JP5838632B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device and an image forming apparatus.

  In an image forming apparatus using an electrophotographic technique, as a technique used for fixing means for fixing a toner image to a transfer material such as paper, a heating roller incorporating a heat source such as a halogen lamp, which is an example of a fixing rotator, A so-called thermocompression bonding, in which a transfer material carrying a toner image is passed through a nip formed by a pressure roller that rotates while being in pressure contact with the heating roller, which is an example of a pressure rotating body, and the toner image is fixed to the transfer material. The method is widely adopted. In this type of fixing technology, the transfer material carrying the toner image by the pressure roller is pressed against the heating roller with a predetermined pressure, and thus is heated by the heating roller and becomes a molten state. It is desirable that all of the melted toner is fixed on the transfer material, but in reality, only a small part of the melted toner adheres to the heating roller due to the adhesive force between the toner and the heating roller. In general, this phenomenon is called an offset phenomenon.

  The types of offset phenomenon include a low temperature offset and a high temperature offset. Low temperature offset means that the toner is not sufficiently heated and the heat is not sufficiently transferred to the inside of the toner layer forming the toner image, so that the toner is not completely melted and fused to the transfer material. A part of the toner layer is crushed and adhered to the heating roller. In this case, since the toner image is not sufficiently fused to the transfer material, a so-called fixing failure occurs in which the toner image can be easily scraped from the output copy. High temperature offset means that when the toner is heated at an unnecessarily high temperature, the viscoelasticity of the toner changes and the adhesion between the toner and the heating roller becomes higher than the cohesion of the toner particles, and the toner adheres to the heating roller. It is.

  On the other hand, for copy images output by an electrophotographic image forming apparatus, there is an increasing demand for higher image quality. In order to ensure the print quality equivalent to the offset image, the trend is to reduce the diameter of the toner or make it spherical like a polymerized toner. For this reason, compared to conventional toners, heat is not easily transmitted to the toner, and the melting is not sufficient, so that there has been a problem that low temperature offset is likely to occur. In particular, it tends to occur when the surface of the paper is uneven, such as uncoated paper.

  As a countermeasure to this problem, as described in Patent Document 1 and the like, a fixing cleaning means that presses a cleaning web such as a non-woven fabric on the heating roller with a pressing roller, and always wipes the surface of the rotating heating roller. It is generally performed. However, spherical and small-diameter toner tends to pass through a slight gap formed between the cleaning web and the heating roller. It is necessary to prevent the gap from being generated as much as possible by pressing the roller. However, it is not desirable to supply a cleaning web having a sufficient area each time a copy is output from the viewpoint of increasing the maintenance frequency of the image forming apparatus or increasing waste from an environmental viewpoint.

  In view of this problem, Patent Document 2 proposes a cleaning unit that can prevent unnecessary web supply by controlling the supply amount of the cleaning web based on image data. In Patent Document 2, as the web feed amount increases as the image data (= toner image area / image area) increases, the feed amount is increased, and slipping from the web paper is less likely to occur.

  Recently, for example, as described in Patent Document 3, a mechanism has been developed in which a cleaning member is not disposed on the fixing roller side (image surface side) but a cleaning web is disposed on the pressure side. This is because when the cleaning web is added to the image surface side, the roller or belt surface side is damaged, and an abnormal image such as a vertical stripe is generated. However, when a cleaning member is added to the pressure surface side, the degree of penetration of the offset toner changes depending on the pressure roller temperature, so that the optimum feeding amount of the cleaning web paper changes. When the pressure roller temperature is lowered, it becomes difficult to soak into the web paper and slippage from the web occurs. On the other hand, when the pressure roller temperature is increased, an abnormal image such as a toner blister is generated.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device and an image forming apparatus capable of solving the above-described conventional problems and outputting an image free from image smear due to offset toner.

In order to achieve the above object, the present invention provides a fixing rotator heated by a heating means, a pressure rotator pressed against the fixing rotator, and a cleaning web delivered to the surface of the pressure rotator. A fixing device having a cleaning unit for cleaning a surface, the detection unit including a detection unit configured to detect a surface temperature of the pressure rotating body, and a control unit configured to control a feed amount of the cleaning web of the cleaning unit; Proposes a fixing device characterized in that the lower the surface temperature of the pressure rotating body detected by the detecting means, the longer the feeding amount of the cleaning web of the cleaning means.

