JPH07295428A - Fixing device - Google Patents

Abstract

PURPOSE:To provide a fixing device that can prevent a paper jam caused by the upward paper discharge without generating the claw mark of a separating claw to an image even in the case of using a color copying machine enabling double-side copying. CONSTITUTION:The same material is used for the outer layers of a fixing roller 51 and a pressure roller 52 so as to be able to cope with a color copying machine. An upper separating claw 69 is separably disposed at the fixing roller 51, while a lower separating claw 68 is separably disposed at the pressure roller 52, and the upper separating claw 69 and the lower separating claw 68 are brought into contact with or separated from the rollers according to the thickness of recording material, for instance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat fixing device for fixing a non-fixed toner image by passing a recording material having an unfixed toner image between a fixing roller and a pressure roller which are pressed against each other, and more particularly, a plurality of heat fixing devices. The present invention relates to a fixing device used in a color image forming apparatus having the image forming means.

[0002]

2. Description of the Related Art As an example of an image forming apparatus as described above, FIGS. 9 and 10 show a 4-drum laser beam printer having a plurality of optical scanning means.

As shown in FIG. 9, the printer is an image forming means having a developing device and the like around an electrophotographic photosensitive member (hereinafter referred to as "photosensitive drum") which is a latent image carrier. Four image forming stations that are barrels are provided, and the image formed on each of the image forming stations on the photosensitive drum is a recording material such as paper (hereinafter referred to as a recording material) on a conveying unit that moves and passes adjacent to the photosensitive drum. , Simply paper).

As shown in FIG. 10, magenta, cyan,
Photosensitive drums 1a, 1b, 1c, and 1d are arranged in the image forming stations Pa, Pb, Pc, and Pd that form images of yellow and black, respectively, and the photosensitive drums are rotatable in the arrow directions. Has become. Furthermore, around each photosensitive drum 1a, 1b, 1c, 1d,
Charger 12a, 12b, 12c, 12d and developing device 2
a, 2b, 2c, 2d, and cleaners 4a, 4b,
4c and 4d are sequentially arranged along the rotation direction of the photosensitive drum, and a transfer unit 3 is arranged below each photosensitive drum. The transfer section 3 has a transfer belt 31 which is a recording material conveying means common to each image forming station, and transfer chargers 3a, 3b, 3c and 3d.

In the printer as described above, the paper P supplied from the paper feed cassette 61 which is the recording material supply means shown in FIG. 9 is supported on the transfer belt 31 and conveyed to each image forming station, and each of the above-mentioned respective The toner images of the respective colors formed on the photosensitive drum are sequentially transferred. When this transfer step is completed, the paper P is separated from the transfer belt 31 and is conveyed to the fixing device 5 by a conveyor belt 62 which is a recording material guide means.

As shown in detail in FIG. 11, the fixing device 5 includes a fixing roller 51 that is rotatably arranged, a pressure roller 52 that rotates while being in pressure contact with the fixing roller 51, and a release agent supply coating. It is configured to have a release agent applying device 53 as a means and roller cleaning devices 54 and 55.
Inside the fixing roller 51 and the pressure roller 52, heaters 56 and 57 such as halogen lamps are provided, respectively. Further, the thermistors 58 and 59 are arranged so as to come into contact with the fixing roller 51 and the pressure roller 52, respectively. By controlling the voltage to the heater 56 and the heater 57 via a temperature adjusting circuit, the fixing roller 51 and the fixing roller 51 are controlled. Also, the temperature of the surface of the pressure roller 52 is adjusted. In this state, when the paper P is conveyed, the fixing roller 51 and the pressure roller 52 rotate at a constant speed, silicone oil is applied to the surface of the fixing roller 51 as a release agent, and the paper P is fixed to the fixing roller 51. When passing between the pressure roller 52 and the pressure roller 52, the unfixed toner image on the surface of the paper P is melted and fixed by being pressed and heated from both the front and back surfaces at a substantially constant pressure and temperature, and a full-color image is formed on the paper P. Is formed. The paper P on which the image is fixed is separated from the pressure roller 52 by the lower separation claw 68, and is discharged to the outside of the machine.

The fixing roller used in the above-mentioned fixing device is coated with a material such as a fluororesin or silicone rubber having a good releasing property, and having excellent heat resistance and abrasion resistance, to form an outer layer thereof. There is. For example, when the image forming apparatus is a color copying machine using an electrophotographic system and particularly attaches importance to image quality, the fixing roller 51 is often made of silicone rubber as an outer layer of the roller. .
This silicone rubber is slightly inferior to the fluororesin in releasability, but when silicone oil is applied as a release agent, the releasability is improved as compared with the fluororesin.

