JP2008040011A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device and an image forming apparatus that can surely prevent a release agent from sticking on a recording medium. <P>SOLUTION: The fixing device 2 passes the recording medium P carrying a toner image between a fixing roller and a pressure roller 24 via a fixing belt 21 interposed and applies heat and pressure to the toner image during the passage to fix the toner image on the recording medium P. The fixing device is provided with trace amount coating roller 35 which applies a trace amount of oil and a separation claw 40 for separating the recording medium P, on the surface of at least one of the fixing belt 21 and the pressure roller 24 with an oil absorber 44 being clamped by claw members 40A and 40B. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  According to the present invention, a recording medium carrying a toner image is passed between rotating first and second fixing members, and when passing, the toner image is recorded by applying heat and pressure to the toner of the toner image. The present invention relates to a fixing device for fixing to a medium.

  2. Description of the Related Art Conventionally, it is well known to employ a fixing device of the above type in an image forming apparatus configured as a copying machine, a printer, a facsimile, or a multifunction machine having at least two of these functions. The fixing device includes a heating roller that has a heat source inside as a first fixing member and is driven to rotate, and a pressure roller that is in pressure contact with the heating roller as a second fixing member and is driven to rotate by the heating roller. There is known a heat roller pair type in which a sheet-like medium is passed through a nip portion formed by both rollers, and the toner image is fixed by heating and pressing. Further, an endless fixing belt that is wound around a heating roller and a fixing roller as a first fixing member and conveys a sheet-like medium on which toner is fixed, and a fixing roller via the fixing belt as a second fixing member There is known a so-called belt fixing device of a type having a pressure roller or the like disposed opposite to the component.

  Also, in this type of fixing device, a heating roller, a pressure roller, a fixing belt, and the like are applied with an application roller for applying silicone oil as a release agent and a sheet-like recording medium after fixing to improve the releasability. Usually, a separation claw as a peeling means for preventing the pressure roller, the heating roller, the fixing belt or the like from being wound is provided.

  By the way, in a fixing device of a type having an application roller and a separation claw, silicone oil that is a release agent scraped off by the separation claw adheres to the recording medium. As a result, there is a problem that oil marks are generated on the recording medium.

Microfilm of Japanese Utility Model Application No. 2-48709 (Japanese Utility Model Application Publication No. 4-9071)

  Patent Document 1 discloses a fixing device in which a minute groove is formed in a separation claw so that water droplets of oil are not formed using a capillary phenomenon. However, although this apparatus can eliminate a large oil reservoir such as water droplets, it cannot be reliably prevented from adhering to the recording medium because oil remains in the separation claw.

  An object of the present invention is to provide a fixing device and an image forming apparatus that can eliminate the above-mentioned conventional defects.

  In order to achieve the above object, the present invention allows a recording medium carrying a toner image to pass between the rotating first and second fixing members, and heat and pressure are applied to the toner of the toner image during the passage. In addition, there is provided a fixing device for fixing the toner image on a recording medium, wherein an oil application member for applying a small amount of oil is provided on at least one surface of the first and second fixing members, And a fixing device in which at least one surface of the second fixing member is provided with a peeling means for separating the recording medium, the peeling means sandwiches an oil absorber by a claw member. Propose the device.

The present invention is effective when the oil absorber is inserted and held in a slit formed in the claw member.
Furthermore, the present invention is effective when the oil absorber is sandwiched between claw members independent of each other.

Furthermore, the present invention is effective when at least two or more support holes are formed in the oil absorber and the claw member is supported through the support holes.
Furthermore, the present invention is effective when the oil absorber is composed of fibers and is subjected to a treatment for preventing the fibers from dropping off.

Furthermore, the present invention is effective when the oil absorber is a felt composed of aramid fibers.
Furthermore, the present invention is effective when the oil absorber has substantially the same shape as the claw member and is disposed at a distance of 0.5 mm to 5 mm from the fixing member.

  In order to achieve the above object, the present invention proposes an image forming apparatus comprising the fixing device according to claim 1.