  According to the present invention, the cleaning web feed amount for removing the toner adhering to the belt or the roller due to the offset is controlled based on the pressure roller temperature so that the image is not stained by the offset toner. An image can be output.

1 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. 1 is a schematic diagram illustrating a fixing device of the present invention. FIG. 5 is a schematic diagram illustrating an operation mechanism for winding of a fixing cleaning unit. 3 is a control flow of the image forming apparatus according to the embodiment of the present invention. 6 is a table showing a relationship between a pressure roller temperature and toner adhesion. 6 is a table showing an example of web control of the fixing device. 10 is a table showing another example of web control of the fixing device. 10 is a table showing still another example of web control of the fixing device. It is a table | surface of the coefficient applied to the web feed amount for every transfer material.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic cross-sectional view illustrating an example of an image forming apparatus. The image forming apparatus shown here includes a plurality of image carriers 2Y, 2C, 2M, and 2K made of a drum-shaped photoconductor, and an intermediate transfer belt 3 made up of an endless belt in contact with the peripheral surface of these image carriers. have. The intermediate transfer belt 3 is wound around support rollers 4, 5, 6, guided by a guide roller 8, and rotationally driven in the direction of arrow A by a drive motor (not shown). On the other hand, the image carriers 2Y to 2K are also driven to rotate counterclockwise in FIG. 1 by a motor (not shown).

  In each of the image carriers 2Y to 2K, toner images of different colors are formed. In the illustrated example, a yellow toner image, a cyan toner image, a magenta toner image, and a black toner image are formed on the image carriers 2Y to 2K. It is formed. The toner image formed on the surface of each image carrier is transferred to the surface of the intermediate transfer belt 3.

  The configuration for forming a toner image on each image carrier 2Y, 2C, 2M, 2K and transferring the toner image to the intermediate transfer belt 3 is substantially the same except that the color of the toner image is different. Therefore, only a configuration in which a toner image is formed on one of the image carriers 2Y and the toner image is transferred to the intermediate transfer belt 3 will be described. As shown in FIG. 1, image forming means for forming a toner image on the surface of the image carrier 2Y is provided around the image carrier 2Y. The image carrier 2Y is counterclockwise in FIG. When rotated in the direction, the image carrier 2Y is charged to a predetermined polarity by a charging device including a charging roller 7 to which a charging voltage is applied. The charged image carrier 2Y is irradiated with a light-modulated laser beam L emitted from an optical writing device (not shown), whereby an electrostatic latent image is formed on the image carrier 2Y. This electrostatic latent image is visualized as a yellow toner image by the developing device 9.

  A primary transfer device composed of a transfer roller 10 is disposed on the opposite side of the intermediate transfer belt 3 from the image carrier 2Y, and a transfer voltage is applied to the transfer roller 10 to form the image carrier 2Y. The toner image is transferred onto the intermediate transfer belt 3 that rotates in the arrow A direction. The transfer residual toner adhering to the image carrier 2Y after the toner image transfer is removed by the cleaning device 11.

  In exactly the same manner as described above, a cyan toner image, a magenta toner image, and a black toner image are respectively formed on the image carriers 2C, 2M, and 2K shown in FIG. 1, and these toner images are transferred to the yellow toner image. Then, the toner images are sequentially transferred onto the intermediate transfer belt 3, and a composite toner image is formed on the intermediate transfer belt 3. The transfer residual toner on each of the image carriers 2C, 2M, 2K after the toner image transfer is removed by the cleaning device is the same as in the case of the first image carrier 2Y.

