JP2000267478A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively prevent defective image quality due to the occurrence of wrinkles on the mold-released layer of a fixing roll equipped with an elastic layer and the mold-released layer. SOLUTION: The fixing device is provided with the fixing roll 1 with the elastic layer 1a and the mold-released layer 1b arranged on the outer peripheral surface of the elastic layer 1a, and a counter member 2 which is arranged in press-contact with the fixing roll 1 and for forming a fixation nip area N between the member 2 and the fixing roll 1, and a recording material K with an unfixed toner image T carried is inserted into the fixation nip area N. In this case, provided that the thickness of the elastic layer 1a at a non-press contact time is expressed by A and the thickness of the layer when the layer is compressed in the fixation nip area N is expressed by B, and when an ratio of B to A is taken as a deformation ratio B/A, the deformation ratio B/A is set to be <=20%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used in an image forming apparatus such as a copying machine or the like, and more particularly, to a method in which a recording material such as paper is passed through a pair of fixing members arranged in pressure contact with each other. A fixing device for fixing an unfixed toner image.

[0002]

2. Description of the Related Art Generally, in an image forming apparatus such as a copying machine, a fixing device is used to fix an unfixed toner image. Conventionally, a fixing device of this type includes a heating roll and a pressure roll that rotate while being pressed against each other, and a recording material such as a sheet carrying an unfixed toner image is inserted between these rolls to unfix the unfixed toner. A so-called heat fixing method for fixing an image is widely used.

In this type of fixing device, from the viewpoint of stably fixing an unfixed toner image on a recording material onto the recording material, a pressure contact area (fixing nip) between the heating roll and the pressure roll is considered. It is preferable to secure a wide area, and from such a viewpoint, at least one of the heating roll and the pressure roll provided with an elastic layer made of silicon rubber or the like is used.

Further, from the viewpoint of preventing the unfixed toner image on the recording material from adhering to the heating roll and the pressure roll, toner hardly adheres to the surfaces of the heating roll and the pressure roll. That is, it is preferable to use a material having high releasability of the toner, and from such a viewpoint, a fluororesin layer such as a PFA resin (a copolymer of tetrafluoroethylene and perfluorovinyl ether) is preferably formed on these surfaces. Coated materials are used (see, for example, JP-A-63-73281).

[0005]

However, if the configuration in which the release layer is provided on the elastic layer as described above is adopted as the heating roll or the pressure roll, for example, 20,000 to 30,000 recording materials can be used. There has been a technical problem that wrinkles occur in the release layer at the time of being inserted into the fixing nip area, and a periodic image disturbance occurs in a fixed image on the recording material thereafter.

As means for solving such technical problems, the above-mentioned publication discloses an average thickness of 50 μm as a release layer on the outer periphery of an elastic layer of a pressure roll which is pressed against a fixing roll having a heating source. A fixing device is described in which a tube made of PFA resin having a thickness of 1 to 60 μm is covered, and the compression amount of the pressure roll is set to 0.5 mm or less.

However, in such a technical means, the compression amount of the pressure roll is uniformly defined regardless of the thickness of the elastic layer, that is, the factor which determines the compression amount of the pressure roll. For this reason, for example, when the thickness of the elastic layer is reduced from the viewpoint of miniaturization or the like, wrinkles may occur in the release layer even if the compression amount of the pressure roll is set to 0.5 mm or less.

The present invention has been made to solve the above technical problems, and provides a fixing device capable of effectively preventing image quality defects due to wrinkling of a release layer. is there.

[0009]

Means for Solving the Problems The present inventor examined various parameters in order to prevent wrinkles occurring in the release layer, and found that there was a correlation between the elastic layer and the deformation rate. And arrived at the determination of the permissible region by experiment, and devised the present invention.

