JPH08123241A - Fixing device - Google Patents

Abstract

PURPOSE: To provide a fixing device where an image supporting body is smoothly and surely bitten inside a nip part. CONSTITUTION: In this fixing device, an unfixed toner image 11 is fixed on the image supporting body with heat and pressure by allowing a heat resistant press-contact member 5 fixedly arranged to press-contact with a heating roll 1 and allowing the image supporting body carrying the unfixed toner image 11 to pass through a nip part between the roll 1 and the member 5. As for the press-contact pressure of the member 5 press-contacting with the roll 1, the pressure on the entrance side of the nip part is set lower than that on the exit side of the nip part.

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 a device utilizing an electrophotographic process such as an electrophotographic copying machine, a facsimile, a printer, etc., and particularly to downsizing of the device, cost reduction, and warm-up. The present invention relates to a fixing device capable of significantly shortening the time.

[0002]

2. Description of the Related Art Conventionally, in a copying machine or the like utilizing an electrophotographic process, it is necessary to fix an unfixed toner image formed on a recording sheet to a permanent image. A pressure fixing method and a heat fixing method are known.

However, the solvent fixing method among the fixing methods is to apply the solvent directly to the unfixed toner image formed on the recording sheet, or to expose the recording sheet on which the unfixed toner image is formed in a solvent atmosphere. The fixing is carried out by passing through the solvent. In the case of this solvent fixing method, the vapor of the solvent is emitted to the outside, and there are many drawbacks such as odor and hygiene. On the other hand, in the case of the pressure fixing method, a pressure-sensitive toner is used as a toner for forming an unfixed toner image, and the unfixed toner image is fixed on the recording sheet only by the pressure. As compared with the solvent fixing method, the present situation is that the fixing property is poor and the pressure-sensitive toner is expensive, so that it is not widely put into practical use like the solvent fixing method.

Therefore, for fixing an unfixed toner image, a heat fixing method in which the toner is melted by heating so that the toner is fused on the recording sheet is widely adopted.

As a fixing device adopting this heat fixing method, as shown in FIG. 12, a heater 101 is provided inside a cylindrical core metal 100, and a heat resistant resin coating layer 10 is provided on the outer peripheral surface thereof.
2 and the heating roller 103 and the heating roller 10
A sheet which is arranged in pressure contact with the pressure roller 3 and has a pressure roller 106 having a heat-resistant elastic layer 105 formed on the outer peripheral surface of a cylindrical core metal 104, and an unfixed toner image 107 is formed between the rollers 103 and 106. There is known a heating roller type in which fixing is performed by inserting 108. This heating roller type fixing device has higher thermal efficiency than other hot fixing methods such as hot air fixing method and oven fixing method, so it has low power consumption and high speed, and there is less risk of fire due to paper jam. It is currently most widely used.

[0006]

However, the above-mentioned prior art has the following problems. That is, in the above-mentioned conventional heating roller type fixing device, as described above, the pressure roller 106 is required in addition to the heating roller 103. In manufacturing the pressure roller 106, the silicone rubber is used as the heat resistant elastic body layer 105. However, since an expensive heat resistant elastic material such as fluororubber is required, there has been a problem that the cost of the apparatus becomes high. Moreover,
In the case of the conventional heating roller type fixing device, in order to ensure a predetermined fixing condition, the contact width (nip width) between the heating roller 103 and the pressure roller 106 is at least 4 to 4.
Since it is necessary to provide about 10 mm, the heating roller 103
Also, it is difficult to reduce the size of the pressure roller 106, and as a result, the entire fixing device becomes large and the configuration becomes complicated, and moreover, the time for raising the heating roller 103 from room temperature to a fixing temperature (hereinafter referred to as warm-up time) is 1 ~
There is a problem that it takes about 10 minutes and a long waiting time is required until the start of the fixing operation.

Therefore, in order to solve these problems, the inventors of the present invention, in the fixing device of the heating roller system, replace one of the pressure rollers with one of the outer peripheral surfaces of the heating roller 110 as shown in FIG. A fixed press-contact member 111 made of a heat-resistant elastic material is arranged in the portion, and the surface of the press-contact member 111 is slidably pressed against the heating roller 110 via a nip portion 112 to be fixed to the heating roller 110. A heat roll type fixing device has been already proposed in which a recording sheet 114 having an unfixed toner image 113 is inserted into a nip region 112 of a static heat-resistant elastic pressure contact member 111 to fix a toner image (Japanese Patent Application No. 5-596). No. 177742).

In the fixing device according to this proposal, a pressure roller is not required, and the heat of the heating roller is not continuously taken by the rotating heating roller, so that the cost and the size can be reduced, and the worm can be used. It was possible to significantly reduce the uptime.

