JP4110010B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND 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]
Japanese Patent Laid-Open No. 09-171321 [Patent Document 2]
Japanese Patent Application Laid-Open No. 09-212026 [Patent Document 3]
JP 2002-106547 A [Patent Document 4]
Japanese Patent Laid-Open No. 2001-296770
In recent years, there has been a strong demand for energy saving in the field of image forming apparatuses, such as recent environmental improvement activities and enactment of the Energy Saving Law. Focusing on the inside of the image forming apparatus, the heat fixing apparatus consumes a large amount of energy, and various techniques have been proposed and implemented for improving energy efficiency.
[0004]
As an example of improving energy efficiency, there is a method of reducing energy consumption efficiency by lowering the standby temperature of the fixing roller when the image forming apparatus is not used. However, according to this method, it takes time to warm up the fixing device at the time of use, resulting in problems such as the user being unable to work immediately.
[0005]
On the other hand, for example, by increasing the rate of increase of the fixing roller temperature (using a fixing roller having a large temperature increase rate), the low temperature is maintained during standby, and the time to reach a predetermined temperature during use = warm-up time Can be shortened. As a method for shortening the warm-up time, it is sufficient to increase the rate of temperature increase as described above, but as one of the methods, a member having a small heat capacity such as a thin metal pipe has recently been used for the fixing roller core metal. Many are used.
[0006]
However, if the core metal of the fixing roller is unnecessarily thinned, the mechanical strength is lowered, and deformation problems such as bending of the fixing roller in the longitudinal direction and collapse 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 in the central portion in the axial direction, and a desired nip width cannot be obtained. Various problems such as generation of paper wrinkles due to a difference in linear velocity between the conveyance center and the end occur.
[0007]
That is, in the case of a low mechanical strength roller such as a thin roller, when the pressure roller 2 is pressed against the fixing roller 1 as shown in FIG. d occurs, and at the same time, the radial cross section as shown in FIG. 9 is crushed (crushed amount = H1-H2). This deformation has occurred in the conventional fixing device, but as described above, the thin fixing roller capable of saving energy is regarded as a problem in image quality due to the size of the deformation. It 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 having a diameter of 40 mm, the thickness t = 0.3 mm and the material made of aluminum, and the outer diameter crushing amount in the pressing direction of the fixing roller. As the load (pressing force) increases, the fixing roller is deflected in the axial direction, and the position of the lower surface (the amount of displacement of the lower surface in FIG. 10) rises. On the contrary, 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 lowered at the center in the roller axial direction, the nip becomes narrow, and a uniform nip cannot be formed, thus causing a fixing failure.
[0009]
As a method for solving these problems, as disclosed in Patent Documents 1 and 2, a structure in which a reinforcing member is provided outside or inside the fixing roller has been proposed.
[0010]
The technique disclosed in Patent Document 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, and the deflection is reduced by a spring. The pressure roller is reinforced. A technique for providing an auxiliary roller only at the center of the pressure roller is also disclosed.
[0011]
The technique disclosed in Patent Document 2 is intended to eliminate the collapse in the roller cross-section direction, and is configured by loading a plurality of reinforcing rings in the fixing roller.
[0012]
By the way, if a ring for reinforcement is loaded in the fixing roller, the deflection of the fixing roller and the collapse of the cross section can be greatly reduced. However, when a reinforcing member is loaded, several new problems arise. obtain.
[0013]
That is,
(1) It is difficult to fix the reinforcing member to the fixing roller.
(2) Since a large load is applied to the reinforcing member for preventing the deformation of the fixing roller, the fixing member is easily detached within the fixing roller unless it is firmly fixed to the fixing roller.
{Circle around (3)} When the reinforcing member is fixed in the fixing roller in a state of being squeezed, high accuracy is required for the reinforcing member, and a technique is also required for the loading operation.
