JP2007206353A - Separation pawl, fixing device, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a trapezoid separation pawl, whereby rubbing by the ridge line of the pawl is softened and image quality is improved. <P>SOLUTION: The separation pawls 10 and 11 whose edges are formed in the shape of a trapezoid are used in a belt fixing device. By forming a tapered surface 12 on the side surfaces of pawl edge parts 10a and 11a in any shape, rubbing of an image with the ridge lines on the conveying surface sides of the separation pawls 10 and 11 is softened. Since the area of the conveying surface is smaller than that of a separation pawl whose edge is rectangular, friction with paper becomes small and jamming is restrained from occurring. However, if the pawl edge parts 10a and 11a have the same area, the pawl edge part 10a of the trapezoid pawl 10 whose side on an upstream side in a conveying direction is short is short, so that pressure per unit length that it abuts on the fixing belt 4 and the pressure roller 5 becomes large, and the surface layers of the fixing belt 4 and the pressure roller 5 are easily somewhat damaged. Therefore, the trapezoid pawl 11 is more excellent from a viewpoint of the life of a component abutting on the pawl. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a separation claw applied to an image forming apparatus such as a facsimile, a printer, a copying machine, and a composite machine using an electrophotographic system, an electrostatic recording system, and the like, and a belt fixing device using the same.

  Some of these belt fixing devices employ a claw in order to reduce friction between the image of the separation claw conveyance surface side ridge line from the fixing belt surface and the image.

A conventional separation claw 8 is shown in FIG. This is brought into contact with the fixing belt 4 and the pressure roller 5 with a spring or the like. As shown in the figure, the shape of the claw tip 8a of the conventional separation claw 8 is rectangular. After an image with a large amount of adhesion is separated, gloss unevenness due to rubbing between the ridge line 9 on the nail conveyance surface side and the image is likely to occur as shown in FIG.
Japanese Patent No. 02864575 JP 2001-022218 A JP 2003-043846 A JP 2000-047511 A JP 09-171318 A

  By the way, with the conventional rectangular separation claw, particularly in an image with a large amount of toner attached, the force that wraps around the belt member is strong even after the separation, and accordingly, the ridge line of the conveyance surface of the separation claw and the image are rubbed, The image quality was degraded. In addition, the rectangular separation claw has a large area on the conveyance surface, and in an image with a large amount of toner adhesion, the possibility of jamming due to friction between the separated paper and the conveyance surface is high.

  In view of the above-described conventional problems, the present invention has a trapezoidal separation nail, thereby reducing the friction caused by the ridgeline of the nail and improving the image quality, as well as the friction between the paper and the conveyance surface of the nail. An object of the present invention is to provide an apparatus that can reduce the occurrence of jam and reduce the occurrence rate of jam and can stably transport paper.

  The separation claw according to claim 1 of the present invention forms a nip with a pressure roller disposed at a position facing a fixing roller around which an endless fixing belt stretched by a plurality of support members is wound, In a separation claw for peeling off a transfer material such as paper using a belt fixing device that heats and fixes an unfixed image of the image, the claw tip of the separation claw has a trapezoidal shape and can be attached to and detached from the fixing belt. The upstream side in the transport direction of the transfer material is longer than the downstream side.

  According to the second aspect of the present invention, the separation claw of the first aspect is formed of a fluorine-based resin.

  According to a third aspect of the present invention, there is provided a belt fixing device including a plurality of the separation claws according to the first or second aspect, wherein at least one of the plurality of support members around which the fixing belt is wound is the pressure roller. It is characterized by facing.

  According to a fourth aspect of the present invention, in the belt fixing device of the third aspect, the plurality of trapezoidal shape separation claws are in sliding contact with the fixing belt and the pressure roller independently of each other.

  An image forming apparatus according to a fifth aspect of the present invention includes the separation claw according to the first or second aspect.

  According to a sixth aspect of the present invention, the belt fixing device according to the third or fourth aspect is provided.

  The present invention has a trapezoidal shape of the separation claw, which not only makes it possible to reduce rubbing due to the ridgeline of the nail and improve the image quality, but also particularly in the upstream side of the trapezoidal shape separation claw in the transport direction. By making it longer than the downstream side, the friction between the paper and the claw conveyance surface is reduced, the jam generation rate can be reduced, the paper can be conveyed stably, and the separation claw can be applied. In contact, the contact pressure per unit length can be reduced, and the life of the contacted component can be improved.

  The best mode for carrying out the present invention will be described below with reference to the embodiments shown in the drawings.

  FIG. 1 is a partial cross-sectional view schematically showing the image forming apparatus, and FIG. 2 is an enlarged cross-sectional view of the fixing apparatus 1 shown in FIG. In the fixing device 1 shown in these drawings, an endless fixing belt 4 is stretched between a fixing roller 2 and a heating roller 3 with a built-in heater, and a pressure roller 5 with a heater is installed at a position facing the fixing roller 2. The fixing roller 2 is pressed with an appropriate pressure.

