JP5581786B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device and an image forming apparatus, and more particularly to a technique preferably applied in a fixing operation of an image forming apparatus using an electrophotographic system.

  In an image forming apparatus using an electrophotographic system, a fixing device for fixing an unfixed toner image transferred onto a recording sheet is mounted. The fixing device fixes the toner image on the recording paper by passing the recording paper on which the toner image is transferred to a fixing nip portion formed by, for example, a fixing roller and a pressure roller.

  In this type of fixing device, the recording paper may be wrinkled during the fixing process. Therefore, in Patent Document 1, as shown in FIG. 6, the thickness of both ends of the elastic layer 26 in the fixing roller 25 that is rotationally driven by a drive motor is made thicker than the center, and the shape of the fixing roller 25 is determined at both ends. Further, a fixing device having a so-called “reverse crown shape” having a smaller diameter at the center is described. By making the shape of the fixing roller 25 into an inverted crown shape, the peripheral speed of the end portion having a large outer diameter becomes faster than that of the central portion, and a pulling force acts on the recording paper in the fixing nip outward in the paper width direction. When the recording paper receives such a force pulling outward in the paper width direction, generation of wrinkles can be suppressed.

  However, when the fixing roller 25 has an inverted crown shape, the nip pressure at the center portion is lowered, and the fixing performance at the center portion is lowered as compared with both end portions. In particular, when thick paper is used as the recording paper, there is a possibility that fixing failure may occur in the central portion. Therefore, it is also conceivable to reduce the difference between the outer diameter of both ends of the fixing roller 25 and the outer diameter of the central portion, suppress the decrease in the nip pressure in the central portion, and suppress the decrease in the fixing performance in the central portion. However, in this case, the distance from the fixing nip to the center of rotation of the fixing roller 25 is almost the same at both ends and the center of the fixing roller 25, and there is a problem that wrinkles of the recording paper cannot be suppressed over time. . Further, in the case of a recording paper such as thin paper which tends to cause wrinkles, there is a problem that wrinkles cannot be sufficiently suppressed.

  Therefore, the present invention has been made in view of the above problems, and the object thereof is to realize good fixability for a wide range of paper types and to suppress the generation of wrinkles on recording paper over time. Is to do so.

In order to achieve the above object, a fixing device according to one aspect of the present invention forms a fixing nip between a heating unit that heats a toner image on a transferred recording paper, and the heating unit. and pressurizing means for pressurizing the recording sheet passing through a deflection forming means for bending the heating means or pressure means along the recording sheet conveyance direction and parallel to the plane, have a heating means or pressure means axis of the will have a different stiffness in the direction parallel to the direction perpendicular to the recording sheet conveyance direction.

  According to the present invention, the heating unit and the pressure unit in the fixing device are provided with a mechanism for bending, the amount of bending can be adjusted so that the recording paper passing through the fixing device does not wrinkle, and the nip width of the fixing nip is recorded. Since it can be maintained almost uniformly in the paper width direction, it is possible to achieve good fixability over a wide range of paper types and to suppress wrinkling of the recording paper over time.

1 is a schematic configuration diagram of a fixing device according to an embodiment of the present invention. FIG. 3 is a side view of the fixing device according to the embodiment of the present invention in the vicinity of the fixing nip (viewed from the recording paper conveyance direction). FIG. 3 is a top view (viewed from the upper part of the apparatus) around the fixing nip of the fixing apparatus according to the embodiment of the present invention. FIG. 4 is a cross-sectional view of a heating roller and a pressure roller of the fixing device according to the embodiment of the present invention. FIG. 5 is a diagram for explaining a force and a nip width acting on a sheet at a fixing nip in the embodiment of the present invention. FIG. 10 is a view showing a conventional fixing roller.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram illustrating an appearance and a control block of a fixing device according to the present embodiment, FIG. 2 is a view of the periphery of the fixing nip as viewed from the recording paper conveyance direction, and FIG. FIG. 4 is a sectional view of the heating roller and the pressure roller.