(4) In addition, when fixing in the fixing roller by welding or the like, not only processing cost is required, but also the load concentrates on the welded part, causing damage to the reinforcing ring.
(5) Since another member is contained inside the fixing roller, the heat capacity is locally increased, and the temperature rise at that portion is delayed.
(6) The structure of the heat source of the fixing roller is limited 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 cored bar. This causes a delay in thermal response).
And so on.
[0014]
[Problems to be solved by the invention]
In view of these problems, for example, Patent Document 3 discloses that a reinforcing rib for obtaining high rigidity of the fixing roller is provided on the inner surface of the fixing roller by drawing. Although this technique is effective against crushing in the circumferential direction, there is a limit to axial bending, especially when it is deployed on a high-speed machine to prevent bending depending on high load conditions. Is currently limited. In addition, it is possible to increase the shape, height, number, etc. of the ribs described above and prevent bending and crushing, but the heat capacity of the fixing roller is increased accordingly, and the effect of shortening the warm-up time is reduced. In addition, as described in the above problem (5), there is a drawback that the heat capacity is locally increased and the temperature rise at that portion is delayed.
[0015]
The technique disclosed in Patent Document 4 is an example in which the above-described problem is solved by providing a roller for preventing bending in each of the bending direction and the crushing direction of the fixing roller. However, according to this technology, the fixing roller bends / crushes with a plurality of rollers, so the temperature rises locally at the contact area due to the heat capacity of the rollers, or the fixing roller is bent / crushed. There is a problem in that the rollers need to be provided in the direction to be suppressed and attached to each of the strong structures, resulting in an increase in cost.
[0016]
The present invention solves the above-mentioned problems in the conventional fixing device and image forming apparatus, prevents deformation of the fixing roller at low cost, and makes the nip with the pressure roller uniform to improve the fixing performance. It is another object of the present invention to provide an image forming apparatus.
[0017]
[Means for Solving the Problems]
According to the present invention, in the fixing device having a cylindrical fixing roller and a pressure roller pressed against the fixing roller, only one is disposed at the axial center of the fixing roller according to the present invention. A bending restricting device is provided that presses the outer peripheral surface of the fixing roller on the side opposite to the pressure roller to restrict the bending of the fixing roller due to the pressure contact of the pressure roller, and the bending restricting device is arranged in parallel in the fixing roller axial direction. The fixing roller includes a plurality of reinforcing members or reinforcing portions for restricting deformation of the roller inside the roller at positions in the roller axial direction corresponding to the pressing members of the deflection regulating device. It is solved by being provided.
[0018]
In order to solve the above problems, the present invention proposes that the pressing member is rotatably supported with a cylindrical cross-sectional shape and rotates in contact with the fixing roller.
In order to solve the above problems, the present invention is such that the shape of the contact portion of the pressing member with the fixing roller has a curvature when viewed from a direction perpendicular to the fixing roller axial direction. Propose that.
In order to solve the above problems, the present invention proposes to provide a cleaning member that comes into contact with the outer peripheral surface of the pressing member, and an attached matter collecting section that contains the attached matter cleaned and collected by the cleaning member. To do.
[0019]
In addition, according to the present invention, the above problem is solved by an image forming apparatus including the fixing device according to any one of claims 1 to 4 .
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 and 2 are a radial sectional view and an axial sectional view showing a main part of an example of a fixing device according to the present invention.
[0021]
In these drawings, the fixing roller 1 is rotatably supported by 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 engaged with a driving source and receives a rotational driving force. In this example, the material of the fixing roller 1 is a thin pipe made of aluminum or iron, 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 disposed inside.
[0022]
Although not shown in the figure, 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 is like that. Normally, when the power of the image forming apparatus is turned on, a current flows to the halogen heater 7 so that the temperature of the fixing roller 1 rapidly rises to a set temperature around 180 ° C.
