JP4557675B2 - Roller and fixing device having the same - Google Patents

Description

  The present invention relates to an electrophotographic image forming apparatus.

  2. Description of the Related Art Conventionally, a fixing device used for fixing a toner image on a sheet in an image forming apparatus is conventionally a heat roller (fixing roller) incorporating a heater and a core metal as shown in, for example, Patent Document 1. Are provided with an elastic body layer (elastic member layer) and a release layer on the outside thereof, and a pressure roller that presses against the heat roller.

  As shown in the schematic configuration diagram of the conventional fixing device 101 in FIG. 4, the heat roller 110 and the pressure roller 120 of the fixing device 101 are in pressure contact with each other, and the elastic layer 122 and the release layer 123 are deformed to form a nip. Forming. The toner image T formed by an image forming unit (not shown) and transferred onto the paper P is heated and pressurized at the nip between the heat roller 110 and the pressure roller 120 and fixed on the paper P.

In order to improve the fixing property of the toner image, it is considered that the nip width should be widened. It has been lowered.
Japanese Patent Laid-Open No. 10-10902 (page 3, FIG. 4)

  The elastic body layer 122 of the pressure roller 120 shown in Patent Document 1 has both end portions parallel to each other and the entire width of the elastic body layer 122 aligned with each other. Therefore, as shown in the side partial sectional view of the end portion of the conventional pressure roller 120 in FIG. 5, if the elastic layer 122 is deformed so as to bulge outward in the axial direction at both ends of the pressure roller 120, the elastic layer 122 Stress is applied to the portion of the body layer 122 in contact with the cored bar 121 toward the outside in the axial direction. The cored bar 121 and the elastic body layer 122 are bonded by a primer or the like at the time of manufacture, but this stress works to peel the elastic body layer 122 from the cored bar 121.

  If the nip width is widened to improve the fixability of the toner image, the way in which both end portions of the elastic layer 122 swell increases, so that the stress applied to the end portion of the elastic layer 122 in contact with the cored bar 121 also increases. . When the pressure roller 120 rotates in a state where the elastic body layer 122 is deformed, this stress is repeatedly applied over the entire circumference of the portion in contact with the cored bar 121 at the end of the elastic body layer 122. Then, it gradually peels off from the cored bar 112, and further cracks occur in the peeled part.

  Thus, in a state where both ends of the elastic layer 122 are damaged, the pressure roller 120 cannot apply a uniform pressure to the paper P at the nip, and the toner image T is fixed at both ends in the transport direction of the paper P. Will be reduced.

  Therefore, in the present invention, even when the nip width is widened, a roller in which the elastic body is not easily peeled off from the cored bar, and this roller is provided as a pressure roller, so that the toner image can be stably fixed on the paper for a long period of time. It is an object of the present invention to provide a fixing device that can perform the above operation.

  (1) The present invention provides a roller including a cored bar and an elastic layer provided around the cored bar, wherein the elastic layer has a first region in contact with the cored bar and the first region. A second region provided on the outer side in the radial direction of the region, the first region having an axial length longer than the second region and the second region with respect to the axial direction. It is located outside.

  (2) Further, the present invention is characterized in that a fixing device including a heat roller with a built-in heater and a pressure roller that presses against the heat roller includes the roller as the pressure roller.

  (1) In the configuration of the present invention, the elastic body layer of the roller is composed of the first region on the inner side in the radial direction and the second region on the outer side, and the first region has an axial length longer than that of the second region. And is located outside the second region with respect to the axial direction. As a result, when this roller is deformed by being pressed against another roller or the like, both ends of the elastic layer swell only in the second region and the first region does not swell, so the elastic layer is peeled off from the cored bar. Such stress is not applied, and the life of the roller can be extended.

  (2) Further, in the configuration of the present invention, since the roller according to the present invention is used as the pressure roller of the fixing device used for fixing the toner image on the paper in the image forming apparatus, it is stable over a long period of time. The toner image can be fixed on the paper.

