling. Furthermore, if a peeling roller cooled constantly is used, the heat removed from the belt by cooling must be supplied by the heating roller, which increases power consumption. Therefore, thermal efficiency is good.

  Next, embodiments of the present invention will be described with reference to the drawings. 1 to 3 are views for explaining a fixing device 60 according to an embodiment of the present invention, and FIG. 1 shows a state in which the peeling roller 66 is retracted.

  The belt 61 is stretched around a pressure roller 63, a heating roller 62, and a tension roller 65. The material of the belt is polyimide with a thickness of 80 to 100 μm, and the surface is coated with a fluorine resin of about 30 μm in order to improve the peelability. In order to improve the fixability of paper having a rough surface, a silicon rubber layer of several hundred μm may be provided between the coat layer and the polyimide layer on the surface.

  The backup roller 64 is pressed against the pressure roller 63 by a spring or the like. A heater 68 is provided in the heating roller 62, and the belt surface temperature is measured by a temperature sensor (not shown) and controlled to maintain a predetermined fixing temperature. The pressure roller 63 and the backup roller 64 are rotated by a drive mechanism (not shown) to convey the paper 4 in the direction of arrow a in the figure.

  The pressure roller 63 has a low hardness rubber layer 631, and the backup roller 64 has a high hardness rubber layer 641. By pressurizing the backup roller 64, the nip shape becomes concave on the pressure roller 63 side, and the paper 4 is discharged in a direction away from the pressure roller 63.

  The peeling claw 67 is disposed near the exit of the nip portion between the pressure roller 63 and the backup roller 64. In this drawing, the peeling roller 66 is in a retracted state and is not in contact with the belt 61.

  FIG. 2 shows a state where the peeling roller 66 has moved. As shown in the figure, the peeling roller 66 moves to a position where the discharge direction of the paper 4 from the nip exit coincides with the surface of the belt 61. Therefore, although not shown, there is no need to change the conveyance path after the fixing device 60. In this state, the peeling claw 67 is retracted so as not to hit the peeling roller 66.

  The tension roller 65 is lowered by the movement of the peeling roller 66 to prevent the belt 61 from being abnormally tensioned.

  The diameter of the peeling roller 66 is 15 mm or less, and 10 mm or less is desirable in the case of a fixing device that does not have an oil application mechanism. If the peeling roller 66 is made hollow, the peeling roller 66 is cooled with gas or liquid, and the temperature of the surface of the belt 61 is made 140 ° C. or less, the peelability is improved. In that case, the diameter may be made 20 mm or less. . In the case of cooling, in addition to improving the releasability, there is an effect of giving gloss to the toner image.

  FIG. 3 shows the configuration of the operating mechanism of the peeling roller 66.

  The peeling roller 66 is supported by a support arm A661, and the support arm A661 is rotated in the direction of arrow c in the figure by a drive mechanism A662. The fulcrum of the support arm A661 is made to coincide with the rotation center of the pressure roller 63. As a result, it is possible to move to a position where peeling is performed and a position where the belt 61 is retracted so as not to contact the belt 61 by a simple rotation operation, and the configuration of the moving mechanism can be simplified.

  The peeling claw 67 is supported by the support arm B671, and the support arm B671 is rotated in the direction of the arrow d in the figure by the drive mechanism B672. The tension roller 65 is supported by a support arm C651, and applies tension to the belt 61 with a spring or the like (not shown). When the peeling roller 66 moves, the support arm C651 rotates in the direction of the arrow b in the figure corresponding to the change in the trajectory of the belt 61.

  The determination unit 601 gives an operation instruction for the drive mechanism A 662 and the drive mechanism B 672 in accordance with signals from the rigidity detection unit 201 and the image pattern recognition unit 202.

  FIG. 4 is a flowchart for explaining the operation of the embodiment of the present invention.

  First, it is determined whether or not to give gloss to the image. This is in accordance with an instruction from an operator of the image forming apparatus. In order to give gloss, the peeling roller 66 is moved. If no gloss is given, the possibility of winding the paper is determined below.

  The determination unit 601 obtains margin information from the image pattern recognition unit 202 and determines whether the margin is sufficient. For example, if the margin is 10 mm or more, it is determined that peeling with the peeling claw 67 is possible, and the next image information is awaited. If the margin is insufficient, information on the image is obtained from the image pattern recognition means 202, and if it is not a solid image with more than two colors and close to the full width of the paper, it is determined that no wrapping will occur and information on the next image is obtained. wait.

  When there is a possibility of winding with a solid image having two or more colors and close to the full width of the paper, the information of the rigidity detecting means 201 is obtained, and it is determined whether or not peeling is possible by the rigidity of the paper. If it is above, peeling is possible, and information on the next image is awaited. If it is determined that the rigidity of the paper is insufficient, the driving mechanism A 662 and the driving mechanism B 672 are operated, and the peeling claw 67 is retracted and the peeling roller 66 is moved to a predetermined position as shown in FIG. I do.