  The fixing device 1 according to the present embodiment is a device mounted on an image forming apparatus using an electrophotographic system, and includes a heating roller 2 as a heating unit, a pressure roller 3 as a pressing unit, and a driving roller 4. The pressure roller 3 is provided so that the driving roller 4 is in pressure contact with the pressure roller 3. The heating roller 2 and the pressure roller 3 are composed of a metal core 5 made of an elastic body such as metal and silicon rubber, and cylindrical elastic layers 17 and 18 made of silicon rubber or the like provided so as to surround the metal core. It is configured.

  The cross section of the heating roller 2 and the pressure roller 3 is configured as shown in FIG. 4, and the shaft core has a structure in which a metal 21 is sandwiched between elastic bodies 22, and the entire shaft core has a cylindrical shape. It has become. A cylindrical elastic layer 17 is rotatably disposed on the outer periphery of the shaft core. In the heating roller 2 and the pressure roller 3, a lubricant 23 is applied between the cored bar 5 (metal part 21, elastic body 22) and the surrounding elastic layer 17, and a metal is placed outside the elastic layer. A thin film 16 is wound.

  Further, as shown in FIG. 3, the heating roller 2 and the pressure roller 3 are in contact with a bending amount adjusting mechanism 19 serving as a bending forming means. The pressing force adjusting mechanism 13 shown in FIG. Form a nip. Both ends of the cored bar portion of each roller are attached to side walls (not shown) of the apparatus main body via fixed bearings 15a and 15b in the paper transport direction.

  As shown in FIG. 3, when the plunger 20 of the deflection adjustment mechanism 19 of the heating roller 2 and the pressure roller 3 is moved to the side opposite to the paper transport direction A, each roller is moved to the bearing 2 with the bearing 15a as a fulcrum. As indicated by the point cutting line B, it bends in the paper transport direction A. When the movement amount of the plunger 20 of the bending amount adjusting mechanism 19 increases, the bending amount of the heating roller 2 and the pressure roller 3 increases. Therefore, by controlling the moving amount of the plunger 20 of the bending amount adjusting mechanism 19, each roller is controlled. Can be controlled. That is, in this embodiment, the bending amount adjusting mechanism 19 functions as a bending forming unit.

  Further, as shown in FIG. 4, the fixing nip is formed by moving the plunger 14 of the pressing force adjusting mechanism 13 of the heating roller toward the pressure roller while each roller is bent.

  As for the heating roller 2 which is a heating means, the metal layer 16 on the surface is heated by an electromagnetic induction heater (not shown).

  FIG. 5 shows the direction of the force acting in the sheet width direction at the fixing nip. As shown in FIG. 5A, when the heating roller 2 and the pressure roller 3 are bent, the force with which each roller tries to convey the paper P in the nip is the direction of the arrow in FIG. become. Since the force acting in the paper width direction is outward, both ends of the paper in the width direction are pulled outward in the fixing nip 24, so that paper wrinkles are less likely to occur.

  Further, the nip width 24 is substantially uniform in the recording paper width direction as shown in FIG. When the deflection amount of the heating roller 2 and the pressure roller 3 is increased, the nip width 24 at the center portion becomes narrower than the end portion and becomes non-uniform. However, the nip width in the practical deflection amount of the heating roller 2 and the pressure roller 3. 24 is so small that the degree of non-uniformity is negligible compared to the nip width of the reverse crown roller. For this reason, uniform fixing performance can be provided in the recording paper width direction.

  Further, it is preferable that the deflection amount of the heating roller 2 and the pressure roller 3 is set to a minimum necessary amount that does not cause wrinkles according to the properties of the recording paper. Furthermore, it is necessary to suppress the generation of wrinkles due to the temporal deterioration of the heating roller 2 and the pressure roller 3. Therefore, the deflection amount output to the display unit 9 in FIG. 1 is compared with the image actually output by the image forming apparatus, and the deflection amount of each roller is adjusted by the operation unit 8 in FIG.