[0023]
An anti-bending device 10 is provided on the side opposite to the pressure roller 2 pressed against the fixing roller 1 so as to contact the outer periphery of the fixing roller. The bending prevention device 10 resists bending of the pressing member 11 having a pressing portion 11 a that protrudes in a semicircular shape and pressed against the fixing roller 1, a holding member 12 that holds the pressing member 11, and the fixing roller 1. It has urging means 13, 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 is held so as to be movable in the vertical direction in the figure, and is urged by the urging means 13 in a direction against the bending of the fixing roller 1. The deflection preventing device 10 is attached to the structural member 8 of the fixing device at the central portion in the axial direction of the fixing roller 1.
[0024]
Here, as a matter of course, the pressing force applied to the fixing roller 1 (via the pressing member 11) by the urging means 13 is an urging force capable of correcting the deflection of the fixing roller 1. In this example, the biasing means 13 such as a spring is provided. However, a configuration in which the tip end position of the pressing portion 11a of the pressing member is fixed in advance to a position where the deflection amount of the fixing roller 1 is corrected may be employed.
[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 optimized according to the specification conditions as appropriate, and is appropriate under the conditions satisfying the specifications such as the core metal thickness of the fixing roller 1, 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 this example, nine reinforcing ribs 9 are provided in the center portion (C region) of the fixing roller with a rib interval of 10 to 20 mm, and three end portions of the roller (E region) with a spacing of 20 to 50 mm. .
[0026]
As described above, as the number of the reinforcing ribs 9 increases, the bending / collapse rigidity of the fixing roller 1 increases. However, since the volume and the heat capacity of the fixing roller increase, the warm-up time is delayed. Therefore, it is necessary to set the output of the halogen heater 7, the thickness of the fixing roller 1, and the number of reinforcing ribs 9 so that the warm-up time becomes the target time. Desirably, the shortening of the warm-up time mentioned above and the increase in the mechanical strength of the fixing roller are contradictory.
[0027]
On the other hand, the crushing of the fixing roller 1 can be improved by the effect of the reinforcing rib 9, but it cannot be said to be perfect depending on the fixing conditions described above. In particular, in a high-speed machine that needs to obtain a necessary nip width with a large applied pressure, it can be judged from the graph of FIG. Regarding the axial deflection of the fixing roller 1, as shown in FIG. 2, when the lower surface of the fixing roller 1 supported at both ends by the fixing roller bearing 4 is pressed by the pressure roller 2, It can be easily imagined that is the maximum amount of deflection.
[0028]
The bending prevention device 10 can be more effectively provided by being provided in the central portion of the fixing roller 1 in the axial direction. At this time, the bending prevention device 10 is located at a position corresponding to the reinforcing rib 9 provided on the inner surface of the central portion of the fixing roller 1. It arrange | positions so that the press part 11a of the bending prevention apparatus 10 may correspond. The number of the pressing portion 11a to coincide with the position of the reinforcement rib 9 is in this example was dispersed in three places, and so as not to concentrate the load on one of the pressing portion 11a. Regarding the crushing of the fixing roller 1, the crushing strength is the strongest at the portion where the reinforcing rib 9 is arranged in the fixing roller axial direction. Even if the reinforcing rib 9 exists in the vicinity of the portion without the reinforcing rib 9, it can be said that the portion is crushed and weak in strength.
[0029]
From the above viewpoint, by matching the pressing portion 11a of the deflection preventing device 10 with the position of the reinforcing rib 9 of the fixing roller 1, it is effectively combined with the effect of preventing the radial ribs from being crushed by the reinforcing rib 9 provided on the inner surface of the fixing roller. The configuration is such that the bending deformation in the axial direction of the fixing roller is suppressed and the fixing failure due to the reduction in the nip width due to the deformation of the fixing roller 1 is prevented.
[0030]
Next, a second embodiment of the fixing device will be described with reference to FIGS. The fixing device of this embodiment is different from the fixing device of the embodiment described with reference to FIGS. 1 and 2 only in the configuration of the bending prevention device 20, and the same portions are denoted by the same reference numerals and redundant description. Is omitted.