  According to this embodiment, it is possible to reduce the frequency of use of the peeling roller 66, and it is possible to prevent the belt 61 from being wrinkled or broken due to repeated stress while using a small-diameter roller having good peelability. The image quality and life of the fixing device can be improved. Furthermore, it is possible to cool the peeling roller 66 to give gloss to the image. When the gloss is not necessary, the peeling roller 66 is retracted to prevent the heat of the belt 61 from being taken away, thereby preventing an increase in power consumption. It becomes possible.

  FIG. 5 is a schematic configuration diagram of the rigidity detecting means 201.

  The thickness detection roller 27 is supported so as to be movable up and down in the drawing, and is pressed against the transport roller 25 by a spring C26. The displacement sensor A20 measures the vertical movement of the thickness detection roller 27.

  A paper detection sensor 29 is disposed downstream of the thickness detection roller 27 and the conveyance roller 25. The transport roller 25 is rotated in the direction of arrow e in the figure by a driving unit (not shown). The transport roller 25 is preferably a rubber roller in order to secure a frictional driving force for transporting the paper, and a hardness of 50 degrees (Asker A type) or more is desirable in order to increase the thickness detection accuracy.

  The rigidity detection lever 33 is supported so as to be rotatable about a fulcrum B36. The spring B32 pulls the rigidity detection lever 33 in the direction of arrow f in the figure and abuts against the stopper 37. The displacement sensor B30 measures the rotational displacement of the rigidity detection lever 33.

  The surface of the registration roller A41 is metal, and the surface of the registration roller B42 is rubber. The registration roller B42 is rotated by a driving mechanism (not shown) to convey the paper in the direction of arrow g in the figure.

  The conveyed paper pushes up the thickness detection roller 27, and the displacement sensor A20 measures the displacement.

  Further, the rigidity detection lever 33 is rotated by the rigidity of the paper, and the output of the displacement sensor B30 is changed. Outputs of the displacement sensor A20 and the displacement sensor B30 are input to the data processing unit 38, and the data processing unit 38 obtains the rigidity of the paper.

  The stiffness of the paper may be obtained only from the thickness of the paper obtained from the value of the displacement sensor A20. However, when the sheets are double-fed, the apparent thickness is thick, but the rigidity of one sheet may be low and the sheet may be wound. If the values of the displacement sensor A20 and the displacement sensor B30 are used, the rigidity can be reliably detected.

  The paper detection sensor 29 detects the leading edge of the paper and conveys the paper at a predetermined distance therefrom. This distance is set to such an amount that the skew can be corrected by pressing the leading end of the sheet against the nip portion between the registration roller A41 and the registration roller B42. After the skew correction, the registration roller A41 and the registration roller B42 convey the paper.

  FIG. 6 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention.

  The image forming apparatus 1 arranges development units 501 to 504 for each color on the transfer belt 2, forms a color image with toner on the transfer belt 2, and transfers the color image to a sheet conveyed from the sheet accumulation unit 4. Then, the fixing device 60 melts and fixes the toner with heat and pressure to form a color image.

  There are four types of developing units: a K developing unit 501 having black toner, a C developing unit 502 having cyan toner, an M developing unit 503 having magenta toner, and a Y developing unit 504 having yellow toner. The developing unit includes a toner hopper 53 that stores toner, a developing roller 52 that forms a toner layer and contacts the photosensitive drum 54 with the toner, a drum cleaner 57 that cleans the photosensitive drum 54, and a charger that charges the photosensitive drum 54. 55, an exposure unit 56 for writing an electrostatic latent image on the photosensitive drum 54.

  The intermediate transfer belt 2 is stretched around a plurality of rollers and is conveyed by a belt driving roller 3. The belt cleaner 91 removes residual toner on the intermediate transfer belt 2. The primary transfer roller 58 is disposed inside the intermediate transfer belt 2 so as to face the photoconductive drum 54.

  The sheet conveyance path 8 passes from the sheet accumulation unit 4 that accumulates sheets, passes between the secondary transfer roller 7 and the intermediate transfer belt 2 via the pick roller 9, the separation roller 11, and the rigidity detection unit 201, and is conveyed to the conveyance belt 81. To the fixing device 60. A conveyance path switching guide 70 for switching the conveyance path is provided downstream of the rigidity detection device 201, and a sheet determined to be double-fed from the thickness and rigidity of the sheet is sent from the double-fed paper withdrawal path 71 to the double-fed paper withdrawal unit 72. .