  According to the present invention, since the peeling means sandwiches the oil absorber, it is possible to reliably prevent oil contamination of the recording medium. Furthermore, the oil absorber can be prevented from falling off, and even if fibers are used in the oil absorber, the fibers can be prevented from falling off.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic diagram showing a tandem color laser printer as an image forming apparatus according to the present invention. The image forming apparatus shown here includes a plurality of image carriers 3Y, 3M, 3C, 3BK arranged in a main body 1 and an endless belt arranged opposite to these image carriers. have. Each of the image carriers 3Y to 3BK is constituted by a drum-shaped photoconductor, and a yellow toner image, a magenta toner image, a cyan toner image, and a black toner image are formed on the surface of each image carrier. The transfer belt 4 is stretched around a plurality of support rollers 15, 16, 17, 18 and driven to run in the direction of arrow A.

  Since the operation of forming a toner image on each of the image carriers 3Y, 3M, 3C, and 3BK is substantially the same, only the configuration of forming a toner image on the image carrier 3Y will be described. The image carrier 3Y is rotated clockwise in FIG. 1, and at this time, the surface of the image carrier 3Y is uniformly charged to a predetermined polarity by the charging device 7. Next, the charged surface is irradiated with a light-modulated laser beam L emitted from the laser writing unit 8. 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 9.

  On the other hand, a paper feeding device 5 is disposed in the lower part of the image forming apparatus main body 1, and this paper feeding device 5 is pressed against a paper feeding cassette 14 for storing the recording medium P and the uppermost recording medium. A paper feed roller 12 that rotates and feeds the uppermost recording medium in the direction of arrow B is provided. The recording medium P sent out from the paper feeding device 5 is fed between the image carrier 3Y and the transfer belt 4 at a predetermined timing by the registration roller pair 13, and is carried on the transfer belt 4. Be transported. A transfer device 10 is disposed at a position almost opposite to the image carrier 3Y across the transfer belt 4, and the yellow toner image on the image carrier 3Y is transferred onto the recording medium P by the action of the transfer device 10. The The transfer residual toner that is not transferred to the recording medium P and remains on the image carrier 3Y is removed by the cleaning device 11.

  In exactly the same manner, magenta toner images, cyan toner images, and black toner images are respectively formed on the image carriers 3M, 3C, 3BK shown in FIG. 1, and these toner images are recorded with the yellow toner image transferred thereto. The images are sequentially transferred onto the medium P.

The recording medium P carrying the four-color superimposed toner image in this way passes through the fixing device 2, and at this time, the superimposed toner image is fixed on the recording medium P by the action of heat and pressure. The recording medium that has passed through the fixing device 2 is discharged onto the paper discharge unit 6 as indicated by an arrow C. Note that this printer has a larger heat capacity than plain paper, which is generally used for copying, etc., OHP sheets, 90K paper such as cards and postcards, thick paper with a basis weight of about 100 g / m ² or more, and envelopes. Any so-called special sheet (hereinafter simply referred to as a special sheet) can be used as a recording medium.

  FIG. 2 is a cross-sectional view showing the fixing device 2. The fixing device 2 includes a first fixing member configured as a fixing belt 21 wound around a heating roller 22 and a fixing roller 23, and the fixing belt 21. A second fixing member configured as a pressure roller 24 in pressure contact with the fixing roller 23, and the fixing belt 21 is tensioned by a tension roller 25 urged by an elastic body (not shown) such as a spring. Is retained. Heaters 26 and 27 are provided inside the heating roller 22 and the pressure roller 24 to heat the fixing belt 21 and the pressure roller 24.

  The fixing roller 22 includes a cored bar 29 and a heat-resistant porous layer elastic body layer 30 that covers the cored bar 29, and is urged in a direction in which it is pressed against the pressure roller 25 by an elastic body (not shown) such as a spring. Has been. One of the heating roller 22 and the fixing roller 23 is rotationally driven by a drive motor (not shown), and thereby the fixing belt 21 is driven to travel clockwise in the drawing. The pressure roller 24 is driven by the rotation of the fixing roller 22 via the fixing belt 21, or the pressure roller 24 is also driven to rotate counterclockwise by a driving device (not shown). Further, a temperature detecting element 33 made of, for example, a thermistor is provided facing the peripheral surface of the fixing belt 21. Similarly, the pressure detecting element 24 also has a temperature detecting element made of, for example, a thermistor facing the peripheral surface thereof. 34 is provided. The temperature detection elements 33 and 34 detect the temperatures of the surfaces of the fixing belt 21 and the pressure roller 24, and the energization of the heaters 26 and 27 is controlled based on the detection result, so that the fixing belt 21 and the pressure roller 24 are It is kept at a temperature suitable for fixing the toner image.