In such a technical means, as the heating roller 110, as shown in FIG. 13, a heater 116 is provided inside a cylindrical cored bar 115 and H is provided on the outer peripheral surface thereof.
TV silicone rubber (High Temperature Vulcaniza
tion Silicone Rubber, RTV Silicone Rubber (Room Temperature Vulcanization Silicone R)
ubber), fluororubber, or other heat-resistant elastic body 117 having a high toner releasing property can be used, and the heating roller 1 can be used.
Since it is necessary to rotate 10 to convey the recording sheet 114, it is necessary that the friction coefficient of the outer peripheral surface of the heating roller 110 with respect to the recording sheet 114 is higher than that of the heat resistant elastic member 111. Therefore, the surface of the heat resistant elastic member 111 has a low friction coefficient substance 118 such as fluororesin.
And the inside thereof is formed of an elastic member 119 for stably applying a pressure (0.5 to 5.0 kg / cm ² ) necessary for fixing.

However, in the case of the fixing device proposed by the present inventors, even if the friction coefficient of the heating roller 110 is set to be larger than the friction coefficient of the heat-resistant elastic member 111, all types of papers can be used. It has been found that it is difficult to smoothly convey the paper into the nip portion 112. In particular, when the recording sheet 114 is thick paper, it has been found that a phenomenon occurs in which the sheet stops at the entrance of the nip portion 112 and is not caught inside the nip portion 112.

That is, in the case of the fixing device according to the above proposal, the heat roller 110 has the friction coefficient of the heat roller 110.
Even if it is set to be larger than the friction coefficient of 1,
Depending on the type and thickness of the recording sheet 114, the leading edge of the recording sheet 114 may be the heating roller 110 and the heat resistant elastic member 111.
The recording sheet 114 is stopped at the entrance of the nip portion 112, the recording sheet 114 is not conveyed into the nip portion 112, and as a result, the unfixed toner image 113 on the recording sheet 114 cannot be fixed. was there.

Therefore, the present invention has been made to solve the above-mentioned problems of the prior art. The object of the present invention is to fix a heat-resistant press-contact member fixedly arranged on a heating roll. It is an object of the present invention to provide a fixing device in which the image support is smoothly and surely bitten into the inside of the nip portion.

[0013]

In order to solve the above-mentioned technical problems, the inventors of the present invention have made various studies on the paper biting property in the nip portion between the heating roller and the heat-resistant pressure contact member fixedly arranged. As a result of overlapping, it was found that the pressure distribution inside the nip part greatly affects the biting property of the paper.

That is, in order for the sheet to be caught in the nip portion between the heating roller and the heat-resistant pressure contact member, the sheet shown in FIG.
As shown in FIG. 4, first, the leading edge of the paper 114 is heated by the heating roll 1.
It is necessary to push down or deform the fixedly arranged press contact member 111, which is in close contact with 10, by an amount corresponding to the paper thickness. Then, once the sheet is caught, it is forcibly conveyed by the frictional force with the heating roll.
In other words, if even the leading edge of the sheet has entered the inside of the nip portion, the sheet can be conveyed relatively easily thereafter.

The present inventors have paid attention to this point and optimized the pressure distribution inside the nip between the heating roller and the pressure contact member. According to this, it was found that the paper biting property is improved by setting the pressure on the inlet side of the nip portion to be lower than the pressure on the outlet side of the nip portion.

That is, in the fixing device according to the first aspect of the present invention, the heat-resistant pressure contact member fixedly arranged on the heating roll is brought into pressure contact with the unfixed toner at the nip portion between the heating roll and the heat-resistant pressure contact member. In a fixing device for fixing an unfixed toner image on an image support by heat and pressure by passing it through an image support carrying an image, the pressure contact pressure of a heat-resistant pressure contact member pressure-contacting the heating roll is The pressure on the inlet side is set to be lower than the pressure on the outlet side of the nip portion.

Further, in the study conducted by the present inventors, it is more desirable that the pressure on the inlet side of the nip portion is low, and the pressure gradually increases toward the outlet side so that the pressure becomes maximum near the outlet of the nip portion. It was found that the asymmetric pressure distribution had the best biteability.

In order to obtain such pressure distribution, a method of increasing the hardness of the fixing member on the outlet side of the nip portion, a method of increasing the pressing displacement on the outlet side of the nip portion, and the like can be mentioned.

Another method is shown in FIG. A method in which a fixedly arranged pressure contact member is composed of a thin film sheet as a fixed belt and an elastic member, and is brought into contact only with the thin film sheet near the entrance of the nip portion, and the elastic member is pressed through the sheet behind the nip portion. Is. In this method, the pressure at the entrance of the nip portion is low because the contact is only with the sheet (region a), but the pressure is high because the elastic member is pressed against the rear of the nip portion (region b). The pressure distribution can be set to be desirable for the biting property of the paper.

