JPH06103418B2 - Fixing device - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a fixing device which is generally applied to an image recording device such as a printing machine, a copying machine, a printer or a facsimile machine.

The present invention relates to a fixing device which is particularly effective for a multifunctional recording device such as double-sided recording or multiple recording in which recording is performed a plurality of times at high speed on one recording material.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device that is effective for a recording apparatus that has a multifunction device such as a bookbinding or sorter after performing recording such as reduction and enlargement of various sizes.

(Prior Art and Problems Thereof) Conventional image recording apparatuses are mainly multi-functional for low-speed recording, and conversely have high-speed recording for few functions, so that the conditions required for the fixing device are not so great. It wasn't strict.

However, in the fixing device for the multifunction high-speed recording apparatus, the present inventors are apt to cause conveyance failure due to continuous recording or during the conveyance of the subsequent recording material, and not only an appropriate image cannot be obtained under the conventional fixing conditions, I have found that it brings many difficult problems.

However, in the conventional fixing device, since at least two defects are always produced, the composite high-speed recording cannot be realized and it has not been put into practical use at present.

The present inventors have tackled such a difficult problem and solved the conventional problems by the present invention.

The present inventors paid attention to the following six points as particularly important conditions required for a fixing device for a multifunction high-speed recording device. That is, condition 1 ... Fixing property, condition 2 ... Releasing property (dirt or jam) Condition 3 ... Offset property, condition 4 ... Curling property after fixing (dirt on cleaning member) Condition 5 ... Image property (image quality), Condition 6 The roller durability (strength, etc.) is 6 points.

As will be described later, none of the fixing devices known in the related art can satisfy all of the conditions 1 to 6 to a satisfactory degree.

(Object) Under the above conditions 1 to 6, the object of the present invention is to perform a high-speed fixing process with a small amount of electric power, to provide excellent fixing properties, and for a long period of time, the roller pair of the fixing device is contaminated with toner by paper powder. It has excellent releasability so that the roller that contacts the toner image has less toner offset and the life of the cleaning member can be extended, and curl of the recording material can be suppressed over a long period of time. It is an object of the present invention to provide a fixing device satisfying all the conditions, that is, the image quality is low, the image quality is excellent, and the durability is free from abrasion and peeling over a long period of time.

Another object of the present invention is to provide a fixing device capable of satisfying the above-mentioned six conditions at a level superior to conventional ones, particularly in the case of multifunctional recording and high-speed recording.

Other objects of the present invention will become apparent in the following description.

In order to achieve the above object, the present invention has a fixing roller that is in contact with an unfixed image and a pressure roller that forms a nip with this fixing roller, and nips and conveys a recording material carrying an unfixed image at this nip. In the fixing device for performing the fixing, the fixing roller has an elastic layer and a releasable resin surface layer thinner than the elastic layer, and the pressure roller has an elastic layer thicker than the elastic layer of the fixing roller. It has a releasable resin surface layer thinner than this elastic layer, and the thickness of the releasable resin surface layer of the pressure roller is smaller than the thickness of the releasable resin surface layer of the fixing roller. It is a thing.

(Explanation of Embodiments) The difference between the present invention and the conventional device will be clearly described with reference to the embodiments of the present invention.

In the following description, the roller that is in contact with the unfixed image is referred to as a fixing roller, and the roller that is in contact with the back surface of the recording material or one side of the recording material (during double-sided recording) is referred to as a pressure roller.

Here, the present invention will be briefly summarized in comparison with Examples. In the present invention, a fixing roller pair for fixing an unfixed material to a recording material is relatively thin on the side in contact with the unfixed material (t ₁ )
A fixing roller 1 having a thin (t ₂ ) releasable resin thin surface layer 13 equal to or less than the elastic layer on the elastic layer 12 and having a heating means 3 therein, and a thicker layer than the elastic layer 12 of the fixing roller 1 ( t ₃ ) Elastic layer 22
A thin (t ₄ ) releasable resin thin surface layer on or below the elastic layer 22
With a pressure roller 2 having 23, their thickness t ₄ <t ₂ <
The fixing device is characterized by satisfying the relationship of t ₁ <t ₃ .