  A small amount application roller 35 for applying silicone oil as a release agent is in contact with the pressure roller 24 by an elastic body (not shown) such as a spring. A minute amount of oil is indirectly applied to the fixing belt 21 by the minute amount application roller 35, thereby improving the releasability of the fixing belt 21 to the toner. Further, a cleaning roller 36 is brought into contact with the surface for the purpose of preventing toner sticking on the surface of the minute amount application roller 35.

  When the recording medium P that carries an unfixed toner image and is conveyed in the direction of arrow A is nipped between the fixing belt 21 and the pressure roller 24 while being guided by the guide member 32, the fixing device 2 Is fixed on the recording medium P by the action of heat and pressure. The recording medium P on which the toner image is fixed is further conveyed in the direction of arrow A by the fixing belt 21. At this time, the recording medium P may be wound around the fixing belt 21. Peeling means configured as a separation claw 40 is provided in the wound range.

  A plurality of separation claws 40 are provided at appropriate intervals in the width direction of the apparatus, and each separation claw 40 is in pressure contact with the fixing belt 21 by an elastic body made of a spring or the like not shown.

  In the fixing device 2 configured in this manner, since the silicone oil is applied to the fixing belt 21, a part of the oil is scraped off by the claw portion 41 of the separation claw 40 and the claw portion 41 of the separation claw 40. Adhere to. As described above, the oil adhering to the separation claw 40 moves to the recording medium P, and there is a problem of generating oil marks on the recording medium P. In this embodiment, dimethyl silicone oil is used as a release agent.

Therefore, in the present invention, in order to solve such a problem, the following measures are taken and described.
3A and 3B, the separation claw 40 of the present embodiment includes two claw members 40A and 40B, and supports the oil absorber 44 so as to sandwich the oil absorber 44 between the two claw members 40A and 40B. ing. The two claw members 40A and 40B are rotatably supported by shafts 45A and 45B supported by the holders 42A and 42B. It is energized.

  By supporting the oil absorber 44 so as to be sandwiched between the two claw members 40A and 40B in this way, the oil absorber 44 can be prevented from falling off and the oil adhering to the separation claw 40 can be absorbed safely. . The oil absorber 44 may be a porous material such as sponge or ceramic as long as it can absorb oil, but in this embodiment, the absorbability of fibers, particularly oil, quality over time, workability, etc. From the viewpoint of cost and the like, a felt made of the most suitable aramid fiber is used. Further, the claw members 40A and 40B are devised to be the same rotation fulcrum, and this is to improve the contact position accuracy of the claw portions 41A and 41B to the fixing belt 21.

  FIGS. 4A and 4B are explanatory views showing another embodiment of the present invention. The separation claw 40 supported by the shaft 45 of this example has two claw members 40A to which the claw portions 41 are joined. , 40B, a slit is formed, and the oil absorber 44 is inserted into the slit.

  By the way, the separation claw 40 shown in FIG. 3 and FIG. 4 is wide because the claw portion 41 sandwiches the felt, so that it is difficult to bring the separation claw 40 into uniform contact. If the separation claw 40 does not contact uniformly, the fixing belt 21 may be damaged or the wound recording medium P cannot be separated.

FIGS. 5A and 5B are explanatory views showing still another embodiment of the present invention.
In FIG. 5, the separation claw 40 is constituted by two independent claw members 40A and 40B, and the oil absorber 44 is supported by the two claw members 40A and 40B. The two claw members 40A and 40B are rotatably supported by a shaft 45 supported by the holders 42A and 42B, and the claw portions 41A and 41B are separated by separate tension springs 43A and 43B (only one is shown in FIG. 3). The turning force in the direction in which 41B presses against the fixing belt 21 is energized. In this way, the claw members 40A and 40B abut independently, so that the claw members 40A and 40B abut on the fixing belt 21 uniformly, and it is possible to prevent defects such as scratches and wrapping caused by the non-uniform abutment.