That is, according to the present invention, as shown in FIG.
A release layer 1b on the outer peripheral surface of the elastic layer 1a;
And a facing member 2 that is disposed in pressure contact with the fixing roll 1 and has a fixing nip area N formed between the fixing roll 1 and the fixing roll 1. In the fixing device in which the recording material K carrying the toner is inserted, the ratio of the thickness A of the elastic layer 1a when the elastic layer 1a is not pressed and the thickness B compressed in the fixing nip region N is defined as a deformation ratio B / A, this deformation ratio B / A is 2
It is characterized by being set to 0% or less.

In such a technical means, the transfer of the unfixed toner image T on the recording material K and the powder adhered on the recording material K is prevented as much as the release layer 1b of the fixing roll 1. Any material can be selected as appropriate, and for example, a fluororesin such as a PFA resin (copolymer of tetrafluoroethylene and perfluorovinyl ether) or a PTFE resin (polytetrafluoroethylene) is used. In a mode in which a fluororesin is used as the release layer 1b, a method of forming the release layer 1b made of the fluororesin includes, for example, a method of applying a fluororesin on the outer peripheral surface of the elastic layer 1a and baking it, or a method of forming a tube in advance. A method of coating the outer peripheral surface of the elastic layer 1a with the fluororesin molded into the elastic layer 1a may be appropriately selected. However, from the viewpoint of securing the releasability, the fluororesin molded into a tube shape may be used as the elastic layer 1a.
a It is preferable to adopt a method of coating the outer peripheral surface.

Although the thickness of the release layer 1b may be appropriately selected, it is necessary to secure good adhesion to the recording material K and the unfixed toner image T on the recording material K in the fixing nip area N. From the viewpoint, it is preferable to set the release layer 1b thin. On the other hand, from the viewpoint of preventing wrinkles from occurring, it is preferable to set the release layer 1b thick to provide strength. From such a viewpoint, specifically, it is preferable to set the thickness of the release layer 1b to 20 to 40 μm.

If the facing member 2 forms a fixing nip region N between the facing member 2 and the fixing roll 1, the facing member 2 is indirectly press-contacted via a roll member or a belt member, for example. The roll member and other pressing members to be arranged may be appropriately selected.

Next, the operation of the above technical means will be described. In FIG. 1, a recording material K carrying an unfixed toner image T enters a fixing nip region N where the fixing roll 1 and the facing member 2 are pressed against each other. At this time, the ratio (deformation ratio) B / A of the thickness A of the elastic layer 1a of the fixing roll 1 when the elastic layer 1a is not pressed and the thickness B compressed in the fixing nip area N is set to 20% or less. When this relationship is satisfied, the occurrence of wrinkles in the release layer 1b is prevented.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on an embodiment shown in the accompanying drawings. First Embodiment FIG. 2 shows a first embodiment of a fixing device for a color copying machine / printer to which the present invention is applied. In FIG. 1, the fixing device according to the present exemplary embodiment includes a pair of rolls that rotate while being pressed against each other, that is, an upper roll 20 as a fixing roll and a lower roll 30 as an opposing member.
The paper 40 on which the unfixed toner image T is formed is inserted between the rolls 20 and 30 to fix the unfixed toner image.

In the present embodiment, the upper roll 20
Is disposed on the side of the sheet 40 that comes into contact with the unfixed toner image T carrying surface. The surface of a metal pipe 21 made of, for example, aluminum is coated with a heat-resistant elastic layer 22. The upper surface is covered with a release layer 23, and an upper heater 24 is built therein as a heating source.

Here, the heat-resistant elastic layer 22 is made of silicon rubber having a thickness of 3 mm, and has a hardness of, for example, 4 mm.
It is set to 0 ° (JIS A).

The release layer 23 comprises the heat-resistant elastic layer 22.
It is coated with a tube-shaped fluororesin (in the present embodiment, composed of a PFA resin (copolymer of tetrafluoroethylene and perfluorovinylether)), and its thickness is set to 30 μm. Have been.

Further, a halogen lamp is used as the upper heater 24, and the surface of the upper roll 20 is heated to 160.degree.

