JP2004258104A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device that prevents deformation of a fixing roller at low costs and makes a nip between the fixing roller and a pressure roller uniform, thereby improving fixing performance, and to provide an image forming apparatus. <P>SOLUTION: The fixing roller 1 has in it reinforcement ribs 9 that restrict deformation of the roller. The warp restricting device 10 having a pressing member 11 which is disposed opposite the pressure roller 2 and abuts on the peripheral face of the fixing roller 1 in order to restrict warp of the fixing roller 1 due to the press-contact of the pressure roller 2, is arranged. The pressing member 11 of the warp restricting device is positioned corresponding to the reinforcement ribs 9 in the fixing roller in the roller axial direction. Thus, while crush of the fixing roller in a radial direction is prevented by the reinforcement ribs 9, deformation of the fixing roller is prevented by hindering the fixing roller from warping and deforming in the axial direction. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fixing device in an image forming apparatus such as a copying machine, a printer, and a facsimile.
[0002]
[Prior art]
[Patent Document 1] JP-A-09-171321 [Patent Document 2] JP-A-09-212026 [Patent Document 3] JP-A-2002-106547 [Patent Document 4] JP-A-2001-296770 [0003] ]
In recent years, there has been a strong demand for energy saving in the field of image forming apparatuses, such as the recent increase in environmental improvement activities and the enactment of the Energy Conservation Law. Focusing on the inside of the image forming apparatus, the heat fixing device consumes a large amount of energy, and various technologies have been proposed and implemented for improving energy efficiency.
[0004]
As an example of improving energy efficiency, there is a method of lowering the standby temperature of the fixing roller when the image forming apparatus is not used, thereby improving energy consumption efficiency. However, according to this method, it takes a long time to warm up the fixing device during use, which causes a problem such that a user cannot immediately work.
[0005]
On the other hand, for example, by increasing the rate of increase in the temperature of the fixing roller (using a fixing roller having a large rate of temperature increase), the low temperature is maintained during standby, and the time required to reach the predetermined temperature during use = warm-up time. Can be shortened. As a method of shortening the warm-up time, it is only necessary to increase the temperature rise rate as described above. One of the methods is to use a member having a small heat capacity such as a thin metal pipe for the fixing roller core in recent years. Many are used.
[0006]
However, if the core of the fixing roller is unnecessarily thinned, the mechanical strength is reduced, and deformation problems such as bending in the longitudinal direction of the fixing roller and crushing of the fixing roller cross section occur. When such a deformation of the fixing roller occurs, the nip formed by the fixing roller and the pressure roller becomes narrow at the center in the axial direction, and a desired nip width cannot be obtained. Therefore, various problems such as generation of paper wrinkles due to a difference in linear velocity between the transport center portion and the end portion occur.
[0007]
That is, when the pressure roller 2 is pressed against the fixing roller 1 as shown in FIG. 8 when the pressure roller 2 is pressed against the fixing roller 1 as shown in FIG. d occurs, and at the same time, collapse of the radial cross section (crush amount = H1-H2) as shown in FIG. 9 is caused. This deformation has occurred to a considerable extent even in the conventional fixing device, but as described above, in the thin fixing roller for energy saving, as the amount of deformation, as a problem in image quality, Has become.
[0008]
The graph of FIG. 10 shows the measurement results of the displacement of the upper and lower surfaces of the fixing roller made of aluminum and the amount of crushing of the outer diameter in the pressing direction of the fixing roller made of aluminum and having a diameter of φ40 mm and a thickness t = 0.3 mm. As the load (pressing force) increases, the fixing roller bends in the axial direction, and the position of the lower surface (the amount of displacement of the lower surface in FIG. 10) increases, but the cross section in the radial direction is remarkably crushed. Conversely, the position of the upper surface of the fixing roller (the amount of displacement of the upper surface in FIG. 10) decreases with the load. Due to this deformation, as described above, the pressure is reduced at the center in the roller axis direction, and the nip is narrowed, so that a uniform nip cannot be formed.