  The oil absorber 44 is felt, and the oil absorber 44 is provided with a round hole 46 and a long hole 47 as shown in FIG. The round hole 46 of the oil absorber 44 is engaged with the shaft 45, and the other long hole 47 is engaged with protrusions 48A and 48B provided on the separation claws 40A and 40B. Since the claw members 40A and 40B rotate independently of each other, the separation claw 40 has a long hole on the other side so as not to hinder the movement. In this way, two holes of the oil absorber 44 are provided and engaged by the shaft 45 and the protrusion 48, thereby preventing the oil absorber 44 from being displaced or protruding.

  By the way, although it is preferable that the oil absorber 44 uses the felt comprised by the aramid fiber, since it is a fiber, it may protrude from the separation nail | claw 40 by dropping or fluffing. When a part of the oil absorber 44 protrudes, it becomes easier for the oil to touch the recording medium than the part.

  Therefore, it is desirable that the felt that is the oil absorber 44 is subjected to a flame treatment to prevent the fiber from protruding or fraying. The same effect can be obtained by applying a so-called sealing process such as a resin coat to the felt surface which is the oil absorber 44. In addition, the higher the density of the felt used for the oil absorber 44, the higher the absorbing power and holding power, which is effective in the present invention.

  Further, the felt used for the oil absorber 44 has substantially the same shape as the claw member of the separation claw 40. However, as described above, when the oil protrudes from the separation claw 40, the oil easily adheres to the transfer paper. It is preferable to form a size slightly smaller than the separation claw 40.

  Furthermore, although oil adheres to the tip of the separation claw 40, since the oil spreads and adheres to a wide range of the tip of the claw, the felt that is the oil absorber 44 and the tip of the separation claw 41 are shown in FIG. When L is L, L is set to 0.5 mm to 5 mm. Thus, even if the felt and the separation claw tip 41 are separated by about 0.5 mm to 5 m, the oil adhering to the tip can be absorbed. This is because the felt can absorb the spread oil by the capillary action of the felt.

  Usually, since the vicinity of the tip of the separation claw is made of a resin having a relatively good release property, the oil can be smoothly moved to the felt. If the felt is disposed at the tip of the separation claw, the felt is collected together with the offset toner, and the felt becomes dirty, and the oil absorption is deteriorated. In addition, there is a concern that toner may fall off from the felt and image smearing may occur. Therefore, it is effective to separate the felt from the tip of the separation claw by about 5 mm.

1 is a configuration diagram showing a printer using a fixing device according to the present invention. FIG. FIG. 3 is an enlarged explanatory view showing a fixing device according to the present invention. (A), (b) is explanatory drawing of the separation nail which shows one Embodiment of this invention. (A), (b) is explanatory drawing of the separation nail which shows other embodiment of this invention. It is explanatory drawing of the separation nail which shows other embodiment of this invention. It is explanatory drawing of the oil absorber which the separation nail | claw of FIG. 5 clamps. It is explanatory drawing of the separation nail which shows further another embodiment of this invention.

Explanation of symbols

2 Fixing Device 21 Fixing Belt 22 Fixing Roller 23 Heating Roller 24 Pressure Roller 35 Trace Application Roller 40 Separation Claw 40A, 40B Claw Member 41 Claw Portion 44 Oil Absorber P Recording Medium

Claims (8)

The recording medium carrying the toner image is passed between the rotating first and second fixing members, and when passing, the toner image is fixed to the recording medium by applying heat and pressure to the toner of the toner image. In the fixing device, an oil application member for applying a small amount of oil is provided on at least one surface of the first and second fixing members, and at least one surface of the first and second fixing members. In the fixing device provided with a separating means for separating the recording medium,
The fixing device is characterized in that the peeling means sandwiches the oil absorber by a claw member.   The fixing device according to claim 1, wherein the oil absorber is inserted and held in a slit formed in the claw member.   The fixing device according to claim 1, wherein the oil absorber is sandwiched between claw members independent of each other.   4. The fixing according to claim 1, wherein at least two or more support holes are formed in the oil absorber, and the claw member is supported through the support holes. apparatus.   The fixing device according to any one of claims 1 to 4, wherein the oil absorber is made of a fiber and is subjected to a treatment for preventing the fiber from dropping off.   The fixing device according to claim 1, wherein the oil absorber is a felt made of an aramid fiber.   The oil absorbing body has substantially the same shape as the claw member, and is disposed at a distance of 0.5 mm to 5 mm from the fixing member. Fixing device.   An image forming apparatus comprising the fixing device according to claim 1.

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