On the other hand, the lower roll 30 is disposed in pressure contact with the upper roll 20 so as to contact the side opposite to the surface of the sheet 40 on which the unfixed toner image T is carried.
A contact nip region (fixing nip region) N having a predetermined width is formed between the heat-resistant elastic layer 32 and the surface of a metal pipe 31 made of, for example, aluminum. A release layer 33 is formed on the surface, and a lower heater 34 as a heating source is built therein.

In this embodiment, the heat resistant elastic layer 32
Is made of silicon rubber having a thickness of 2 mm, which is thinner than the heat-resistant elastic layer 22 of the upper roll 20, and its hardness is set to 60 ° (JIS A).

The release layer 33 is formed of the heat-resistant elastic layer 32.
It is coated with a fluororesin (formed of a PFA resin in the present embodiment) formed in a tube shape, and has a thickness of 30 μm.

Further, a halogen lamp is used as the lower heater 34, and the surface of the lower roll 30 is
It is designed to heat to 60 ° C.

The upper roll 20 is rotatably driven by a driving force from a drive motor 25, and the lower roll 30 rotates following the upper roll 20. The driving of the upper roll 20 and the lower roll 30 is not limited to this.
A driving force may be supplied to the lower roll 30 side.

An oil coating device 26 for supplying silicon oil as a release agent to the surface of the upper roll 20 is provided on the periphery of the upper roll 20 on the upstream side in the rotation direction of the fixing nip region N. Upper roll 20
A cleaning device 27 (e.g., a web cleaner) that cleans toner, paper dust, and the like transferred onto the surface of the upper roll 20 is provided downstream of the fixing nip area N in the rotation direction. Here, the oil application device 2
6 is not limited to the above-described system, and it is needless to say that another system may be used and the oil coating device 26 may not be provided. Reference numeral 41 denotes a guide plate for guiding the paper 40 carrying the unfixed toner image T to the fixing nip area N, and reference numerals 42 and 43 are provided near the exit side of the fixing nip area of the upper roll 20 and the lower roll 30. And peeling nails 51 and 52 for peeling the paper 40 adhered to the lower roll 30.
It is a temperature sensor for measuring the surface temperature of the lower roll 30 and the lower roll 30.

Next, the fixing nip area N will be described in detail. In the present embodiment, as described above, since the thickness of the heat-resistant elastic layer 22 of the upper roll 20 is set to be thicker than the thickness of the heat-resistant elastic layer 32 of the lower roll 30, the substantial hardness of the lower roll 30 is smaller than that of the lower roll 30. As shown in FIG. 3, when the lower roll 30 bites into the upper roll 20, the heat-resistant elastic layer 22 of the upper roll 20 is elastically deformed in the compression direction, and the biting region forms the fixing nip region N. Is formed.

The heat-resistant elastic layer 2 of the upper roll 20
2, the ratio of the thickness A when not pressed and the thickness B compressed in the fixing nip area N, that is, the deformation ratio B / A is, for example, 1
It is set to 7%. Therefore, in the present embodiment, the heat-resistant elastic layer 2 of the upper roll 20 in the fixing nip region N is used.
The deformation amount of No. 2 is 0.51 mm.

Next, the operation of the fixing device according to this embodiment will be described. The paper 40 carrying the unfixed toner image T enters the transfer nip area N formed by the pressure contact between the upper roll 20 and the lower roll 30. And
The unfixed toner image T is fixed on the paper 40 by the heat from the upper roll 20 and the lower roll 30 and the pressure received from the fixing nip area N.

The present inventor used the fixing device shown in FIG.
The relationship between the deformation ratio B / A and the wrinkles generated in the release layer 23 of the upper roll 20 was investigated by adjusting the deformation ratio B / A. In this investigation, a predetermined number of sheets of paper 40 were continuously passed through the fixing nip area N, and the release layer 23 of the upper roll 20 was
This was done by checking whether wrinkles occurred. In addition, in this investigation, in addition to the case where the thickness of the heat-resistant elastic layer 22 shown in this embodiment is 3 mm, the thickness of the heat-resistant elastic layer 22 is 1 mm.
mm. In this survey,
The thickness of the release layer 23 was all 30 μm.