  On the other hand, a support roller 6 positioned at the lowermost of the support rollers around which the intermediate transfer belt 3 is wound is provided with a transfer roller 16 as an example of a secondary transfer device with the intermediate transfer belt 3 interposed therebetween. A transfer material P made of, for example, paper or a resin sheet is fed between the transfer roller 16 and the intermediate transfer belt portion wound around the support roller 6 as indicated by an arrow. At this time, a predetermined transfer voltage is applied to the transfer roller 16, whereby the composite toner image on the intermediate transfer belt 3 is transferred onto the transfer material P. Instead of the transfer roller 16, a transfer device such as a transfer belt, a transfer brush, or a corona discharger can be used. Either type of transfer device is used to transfer the toner image transferred to the intermediate transfer belt 3 to the transfer material P. The transfer material P onto which the toner image has been transferred is further conveyed leftward in FIG. 1 and passes through the fixing device 20.

FIG. 2 is a schematic configuration diagram illustrating a configuration of the fixing device 20.
In FIG. 2, the fixing device 20 is a belt fixing system, and a fixing belt 23 wound around a heating roller 21 and a fixing roller 22 as a fixing rotating body, and a fixing roller via the fixing belt 23 as a pressure rotating body. And a pressure roller 24 in pressure contact therewith. The fixing roller 22, the pressure roller 24, and the heating roller 21 are rotatably supported in the longitudinal direction of a casing (not shown) of the fixing device 20, and are each rotated in the direction of an arrow by a driving unit (not shown). Various heating methods can be applied to the heating roller 21. In this example, the heating roller 21 is heated by a heater lamp 25 as a heat source disposed in the hollow.

  The fixing belt 23 is an endless belt formed of a PI layer having a thickness of 90 μm, and has an outer peripheral surface coated with an offset preventing agent such as a PFA film. The fixing roller 22 and the pressure roller 24 are rubber rollers arranged to face each other. When the pressure roller 24 is pressed toward the center of the fixing roller 22 via the fixing belt 23, the pressure roller 24. And a fixing belt 23 form a nip portion. Reference numeral 26 denotes a tension roller that applies tension to the fixing belt 23, and is formed of a cylindrical aluminum tube. The pressure roller 24 can be depressurized to the fixing roller 22 by a depressurization mechanism (not shown). Reference numeral 27 denotes a heater lamp disposed in the hollow of the pressure roller 24.

  The driving means (not shown) includes a motor and a reduction gear train, and is gear-connected to the fixing roller 22. When the driving means is rotationally driven in the arrow direction shown in FIG. 2, the fixing roller 22 rotates in the arrow direction. As the fixing roller 22 rotates, the pressure roller 24 and the fixing belt 23 that are in pressure contact with the fixing roller 22 rotate in the direction of the arrow at the same speed.

  Heat from the heater lamp 25 disposed in the hollow of the heating roller 21 is transmitted to the fixing belt 23 through the heating roller 21, and the fixing belt 23 is heated. By the reverse rotation of the pressure roller 24 and the fixing belt 23, the transfer material P is conveyed while the toner image T is heated and melted at the nip portion.

  In the fixing device having the above-described configuration, the transfer material P on which the toner image is formed is conveyed in the arrow direction shown in FIG. 1 from the pre-fixing guide 28 arranged on the upstream side of the fixing belt 23 in the transfer material conveyance direction. The toner image of the transfer material is fixed by heating and melting at the nip portion. Thereafter, the transfer material P is separated from the fixing belt 23 by the separation plate 29 after the exit of the nip, and discharged to the transfer material discharge portion (not shown) by the conveyance roller 17 arranged on the downstream side in the transfer material conveyance direction. Is done. A paper discharge sensor 18 is disposed at the fixing outlet in order to confirm that the transfer material has passed at a predetermined timing.

  The fixing device 20 is provided with a fixing cleaning means 30. The fixing cleaning means 30 includes a cleaning web 31 in which an aromatic polyamide non-woven fabric is impregnated with silicone oil as a release agent, a supply roller 32 winding a new web, a take-up roller 33 for collecting a used web, foaming It consists of a pressure roller 34 made of silicon resin. A predetermined amount of the cleaning web 31 wound around the winding roller 33 is fed by a web motor 36 described later, and a winding operation is performed with a constant torque. The pressing roller 34 presses the cleaning web 31 against the pressure roller 24 by a support member (not shown) and a pressing spring (not shown). A 3 to 6 mm cleaning nip is formed between the cleaning web 31 and the pressure roller 24 by this pressing, and the toner T adhering to the surface of the pressure roller 24 due to the offset rotates the pressure roller 24 in the direction of the arrow. As a result, the cleaning web 31 is wiped by the cleaning nip.