Further, the material of the fixing roller also takes into consideration the influence on the discharge of the paper P. That is, the paper P
Is discharged so as to wind around the fixing roller 51 side (hereinafter referred to as upper paper discharge) or discharged around the pressure roller 52 side (hereinafter referred to as lower paper discharge). The separation claw needs to be brought into contact with the fixing roller 51 or the pressure roller 52, but when the separation claw is brought into contact with the fixing roller 51, a nail mark appears on the image, and therefore it cannot be used. Therefore, conventionally, the rubber material, the rubber thickness, etc. are designed so that the fixing roller 51 is softer than the pressure roller 52, and the amount of deformation of the roller in the nip portion is larger in the fixing roller 51. The sheet is discharged downward by the curvature of the nip, and the lower separation claw 68 is provided on the pressure roller 52 side for separation.

[0009]

However, among the conventional color copying machines capable of double-sided copying, the toner surface comes into contact with both the fixing roller 51 and the pressure roller 52. Since the outer layer is made of the same material, particularly the silicone rubber having excellent releasability is often used as the outer layer of both rollers 51 and 52, it is difficult to eject the sheet downward due to the curvature of the nip as described above. Met. As a result, depending on the paper quality and environment, the paper may be ejected upward, and paper jam may occur.

Therefore, the first invention according to the present application solves the above-mentioned problems, and even when it is used in a color copying machine capable of double-sided copying, it does not generate a nail mark of a separating nail on an image and is discharged upward. An object of the present invention is to provide a fixing device capable of preventing paper jam due to paper.

In addition to the above-mentioned object, the second invention of the present application is particularly applicable to the fixing roller or the pressure roller of the recording material even if the recording material is thin, without generating a nail mark by the separating claw. An object of the present invention is to provide a fixing device capable of preventing wrapping.

Further, in addition to the above-mentioned object, the third invention according to the present application wraps a recording material around a fixing roller or a pressure roller without generating a nail mark by a separating nail even when the humidity is high. An object of the present invention is to provide a fixing device capable of preventing the above.

Further, in addition to the above-mentioned object, the fourth invention of the present application is particularly applicable to a fixing roller or a pressure roller of a recording material without causing a nail mark by a separating nail even when the amount of image information is small. It is an object of the present invention to provide a fixing device capable of preventing the winding of the sheet.

[0014]

According to a first aspect of the present invention, the above object is to provide a fixing roller having a release layer on an elastic layer, and the same material as the release layer of the fixing roller. And a pressure roller having an elastic layer on the elastic layer having a smaller thickness than the fixing roller, and the recording material having an unfixed image is nipped and conveyed at a pressure contact portion formed by both rollers. In a fixing device that heats and fixes an unfixed image on the recording material, an upper separation claw that is disposed so as to be able to come into contact with and separate from the fixing roller and a permanent contact with the pressure roller is provided so as to be in contact with or separated from the pressure roller. The upper separation claw and the lower separation claw are provided with a lower separation claw and a means for detecting the elasticity of the recording material, and the fixing is performed only when the elasticity of the recording material detected by the means is equal to or less than a predetermined value. This is achieved by being set so as to contact the roller and the pressure roller.

According to the second invention of the present application,
The purpose is to detect the strength and weakness of elasticity of the recording material,
This is achieved by being a means for detecting the thickness of the recording material.

Further, according to the third invention of the present application, the above object is achieved by that the means for detecting the strength or weakness of elasticity of the recording material is a means for detecting humidity.

According to the fourth invention of the present application,
The purpose is to detect the strength and weakness of elasticity of the recording material,
This is achieved by being a means for detecting the amount of image information.

[0018]

According to the first invention of the present application, when the elasticity of the recording material is detected to be equal to or less than the predetermined value by the means for detecting the elasticity of the recording material, the recording material is fixed to the fixing roller. Alternatively, it may be discharged from the pressure contact portion between the fixing roller and the pressure roller so as to wind around the pressure roller. Therefore, for the fixing roller, by contacting the upper separation claw, and for the pressure roller, The recording material to be wrapped is separated from the roller by keeping the lower separation claw in constant contact, or by bringing the lower separation claw into contact when detected as described above. On the other hand, when the elasticity of the recording material exceeds the predetermined value,
Even if the upper separation claw and the lower separation claw are not brought into contact with each other, the recording material is separated only by the curvature of the pressure contact portion. Thus, according to the present invention, the contact of the separating claw with the roller can be suppressed to a necessary minimum, and the recording material can be reliably separated without causing a separation claw mark on the image.