[0009]
As a method for solving these problems, a structure in which a reinforcing member is provided outside or inside a fixing roller has been proposed, as disclosed in Patent Documents 1 and 2.
[0010]
The technique disclosed in Patent Literature 1 is intended to eliminate the deflection in the longitudinal direction of the fixing roller. The reinforcing roller is brought into contact with the pressure roller from the outside thereof, and a spring is applied in a direction to reduce the deflection. To reinforce the pressure roller. A technique of providing an auxiliary roller only at the center of the pressure roller is also disclosed.
[0011]
Further, the technique disclosed in Japanese Patent Application Laid-Open No. H11-133873 aims to eliminate collapse in the roller cross-sectional direction, and is configured by mounting a plurality of rings for reinforcement in a fixing roller.
[0012]
By mounting a ring for reinforcement inside the fixing roller, it is possible to greatly reduce the deflection and crushing of the cross section of the fixing roller.However, when a reinforcing member is mounted, some new problems arise. obtain.
[0013]
That is,
{Circle around (1)} It is difficult to fix the reinforcing member to the fixing roller.
{Circle around (2)} Since a large load is applied to the reinforcing member for preventing the deformation of the fixing roller, if the fixing member is not firmly fixed to the fixing roller, the reinforcing member will soon come off inside the fixing roller.
{Circle around (3)} When the reinforcing member is fixed in the fixing roller in a shrinking state, high accuracy is required for the reinforcing member, and the loading operation requires a technique.
{Circle around (4)} When the fixing roller is fixed in the fixing roller by welding or the like, not only the processing cost is increased, but also the load is concentrated on the welded portion, which may cause damage to the reinforcing ring.
{Circle around (5)} Since another member is contained inside the fixing roller, the heat capacity is locally increased, and the temperature rise in that portion is delayed.
{Circle around (6)} The configuration of the heat source of the fixing roller is restricted due to the reinforcing member (for example, when the fixing roller is heated by an internal halogen heater, the inner reinforcing member is heated before conducting heat to the core metal. And a delay in thermal response occurs).
And so on.
[0014]
[Problems to be solved by the invention]
To solve these problems, for example, Patent Document 3 discloses that a reinforcing rib for obtaining high rigidity of a fixing roller by drawing is provided on the inner surface of the fixing roller. According to this technique, it is effective against crushing in the circumferential direction, but there is a limit to bending in the axial direction, and especially when deployed in a high-speed machine, it is necessary to prevent bending under high load conditions. Is currently limited. Further, it is possible to prevent the bending and crushing by increasing the rib shape, the rib height, the number, and the like of the above-described ribs, but the heat capacity of the fixing roller increases and the effect of shortening the warm-up time decreases. In addition, as described in the above problem (5), there is a disadvantage that the heat capacity is locally increased and the temperature rise in that portion is slow.
[0015]
Further, the technique disclosed in Patent Document 4 is an example in which the above-described problem is solved by providing rollers for preventing bending in each of the bending direction and the crushing direction of the fixing roller. However, according to this technology, since the bending and crushing of the fixing roller is suppressed by a plurality of rollers, the temperature rise locally becomes slow at the contact portion due to the heat capacity of the roller, and the bending and crushing of the fixing roller are prevented. It is necessary to provide the rollers in the direction of suppressing them and to attach them to each of the strong structures, resulting in a problem that the cost is increased.
[0016]
The present invention solves the above-mentioned problems in the conventional fixing device and image forming apparatus, and can prevent deformation of the fixing roller at low cost, and can improve the fixing performance by making the nip with the pressure roller uniform. And an image forming apparatus.
[0017]
[Means for Solving the Problems]
According to the present invention, in a fixing device having a cylindrical fixing roller and a pressure roller pressed against the fixing roller, the fixing roller includes a reinforcing member for regulating deformation of the roller inside the roller. A deflection control device that has a reinforcing portion and has at least one pressing member that abuts on the outer peripheral surface of the fixing roller on the side opposite to the pressing roller, and that controls the deflection of the fixing roller due to the pressing of the pressing roller. And fixing the pressing member of the deflection control device in the axial direction of the fixing roller to the reinforcing member or the reinforcing portion inside the fixing roller.