  FIG. 3 is a schematic diagram for explaining a winding operation mechanism of the fixing cleaning unit 30. The feed amount of the cleaning web 31 is determined by the rotation amount of the take-up roller 33. The take-up roller 33 has a reduction gear 35 attached to a rotation shaft installed in parallel with the take-up roller 33, and rotates by the rotation of a web motor 36 constituted by a step motor via the reduction gear 35. In the present embodiment, the gear reduction ratio is set so that the cleaning web 31 is fed by 0.82 mm by one step rotation of the web motor 36. The web motor 36 is fed by a motor control unit 37 so that a new web is sent out by intermittent control in which the motor operates once for a predetermined number of sheets.

  In the fixing device 20 of the present embodiment, the feed amount of the cleaning web 31 is changed by changing the time for operating the web motor 36 (hereinafter referred to as the web motor operation time). The motor operation interval is 15 sec (cycle).

Next, FIG. 4 shows a control flow of the image forming apparatus having the fixing device 20 described above.
In the fixing device 20, the temperature of the pressure roller 24 during paper passing is detected by the temperature sensor 38 and the feeding amount of the cleaning web 31 is controlled. If the temperature of the pressure roller 24 is low, the offset toner is not sufficiently melted with respect to the web paper as the cleaning web 31, so that it adheres again to the surface of the pressure roller and adheres to the transfer material as toner fixation. . FIG. 5 shows the relationship between the pressure roller temperature and toner adhesion. In order to prevent the toner from sticking, it is necessary to lengthen the operation time of the web motor 36.

  In the fixing device of the present embodiment, as is apparent from FIG. 5, slipping from the web occurs when the temperature is 90 ° C. or lower, and dirt adheres to the image. For this reason, based on the temperature of the pressure roller 24, the determination which lengthens the feed amount of the cleaning web 31 is performed, and it controls according to the determination. Specifically, a web feed amount necessary for the surface temperature of the pressure roller 24 is stored in the web control table storage unit 39 in advance, and when printing is started, the temperature sensor 38 detects the surface temperature of the pressure roller 24. The web feed amount required is calculated from the web control table storage unit 39 based on the detected temperature, and the web motor control unit 37 determines a desired operation time based on the calculated value to Make it work. In the fixing device 20, the control is always performed as described above during the sheet passing.

FIG. 6 shows an example of the web control table stored in the web control table storage unit 39.
The web control table shown in FIG. 6 is set so that the web motor operating time is lengthened as the surface temperature of the pressure roller 24 decreases. When the surface temperature of the pressure roller 24 is lowered, the offset toner does not soak into the cleaning web 31 as described above (it stays on the web paper as toner particles), and thus a slip-through phenomenon from the cleaning web 31 is likely to occur. turn into. For this reason, by setting the web motor operating time longer, the offset toner is collected by the take-up roller without adhering to the transfer material again. As a result, it is possible to maintain a state where there is no slip-through from the cleaning web 31. Moreover, the winding time of the motor is changed on one side and both sides. In the case of duplex printing, in addition to offset to the belt side, offset to the pressure side also increases the amount of input to the cleaning web 31. For this reason, the web control table shown in FIG. 6 is changed so that the winding amount of the cleaning web 31 is larger than that on one side.

  If changed in this way, based on the value detected for the pressure roller 24, the feed amount of the cleaning web 31 is changed between single-sided printing and double-sided printing, so that an image free from image smear due to offset toner is output. Can do.

  By the way, in the image forming apparatus in which the paper interval during paper passing changes depending on the paper size of the transfer material P to pass paper, the amount of toner offset to the cleaning web 31 changes when the paper interval during paper passing changes. It is preferable to control the winding amount of the cleaning web 31 according to the P paper size.