According to the present invention, the above conditions 1 to 6 are satisfied, long-term use is suppressed, curl generation on the recording material is suppressed to a minimum, the offset toner is small, the fixing property is excellent, and the image quality is good. I was able to. Further, the roller pair can be prevented from being soiled, and the occurrence of jam can be greatly reduced.

FIG. 1 shows a schematic explanatory view of an embodiment of the present invention, and FIG. 2 shows an explanatory view of a main part configuration of the embodiment shown in FIG.

In FIG. 1, 1 is a relatively thin elastic layer such as silicon rubber or fluororubber on a core metal 11 such as aluminum having good heat conduction.
12 is further provided, and a fluorine resin such as a tetrafluoroethylene resin-perfluoroalkoxyethylene resin copolymer (hereinafter referred to as PFA) or a tetrafluoroethylene resin (PTFE) is provided on the elastic layer 12 as an upper layer. The fixing roller is covered with a thin resin layer (a predetermined thickness within the range of 1 μ to 70 μ in this example) as a resin layer.

Reference numeral 2 is a pressure roller that rotates in pressure contact with the fixing roller 1.
A relatively thick elastic layer that is thicker than the elastic layer 12 such as silicon rubber or fluorine rubber on the core metal 21 such as stainless steel or iron.
22 is further provided, and a mixed layer of fluorocarbon resin such as PFA, PTFE, hexafluoroethylene propylene (hereinafter referred to as FEP) and fluororubber is formed on the upper layer to be thinner than the thick elastic layer 22 (10 μm in this example). It is a pressure roller coated with a predetermined thickness within the range of up to 100 μm.

Due to this mixed layer, the surface of the pressure roller has a resin surface layer of a thickness of several .mu.m, which is formed by the fluorine resin floating during firing and which is almost entirely made of fluorine resin.

Reference numeral 3 is a heater such as a halogen lamp for heating the fixing roller from the inside, and the fixing roller surface temperature is always set to the optimum temperature at which the toner can be melted by the heater 3, the temperature detecting element 4, and the control means 31. Maintained.

Reference numeral 5 denotes an offset prevention liquid application means that also serves as a cleaning means for applying an offset prevention liquid such as silicon oil to the surface of the fixing roller. The coating means 5 may be felt-like, but a web is used in this example. The web 51 containing the offset prevention liquid is brought into contact with the fixing roller 1 by the elastic pressing roller 52 such as silicon sponge, and a small amount of the offset prevention liquid is applied to the surface of the fixing roller 1. Further, the web 51 is gradually taken up from the supply roller 54 by the take-up roller 53, and the contact surface of the web with the fixing roller 1 can be sequentially recognized by the control means (not shown).

The recording paper P carrying the unfixed toner image T is fed to the entrance guide 6
The toner image T is permanently fixed to the recording paper P by passing between the roller pair 1 and 2 while being guided by the sheet.
The separation claw 41 that contacts the surface of the roller 1 is provided to separate the recording material from the surface 1 of the roller.

In the above structure, as shown in FIG. 2, the important structure is that the thickness t ₁ of the elastic layer 12 of the fixing roller 1 and the fixing roller 1 are
The thickness t ₂ of the resin layer 13 and the thickness of the elastic layer 22 of the pressure roller 2
There is the following relationship between t ₃ and the thickness t ₄ of the resin layer 23 of the pressure roller 2.

That is, t ₁ > t _{2 for} the roller 1, t ₃ > t _{4 for} the roller 2, and t ₄ <t ₂ <t ₁ <t ₃ between the rollers 1 and 2.

With this configuration, all of the conditions 1 to 6 which could not be obtained in the past can be satisfied as good effects.

The characteristics of this effect will be compared and explained in the table below, but basically, due to the mutual effect of the fixing roller and the pressure roller, mutual defects are compensated for, mutual advantages are improved, and the obtained image quality and The fixing property can be made excellent and the excellent durability can be obtained.

Before describing specific numerical examples, a double-sided recording apparatus will be described as an apparatus in which the present invention is particularly effective and the effect of its application is more stable.

The apparatus shown in FIG. 4 has an image forming section for forming an image on paper by the electrophotographic copying method. This image forming process is publicly known, and its explanation is omitted. Further, in this example, a normal recording paper is used as the transfer material.