  Reference numerals 6 and 7 in FIG. 2 denote separation claws that contact the fixing belt and the pressure roller, respectively. In FIG. 2, for separation, the separation claw is drawn in contact with the fixing belt 4 and the pressure roller 5 one by one. Is.

  FIG. 3 is a view showing the separation claws 10 and 11 having trapezoidal tips at the tips used in the belt fixing device according to the present invention. In either shape, by forming the tapered surface 12 on the side surfaces of the claw tip portions 10a and 11a, it is possible to alleviate the rubbing between the ridge line on the conveying surface side of the separation claw 10 and 11 and the image.

  In addition, since the area of the conveying surface is smaller than that of a rectangular claw tip, friction with the paper is reduced, and jamming can be suppressed.

  However, for example, in the trapezoidal claw 10 having the shape of the embodiment of FIG. 3A and the trapezoidal claw 11 having the shape of the embodiment of FIG. 3B, when the areas of the claw tip portions 10a and 11a are the same, FIG. The trapezoidal claw 10 having a short side on the upstream side in the conveyance direction in the example of FIG. 3B has a shorter claw tip 10a than the trapezoidal claw 11 having a long side on the upstream side in the conveyance direction in FIG. In addition, the pressure per unit length in contact with the pressure roller 5 is increased, and the surface layers of the fixing belt 4 and the pressure roller 5 are slightly damaged. Therefore, in these two embodiments, the trapezoidal claw of the embodiment of FIG. 3 (B) is superior from the viewpoint of the life of the parts that abut the claw.

  Here, differences from the prior art and features of the present invention will be described. For example, when the length of the claw tip is A and the pressing force by the spring is F, the pressing force per unit length (hereinafter referred to as linear pressure) is F / A. In the conventional rectangular nail as shown in FIG. 4 in which the nail tip and the rear end have the same length A, it has been a concern that an image with a large amount of adhesion causes edge rubbing due to wrapping and lowers the image quality. As described above. Therefore, by making the upstream side (claw tip), which is a normal trapezoidal claw, shorter than the downstream side (claw rear end), the friction of the ridgeline due to winding is reduced. . This effect does not change even if the length of either the front end or the rear end of the nail is shortened.

  However, the length of the tip of the nail is determined when an optimum value for ensuring separation of paper or a scratch due to contact with the belt surface layer (a belt scratch due to the nail becomes more noticeable as the linear pressure increases) or paper separation is considered. It becomes a fixed value, and usually this length cannot be changed. Here, as described above, if the length of the nail tip is determined to be A, for a trapezoidal nail with a nail tip shorter than the rear end, for example, the rear end length is 2A, and the nail tip is For trapezoidal claws that are longer than the rear end, if the length of the rear end is A / 2, both have the same length A, so the linear pressure is the same, and the level of scratches due to contact with the belt surface layer is also the same The level of paper separation is naturally the same. However, since the former trapezoidal claw has a larger surface area of the claw than the latter trapezoidal claw, the area where the separated paper is rubbed against the surface of the claw is increased, and the occurrence rate of jam is increased. Therefore, the shape of the trapezoidal claw is preferably shown in FIG. The image quality is the same as that of the conventional trapezoidal claw 8, and the quality superior to that of the conventional trapezoidal claw 8 can be ensured for paper conveyance.

  By using a non-adhesive fluororesin as a material for the separation nail, it is possible to make it difficult for toner to adhere to the separation nail. In addition, the trapezoidal separation claw can be brought into sliding contact with the fixing belt 4 and the pressure roller 5 without hitting one piece.

Partial sectional view showing an outline of the image forming apparatus 1 is an enlarged sectional view of the fixing device 1 shown in FIG. The figure which shows the separation nail | claw which made the front-end | tip trapezoid shape used for the belt fixing apparatus which concerns on this invention Diagram showing conventional separation claw

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixing device 2 Fixing roller 3 Heating roller 4 Fixing belt 5 Pressure roller 5 Pressure roller 6, 7 Separation claw 8 Separation claw 8a Claw tip part 9 Edge line 10, 11 Separation claw 10a, 11a Claw tip Part 12 Tapered surface on the side A Length of claw tip

Claims (6)

A belt fixing device that forms a nip by a pressure roller disposed at a position facing a fixing roller around which an endless fixing belt stretched by a plurality of support members is wound, and heat-fixes an unfixed image on a sheet. In the separation claw for separating the transfer material such as paper, the tip of the separation claw is trapezoidal and can be separated from and attached to the fixing belt, and the upstream side in the conveyance direction of the transfer material Separation claw characterized in that is longer than the downstream side. 2. The separation claw according to claim 1, wherein the separation claw is made of a fluorine resin. 3. A belt fixing device having a plurality of separation claws according to claim 1 or 2, wherein at least one of the plurality of support members wound around the fixing belt is opposed to the pressure roller. 4. The belt fixing device according to claim 3, wherein the plurality of trapezoidal shape separation claws are in sliding contact with the fixing belt and the pressure roller independently of each other. An image forming apparatus comprising the separation claw according to claim 1. An image forming apparatus comprising the belt fixing device according to claim 3.