Further, in the fixing device according to the second aspect of the present invention, the heat-resistant pressure contact member fixedly arranged on the heating roll is brought into pressure contact with the unfixed toner at the nip portion between the heating roll and the heat-resistant pressure contact member. In a fixing device for fixing an unfixed toner image on an image support by heat and pressure by passing through the image support carrying an image, the heat resistant pressure contact member is fixed to a heating belt and a fixing belt. The belt is composed of a pressing member that presses against the heating roll, and the fixing belt is pressed against the heating roll by applying tension.

By doing so, the fixed belt can always be pressed against the surface of the heating roll in a good condition,
It is possible to keep the biting property of the paper excellent for a long period of time.

[0022]

In the fixing device according to the first aspect of the present invention, the pressure contact pressure of the heat-resistant pressure contact member that pressure contacts the heating roll is such that the pressure at the inlet side of the nip portion is lower than the pressure at the outlet side of the nip portion. Since the pressure is relatively low on the inlet side of the nip portion between the heating roll and the fixedly arranged pressure contact member, the tip of the image support can be smoothly and surely bitten into the nip portion. The image carrier is excellent in transportability, and stable fixing operation can be performed.

Further, in the fixing device according to the second aspect of the present invention, the heat resistant pressure contact member is composed of a fixing belt which contacts the heating roll and a pressure contact member which presses the fixing belt against the heating roll. Since the fixing belt is pressed against the heating roll by applying tension, as described above, the fixing belt can always be pressed against the surface of the heating roll in a good condition, and the paper biting property is improved for a long period of time. It is possible to maintain.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to illustrated embodiments.

FIG. 1 shows an embodiment of the fixing device according to the present invention.

In the figure, reference numeral 1 denotes a heating roll. The heating roll 1 has a diameter of 15 m, for example.
m, a thickness of 0.3 mm, and a length of 225 mm, and a silicone RTV rubber as a release layer 3 of 30 μm on the surface of the iron core 2.
What is dip-coated to the thickness of is used. Also,
At the center of the heating roll 1, 100 is provided as the heating source 4.
Infrared lamps of v and 300 w are provided, and the surface temperature of the heating roll 1 is detected by a temperature sensor (not shown) and is controlled to be always 150 ° C. by a temperature controller (not shown).

By the way, the heat-resistant pressure-contact member fixedly arranged is pressure-contacted to the surface of the heating roll, and the pressure-contact pressure of the heat-resistant pressure-contact member which pressure-contacts the heating roll is the pressure on the inlet side of the nip portion. It is set to be lower than the pressure on the outlet side of the nip portion.

That is, in this embodiment, the heating roll 1
A heat-resistant pressure-contact member 5 fixedly arranged on the surface of is heat-pressed, and the heat-resistant pressure-contact member 5 is composed of a thin film sheet 6 as a heat-resistant fixed belt and a heat-resistant elastic member 7. . As the thin film sheet 6, for example,
A 120-μm-thick glass fiber woven or non-woven fabric impregnated with a fluororesin and cured is used. As the thin film sheet 6, a sheet made only of tetrafluoroethylene (registered trademark: Teflon) or the like can be used, but a sheet made of glass fiber woven cloth impregnated with fluororesin and cured was used. In this case, the cost is lower than that of a sheet made of tetrafluoroethylene or the like, and a woven fabric or a non-woven fabric of glass fibers impregnated and cured with a fluororesin is a fine fiber along the weave of the glass fibers. Since the unevenness remains on the surface of the thin film sheet 6, it is possible to avoid the close contact with the recording paper as the image support, and it is possible to exhibit a good transportability of the recording paper into the nip.

Further, as the heat resistant elastic member 7, for example, a silicone rubber sponge is used, and as the silicone rubber sponge 7, a rubber hardness tester for Asker C type sponge (manufactured by Kobunshi Kagaku Co., Ltd.) has a load of 300 g.
Is used, a silicone rubber sponge having a rubber hardness of 35 ± 3 ° is used. As shown in FIG. 1, the heat-resistant elastic member 7 has a trapezoidal cross-sectional shape with adjacent inner angles set to 90 °, and has a flat surface and a short length. The upper bottom portion is arranged so as to come into pressure contact with the surface of the heating roll 1.