[0018]
In order to solve the above-mentioned problems, the present invention proposes that the pressing member is rotatably supported in a cylindrical cross-sectional shape, and rotates in contact with the fixing roller.
Further, in order to solve the above-mentioned problem, the present invention proposes to provide a cleaning member that comes into contact with the outer peripheral surface of the pressing member, and an adhering matter collecting unit that stores the adhering matter cleaned and collected by the cleaning member. I do.
[0019]
According to the present invention, the above object is achieved by an image forming apparatus including the fixing device according to any one of claims 1 to 3.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 and 2 are a sectional view in a radial direction and a sectional view in an axial direction showing a main part of an example of the fixing device according to the present invention.
[0021]
In these figures, the fixing roller 1 is rotatably supported on a fixing side plate 5 via a heat insulating bush 3 and a fixing roller bearing 4, and a gear 6 attached to one end of the fixing roller is not shown. It is adapted to receive a rotational driving force by meshing with a driving source. In this example, the material of the fixing roller 1 is a thin pipe of aluminum or iron as a base material, the thickness is about 0.3 to 2.0 mm, and a release layer such as a fluororesin is formed on the outer peripheral surface. , A halogen heater 7 is provided therein.
[0022]
Although not shown, a temperature sensor is arranged in contact with or close to the peripheral surface of the fixing roller 1, and energization to the halogen heater 7 is controlled based on the temperature of the fixing roller 1 detected by the temperature sensor. It has become. Normally, when the power of the image forming apparatus is turned on, a current flows to the halogen heater 7, and the temperature of the fixing roller 1 rapidly rises to a set temperature of about 180 ° C.
[0023]
A bending prevention device 10 is provided on the side opposite to the pressure roller 2 pressed against the fixing roller 1 so as to be in contact with the outer periphery of the fixing roller. The bending prevention device 10 has a pressing member 11 having a pressing portion 11 a that protrudes in a semicircular shape and is pressed against the fixing roller 1, a holding member 12 that holds the pressing member 11, and resists bending of the fixing roller 1. It has urging means 13 such as a spring for urging the pressing member 11 in the direction. The pressing member 11 is fitted to the holding member 12 and held so as to be movable in the vertical direction in the figure, and is urged by urging means 13 in a direction against the bending of the fixing roller 1. The bending prevention device 10 is attached to the structural member 8 of the fixing device at the axial center of the fixing roller 1.
[0024]
Here, naturally, the pressing force on the fixing roller 1 (via the pressing member 11) by the urging means 13 is an urging force capable of correcting the bending of the fixing roller 1. In this example, the urging means 13 such as a spring is provided, but a configuration may be employed in which the distal end position of the pressing portion 11a of the pressing member is previously adjusted to a position where the amount of bending of the fixing roller 1 is corrected.
[0025]
As shown in FIG. 2, a plurality of reinforcing ribs 9 formed by drawing as disclosed in Patent Document 3 are provided on the inner surface of the fixing roller 1. The number of the reinforcing ribs 9 should be appropriately optimized according to the specification conditions, and the number of the reinforcing ribs 9 should be optimized under the conditions satisfying the specifications such as the core metal wall thickness, the core metal material, the fixing roller diameter, the pressing force, and the warm-up. The number and the cross-sectional shape of the reinforcing rib are set. In the present embodiment, nine reinforcing ribs 9 are provided at the center portion (C region) of the fixing roller at a paper interval of 10 to 20 mm and three reinforcing ribs 9 are provided at an end portion of the roller (E region) at an interval of 20 to 50 mm. .