The results are shown in FIGS. 4 (a) and 4 (b). Here, FIG. 4A shows that the thickness of the heat-resistant elastic layer 22 is 3 m.
4 (b) shows the result when the thickness of the heat-resistant elastic layer 22 is 1 mm. From both, the following is understood. First, in the region where the deformation ratio B / A is 17% or less,
No wrinkles are generated in the release layer 23 even after 200,000 sheets are passed. When the deformation ratio B / A is 19%, wrinkles occur in the release layer 23 when 55,000 sheets are passed, but this is not at a level that causes poor image quality. Further, the deformation rate B
If / A exceeds 20%, wrinkles occur in the release layer 23 after 30,000 sheets are passed, resulting in poor image quality.

Further, the present inventor investigated the relationship between the thickness of the release layer 23 of the upper roll 20 and wrinkles generated in the release layer 23 using the fixing device shown in FIG. This inspection was performed by passing a predetermined number of sheets of paper 40 continuously through the fixing nip area N and checking whether wrinkles occurred in the release layer 23 of the upper roll 20 in the same manner as the above-described inspection. In this investigation, the thickness of the heat-resistant elastic layer 22 was all 3 mm.

FIG. 5 shows the result. As a result, when the thickness of the release layer 23 was set to 10 μm, wrinkles occurred in the release layer 23 after passing one thousand sheets, resulting in poor image quality. The release layer 2
If the thickness exceeds 50 μm, the release layer 23 becomes hard, so that the paper 40 and the unfixed toner image T on the paper 40 cannot be sufficiently adhered to each other in the fixing nip area N, resulting in poor image quality. Has been confirmed to be likely to occur.

In the present embodiment, the PFA resin formed in a tube shape is used as the release layer 23, and the PFA resin formed by coating and baking is used as the release layer 23. Since the bonding force between the internal atoms is strong, it is likely to be hard and wrinkles are easily generated. However, in this embodiment, since the deformation ratio B / A is set to 20% or less as described above, such PF that is easy to get rid of
The generation of wrinkles is also prevented in the A resin.

In the present embodiment, the lower roll 30 includes the heat-resistant elastic layer 32 and the release layer 33, but is not limited thereto, and may be, for example, a metal roll. However, from the viewpoint of ensuring release properties, it is preferable to provide a release layer on the outer peripheral surface.

Further, in the present embodiment, the lower roll 30 is used as the facing member. However, the present invention is not limited to this. For example, an endless belt stretched over a plurality of roll groups is disposed in pressure contact with the upper roll 20. Needless to say, the present invention may be applied to a fixing device of a type in which a fixing member such as a roll member or a pressing member is provided on the back side of the endless belt corresponding to the pressing position to form the fixing nip region N.

Further, in the present embodiment, the lower roll 30
Is formed in the upper roll 20 to form the fixing nip region N. However, the present invention is not limited to this, and the upper roll 20 may be formed in the lower roll 30 to form the fixing nip region N.

Further, in the present embodiment, the fixing device for fixing the sheet 40 on which the unfixed toner image T is carried on only one side has been described. However, the present invention is not limited to this. Needless to say, the present invention is also applicable to a double-sided fixing device for fixing the paper 40 carried on both sides.

Embodiment 2 This embodiment is substantially the same as Embodiment 1 except that FIG.
As shown in the figure, upper roll 20 and lower roll 30
However, the fixing nip region N is formed by compressive deformation together during the pressing. Note that among the components of the fixing device according to the present embodiment, the same components as those of the fixing device according to the first embodiment are denoted by the same reference numerals as those in the first embodiment, and detailed description thereof will be given here. Omitted.