According to the second invention of the present application,
When the thickness of the recording material is detected to be less than or equal to the predetermined value, the elasticity of the recording material is weak, and the recording material may be discharged so as to wind around the fixing roller or the pressure roller as described above. Since the upper separation claw and the lower separation claw are brought into contact with the fixing roller and the pressure roller as described above, the recording material is separated without being wound around the roller. On the other hand, when the thickness of the recording material exceeds the predetermined value, the elasticity of the recording material is strong, and as described above, the recording material is separated from the roller only by the curvature of the pressure contact portion. Thus, according to the present invention, the contact of the separating claw with the roller can be suppressed to a necessary minimum, and the recording material can be reliably separated without causing a separation claw mark on the image.

Further, according to the third invention of the present application, when the humidity is detected to be equal to or higher than a predetermined value, the elasticity of the recording material becomes weak, and as described above, the recording material is a fixing roller or a roller. It may be discharged so as to wind around the pressure roller, but since the upper separation claw and the lower separation claw are brought into contact with the fixing roller and the pressure roller as described above, the recording material is separated without winding around the roller. . On the other hand, when the humidity is less than the predetermined value, the elasticity of the recording material is strong and, as described above, the recording material is separated from the roller only by the curvature of the pressure contact portion. Thus, according to the present invention, the contact of the separating claw with the roller can be suppressed to a necessary minimum, and the recording material can be reliably separated without causing a separation claw mark on the image.

According to the fourth invention of the present application,
When the amount of image information is detected to be less than or equal to a predetermined value, the elasticity of the recording material becomes weak, and the recording material may be discharged so as to wind around the fixing roller or the pressure roller as described above. Since the upper separation claw and the lower separation claw are brought into contact with the fixing roller and the pressure roller as described above, the recording material is separated without being wound around the roller. On the other hand, when the image information amount exceeds the predetermined value, the elasticity of the recording material is strong, and as described above, the recording material is separated from the roller only by the curvature of the pressure contact portion. Thus, according to the present invention, the contact of the separating claw with the roller can be suppressed to a necessary minimum, and the recording material can be reliably separated without causing a separation claw mark on the image.

[0022]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic configuration diagram of a fixing device according to the present embodiment. As shown in FIG. 1, in the present embodiment, an upper separation claw 69 that can be brought into contact with and separated from the fixing roller 51 is provided. Different from the example.
In this embodiment, a case where paper is used as the recording material will be described.

As described above, generally, in a full-color copying machine, lower discharge is achieved by the curvature of the nip without using the upper separating claw, but in a full-color copying machine capable of double-sided copying, the fixing roller is used. Since it is necessary to use the same material for the outer layers of 51 and the pressure roller 52,
In extremely rare cases, the upper sheet was ejected.

Therefore, in this embodiment, the upper separating claw 69 is attached to the fixing roller 51 so as to be able to come into contact with and separate from the fixing roller 51 so that the upper separating claw 69 comes into contact only when the upper sheet is discharged.

The lower separating claw 68 is similar to the upper separating claw 69, PI (polyimide), PE.
A sheet-shaped film of I (polyether imide) or PFA, or a film reinforced with a SUS plate or the like is used.

Here, the case where the upper sheet is likely to be discharged means that the sheet which should be separated in the lower curvature direction is wound around the fixing roller 51 side and discharged, that is, the stiffness of the sheet is weak. That is the case. Generally, the thinner the waist of paper, the weaker it becomes. As a result of an actual examination, as shown in FIG. 2, it was found that the upper sheet was rarely discharged only for the paper having the basis weight of 64 g / m ² .

Therefore, in this embodiment, a means for detecting the thickness of the paper is provided in the main body as a means for detecting the elasticity of the recording material, and the fixing roller 5 of the upper separation claw 69 is correspondingly provided.
It is designed to control contact with and separation from 1.

The upper separating claw 69 is generally made of heat resistant resin such as PAI (polyamide imide), PEEK (polyether ether ketone), PPS (polyphenylene sulfide) or the like, and PTFE or PFA for preventing adhesion of toner or silicone oil. A coated product is used.