In FIG. 4, the present embodiment shows a copying machine 17 and a double-sided device unit 1.
8. It is composed of an automatic document circulation feeder (RDF) 19 and a paper binding device (stapler) 20. The image forming process in the copying machine 17 is known as described above. The document on the platen glass 9 is scanned by the optical system 10, the reflected light is projected on the photoconductor 24 to form an electrostatic latent image, and the latent image is visualized as a toner image by the developing device 25. Turn into. The paper on which this toner image is transferred is fed from the paper feed table 27 to the paper feed roller 28.
Is sent out by the resist roller 29 to the photosensitive member.
Aligned with toner image on 24. After that, the toner image is transferred onto the surface of the paper by the transfer charger 30. Then, it is separated from the surface of the photoconductor by the separation charging device 14 and is conveyed toward the fixing device 36 by the belt 35.
It should be noted that other known means such as a cleaner 32 required for image formation other than those described above are arranged in the peripheral portion of the photoconductor. Fuser
The sheet on which the toner image is fixed after passing through 36 is guided by this guide 38 and discharged to the sorter 20 because the switching guide 38 is at the position shown by the dotted line in the case of copying on only one side. However, in the case of double-sided copying, when the copying on one side is completed, the switching guide 38 is at the position indicated by the solid line in the figure.
Guided to 18.

The double-sided device unit 18 receives the sheet on which the first side copying is completed by the copying machine 17, and sends the sheet again at the next second side copying. In the present embodiment, the auxiliary paper feed table P is provided, and when the paper feed table P is selected in the main body of the copying machine 17, the paper is fed by the paper feed roller 42 to the inside of the auxiliary paper feed table P. It is also possible to send out the sheet of paper and convey it to the transfer section of the main body. The sheet guided to the double-sided device unit 18 by the switching guide 38 and the roller pair 40 described above is discharged by the roller pairs 44, 45 and 46 onto the tray 47 inclined to the upper right in the figure. At this time, the guide sidewall 48 that determines the position of the paper in the lateral direction (the direction perpendicular to the transport direction)
Thus, the lateral positions of the sheets are aligned. Then, the rear end of the sheet is pressed downward by the rotating body 49 having an elastic protrusion on the outer peripheral portion, and the sheet is dragged obliquely downward (left side in the drawing). At this time, by the stop member 50, which will be described in detail later, and the rollers 51 and 52 that cooperate with the stop member 50, the sheets continuously stored in the tray 47 are sent in a shifted state. The fed paper is brought into contact with the roller 53 and the outer peripheral surface of the roller 53, and the roller 5
A belt 58 stretched around 4,55,56,57 is used to make a U-turn, and the front and back sides are reversed to convey. A guide 59 is arranged above the belt 58, and a pressing roller 60 is arranged so as to face the roller 56 by sandwiching the belt 58.
The upper sheet is transported reliably. Further, the guide 59 and the roller 60 can be integrally opened and closed to facilitate the work of removing the jammed paper on the belt 58 when a jam occurs. A roller 61 for re-feeding is arranged at a position opposite to the roller 57 on which the belt 58 is stretched, and cooperates with a sensor 62 for detecting paper passage and a pair of conveying rollers 63.
The sheets conveyed by 58 are sent out one by one from the beginning toward the right in the figure, and thereafter, they are conveyed to the registration roller 29 through the roller pairs 64 and 43 in order. The sheet is sent to the transfer section in synchronism with the image on the second surface formed on the surface of the photoconductor by the registration roller 29, and the second sheet is transferred.
Transfer is performed on the surface. After the transfer is completed, the paper is separated from the surface of the photoconductor, the image is fixed by the fixing device 15, and the paper is conveyed to the switching guide 38. At this point in time, the guide 38 is at the position indicated by the dotted line in the figure, and is therefore ejected out of the machine. Double-sided device section
Reference numeral 18 enables double-sided copying by repeating such operations. Further, as can be seen from the figure, the sheet after fixing tends to warp toward the image forming surface side due to the influence of the configuration of the fixing roller of the fixing device 15 and the sheet conveying path immediately after fixing. However, in this example, in order to change the conveying direction of the sheet, the roller 1 bends the sheet toward the image forming surface side, and since it takes time to pass through the curved portion, the warp of the sheet ( Curl) can be reduced.