Further, the thin film sheet 6 and the heat resistant elastic member 7 are arranged so as to be pressed against the surface of the heating roll 1 by the reaction force due to the bending of the metal plate 8 arranged in a cantilever shape. The metal plate 8 has, for example, a thickness of 0.
A metal plate made of stainless steel of 2 mm is used. Further, the metal plate 8 is located on the front side in the traveling direction of the recording paper and is a base end portion 8a bent downward in the vertical direction.
And a horizontal plate portion 8b which is bent in the horizontal direction from the upper end of the base end portion 8a and extends for a predetermined length, and from the tip end of the horizontal plate portion 8b to the lower right of the heating roll 1. The inclined plate portion 8c is bent so as to be inclined, and the tip portion 8d is bent from the tip of the inclined plate portion 8c so as to be substantially parallel to the surface of the heating roll 1. The metal plate 8 has a base end portion 8a fixedly attached to a houn jig 9 or the like of a fixing device in a so-called cantilever shape. Due to the elastic force of the metal plate 8 to return to the upper side, The thin film sheet 6 and the heat resistant elastic member 7 are pressed against the surface of the heating roll 1.
The metal plate 8 is not limited to the shape shown in FIG. 1, but may be formed into another shape such as a substantially L-shaped cross section as shown in FIG. Of course good.

The heat resistant elastic member 7 has an upper bottom portion 7
The lower bottom portion 7b set to be longer than a is the tip portion 8 of the metal plate 8.
The thin film sheet 6 is fixed to the surface of the heating roll 1 from the tip of the metal plate 8 through the side surface 7C of the heat resistant elastic member 7 and the upper bottom portion 7a while being fixed to the surface of the heating roll 1 by means such as adhesion. It is laid over so as to be pressed against each other, and further arranged so as to be laminated on the surface of the horizontal plate portion 8b of the metal plate 8, and its base end portion 6b is fixed to the base end portion of the horizontal plate portion 8b of the metal plate 8. There is.

As a result, on the surface of the heating roll 1,
As shown in FIG. 1, a nip region 10 in which the heating roll 1 and the thin film sheet 6 are in pressure contact is formed over the nip width, and in the nip region a, only the thin film sheet 6 is in pressure contact with a relatively weak pressure. In addition, in the nip region b, the thin film sheet 6 and the heat resistant elastic member 7 are pressed against each other with a relatively strong pressure. FIG. 3 shows the distribution of pressure contact pressure between the heating roll 1, the thin film sheet 6 and the heat resistant elastic member 7.

Then, the heating roll 1 and the thin film sheet 6
As shown in FIG. 1, the recording paper 12 as an image indicator carrying the unfixed toner image 11 is inserted into the nip portion 10 between the heat-resistant elastic member 7 and the heat-resistant elastic member 7, so that the recording paper 12 is heated and pressed onto the recording paper 10. The unfixed toner image 11 is fixed.

The heat resistant pressure contact member 5 and the heating roll 1 are
For example, it is set so that the nip width of 6 mm is applied. The total pressure contact load at this time is set to, for example, 5 kg, and the deformation of the heating roll 1 due to this load can be almost ignored. Further, in order to obtain a smooth biting property of the recording paper 12 into the nip portion 10, as shown in FIG. 1, the entrance side of the nip portion 10 is in contact with only the thin film sheet 6 (area a). It is configured. The width of the nip area a is set to about 3 mm, for example. Further, the elastic member 7 is pressed behind the nip portion 10 via the thin film sheet 6 (region b). The pressure on the inlet side of the nip portion 10 is set to, for example, about 0.1 kg / cm ² as shown in the figure, while the maximum pressure behind the nip portion 10 is 0.8 k.
It is set to g / cm ² . The maximum pressure is applied to the rear of the nip portion 10 not only in the biting property of the recording paper 12 but also in the pressure effect of crushing the toner at the time of fixing. This is in consideration of the merit that the uniformity of the melted state of the image is obtained. The pressure distribution and pressure value of the nip portion 10 between the heat resistant pressure contact member 5 and the heating roll 1 can be arbitrarily set by appropriately changing the shape, hardness and elastic modulus of the elastic member 7, Desirably, the maximum pressure in the nip portion is located further on the rear end side than in the figure, that is, near the outlet of the nip portion 10 in order to obtain good fixing property.

Various recording papers 12 were run inside the nip portion 10 having such a pressure distribution, and a test was conducted on the paper biting property. As a result, it was confirmed that not only postcards as cardboards, but also envelopes and OHP papers have sufficient biting property and paper transportability. As a stress test, when Fuji Xerox's A4-L paper was piled up and the biting property was examined, it was confirmed that it was possible to bite up to quadruple feeding, and that it has sufficient performance for practical use. Proved.

FIG. 4 shows another embodiment of the present invention. The same parts as those in the above embodiment are designated by the same reference numerals. In this embodiment, the heat-resistant pressure welding is fixedly arranged. The member is not composed of a combination of a thin film sheet and an elastic member, but is composed of a combination of a plurality of heat resistant elastic members 7 ′, 7 ″, 7 ″ ′ having different rubber hardnesses.