[0031]
In the present embodiment, the deflection preventing device 20 includes three rollers 21, a roller shaft 22 that supports the rollers 21, a bearing 23, a holding member 12, and biasing means 13 and 13. The bearing 23 is held by the holding member 12 so as to be movable in the vertical direction in the figure, and is pressed downward by the urging means 13, 13 so that the three rollers 21 resist the bending of the fixing roller 1. Energize to. Thereby, the deformation of the fixing roller 1 is limited. The roller 21 rotates along with the fixing roller 1.
[0032]
Here, as a matter of course, the pressing force to the fixing roller 1 (via the roller 21) by the urging means 13 is an urging force capable of correcting the deflection of the fixing roller 1. In this example, the biasing means 13 such as a spring is provided. However, as shown in FIG. 6, a configuration may be adopted in which the leading end position of the roller 21 is fixed in advance to a position where the amount of deflection of the fixing roller 1 is corrected.
[0033]
The roller 21 may be made of metal or heat resistant resin, and a release layer such as PAF or PTFE may be provided on the surface (outer peripheral surface) to prevent toner adhesion.
The roller 21 is arranged so that the roller 21 is aligned with the reinforcing rib 9 provided on the inner surface of the center portion of the fixing roller 1 in the same manner as the pressing portion 11a of the deflection preventing 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) and prevents toner adhesion as much as possible. the number of rollers 21) Ru der three places (three) in this embodiment.
[0034]
FIG. 6 shows a third embodiment in which the roller bearing 23 is fixed to the roller holding member 24. In this example, the same effect can be obtained. The deflection preventing device 20C is configured so that the roller 21 is disposed at a position where the fixing roller 1 contacts. Thereby, the deformation of the fixing roller 1 is limited.
[0035]
In the example shown in FIG. 7, the toner removing member 25, for example, a scraper, is placed under an appropriate pressure so as to come into contact with the surface of the roller 21 of the deflection preventing device 20 </ b> C. For contact of the toner removing member 25 with the roller 21, an urging means (not shown) may be used, 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 also simultaneously rotates in the direction of the arrow (counterclockwise) in the figure. ) The toner that is driven to rotate and adheres to the surface of the roller 21 can be cleaned at the tip of the toner removing member 25.
[0037]
The material of the toner removing member 25 may be, for example, a stainless steel plate having a thickness of about t = 0.1 mm, or may be a polyimide film, and the vicinity of the fixing roller 1 controlled at around 180 ° C. Those having sufficient heat resistance are also preferred when they are disposed in the.
[0038]
By the way, as described above, the roller 21 contacts and presses the fixing roller 1, so that 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 of the roller 21 or the entire surface. However, when toner adheres to the surface of the roller 21, the roller 21 may have a larger pressing force than the appropriate pressing force. There is a risk of pressing the fixing roller 1 with a strong load. Further, when the toner adhering to the outer peripheral surface of the roller 21 is retransferred to the surface of the fixing roller, the toner may be transferred onto the transfer paper P and an abnormal image may be formed. Therefore, in this example, the toner removing member 25 is brought into contact with the outer peripheral surface of the roller 21 to prevent the toner from adhering to the outer peripheral surface of the roller. Further, a toner collection unit 26 for accumulating the removed toner is provided at a downstream position in the roller rotation direction of the toner removing member 25, and an image obtained by dropping the toner separated and removed by the toner removing member 25 onto the fixing roller 1. 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 the roller support member 24 (see FIG. 6). However, as shown in FIGS. Of course, it is 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 roller 21.