[0026]
As described above, as the number of the reinforcing ribs 9 increases, the flexure / crushing rigidity of the fixing roller 1 increases, but the warm-up time becomes slow because the volume and the heat capacity of the fixing roller increase. Therefore, it is necessary to set the output of the halogen heater 7, the thickness of the fixing roller 1, and the number of the reinforcing ribs 9 so that the warm-up time becomes a target time. Desirably, the shortening of the warm-up time and the increase in the mechanical strength of the fixing roller are in an opposite relationship.
[0027]
On the other hand, although the crushing of the fixing roller 1 can be improved by the effect of the reinforcing rib 9, it cannot be said that it is perfect depending on the fixing conditions described above. It can also be determined from the above-described graph of FIG. 10 that particularly in a high-speed machine in which a necessary nip width needs to be obtained by a large pressing force, both the bending and the crushing tend to increase. As shown in FIG. 2, when the lower surface of the fixing roller 1, whose both ends are supported by the fixing roller bearing 4, is pressed by the pressing roller 2, the central portion of the fixing roller 1 is deformed. Can be easily imagined to be the maximum amount of deflection.
[0028]
By providing the bending prevention device 10 at the central portion in the axial direction of the fixing roller 1, the effect can be further improved. In this case, the bending prevention device 10 is provided at a position corresponding to the reinforcing rib 9 provided on the inner surface of the central portion of the fixing roller 1. It is arranged so that the pressing portion 11a of the bending prevention device 10 matches. The number of the pressing portions 11a that match the positions of the reinforcing ribs 9 may be at one location in the center of the fixing roller, or may be dispersed at several locations in the center. In the present example, it is distributed at three places. In the case where the fixing roller 1 is located at one location, the location that comes into contact with the fixing roller 1 is also one location, so that even if the roller is damaged by the pressing portion 11a against the fixing roller 1, damage can be minimized. On the other hand, in order to prevent the load from being concentrated on one pressing portion 11a, the pressing portion 11a may be provided dispersedly at several places. Regarding the crushing of the fixing roller 1, the crushing strength is highest at the position where the reinforcing rib 9 is arranged in the fixing roller axial direction. It can be said that the portion where the reinforcing rib 9 is not present is a place where the reinforcing rib 9 is crushed and the strength is weak even if the reinforcing rib 9 is present in the vicinity.
[0029]
From the viewpoints described above, by matching the pressing portion 11a of the bending prevention device 10 with the reinforcing rib 9 of the fixing roller 1, the reinforcing rib 9 provided on the inner surface of the fixing roller can be effectively combined with the effect of preventing crushing in the radial direction. The configuration is such that bending deformation in the axial direction of the fixing roller is suppressed to prevent defective fixing due to a reduction in the nip width due to deformation of the fixing roller 1.
[0030]
Next, a second embodiment of the fixing device will be described with reference to FIGS. The fixing device according to the present embodiment is different from the fixing device according to the embodiment described with reference to FIGS. 1 and 2 only in the configuration of the deflection preventing device 20. Is omitted.
[0031]
In the present embodiment, the bending prevention device 20 includes three rollers 21, a roller shaft 22 that supports the rollers 21, a bearing 23, a holding member 12, and urging units 13. The bearing 23 is held by the holding member 12 so as to be movable in the up and down direction in the figure, and is pressed downward in the figure by the urging means 13, 13 so that the three rollers 21 resist the bending of the fixing roller 1. Energize to. This limits the deformation of the fixing roller 1. The roller 21 rotates with the fixing roller 1.
[0032]
Here, the pressing force on the fixing roller 1 (via the rollers 21) by the urging means 13 is, of course, an urging force capable of correcting the bending of the fixing roller 1. In this example, the urging means 13 such as a spring is provided. However, as shown in FIG. 6, a configuration may be employed in which the tip end position of the roller 21 is previously adjusted to a position where the amount of deflection of the fixing roller 1 is corrected.
[0033]
The roller 21 is made of a metal or a heat-resistant resin, and a release layer such as PAF or PTFE for preventing toner from adhering may be provided on the surface (outer peripheral surface).