The other structure and operation are the same as those of the previous embodiment, and the description thereof will be omitted.

FIG. 5 shows an embodiment of the fixing device according to the second aspect of the present invention. The same parts as those in the above-mentioned embodiment are designated by the same reference numerals and will be described. In the embodiment, the heat-resistant pressure contact member is composed of a fixed belt that comes into contact with the heating roll and a pressure contact member that brings the fixed belt into pressure contact with the heating roll. It has become.

By the way, in the case of the invention described in claim 1, the pressure-contact pressure of the heat-resistant pressure-contact member 5 in pressure-contact with the heating roll 1 is the pressure on the inlet side of the nip portion 10 of the nip portion 10. Since the pressure is set to be lower than the pressure on the outlet side, the pressure on the inlet side of the nip portion 10 is relatively low, so that the leading end of the recording paper 12 can be smoothly and surely caught in the nip portion 10, and the recording paper 12 is excellent in transportability, and stable fixing operation can be performed.

However, even with the fixing device having such a structure, when the oil as the release agent is applied to the very thick paper 12 or the heating roll 1, the paper 12 stops in the middle of the nip portion 10. In some cases, it may not be caught in the inside of the nip portion 10. This is because the pressure in the nip region a, which is in contact only with the thin film sheet 6, is too weak to apply a sufficient conveying force to the recording paper 12, and the heat resistant elastic member is interposed via the thin film sheet 6. It is considered that this is because the high pressure in the nip region b where 7 is pressed cannot be overcome and the process stops.

Therefore, in the fixing device according to the second aspect of the present invention, it is possible to always achieve smooth and reliable transportability even when oil is applied to very thick paper or a heating roll. It is the one.

That is, in this embodiment, the thin film sheet 6 is used.
By increasing the pressure of the portion of the nip region a which is in contact with itself, a sufficient conveying force is applied to the recording paper 12 and the high pressure of the portion where the elastic member 7 is pressed through the thin film sheet 6 is overcome. It is configured to be able to.

Further, as shown in FIG. 5, the base end portion of the thin film sheet 6 is extended downward in the vertical direction via a roller 20 which is rotatably arranged, and the thin film sheet 6 has a proximal end portion. At the base end, about 1 to about 1 by the spring 21
A tensile load of about 2 kgf is applied. As a result, as shown in FIG. 6, the pressure on the inlet side of the nip portion 10 is evenly applied with a pressure of about 0.1 to 0.2 kg / cm ² , whereas the maximum pressure behind the nip portion 10 is The same as in the above embodiment, the pressure is 0.8 kg / cm ² .

By doing this, the very thick paper 12
Even when oil is applied to the heating roller 1 or the heating roller 1, the recording paper 12 can smoothly pass through the nip portion 10 without stopping in the middle of the nip portion 10, and the fixing process can always be performed well.

FIG. 7 shows an experimental result when a large amount of oil is applied to thick paper having this effect. As is apparent from FIG. 7, by applying a tension of about 1 kgf to the base end portion of the thin film sheet 6, it is possible to smoothly pass through the nip portion 10 even when a large amount of oil is applied to thick paper, and the fixing process is always performed. It can be seen that

The other structure and operation are the same as those of the above-mentioned embodiment, and the description thereof will be omitted.

FIG. 8 shows another embodiment of the fixing device according to the first or second aspect of the present invention.
The same parts as those in the above-described embodiment will be described by giving the same reference numerals. In this embodiment, in the case of fixing an unfixed toner image such as a color image having a large toner amount of the unfixed toner image on the image support. The present invention relates to a fixing device suitable for.

By the way, in the case of the embodiment of the invention described in claim 1 or 2, the pressure contact pressure of the heat resistant pressure contact member 5 in pressure contact with the heating roll 1 is the inlet side of the nip portion 10. Since the pressure is set to be lower than the pressure on the outlet side of the nip portion 10, the pressure is relatively low on the inlet side of the nip portion 10 between the heating roll 1 and the pressure contact member 5 fixedly arranged. The leading end of the recording sheet 12 can be smoothly and surely caught in the nip portion 10, the recording sheet 12 can be easily conveyed, and a stable fixing operation can be performed.

However, even in the fixing device having such a structure, as shown in FIG. 9, a peeling claw 40 for peeling the recording paper 12 is required behind the nip portion 10. The recording paper 12 on which the toner image 11 is placed winds up from the exit of the nip portion 10 to the position of the peeling claw 40, where the peeling claw 4 moves.
0 will force the peeling. For a normal image such as a black and white image, the leading edge of the recording paper 12 is peeled off by the peeling claw 4.
If the recording paper 12 is peeled off at 0, the recording paper 12 behind it is peeled off naturally due to the stiffness of the paper, and therefore the recording paper 12 is not so peeled off.