As shown in FIG. 3, the detecting means for detecting the thickness of the paper is a registration roller 70 which is axially supported and a registration roller which is held by the registration roller 70 from above and is movable up and down. Has 71. This 7
When the paper P having a different basis weight passes between the two registration rollers 0 and 71, the position of the registration roller 71 changes,
It is transmitted to the potentiometer 74 by the clutch 73,
The thickness of the paper P is detected.

In this embodiment, the thickness of the paper P is detected by providing this detecting means in the paper feeding section. That is, as shown in FIG. 4, the upper separation claw 69 is normally separated from the fixing roller 51, and comes into contact with the fixing roller 51 only when the detection unit detects that the sheet is 64 g / m ² in size. Controlled.

As a result, since the paper having a basis weight of 64 g / m ² is normally discharged downward, no trace of separation by the upper separation claw is generated, and even if it is discharged rarely upward. Since the paper is separated by the upper separation claw 69, paper jam does not occur. Further, in the case of strong paper such as plain paper, since the upper separation claw 69 is separated from the fixing roller 51, the fixing roller 51 is not affected by scratches.

As for the lower separating claw 68, the paper which is actually wound around the lower side and ejected and separated by the claw is 6
In the case of 4 g / m ² paper alone and other thick paper, separation is performed only by curvature without relying on nails. Therefore, the lower separation claw 68 can be similarly brought into contact with and separated from the lower separation claw 68 by the detection means.
The toner and silicone oil can be prevented from adhering to the lower separation claw 68 by contacting the pressure roller 52 only when the paper of 4 g / m ² is detected.
It is also possible to prevent damage to the

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIGS. The same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

In this embodiment, the contact / separation of the upper separating claw 69 is controlled by judging other conditions that the stiffness of the paper becomes weak. The waist strength of paper varies depending on the environment even if the paper has the same basis weight. That is, in an environment with low humidity,
Since the amount of moisture absorbed by the paper is small, the stiffness of the paper is strong, but on the contrary, in a high humidity environment, the amount of moisture absorbed is large and the stiffness of the paper becomes weak. Therefore, as the examination results are shown in FIG. 5, the higher the humidity is, the higher the rate of upward paper discharge occurs.

Therefore, in this embodiment, as shown in FIG. 6, the contact / separation of the upper separation claw 69 is controlled according to the environment. That is, since the main body of the copying machine is provided with a temperature / humidity sensor (not shown), when the humidity becomes high (humidity 70% or more), the upper separation claw 69 causes the fixing roller 51 to move.
It was controlled so as to abut. Thereby, even when the humidity is high and the stiffness of the paper is weak, the same effect as that of the first embodiment can be obtained. Further, by combining the present embodiment and the first embodiment, a larger effect can be obtained.

The lower separating claw 68 is also discharged while being wound downward and separated by the claw when the humidity is high, and when the humidity is low, it is separated only by the curvature without depending on the claw. Is being done. Therefore, the lower separation claw 68 can be similarly contacted and separated, and the toner and the silicone oil are prevented from adhering to the lower separation claw 68 by contacting the pressure roller 52 only when it is detected that the humidity is high. Moreover, it is possible to prevent the pressure roller 52 from being damaged.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to FIGS. 7 and 8. The same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

In the present embodiment, the contact / separation of the upper separation claw 69 is controlled by judging other conditions that make it easier for the paper to be discharged upward.

In this embodiment, contact / separation is controlled according to the amount of image information. That is, when the amount of image information is large to some extent, a large amount of toner adheres to the paper, and the stiffness of the paper becomes strong. On the contrary, when the amount of image information is small, the amount of adhered toner is small. , The waist becomes weak.

Therefore, in the present embodiment, the output levels of the digital pixel signals for each pixel are integrated by the video count method during copying, and the contact / separation of the upper separation claw 69 is controlled accordingly. FIG. 7 is a diagram showing a schematic configuration of the present embodiment, in which an input image signal from the reader is A / D converted, and the output level of the digital signal is integrated for each pixel to obtain a video count number. According to this video count,
As described above, the contact / separation of the upper separation claw 69 is controlled. As a result, even when the amount of image information is small and the stiffness of the paper is weak, the same effect as that of the first embodiment can be obtained.

Further, by combining this embodiment with the first and second embodiments, a larger effect can be obtained.