The automatic document circulating and feeding device (RDF) 19 separates the originals O loaded on the original placing table 65 by the belts 66 and 67 from the lowermost part thereof and pulls them out one by one. After this, the manuscript O is
After the U-turn is made so that the document surface faces downward, the document 16 is conveyed to a predetermined position on the document glass 9 by a belt 16 stretched over its entire length. In this way, the image surface of the conveyed original O is scanned by the optical system 10 and copied on the paper as described above. The scanned original is
By the reverse rotation of the belt 16, the belt 16 is conveyed through between the rollers 69 and 70, and then is ejected to the uppermost portion of the document stacked on the stacking table 65 by the roller pair 75. By repeating this operation, the originals stacked on the stacking table 65 can be copied in the order. Even in the case of a double-sided original, the belt 16 and the rollers 72, 73, 74, 76, 77, 78, and 79 can perform copying by reversing the front and back of the original and scanning the original image. I can. Since the reversing operation is not directly related to the present invention, its explanation is omitted.

The automatic binding device (stapler) 20 binds the copied sheets discharged from the copying machine 17. This stapler
20, a tray 81 for stacking sheets, other sheet processing devices,
For example, a connecting path 82 to the sorter is provided. When binding is designated, the sheet conveying path is switched to the path toward the roller pair 83, and the sheets are stacked on the tray 84. When a predetermined number of sheets are stacked on the tray 84, the staple placement device 85 operates and the binding operation is performed. The bound sheet bundle is placed on the loading platform 86. After that, the next sheet to be bound can be received.

For comparison, the numerical values and manufacturing method of this embodiment will be described.

(Example) In the fixing device having the above configuration, as the fixing roller 1, fluorine rubber was coated with PFA,
The outer diameter of the central part is 59.3 mm, and both ends have an outer diameter of 59.3 mm + 200 μm
A roller having a reverse crown amount of 100 μm was used.

This roller was manufactured as shown below and had a central diameter of 58.3 mm and a reverse crown of 10 mm.
Prepare a 0μ aluminum cored bar, sandblast the surface, degrease and dry it, wrap a fluorocarbon rubber sheet through a primer, press vulcanize at 150 ° C for 40 minutes,
Then, after the secondary vulcanization at 200 ℃ for 2 hours, the rubber wall thickness 0.4
It was uniformly ground to a thickness of 8 mm (t ₁ ′).

Then, PFA was electrostatically coated to a thickness of 20 μm (t ₂ ′) through a primer and baked at 310 ° C. for 30 minutes.

As the pressure roller 2, a roller having an outer diameter of 60.0 mm in which silicon rubber is coated with a mixed layer of fluorine rubber and fluorine resin is used.

This roller was manufactured as shown below, as a cored bar, an iron cored bar with an outer diameter of 50 mm was prepared, the surface was sandblasted, degreased and dried, and then a silicone rubber sheet was wound through a primer, After press vulcanization at 170 ° C. for 30 minutes and then secondary vulcanization at 200 ° C. for 1 hour, the rubber was ground to a thickness of 4.98 mm (t ₃ ′). Furthermore, apply a mixed liquid of fluororubber and fluororesin to a thickness of 50μ on this rubber roller, dry with an infrared heater for 15 minutes, and then at 30 ° C at 30 ° C.
Min and further, baked at 280 ° C. for 40 minutes to produce a pressure roller having an outer diameter of 60 mm.

During the firing, the roller surface tends to have a low surface energy surface, so that the fluorine resin component floats to the surface layer due to the micro Brownian motion. Then, when the surface layer is covered with the fluorocarbon resin and has a sufficiently low surface energy surface, the transfer of the fluorocarbon resin to the surface layer stops.

As a result, the surface layer of the pressure roller having a thickness of 2 to 3 [mu] is made of fluororesin, and the lower layer is a layer having more fluororubber. As fluorine resin, FEP, PFA, PTFE
Etc. can be used, and the ratio of fluorocarbon rubber and fluorocarbon resin is
20: 1 to 1: 2 are preferred.

The rubber hardness of both rollers may be selected from 20 to 80 degrees (J / SA).

The above rollers are pressed against each other at a total pressure of 60 kg, and the peripheral speed is 340 mm / se.
Double-sided copying was performed with 50 sheets of A4 paper per minute.

The amount of silicone oil applied to the fixing roller 1 is 3 × 10 ^-4
g / A4 ・ One piece.