The disposition position of the roller 21 is such that the roller 21 coincides with a position corresponding to the reinforcing rib 9 provided on the inner surface of the central portion of the fixing roller 1, similarly to the pressing portion 11 a of the bending prevention device 10 in the above embodiment. Deploy. Further, the shape of the contact portion of the roller 21 with the fixing roller is preferably such that the tip has a curvature (as viewed from the direction of FIG. 4) to prevent toner adhesion as much as possible. Although the number of the rollers 21 is three in this example (three), the heat of the fixing roller 1 may be deprived by increasing the number of contact points unnecessarily. Therefore, as shown in FIG. Roller 21).
[0034]
FIG. 6 shows a third embodiment in which the roller bearing 23 is fixed to the roller holding member 24. In this example, a similar effect can be obtained. The bending prevention device 20C is configured so that the roller 21 is arranged at a position where the fixing roller 1 contacts. This limits the deformation of the fixing roller 1.
[0035]
In the example shown in FIG. 7, a toner removing member 25, for example, a scraper is arranged by applying an appropriate pressure so as to contact the surface of the roller 21 of the deflection preventing device 20C. The contact of the toner removing member 25 with the roller 21 may be performed by using an urging means (not shown), or the toner removing member 25 may be fixedly arranged and the elasticity of the toner removing member itself may be used.
[0036]
The contact portion of the toner removing member 25 with the roller has a sharp shape, and when the fixing roller 1 rotates in the direction of the arrow (clockwise) in the figure, the roller 21 is simultaneously moved in the direction of the arrow (counterclockwise in the figure). ), The toner is adhered to the surface of the roller 21 and can be cleaned by the tip of the toner removing member 25.
[0037]
The material of the toner removing member 25 may be, for example, a stainless plate having a thickness t of about 0.1 mm or a structure such as a polyimide film, and the vicinity of the fixing roller 1 controlled at about 180 ° C. It is preferable that the material has sufficient heat resistance even when it is arranged in a space.
[0038]
By the way, since the roller 21 contacts and presses the fixing roller 1 as described above, the toner slightly offset to the fixing roller 1 may be transferred to the roller 21 during the image forming operation. A release layer such as PFA or PTFE having excellent releasability may be added to the surface or the entire surface of the roller 21 itself. There is a possibility that the fixing roller 1 will be pressed by a strong load. Further, when the toner adhered to the outer peripheral surface of the roller 21 is re-transferred to the surface of the fixing roller, the toner may be transferred onto the transfer paper P, resulting in an abnormal image. Therefore, in the present embodiment, the toner removing member 25 is configured to contact the outer peripheral surface of the roller 21 to prevent the toner from adhering to the outer peripheral surface of the roller 21. At the downstream position of the toner removing member 25 in the roller rotation direction, there is provided a toner collecting unit 26 for accumulating the removed toner, and the image formed by the toner separated and removed by the toner removing member 25 falling to the fixing roller 1 is provided. It is configured to prevent abnormalities. In the example of FIG. 7, the position of the roller 21 is fixed by a roller bearing 23 attached to a roller support member 24 (see FIG. 6). However, as in the embodiment of FIGS. It is of course possible to provide the toner removing member 25 and the toner collecting unit 26 with respect to the configuration in which the fixing roller 1 is pressed via the fixing roller 21.
[0039]
Although the present invention has been described with reference to the illustrated examples, the present invention is not limited thereto. The number, spacing, and shape of the ribs provided inside the fixing roller are arbitrary, and are not limited to ribs formed by drawing, but may be those provided with a reinforcing ring. In addition, the number of pressing portions of the deflection restricting member provided in accordance with the position of the rib (reinforcing portion) or the reinforcing ring (reinforcing member) (coordinated in the axial direction of the roller) is one or the same as shown in the illustrated example. The number is not limited to three. The heating method of the fixing roller is not limited to the halogen heater, and any heating method such as induction heating and resistance heating can be adopted. The location of the heating means is not limited to the inside of the roller, but may be heating from the outside of the roller.