Further, the lower separation claw 68 is also discharged while being wound downward and separated by the claw when the image information amount is small and when the image information amount is large.
Separation is performed only by the curvature without depending on the nail. Therefore, the lower separation claw 68 can be similarly contacted and separated, and when the image information amount is small, the lower separation claw 68 can be prevented from adhering to the toner or silicone oil by contacting the pressure roller 52. Moreover, it is possible to prevent the pressure roller 52 from being damaged.

In each of the above embodiments, the lower separation claw 68 is used.
However, since the influence of the separating claw of the pressing roller 52 on the image is smaller than that of the fixing roller 51, the lower separating claw is a pressing roller. Even if it is always in contact with 52, there is practically no problem.

[0045]

As described above, the first aspect of the present application
According to the invention, since the outer layers of the fixing roller and the pressure roller are formed of the same material, a good fixing operation can be performed even when the fixing roller and the pressure roller are used in a color copying machine capable of double-sided copying. The claws are arranged so as to be able to come into contact with and separate from the fixing roller, and the lower separation claws are arranged so as to be in constant contact with or separated from the pressure roller so that the separation claws come into contact with each other depending on the elasticity of the recording material. Since they are separated from each other, it is possible to satisfactorily discharge the image without making a separation claw mark on the image and without damaging the image.

According to the second invention of the present application,
Since the strength of elasticity of the recording material is determined by detecting the thickness of the recording material, it is possible to perform good ejection according to the type of the recording material without damaging the image.

Further, according to the third invention of the present application, since the strength of the elasticity of the recording material is judged by detecting the humidity, the image is not scratched, and it is good in accordance with the change of the environment. Ejection can be done.

According to the fourth invention of the present application,
Since the level of elasticity of the recording material is determined by detecting the image information amount, it is possible to perform good ejection according to the difference in the image information amount without damaging the image.

[Brief description of drawings]

FIG. 1 is a sectional view showing a schematic configuration of a fixing device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a result of a study on the number of times of occurrence of upward paper discharge performed in the first embodiment of the present invention.

FIG. 3 is a schematic diagram of means for detecting the thickness of the recording material in the first embodiment of the present invention.

FIG. 4 is a flowchart of contact / separation operation control of the separation claw according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a result of a study on the number of times of occurrence of upper sheet discharge performed in the second embodiment of the present invention.

FIG. 6 is a flowchart of contact / separation operation control of a separation claw according to the second embodiment of the present invention.

FIG. 7 is a block diagram for explaining a method of detecting the amount of image information in the third embodiment of the present invention.

FIG. 8 is a flowchart of contact / separation operation control of a separation claw according to a third embodiment of the present invention.

FIG. 9 is a schematic sectional view of a conventional full-color copying machine.

FIG. 10 is a schematic sectional view around an image forming station of a conventional full-color copying machine.

FIG. 11 is a schematic sectional view of a fixing device of a conventional full-color copying machine.

[Explanation of symbols]

51 Fixing Roller 52 Pressure Roller 68 Lower Separation Claw 69 Upper Separation Claw 70, 71 Registration Roller (Member Constituting Means for Detecting Thickness of Recording Material) 72 Spring (Constituting Means for Detecting Thickness of Recording Material) Member) 73 Clutch (member constituting means for detecting thickness of recording material) 74 Potentiometer (member constituting means for detecting thickness of recording material) P Recording material

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ryuichiro Maeyama 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (4)

[Claims] 1. A fixing roller having a releasing layer on an elastic layer, and a releasing layer made of the same material as the releasing layer of the fixing roller, on an elastic layer having a smaller thickness than the fixing roller. And a pressure roller having the pressure roller, the recording material having an unfixed image is nipped and conveyed at a pressure contact portion formed by both rollers to heat and fix the unfixed image on the recording material. An upper separation claw disposed so as to come into contact with and away from the pressure roller, a lower separation claw provided at a constant contact with the pressure roller or so as to come into contact with the pressure roller, and a means for detecting the elasticity of the recording material. The upper separation claw and the lower separation claw are set so as to come into contact with the fixing roller and the pressure roller only when the elasticity of the recording material detected by the means is below a predetermined value. apparatus. 2. The fixing device according to claim 1, wherein the means for detecting the level of elasticity of the recording material is a means for detecting the thickness of the recording material. 3. The fixing device according to claim 1, wherein the means for detecting the level of elasticity of the recording material is a means for detecting humidity. 4. The fixing device according to claim 1, wherein the means for detecting the level of elasticity of the recording material is a means for detecting the amount of image information.