As a result, the diameters of both rollers themselves did not change, and even if different paper sizes were passed, there was no change and good fixability was maintained, and in this embodiment, 400,000 double-sided sheets could be passed.

The conventional fixing device has a drawback that conditions 1 to 6 cannot be satisfied satisfactorily, and when a roller having a rubber surface is used for at least one of the rollers to obtain elasticity, the durability is up to 110,000 sheets.

On the other hand, in the fixing device of the present invention, all of the conditions 1 to 6 are satisfactorily satisfied, and the durability can withstand use of 150,000 sheets or more.

The more effective numerical range in the practice of the present invention is as follows.

Although the thickness t ₁ of the elastic layer 12 of the fixing roller is suitable,
Since it is meaningless as an elastic layer when it is extremely thin, it is preferable to provide 0.1 mm or more (although it may be slightly different depending on the material of the elastic body) to have this meaning.

Further, the thickness t ₃ of the elastic layer 22 of the pressure roller may be appropriately set so as to be elastically richer than that of the fixing roller itself.
Considering the problem of paper wrinkles on formation or under other conditions, it is preferable to set a thickness of 10 mm as a reliable upper limit.
The thickness of 10 mm will be somewhat different depending on the material of the elastic body, but this value is almost satisfactory.

If the resin layer thicknesses t ₂ and t ₄ both exceed 70 μ, the existence value of the elasticity of the lower layer will be reduced and the synergistic effect of both rollers will be lost. The thickness is preferably

The above description has provided a guideline for setting limits in use, but there is a more excellent range in terms of effect even in these numerical ranges.

When the resin layers t ₂ and t ₄ are changed, if it is smaller than 1 μm, the contact members such as the separation claw 41 are apt to be worn and the durability is 15
It will be about 10,000 sheets, but if it is 1μ or more, it will be 20
The durability was over 10,000 sheets. Therefore, when the resin thicknesses t ₂ and t ₄ are set to 1 μ or more and 70 μ or less, the effect under the conditions 1 to 6 is increased, which is a more preferable range. This numerical range is
It is a condition independent of the thickness range of the lower elastic body layer and the like, and more preferable condition is that the thickness t ₂ of the fixing roller resin layer is
This is because if it is in the range of 10 μ or more and 50 μ or less, the fixing property becomes more stable, and if the abrasion resistance can be improved to nearly 300,000 sheets, it becomes a good balance.

When the elastic layer thickness t ₁ of the fixing roller is 15 mm or less, the amount of heat generated by the heating means in the fixing roller can be reduced, and more effective use of heat can be achieved. Further, the occurrence of interfacial peeling between the cored bar and the layer 12 can be significantly reduced, so that the life of the fixing roller itself and the stability of the fixing property can be achieved, which is preferable. Therefore, 0.1
Setting ≦ t ₁ ≦ 1.5 (unit: mm) is convenient as a further condition.

Furthermore, if the thickness t ₂ of the pressure roller elastic layer is smaller than 1 mm, the pressure contact width, which is the fixing area, becomes extremely small, although it may have some entanglement with the elasticity of the fixing roller, so that the output of the heating source is increased. Therefore, it is preferable to set 1 ≦ t ₃ ≦ 10 (unit: mm) in order to easily and surely obtain image quality and fixability.

Further, as the pressure roller, the rubber thickness is set to be sufficient for the purpose of requiring sufficient elasticity to secure a sufficient nip.
The thickness is preferably 2 mm or more and the resin thickness is less than 10 μ. Further, when coating a fluorine resin on rubber, for example, electrostatic coating of PFA powder or coating of PTFE resin liquid, in order to form a uniform coating film, 10 μm or more, more Preferably 20μ
The above film thickness is required.

Therefore, the above is suitable for the manufacturing method of the fixing roller.

On the other hand, as the pressure roller, in order to secure a good nip, the resin thickness of the surface layer is preferably thinner.

Moreover, since the pressure roller does not contact the unfixed image and the heating amount is smaller than that of the fixing roller, the durability is good even if the resin thickness is thin.

As a method for manufacturing the pressure roller, as described in the examples, a mixed solution of fluorocarbon resin and fluorocarbon rubber is applied onto a rubber by a spray gun or the like, and the surface layer is formed by Brownian motion of the fluorocarbon resin during firing. By raising the thin fluorine resin (about this range because the Brownian motion stops at the end of the formation of the surface resin layer), a resin having good performance was obtained.