However, a recording paper 12 on which a large amount of toner images 11 of three colors such as cyan, magenta, and yellow are placed is sufficiently melted and mixed so as to obtain a desired color, and a color image to be colored and fixed is fixed. In this case, even if the front end of the recording paper 12 is peeled by the peeling claw 40, the paper 12 behind the recording paper 12 is not easily peeled off from the heating roll 1, so that the image is always rubbed by the peeling claw 40. Since the toner image 11 is still in a molten state when it is rubbed by the peeling claw 40, the image is damaged and cannot be used. In order to prevent this, if the paper thickness is thick, that is, the paper is stiff and it is difficult to wind around the heating roll 1, this problem does not occur, but this is not a fundamental solution.

Therefore, this embodiment provides a fixing device which solves the above problems. It provides a novel pad nip type fixing device applicable not only to black and white images but also to color copying machines. And
It does not require the peeling claw 30 even when the recording paper 12 on which a large amount of toner is placed is thin and the color of the recording paper 12 having a weak stiffness is fixed, without using any peeling device at the exit of the nip portion 10. The present invention provides a pad nip type fixing device that can be peeled off (hereinafter referred to as self-stripping).

In fixing a color image, considering that a large amount of heat must be applied to the toner because the multilayer unfixed toner image 11 develops a desired color, a pad nip system capable of forming a wide nip portion. Is suitable.

The present inventors discovered the following phenomenon while studying a method capable of self-stripping even thin paper, that is, a method of reducing the adhesive force between the heating roll and the molten toner.

The fact is that the adhesive force at the interface between the molten toner 11 and the surface of the heating roll 1 is not simply determined by the physical property values of the surface chemicals of the two, but is greatly affected by the distortion of the surface of the heating roll 1. Is. That is, when the molten toner is in contact with the surface of the heating roll 1 having surface distortion in advance, and when the surface distortion is released momentarily, the toner 11 and the surface of the heating roll 1 are separated from each other. It is a phenomenon that the adhesive force is reduced.

Specifically, the surface of the heating roll 1 is coated with a material which can be elastically deformed relatively easily from the outside due to a load to generate distortion, for example, a heat resistant elastic body such as silicone rubber or fluororubber. In this case, near the outlet of the nip portion, a small-diameter hard roll is pressed and fixed while being distorted, and at the moment when the strain is released at the outlet of the nip portion, the adhesive force between the toner and the heating roll surface is It means that the amount is sharply reduced and it is easy to be self-stripping.

The surface of the soft roll covered with the elastic body is deformed when pressure is applied, and the soft roll is in contact with the toner in a distorted state. When the pressure is suddenly removed from this strained state, the strain is released and the original state is restored. At this time, micro-slip occurs at the interface between the toner and the roll. It is a hypothesis that the presence of this micro slip is an effect of reducing the adhesive force.

Therefore, in the fixing device according to this embodiment,
The heat-resistant pressure contact member fixedly arranged on the heating roll is brought into pressure contact, and the image support carrying the unfixed toner image is passed through the nip portion between the heating roll and the heat-resistant pressure contact member, whereby unfixed by heat and pressure. In the fixing device for fixing the toner image on the image support, the pressure contact pressure of the heat-resistant pressure contact member pressure-contacting the heating roll is set so that the pressure at the inlet side of the nip portion is lower than the pressure at the outlet side of the nip portion. In addition, while using a heating roll having an elastic layer, the pressure-contact pressure of the heat-resistant pressure-contacting member pressed against the surface of the heating roll is set to be relatively high, so that the elastic layer of the heating roll is strained. It is configured to generate. In order to efficiently generate strain on the surface of the heating roll under a low load, the heat resistant pressure contact member is preferably harder than the elastic member coated on the heating roll.

FIG. 8 shows a fixing device according to this embodiment.

In the figure, reference numeral 30 indicates a heating roll. This heating roll 30 has an outer diameter of 25 mm and an inner diameter of 2 mm.
The elastic layer 3 is formed on the surface of the 2 mm aluminum cylinder 31.
2, HTV silicone rubber (JIS-A rubber hardness 32 degrees) is coated to a thickness of 0.5 mm, and silicone RTV rubber is dip-coated to a thickness of 50 μm as a release layer 33 on the surface. The surface is finished to be close to a mirror surface. In addition, the heating roll 3
At the center of 0, a 100v, 300w halogen lamp is provided as a heating source 34.
The surface temperature of the sensor is detected by the temperature sensor 35 and is constantly set to 1 by a temperature controller (not shown).
It is controlled to be 50 ° C. Further, dimethylsilicone oil viscosity of 3000 cs (KF-96: manufactured by Shin-Etsu Chemical Co., Ltd.) as a release agent is uniformly supplied to the surface of the heating roll 30 by the oil supply system 36.