[0040]
The configuration of the image forming apparatus other than the fixing device is the same as that of a conventionally known device, and a description thereof will be omitted. Further, the image forming apparatus can take any form such as a copying machine, a printer, a facsimile, or a multifunction peripheral.
[0041]
【The invention's effect】
As described above, according to the fixing device and the image forming apparatus of the present invention, the position of the pressing member of the deflection control device in the axial direction of the fixing roller matches the reinforcing member or the reinforcing portion provided inside the fixing roller. In addition to the effect of preventing the crushing in the radial direction by the reinforcing member or the reinforcing portion provided on the inner surface of the fixing roller, the fixing nip caused by the reduction of the nip width due to the deformation of the fixing roller by effectively suppressing the bending deformation in the fixing roller axial direction. Defects can be prevented. Further, since the deformation (crushing and bending) of the fixing roller can be prevented with a small number of reinforcing members or reinforcing portions, the deformation of the fixing roller can be prevented while reducing the cost.
[0042]
According to the configuration of the second aspect, the pressing member is rotatably supported in a cylindrical cross-sectional shape, and rotates in contact with the fixing roller, so that the surface of the fixing roller can be prevented from being damaged.
[0043]
According to the third aspect of the present invention, since the cleaning member that comes into contact with the outer peripheral surface of the pressing member and the deposit recovery section that stores the deposit cleaned and collected by the cleaning member are provided, the fixing roller is transferred to the pressing member. It can clean toner and paper dust. Further, it is possible to prevent an abnormal image caused by retransfer of the cleaned and collected toner and paper powder to the fixing roller.
[Brief description of the drawings]
FIG. 1 is a radial cross-sectional view showing a main part of an example of a fixing device according to the present invention.
FIG. 2 is an axial sectional view showing a main part of an example of the fixing device according to the present invention.
FIG. 3 is a radial cross-sectional view illustrating a main part of a second embodiment of the fixing device.
FIG. 4 is an axial sectional view showing a main part of a second embodiment of the fixing device.
FIG. 5 is a radial cross-sectional view showing a modification of the second embodiment provided with a deflection preventing device having one roller (pressing member).
FIG. 6 is a radial sectional view showing a main part of a third embodiment of the fixing device.
FIG. 7 is a radial cross-sectional view showing a modification of the third embodiment in which a toner removing member and a toner collecting section are provided.
FIG. 8 is a schematic diagram for explaining an axial deflection of a fixing roller in a conventional fixing device.
FIG. 9 is a schematic diagram for explaining radial collapse of a fixing roller in a conventional fixing device.
FIG. 10 is a graph showing a relationship between a load due to a pressure roller and a deformation amount of a fixing roller.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fixing roller 2 Pressure roller 9 Reinforcement rib 10, 20 Bending prevention device 11 Pressing member 11a Pressing portion 12 Holding member 13 Energizing means 21 Roller (pressing member)
25 Toner removal member (cleaning member)
26 Toner Collection Section (Adhesion Collection Section)

Claims (4)

In a fixing device having a cylindrical fixing roller and a pressure roller pressed against the fixing roller,
The fixing roller has a reinforcing member or a reinforcing portion for regulating deformation of the roller inside the roller,
A deflection regulating device that has at least one pressing member that abuts on the outer peripheral surface of the fixing roller on the side opposite to the pressure roller, and that regulates deflection of the fixing roller due to pressure contact of the pressure roller;
A fixing device, wherein a position of a pressing member of the deflection control device in an axial direction of the fixing roller coincides with the reinforcing member or the reinforcing portion inside the fixing roller. The fixing device according to claim 1, wherein the pressing member is rotatably supported in a cylindrical cross-sectional shape, and rotates in contact with the fixing roller. The fixing device according to claim 2, further comprising: a cleaning member that contacts an outer peripheral surface of the pressing member; and an adhering matter collecting unit that stores the adhering matter cleaned and collected by the cleaning member. An image forming apparatus comprising the fixing device according to claim 1.

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