In the present embodiment, the upper roll 20
The lower roll 30 has the same configuration. That is, in the present embodiment, the heat-resistant elastic layers 22 and 32 are both made of silicon rubber having a thickness of 3 mm and a hardness of 40 ° (JIS A), and the release layers 23 and 33 are also both thick. It is made of 30 μm PFA resin. In the present embodiment, the configurations of the upper roll 20 and the lower roll 30 are set to be the same. However, the present invention is not limited to this. If the upper roll 20 and the lower roll 30 elastically deform, respectively, the heat-resistant elastic layer 22 and the The thickness, hardness, and the like of 32 may be appropriately selected.

In this embodiment, the ratio of the thickness A of the heat-resistant elastic layer 22 of the upper roll 20 when the heat-resistant elastic layer 22 is not pressed to the thickness B compressed in the fixing nip region N, that is, the deformation ratio B / A is, for example, 17%. %, That is, the ratio of the thickness A ′ of the heat-resistant elastic layer 32 of the lower roll 30 at the time of non-pressure contact and the thickness B ′ compressed in the fixing nip region N, that is, the deformation ratio B ′ /
A ′ is set to, for example, 17%.

As a result, in this embodiment, the upper roll 20 and the lower roll 30 are elastically deformed in the compression direction in the fixing nip region N.
/ A and B '/ A' are set to 20% or less,
A situation in which wrinkles occur in the release layers 23 and 33 does not occur.

Further, the upper roll 20 and the lower roll 3
Since 0 is elastically deformed, curling of the sheet 40 passing through the fixing nip area N is suppressed.

In particular, in a mode in which the unfixed toner image T carried on both sides of the sheet 40 is fixed, the image quality of the image fixed on the sheet 40 can be improved.

[0044]

As described above, according to the present invention,
In a fixing device having an elastic layer and a fixing roll having a release layer provided on an outer peripheral surface of the elastic layer and pressing an opposing member to form a fixing nip area, the thickness A of the elastic layer when not pressed and When the ratio with the thickness B to be compressed in the fixing nip area N is defined as a deformation ratio B / A, the deformation ratio B / A is set to 20% or less. It is possible to effectively prevent the occurrence of an image quality defect accompanying this.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an outline of a fixing device according to the present invention.

FIG. 2 is an explanatory diagram illustrating an outline of a fixing device according to the first embodiment.

FIG. 3 is an enlarged view near a fixing nip area of the fixing device according to the first exemplary embodiment;

FIG. 4 (a) is a graph when the thickness A of the elastic layer is 3 mm;
(B) is a chart showing a state of occurrence of wrinkles in the release layer when the thickness A of the elastic layer is 1 mm.

FIG. 5 is a table showing the relationship between the thickness of a release layer and the state of occurrence of wrinkles.

FIG. 6 is an enlarged view of the vicinity of a fixing nip region of a fixing device according to a second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Fixing roll, 1a ... Elastic layer, 1b ... Release layer, 2 ... Opposing member, N ... Fixing nip area, 20 ... Upper roll, 21
... Metal pipe, 22 ... Heat-resistant elastic layer, 23 ... Release layer, 2
4 Upper heater, 30 Lower roll, 31 Metal pipe, 32 Heat resistant elastic layer, 33 Release layer, 34 Lower heater, 40 Paper

Claims (3)

[Claims] A fixing roller having an elastic layer and a release layer provided on an outer peripheral surface of the elastic layer; and an opposing member which is disposed in pressure contact with the fixing roll and forms a fixing nip area between the fixing roll and the fixing roll. A fixing device in which a recording material carrying an unfixed toner image is passed through the fixing nip region, wherein a thickness A of the elastic layer when not pressed and a thickness compressed in the fixing nip region. A fixing device characterized in that when the ratio of the deformation ratio B to the deformation ratio B / A is set to 20% or less. 2. The fixing device according to claim 1, wherein the release layer of the fixing roll is formed by coating the outer peripheral surface of the elastic layer with a fluororesin formed in a tubular shape. apparatus. 3. The fixing device according to claim 1, wherein the thickness of the release layer of the fixing roll is set to 20 to 40 μm.