By the way, in this embodiment, the heat-resistant press-contact member 5 fixedly arranged is composed of a heat-resistant thin film sheet 6 and a heat-resistant elastic member 7 as in the above-mentioned embodiment. As the heat-resistant elastic member 7, JIS-A
Silicone rubber having a rubber hardness of 60 ° is used, and the heat resistant elastic member 7 is pressed against the surface of the heating roll 30 via the thin film sheet 6 so that the elastic layer 32 and the release layer of the heating roll 30. 33 is distorted. Further, the width of the nip region 10 is set to 4 mm.

In this embodiment, since the silicone rubber 7 is pressed against the surface of the heating roll 30 via the thin film sheet 6 at the outlet of the nip portion 10, the elastic layer 32 of the heating roll 30 and the mold release are separated. The layer 33 is deformed and the surface thereof is distorted. Further, a driving force is transmitted from a drive motor (not shown) to the heating roll 30, and the heating roll 30 is rotationally driven at a speed of 60 mm / sec in the direction of the arrow.

In the fixing device thus constructed, 2.0 m of color toner is placed on the recording paper 12 having various weights (thicknesses).
FIG. 10 shows the result of examining the self-stripping property at the exit of the nip portion 10 through the unfixed toner image 11 transferred at a density of g / cm ² . In this drawing, the paper feed direction A is the case where the paper fibers are fed in parallel with the heating roll 30, and the paper feed direction B is the case where it is perpendicular.
In the case of the feeding direction A, due to the structure of the paper, the paper has a weak stiffness, and even if the paper thickness is the same, self-stripping tends to be difficult.

From the above data, it can be seen that as the load of the pressure contact member 5 is increased, the self-stripping can be performed even for the paper having a small weight (thin paper thickness).

[Measurement of Strain] The surface strain of the elastic roll under a certain load can be measured as follows.
Generally, when the hard roll and the soft roll are pressed against each other under a certain load, the surface of the soft roll is elastically deformed in the nip region, and a certain strain ε is generated in the circumferential direction of the surface. When the roll pair is rotated in this state and the recording sheet passes through the nip area, the length of the recording sheet sent out by one rotation of the elastic roll that has been distorted is greater than the length of the roll circumference. The transport amount increases by the circumferential strain ε.

That is, the strain ε is expressed by the following formula 1. From this equation, the actual strain ε can be measured. The strain in the example of the present invention is a value assumed by this measuring method. With a strain of 3%, 90 g / cm ² or more enables self-stripping of paper fed in the B direction.
From 0%, self-stripping in the A direction of thin paper, which is the most difficult to peel off, is possible.

[Equation 1]

The effect of reducing the adhesive force at the interface between the toner and the heating roll by releasing the distortion at the exit of the nip portion can be applied not only to the pad nip system as in the present invention but also to the roll nip system. In this case, if the surface hardness of the heating roll is equal to or softer than that of the pressure roll, distortion of the fixing roll is likely to occur, and self-stripping is likely to occur correspondingly.

Comparative Example Here, in the same fixing device as that of the above-mentioned embodiment, the heat-resistant elastic member 5 fixedly arranged was removed, and instead of this, a pressure roll was provided to form a nip with the heating roll. The relationship between the self-stripping property when used (that is, the roll nip system) and the load was examined.

The pressure roll used here has a diameter of 25 mm, which is the same as that of the heating roll, and the surface thereof is coated with Teflon (registered trademark) to a thickness of 50 μm. The heating roll uses HTV silicone rubber (JI
S-A rubber hardness 32 °) is coated with a thickness of 1.0 mm, and silicone RTV rubber is further dip-coated with a thickness of 50 μm as a top coat layer on the surface to make the surface close to a mirror surface state. Has been finished. The surface temperature of both rolls was controlled at 160 ° C., and the same unfixed toner image as in the example was applied between the roll nip at 30 mm / se.
Through the fixing speed of c, the self-stripping property at that time was examined.

The results are shown in FIG. With the roll nip method, it is possible to perform self-stripping of B-direction feed paper at a strain of 0.5% and 90 g / cm ² or more.
Thin paper (50g / m ² ) that is most difficult to peel off from a strain of 3%
It is possible to perform self-stripping by feeding in the A direction.

As can be seen from the above, the pad nip method is capable of self-stripping with a smaller distortion than the roll nip method.

The reason for this is that in the pad nip system, since the strain is instantaneously applied in the vicinity of the exit of the pad nip, the change rate of the strain is large even with a small strain, and as a result, microscopic slip occurs at the interface between the toner and the heating roll surface. It is considered that this is likely to occur.