  Embodiments of the present invention will be described with reference to FIGS. 1 is a schematic configuration diagram of a fixing device 1 according to an embodiment of the present invention, FIG. 2 is a side partial sectional view of an end portion of a pressure roller 20 according to an embodiment of the present invention, and FIG. 3 is a pressure roller of FIG. It is side surface partial sectional drawing of the edge part of 20. FIG.

  In the fixing device 1 of the image forming apparatus, as shown in FIG. 1, the heat roller 10 and the pressure roller 20 are pressed against each other in a rotatable manner, and the elastic layer 22 and the release layer 23 are deformed to form a nip.

  The pressure roller 20 includes an elastic body layer 22 such as rubber around a metal core 21 made of metal such as iron and a release layer 23 made of PFA on the outside thereof. At the time of manufacturing, the cored bar 21 and the release layer 23 coated with the primer are placed in a mold, and molten rubber is poured as the elastic layer 22 and heated to be molded. The core metal 21 and the elastic body layer 22 are bonded by the primer, and the elastic body layer 22 rotates without slipping from the core metal 21 even in a state where it is pressed against the heat roller 10.

  The toner image T transferred to the paper P in an image forming unit (not shown) is heated and pressurized in the nip of the fixing device 1 and fixed on the paper P. Since the metal core 21 and the elastic body layer 22 are bonded, it is possible to apply pressure uniformly to the paper P and to fix the toner image T stably.

  In the embodiment of the present invention, the elastic body layer 22 is composed of a first region 22a in contact with the core metal and a second region 22b provided on the radially outer side of the first region 22a as shown in FIG. The first region 22a is longer in the axial direction than the second region 22b and is located outside the second region 22b with respect to the axial direction. Although only the shape of one end of the pressure roller 20 is shown in FIG. 2, both ends have the same shape. Examples of a method of forming the elastic body layer 22 in this shape include making it into this shape with a mold into which the elastic body is poured, and cutting the elastic body.

  When the pressure roller 20 is in pressure contact with the heat roller 10, both ends of the elastic layer 22 are deformed so that only the second region 22b is expanded as shown in FIG. 3, and the first region 22a is not deformed.

  In the case of the pressure roller 120 having the conventional shape, as already shown in FIG. 5, stress that peels the elastic layer 122 from the core metal 121 is applied to the elastic layer 122 when pressed against the heat roller 110. When the pressure roller 120 is in pressure contact with the heat roller 110 and rotates, this stress is repeatedly applied, and the elastic body layer 122 adhered to the cored bar 121 is gradually peeled from the cored bar 121 from both ends, and further peeled off. In some cases, cracking occurred. In this state, since sufficient pressure cannot be applied to the paper P at both ends of the pressure roller 120, the toner image T cannot be stably fixed on the entire paper P.

  However, by configuring the elastic body layer 22 in this way, the first region 22a is not deformed, and thus stress that peels the elastic body 22 from the core metal 21 is not applied. Therefore, the elastic layer 122 can be stably fixed on the paper P for a long time without being peeled off from the cored bar 121.

  The present invention can be used in general for a roller that is deformed by applying pressure and a fixing device for an image forming apparatus.

1 is a schematic configuration diagram of a fixing device according to an embodiment of the present invention. Side surface fragmentary sectional view of the edge part of the pressure roller which concerns on embodiment of this invention Side surface partial sectional view of the end of the pressure roller of FIG. Schematic configuration diagram of a conventional fixing device Side surface partial sectional view of the end of the pressure roller of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixing device 10 Heat roller 20 Pressure roller 21 Core metal 22 Elastic body layer 22a 1st area | region 22b 2nd area | region

Claims (2)

In a roller provided with a cored bar and an elastic layer provided around the cored bar,
The elastic layer includes a first region in contact with the cored bar and a second region provided outside the first region in the radial direction, and the first region has an axial length. A roller that is longer than the second region and is located outside the second region with respect to the axial direction.   A fixing device comprising: a heat roller having a built-in heater; and a pressure roller for pressure-bonding to the heat roller, wherein the roller according to claim 1 is provided as the pressure roller.

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