[0039]
As mentioned above, although this invention was demonstrated by the example of illustration, this invention is not limited to this. The rib provided in the fixing roller is not limited to a rib formed by drawing , but may be a rib loaded with a reinforcing ring. Further, the number of the pressing portions of the deflection regulating member (matching the position in the roller axis direction) provided in accordance with the position of the rib (reinforcing portion) or the reinforcing ring (reinforcing member) 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 or resistance heating can be adopted. Further, the location of the heating means is not limited to the inside of the roller, and heating from the outside of the roller may be used.
[0040]
Note that the configuration of the image forming apparatus other than the fixing device is the same as that conventionally known, 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 machine, or a multifunction machine.
[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 regulating device in the axial direction of the fixing roller is matched with the reinforcing member or the reinforcing portion provided inside the fixing roller. Fixing due to the reduction of the nip width due to the deformation of the fixing roller by effectively suppressing the bending deformation of the fixing roller in the axial direction together with the effect of preventing the radial crushing by the reinforcing member or the reinforcing portion provided on the inner surface of the fixing roller Defects can be prevented. Further, since the deformation (crushing or 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 second aspect of the present invention, the pressing member is rotatably supported with a cylindrical cross-sectional shape and rotates in contact with the fixing roller, so that damage to the surface of the fixing roller can be prevented.
[0043]
According to the configuration of the fourth aspect, the cleaning member that contacts the outer peripheral surface of the pressing member and the deposit collecting unit that stores the deposit collected and collected by the cleaning member are provided, so that the fixing roller transfers to the pressing member. Toner, paper dust, etc. can be cleaned. Further, it is possible to prevent an abnormal image that is generated when the cleaned / collected toner, paper dust, and the like are retransferred 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 a cross-sectional view in the axial direction showing a main part of an example of a fixing device according to the present invention.
FIG. 3 is a radial cross-sectional view showing a main part in a second embodiment of the fixing device.
FIG. 4 is a cross-sectional view in the axial direction showing a main part in 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 cross-sectional view showing a main part in a third embodiment of the fixing device.
FIG. 7 is a radial cross-sectional view showing a modified example of the third embodiment provided with a toner removing member and a toner collecting portion.
FIG. 8 is a schematic diagram for explaining axial deflection of a fixing roller in a conventional fixing device.
FIG. 9 is a schematic diagram for explaining radial crushing of a fixing roller in a conventional fixing device.
FIG. 10 is a graph showing the relationship between the load applied by the pressure roller and the deformation amount of the fixing roller.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fixing roller 2 Pressure roller 9 Reinforcement rib 10,20 Deflection prevention device 11 Pressing member 11a Pressing part 12 Holding member 13 Energizing means 21 Roller (pressing member)
25 Toner removal member (cleaning member)
26 Toner recovery unit (attachment collection unit)

Claims (5)

In a fixing device having a cylindrical fixing roller and a pressure roller pressed against the fixing roller,
A deflection regulating device that is disposed only at the center in the axial direction of the fixing roller and presses the outer peripheral surface of the fixing roller on the side opposite to the pressure roller to regulate the deflection of the fixing roller due to the pressure contact of the pressure roller. Provided,
The deflection regulating device has a plurality of pressing members arranged in parallel in the fixing roller axial direction,
The fixing roller is provided with a plurality of reinforcing members or reinforcing portions for restricting deformation of the roller at a position in the roller axial direction corresponding to each pressing member of the deflection regulating device. apparatus.   The fixing device according to claim 1, wherein the pressing member is rotatably supported with a cylindrical cross-sectional shape, and rotates in contact with the fixing roller. 3. The fixing according to claim 1, wherein a shape of a contact portion of the pressing member with the fixing roller is a shape having a curvature when viewed from a direction perpendicular to the fixing roller axial direction. apparatus. Wherein to a cleaning member in contact with the outer peripheral surface of the pressing member, characterized by providing a deposit collecting portion for accommodating the deposit was cleaned and collected by the cleaning member, a fixing device according to claim 2 or 3 . An image forming apparatus comprising: a fixing device according to any one of claims 1-4.

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