(Comparison between Example of Present Invention and Conventional Device or Assumed Device) In Table 1 below, the effect results of the above-mentioned Conditions 1 to 6 are summarized and displayed.

In Table 1 below, ◯ indicates good, Δ indicates aging-related, and X indicates unusable. ○ It is not suitable except for the steps.

In Table 1, the thinness and thickness that describe the elastic layer indicate the relative relationship between the fixing and pressing elastic layers, and the thinness and thickness that describe the resin surface layer refer to the thickness of the elastic layer of each roller. It shows the relative relationship to.

The respective comparative examples in Table 1 are shown below. These are comparative examples in which the outer diameter dimensions are exactly the same as those in the above-mentioned embodiment but the material of the roller is changed.

(Comparison 1) As the fixing roller 1, a roller in which 30 μm-thick PTFE or PFA is coated on an aluminum cored bar, and as a pressure roller on an iron cored bar 5
In the case of a fixing device using a roller coated with a mm-thick heat-vulcanizable silicone rubber, the following problems occurred.

1) Fixability was incomplete, and fixing failure occurred when continuous paper was passed in a low temperature environment. Moreover, when the image on the first side was conveyed during screen copying, the surface of the pressure roller was rubbed against the surface of the dirty pressure roller, resulting in an image defect.

2) Oil-applied web 51 that also functions as a cleaning member
Toner adhered to the fixing roller (this is toner that has been offset to the fixing roller), and the offset toner that cannot be completely removed is generated on the web, and the next copy paper may be soiled.

3) The amount of curl of the copy paper was large, which caused problems in transportability during double-sided copying and in compounding in a sorter.

4) The image was crushed, and a part of the image was offset, resulting in deterioration of image quality.

5) The toner stain on the pressure roller becomes noticeable at 20,000 to 30,000 sheets, and at about 50,000 to 100,000 sheets, a part of the toner contaminating the pressure roller peels off from the pressure and it becomes copy paper. It adhered and caused a serious deterioration in image quality.

Comparison 1 is extremely inferior to this embodiment in comparison with this embodiment. Note that the durability condition 6 is marked with a symbol Δ, which means that there are few members that come into contact with the pressure roller 2 and copy recording on one side is possible even if the pressure roller 2 becomes dirty. .

(Comparison 2) As the fixing roller 1, a roller in which a 0.5 mm thick heat vulcanizing (HTV) silicon rubber is coated on an aluminum core metal (180
℃ × 8hvs dimethyl silicone oil viscosity at25 ℃ 100cs with an oil swelling process), as a pressure roller 2, a fixing device using a roller 5mm thick heat-vulcanizing silicone rubber coated on an iron core In this case, the following problems occurred.

1) The releasability of the fixing roller impregnated with 40,000 to 110,000 sheets is deteriorated, there is a problem in durability, roller stain becomes noticeable, and both upper and lower rollers cause an increase in stain offset. Has the drawback that it occurs frequently. Also, the roller may be damaged during jamming. Similar problems occurred when low temperature vulcanization type (LTV) silicone rubber or room temperature vulcanization type (RTV) silicone rubber was used instead of heat vulcanization type silicone rubber.

2) Conditions 3 to 5 were also good at the initial stage, but when the releasability of the fixing roller was deteriorated during durable use, the characteristics were suddenly deteriorated.

(Comparison 3) As a fixing roller, a roller in which 0.47 mm of fluorine rubber is coated on an aluminum cored bar, and a liquid fluorine rubber of 30 μm thickness is further coated on the outer periphery of the roller is used as a pressure roller on the iron core. 5 mm
In the case of a fixing device using a roller coated with thick HTV silicone rubber, the following problems occurred. Jam occurred frequently after passing around 3,000 sheets. Oil application amount is 5
Even if it was doubled, a jam occurred. The image deterioration due to the offset was remarkable, and the roller was damaged at the time of jamming about 8,000 sheets, and it became unusable. The same result was obtained by using fluorosilicone rubber as the fluorine rubber on the surface layer of the fixing roller.

The structures of Comparative Examples 4 to 11 are shown in the table below, and the description thereof will be briefly made using the problems and drawbacks described in Comparative Example 1.