The total load of the pad nip method is 1 to 5
While it is kg, the roll nip method requires 10 kg or more. With the pad nip method, it is possible to significantly reduce the load, and therefore it is possible to reduce the surface friction of the fixing roll and the driving torque of the apparatus. Further, since the load is small, the rigidity of the roll is small, and the roll diameter and the thickness of the roll core can be reduced.

Furthermore, in the conventional roll nip system, it is necessary to separate the two rolls at the time of non-fixing to prevent the heating roll from being deformed, but this device is not necessary, and the device can be simplified. Further, it can be applied to a long roll, for example, a fixing device for a large drawing.

Generally, rubber has a small thermal conductivity and thermally acts as a heat insulating material. In order to stabilize the temperature of the heating roll, it is preferable that the rubber is as thin as possible.

In the conventional roll nip system, in order to obtain a wide nip width, the rubber thickness of the heating roll must be increased, and there is a limit to the thinning of the rubber. However, in the pad nip system of the present invention, since the nip is formed by the pad, it is not necessary to increase the rubber thickness, and it is sufficient if the rubber has such a thickness that the self-stripping distortion can be uniformly formed. As described above, the pad nip method has a feature that the nip width and the strain can be independently changed.

Specifically, the conventional roll nip system requires an elastic body of at least 1 m, preferably 1.5 mm or more, but in the present invention, it is 0.1 mm or more, preferably 0.3 mm or more. It has good merit in stabilizing temperature and shortening warm-up.

As is clear from the above description, the present invention enables self-stripping by pressing the fixing pad 5 against the surface of the fixing roll to generate distortion. Therefore, it can be applied to color fixing devices other than monochrome fixing. Further, the pad nip method has many advantages such as high speed, high reliability, and high image quality as compared with the roll nip method, and its utility value is extremely large in industry.

The other structure and operation are the same as those of the above-mentioned embodiment, and the description thereof will be omitted.

[0079]

The present invention has the above-described structure and operation, and in a fixing device for fixing by fixing a heat-resistant pressure contact member fixedly arranged on a heating roll, the inside of the nip portion can be smoothly and surely. It is possible to provide a fixing device in which the image support is bitten.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a fixing device according to claim 1 of the present invention.

FIG. 2 is a configuration diagram showing a modified example of the fixing device according to the embodiment.

FIG. 3 is a graph showing the pressure distribution in the nip portion.

FIG. 4 is a configuration diagram showing another embodiment of the fixing device according to the first aspect of the present invention.

FIG. 5 is a configuration diagram showing an embodiment of a fixing device according to claim 2 of the present invention.

FIG. 6 is a graph showing the pressure distribution in the nip portion.

FIG. 7 is a chart showing an experimental result of the fixing device according to the embodiment.

FIG. 8 is a block diagram showing another embodiment of the fixing device according to claim 1 or 2 of the present invention.

FIG. 9 is a configuration diagram showing still another embodiment of the fixing device according to claim 1 or 2 of the present invention.

FIG. 10 is a chart showing the self-stripping property of the apparatus shown in FIG.

FIG. 11 is a chart showing the self-stripping property of a conventional fixing device.

FIG. 12 is a block diagram showing a conventional fixing device.

FIG. 13 is a block diagram showing another conventional fixing device.

FIG. 14A and FIG. 14B are schematic diagrams showing a sheet entering state in a conventional fixing device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 heating roll, 5 heat resistant pressure contact member, 6 thin film sheet, 7 heat resistant elastic member, 11 unfixed toner image, 12
Recording sheet.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toru Inoue 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Xerox Co., Ltd.

Claims (2)

[Claims] 1. A heat-resistant press-contact member fixedly arranged on a heating roll is brought into pressure contact, and an image support carrying an unfixed toner image is passed through a nip portion between the heat-roll and the heat-resistant press-contact member, whereby heat is applied. In the fixing device for fixing the unfixed toner image on the image support by the pressure and the pressure, the pressure contact pressure of the heat-resistant pressure contact member that pressure contacts the heating roll is lower than the pressure at the exit side of the nip part. The fixing device is characterized in that 2. A heat-resistant pressure contact member fixedly arranged on a heating roll is brought into pressure contact, and an image support carrying an unfixed toner image is passed through a nip portion between the heat roll and the heat-resistant pressure contact member, whereby heat is applied. In the fixing device for fixing the unfixed toner image to the image support by pressure, the heat-resistant pressure contact member is composed of a fixing belt that contacts the heating roll, and a pressure contact member that presses the fixing belt against the heating roll, A fixing device, wherein tension is applied to the fixing belt to bring it into pressure contact with a heating roll.