  In the present embodiment, as described above, since the bend amount adjusting mechanism is provided to bend the heating roller and the pressure roller in the fixing device, the bend amount is adjusted so that wrinkles are not generated on the recording paper passing through the fixing device. can do. Specifically, it is as follows.

  When a pulling force is applied to the recording paper in the width direction inside the fixing nip, undulation occurs behind the fixing nip of the recording paper, and the recording paper enters the fixing nip with the undulation occurring. Here, if the force in the width direction working in the fixing nip is large, the undulation will be large, and if the force is small or outward, the undulation will be small. If the waviness generated behind the fixing nip of the recording paper is large, the probability that the recording paper will be wrinkled after passing through the fixing nip is high, but if the waviness is small, the probability that the recording paper is wrinkled is low. Therefore, in order to prevent the generation of wrinkles, the heating roller and the pressure roller in the fixing device should be bent so that the recording paper is conveyed and at the same time a pulling force is given to the width direction.

  Further, even if the deflection amount is increased by the deflection amount adjusting mechanism, the local nip pressure drop seen in the reverse crown fixing roller or the like does not occur. Furthermore, if the curvatures of deflection of the heating roller and the pressure roller are not too large, the nip width of the fixing nip is substantially uniform in the recording paper width direction.

  As described above, according to the present embodiment, by controlling the deflection amount of the heating roller or the pressure roller, it is possible to obtain the minimum deflection amount that does not cause wrinkles on the recording paper, and the nip width of the fixing nip can be reduced. It is possible to suppress wrinkling of the recording paper while maintaining the uniformity as much as possible, that is, while maintaining uniform fixability in the recording paper width direction.

  The above-described embodiment is a preferred embodiment of the present invention, and the scope of the present invention is not limited to the above-described embodiment alone, and various modifications are made without departing from the gist of the present invention. Implementation is possible.

DESCRIPTION OF SYMBOLS 1 Fixing roller 2 Heating roller 3 Pressure roller 4 Drive roller 5 Roller metal 6 Deflection amount adjustment mechanism 7 Power supply 8 Operation part 9 Display part 10 Control part 11 Heating roller metal 12 Pressure roller metal 13 Pressing force adjustment mechanism 14 Pushing force adjusting mechanism plunger 15a Heating roller mandrel bearing 15b Pressure roller mandrel bearing 16 Metal thin film 17 Heating roller elastic layer 18 Pressure roller elastic layer 19 Deflection amount adjusting mechanism 20 Deflection amount adjusting mechanism plunger 21 Mandrel metal part 22 Core Gold elastic body portion 23 Lubricant 24 Fixing nip 25 Reverse crown shaped fixing roller 26 Reverse crown shape fixing roller elastic body portion P Recording paper A Recording paper transport direction B Fixing roller bending shape

Japanese Patent Laid-Open No. 05-040428

Claims (5)

Heating means for heating the toner image on the transferred recording paper;
A pressurizing unit that forms a fixing nip with the heating unit and pressurizes the recording paper passing through the fixing nip;
Bend forming means for bending the heating means or the pressurizing means along a plane parallel to the recording paper conveyance direction;
I have a,
The axis of the heating means or the pressing means, the fixing device characterized in that it have a different stiffness in the direction parallel to the direction perpendicular to the recording sheet conveyance direction. Heating means for heating the toner image on the transferred recording paper;
A pressurizing unit that forms a fixing nip with the heating unit and pressurizes the recording paper passing through the fixing nip;
Bending means for bending the heating means or the pressurizing means along a plane parallel to the recording paper conveyance direction,
The fixing device according to claim 1, wherein the deflection forming unit controls a deflection amount of the heating unit or the pressing unit based on a pressing amount to the heating unit or the pressing unit . 3. The fixing device according to claim 1, wherein the bend forming unit presses both ends of an axial core portion of the heating unit or the pressurizing unit in a direction parallel to a recording paper conveyance direction. Wherein the deflection forming means, based on the type of recording paper, a fixing device according to any one of claims 1 to 3, characterized in that to control the pressing amount to the heating means or the pressing means. Image forming apparatus characterized by mounting the fixing device according to any one of claims 1 to 4.

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