(Comparison 4: The following were used as typical ones) As the fixing roller 1, a roller in which 30 μm-thick PFA is coated on the Alki core bar, and as the pressure roller 2 is 4.5 mm on the iron core bar.
When a thick silicon rubber was coated and a 0.5 mm thick PFA tube was further coated on the outer circumference, the following problems occurred.

The disadvantages 1) to 4) described in the comparison 1 similarly occur.

In Comparative Example 4, the offset amount increases with poor fixing, but because both roller surfaces are made of resin, roller stains and other defects did not appear significantly, so a circle was marked.

(Comparison 5) Comparison 5 is a fixing device in which the constitution of the pressure roller 2 of the embodiment is simply a rubber roller, and the defect 5) shown in Comparison 1 occurs. The stain on the pressure roller is more remarkable than that of the fixing device shown in Comparative Example 2. Further, the image quality was deteriorated due to the stain of the pressure roller.

(Comparison 6) Comparison 6 is a fixing device in which the pressure roller of Comparison 5 is replaced with a resin roller in which resin is provided on a core metal. This has poor fixability and causes a large amount of offset. It is considered that this is because there is no sufficient elastic relationship for obtaining good fixing.

It is conceivable to increase the pressure so as to increase the pressure contact width to achieve the improvement of the fixing property, but the fixing property is not so good, and the curl amount is rather large. In comparison 6 as well, the drawbacks 1) and 2) of comparison 1 occurred, but the results were worse than in comparison 1.

(Comparison 7) Comparison 7 is a fixing device in which a simple rubber roller is used as the fixing roller of the embodiment, and shows a defect according to Comparison 2.

Although good results were obtained as the initial performance, even if a rubber having a good releasability was used, the releasability of the fixing roller deteriorated after 40 to 110,000 sheets, and the roller was conspicuously contaminated to cause frequent jams. Further, also in the conditions 3 to 5, a sharp deterioration in characteristics occurred.

Comparisons 8 to 11 are those in which the layer thicknesses were changed with respect to the examples, and therefore the configurations are shown using the above-mentioned relational expressions of the thicknesses of t ₁ , t ₂ , t ₃ and t ₄ .

(Comparison 8) t ₁ > t ₃ , t ₁ > t ₂ , t ₃ > t ₄ Ripple (vertical fluctuation) of the fixing roller surface temperature was large from the beginning due to poor thermal response, and during continuous paper feeding The temperature drop of the fixing roller surface was remarkable, and fixing failure occurred even at room temperature.

Approximately 20,000 after passing the paper while ignoring the above problems
During sheet-feeding, adhesion was peeled off between the core metal of the fixing roller and the elastic layer, making it unusable.

(Comparison 9) t ₁ <t ₃ , t ₁ <t ₂ , t ₃ > t _{4 The} disadvantages 1) and 2) shown in Comparison 1 similarly occur 3) and 4)
Also occurred almost in the same manner (slightly better than the comparison 1).

(Comparison 10) t ₁ <t ₃ , t ₁ <t ₂ , t ₃ <t ₄ Almost the same as Comparison 9, but as the thickness t ₄ increases, the image quality and fixability also deteriorate, and Δ In some cases, the mark becomes an X mark.

(Comparison 11) t ₁ <t ₃ , t ₁ > t ₂ , t ₃ <t _{4 It} has a drawback similar to that of Comparison 9.

If the paper is continuously fed in a low temperature environment, fixing failure may occur. Moreover, the amount of toner stains adhered to the cleaning web was higher than that in this example.

As can be understood from the above comparative examples, in the examples of the present invention,
Since all of the above conditions 1 to 6 can be satisfied and the effect can be maintained over a long period of time, the fixing device is far superior to the conventional device and is a device having a good practicality.

The present invention is a fixing device having good initial characteristics and capable of exhibiting its excellent effect over a long period of time compared with the conventional one.

Here, the effects of the present invention will be further compared in terms of data. However, in these, the problem of durability is not touched, and the offset rate, curl amount, and image quality are compared.

FIG. 3 shows the tendency of the number of copies and the density reduction rate.

FIG. 3 is a numerical representation of the fixability of the examples and representative comparative examples. A 700 W halogen heater was used as the heater 3, and 250 sheets of A3 size and 82 g / m ² of paper thickness were continuously fed immediately after the 1 weight lamp was turned off in the morning at 10 ° C. to enable copying. It is a thing.