  Therefore, in the fixing device 20, the winding amount of the cleaning web 31 is controlled based on the web control table shown in FIG. 7 according to the temperature of the pressure roller 24 and the sheet size of the transfer material P. In the case of a transfer material having a pressure roller 24 at a certain temperature or less and a paper size with a wide space, it is possible to suppress slipping from the cleaning web 31 by increasing the winding time of the cleaning web 31. .

  In this way, the temperature of the pressure roller 24 is detected, and based on the detected value, the transfer amount of the cleaning web 31 is changed according to the size of the transfer material that passes the paper. Stable print quality can be maintained.

  By the way, when the transfer material P to be passed is coated paper, the offset amount with respect to the cleaning web 31 is smaller than that of uncoated paper. This is presumably because the coated paper has a smooth surface compared to the uncoated paper, so that heat is easily transmitted to the toner and the offset amount is small.

  Therefore, in the fixing device of the present embodiment, the web motor operation time is set to be shorter in the case of the coated paper as compared to the uncoated paper. Specifically, when the transfer material P is coated paper and uncoated paper, the winding time of the cleaning web 31 is set as shown in the web control table shown in FIG. As a result, it is possible to maintain a state where there is no slip-through from the cleaning web 31.

  Thus, stable printing quality can be maintained by detecting the temperature of the pressure roller and changing the feed amount of the cleaning web 31 between coated paper and uncoated paper based on the detected value.

  Further, in the fixing device 20, an optimum feed amount is grasped in advance for each transfer material P used by the user and stored in the control unit. For this optimum web feed amount, a value obtained by multiplying the detected value of the temperature of the pressure roller 24 by a certain coefficient is controlled as the web feed amount. Thus, by controlling the optimum feed amount for each paper type, it is possible to maintain a high-quality image without slipping over time. FIG. 9 shows a web feed amount table of coefficients to be applied to the detected value of the temperature of the pressure roller 24 with respect to the optimum web feed amount. A web feed amount reference table preset for each transfer material used in this manner is stored in the memory of the control means, and the feed amount of the cleaning web 31 is controlled by the temperature of the pressure roller 24, so that Even for a transfer material, an optimal web feed amount is always ensured and a stable image can be output.

As mentioned above, although preferable embodiment of this invention was described, this invention is not limited only to the said embodiment, Various modifications can be made.
For example, although the belt fixing type fixing device 20 has been described, the fixing device 20 may be a roller fixing type, and therefore the fixing rotator may be a fixing roller. Further, the pressure rotating body is not limited to the pressure roller, and the present invention can also be applied to a fixing device using a pressure belt.

DESCRIPTION OF SYMBOLS 20 Fixing device 21 Heating roller 22 Fixing roller 23 Fixing belt 24 Pressure roller 30 Fixing cleaning means 31 Cleaning web 32 Supply roller 33 Winding roller 36 Web motor 37 Web motor control part 38 Temperature sensor

JP 2002-258657 A JP-A-2005-024619 JP 2008-04-0053 A

Claims (6)

In a fixing device having a fixing rotator heated by a heating unit, a pressure rotator pressed against the fixing rotator, and a cleaning unit that sends a cleaning web to the surface of the pressure rotator to clean the surface. ,
Detecting means for detecting a surface temperature of the pressure rotating body;
Control means for controlling the delivery amount of the cleaning web of the cleaning means,
The fixing device is characterized in that the lower the surface temperature of the pressure rotator detected by the detecting means, the longer the feeding amount of the cleaning web of the cleaning means.   The fixing device according to claim 1, wherein the control unit changes a feeding amount of the cleaning web between single-sided printing and double-sided printing.   The fixing device according to claim 1, wherein the control unit changes the amount of the cleaning web fed according to a transfer material size for passing the paper.   The fixing device according to claim 1, wherein the control unit changes a feeding amount of the cleaning web between coated paper and uncoated paper.   5. The fixing device according to claim 1, wherein a reference table of a feeding amount of the cleaning web set in advance for each transfer material to be passed is provided in a memory of the control means.   An image forming apparatus comprising the fixing device according to claim 1.

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