  When an image is formed, the surface of the photosensitive drum 54 is charged by the charger 55, and light corresponding to the image is applied by the exposure device 56 to drop the potential on the photosensitive drum 54. The portion reaches the developing roller 52 by the rotation of the photosensitive drum 54, and when it comes into contact with the toner layer, the charged toner adheres to the image position and a toner image is formed.

  The toner image on the photosensitive drum 54 is transferred onto the intermediate transfer belt 2 at a portion where the primary transfer roller 58 presses the intermediate transfer belt 2.

  The toner image on the photosensitive drum 54 of each developing unit is transferred onto the intermediate transfer belt 2 to form a color toner image. As the intermediate transfer belt 2 is conveyed, the toner image is transferred onto the sheet conveyed at the site of the secondary transfer roller 7. The sheet on which the toner image is transferred is conveyed to the fixing device 60 by the conveyance belt 81, and the toner is melted and fixed by heat and pressure to form a color image.

  When the image pattern recognition unit 202 and the rigidity detection unit 201 determine that the peeling roller 66 is necessary, the peeling roller 66 is moved to peel the paper. The peeling roller 66 is also moved when it is instructed that the image needs to be glossy.

  According to this embodiment, it is possible to reduce the frequency of use of the peeling roller 66, and it is possible to prevent the belt 61 from being wrinkled or broken due to repeated stress while using a small-diameter roller having good peelability. The image quality and life of the fixing device can be improved. Further, it is possible to cool the peeling roller 66 to give gloss to the image, and when the gloss is not necessary, the peeling roller 66 is retracted to prevent the heat of the belt 61 from being taken away, thereby preventing an increase in power consumption. Is possible.

FIG. 3 is a schematic configuration diagram of the fixing device according to the embodiment of the present invention before moving the peeling roller. It is a schematic block diagram after the peeling roller movement of the fixing device which concerns on the Example of this invention. 1 is a schematic configuration diagram of a fixing device according to an embodiment of the present invention. 6 is an operation flowchart of the fixing device according to the embodiment of the present invention. It is a schematic block diagram of the rigidity detection means used in the Example of this invention. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention.

Explanation of symbols

  1: image forming apparatus, 2: intermediate transfer belt, 3: belt driving roller, 4: paper stacking means, 7: transfer roller, 8: transport path, 9: pick roller, 11: separation roller, 20: displacement sensor A, 12: thickness detection lever, 22: spring A, 23: thickness detection roller, 24: fulcrum A, 25: transport roller, 30: displacement sensor B, 32: spring B, 33: rigidity detection lever, 34: driven roller , 35: spring C, 36: fulcrum B, 37: stopper, 38: rigidity determining means, 52: developing roller, 54: photosensitive drum, 55: exposure device, 56: charger, 57: drum cleaner, 58: primary Transfer roller, 60: fixing device, 61: fixing belt, 62: heating roller, 63: pressure roller, 64: backup roller, 65: tension roller, 6: Peeling roller, 70: Conveyance path switching guide, 71: Double paper retraction path, 72: Double paper retraction section, 81: Conveyance belt, 91: Belt cleaner, 201: Rigidity detection means, 202: Image pattern recognition means 501 to 504: development unit, 601: determination means.

Claims (3)

A latent image forming unit that forms a latent image on a photoconductor; a developing unit that forms a toner image by attaching toner to the latent image; an intermediate transfer belt to which a toner image on the photoconductor is transferred; A first transfer means for transferring a toner image on the photosensitive member to an intermediate transfer belt; a paper transfer means for transferring paper; a second transfer means for transferring a toner image on the intermediate transfer belt to paper; In an electrophotographic image forming apparatus having a fixing device that melts and fixes a toner image on a sheet, the fixing device includes a heating roller, a pressure roller having an elastic surface, a tension roller, and the heating roller. A fixing belt stretched between the pressure roller and the tension roller, a backup roller pressed against the pressure roller via the fixing belt, and along the outer periphery of the pressure roller A movable has its pressure small diameter stripping roller from the roller, and moving means for moving the peeling roller in the sheet conveying direction of the nip portion outlet of the pressure roller and the backup roller,
Rigidity detection means for detecting the rigidity of the paper, image pattern recognition means for recognizing an image recorded on the paper, and determination for judging movement of the peeling roller from signals of the rigidity detection means and the image pattern recognition means Means and
An image forming apparatus configured to move the peeling roller so that a sheet discharge direction of the nip portion and a surface of the fixing belt to the peeling roller substantially coincide with each other according to a signal from the determination unit. .   2. The image forming apparatus according to claim 1, further comprising a peeling claw that can be retracted in accordance with the movement of the peeling roller in the vicinity of a nip exit between the pressure roller and the backup roller.   3. The image forming apparatus according to claim 1, wherein the peeling roller is hollow and cooled by a gas or a liquid.

Images