The fixing property was evaluated by the following formula, using as a chart a solid black of φ24 provided with 9 points in A3 size.

Db: Copy image reflection density before rubbing Da: Symbol C (made by Kojin: Symbol paper) with a load of 40 g / cm ² and the reflection density after rubbing the image 10 times over a φ24 image As is clear from FIG. 3, it is understood that this example shows a good fixing property.

Further, it can be seen that the fixing property is particularly good when the fixing roller side is an elastic body.

It is considered that this is because the heat transfer efficiency is good because the fixing roller follows the fixing roller on the unevenness on the copy paper.

Table 2 above shows an oil-coated web that also serves as a cleaning member.
The amount of toner adhering to 51 (that is, offset to the fixing roller) is shown as an offset rate,
It was calculated from the following formula.

From Table 2, it can be seen that in this embodiment, the offset is extremely small, the feed speed of the web can be reduced, and the life of the web can be extended.

The toner offset to the fixing roller is also smaller in the fixing roller having elasticity. Comparative Example 3 has a large amount of toner offset because the releasability of the fluorine rubber or fluorosilicone rubber material itself is poor.

Table 3 shows the curl amount of the copy paper after fixing. If the curl is large, it causes various troubles such as compounding to a sorter, transportability on both sides, separation from the photosensitive drum on both sides (in the case of electrostatic decomposition), wrinkles in fixing on both sides, and the like. Further, the curl amount shown in Table 3 is measured as shown in the figure below by holding the center of the side edge of the copy paper, which has passed 20 sheets continuously, with respect to the transport direction with a finger. With respect to curl, good results were obtained in this example, and as a result, the electrostatic separation transfer and separation latitude could be expanded.

The above embodiment has a configuration capable of further improving these effects. This is also characterized in that a charge removing member is added to the heating roller, the fixing roller, or both.

As shown in FIG. 1, it is possible to further reduce the offset amount in the above table to 1/2 to 1/3 by bringing the grounding brush 7 into contact with it.

It is preferable that the static elimination brush is brought into contact with the pressure roller by contacting its tip side 71 with the pressure roller as shown in FIG.

This makes it possible for the tip side surface 71 of the static elimination brush to also serve as a cleaning member for dirt such as paper powder and toner that has been offset to the pressure roller, and the tip portion of the static elimination brush can be kept clean for a long period of time. Therefore, the static elimination effect is sustained.

Further, the contact position of the charge removal brush was closer to the nip portion on the copy paper discharge side, and the charge removal effect was larger and a good result was obtained.

Further, a good image with less dustiness was obtained by bringing the static elimination brush 8 close to or in contact with the fixing roller.

Providing the static eliminating member in this manner requires the conditions 1 to
6 is satisfied at an even higher level, which is more important for the present invention and is a preferred embodiment.

As described above, according to the present invention, the rollers are configured to have the function separation type, and the fixing device including the roller pair described above is used.
It was possible to obtain a fixing device applicable to a multi-function high speed copying machine.

The present invention has a novel structure that has not been seen in the past, sufficiently satisfies the above-mentioned six conditions that have not been considered in the past, and exhibits excellent effects on each of them. It has a very important effect that there is almost no.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view of an embodiment of the present invention, FIG. 2 is a schematic explanatory view of a main part of FIG. 1, and FIG. 3 is a relational diagram showing an experimental result of the number of copies and a density reduction rate. The figure is a schematic explanatory view of an example of a double-sided recording apparatus in which the present invention is particularly effective. 1 is a fixing roller, 2 is a pressure roller, 3 is a heater, 12, 2
2 is an elastic layer, 13 and 23 are resin layers, and 7 and 8 are static elimination brushes.

Claims (1)

[Claims] 1. A fixing which comprises a fixing roller in contact with an unfixed image, and a pressure roller forming a nip with the fixing roller, wherein a recording material carrying an unfixed image is nip-conveyed and fixed in the nip. In the apparatus, the fixing roller has an elastic layer and a releasable resin surface layer thinner than this elastic layer, and the pressure roller has an elastic layer thicker than the elastic layer of the fixing roller and more than this elastic layer. A fixing device having a thin releasable resin surface layer, wherein the thickness of the releasable resin surface layer of the pressure roller is smaller than the thickness of the releasable resin surface layer of the fixing roller.