JP2003076201A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device in which a peeling sheet tip part is easily mounted by making it fully approach to the exit side of a nip, and to provide an image forming apparatus. SOLUTION: The fixing device is provided with roller parts 25r and 41r having a circular elastic layer 252, a fixing roller 25 or a belt fixing means 42 which heats the releasing layers 253 and 401 of either the circular layer 253 of the outer periphery of the roller part or an endless belt 40 by using a heat source 254, and a pressurization means Pm to press an endless pressurization surface Fc to the fixing roller 25 and the belt fixing means 42. An unfixed toner image t on a recording material S is hot-pressed and fixed by using a fixing nip N formed by the means 25, 42 and Pm. The peeling sheet 28 to peel the recording material S holding a toner image from the releasing layer is provided in the vicinity of the exit side g of the fixing nip N. The peeling sheet 28 is attached with a predetermined gap d to the releasing layer while having a curvature which almost meets the outside diameter shape of the releasing layer unitedly rotated with the roller parts 25r and 41.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus provided with a fixing device and an identification fixing device for fixing an unfixed toner image transferred onto a recording material by, for example, heat and pressure. Alternatively, the present invention relates to a fixing device and an image forming apparatus that are provided with a unit that separates the recording paper from the release layer on the fixing belt side.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic copying machine, a laser beam printer, a facsimile, etc., an unfixed toner image corresponding to an original image is formed on a recording material in an image forming section, and recording is carried on the unfixed toner image. The material is heated and pressed by a fixing device to be fixed on the recording material, and a permanent image is formed on the recording material.

As a fixing device used in such an image forming apparatus, for example, a fixing roller having a heater as a heat source therein and an elastic layer and a release layer provided on the outer periphery of a core metal is provided in opposition thereto. There is a fixing device including a pair of rollers that form a fixing nip with a pressure roller and heats and presses the unfixed toner image carried on the recording material by the fixing nip to fix it on the recording material. JP 2001-
It is disclosed in Japanese Patent No. 83832 and Japanese Patent Laid-Open No. 9-146404. A fixing roller is used which has a fixing roller and a pressing unit opposite to the fixing roller, and the pressing unit includes an endless belt and a pressure member arranged inside the endless belt to press the endless belt against the fixing roller. An example of this fixing device is disclosed in Japanese Patent Laid-Open No. 11-133776.

Further, a fixing roller is stretched around a heating roller having a heat source inside and a fixing roller having an elastic layer on the outer periphery of a core metal, and the pressure roller is pressed against the fixing roller side while sandwiching the fixing belt. A fixing nip is formed by the fixing belt and the pressure roller, and the fixing nip has a fixing belt that heats and presses the unfixed toner image carried on the recording material to fix it on the recording material. There is a device, an example of which is disclosed in Japanese Patent Application Laid-Open No. 9-138598.

In each of the fixing devices, an elastic layer is provided at least on the outer periphery of the fixing device and the pressing device, which rotate in pressure contact with each other, and the annular elastic layer is pressed by the pressing device. Thus, a curved fixing nip is formed.
This fixing nip heats and presses the unfixed toner image carried on the recording material. At that time, the toner is heated and melted to a state where the viscosity is low, and then the toner is pressed to a predetermined fixing on the fiber of the recording material. It is firmly established. After fixing, the recording material sent from the exit side of the fixing nip needs to be separated from the fixing means side, but the recording material is affected by the adhesive force of the toner,
There is a tendency for the toner to be displaced toward the fixing unit side and to be caught therein, and this separation performance changes depending on the state of toner adhesion to the surface of the fixing roller.

Usually, in order to prevent the recording paper from being displaced and caught on the fixing means side under the influence of the adhesive force of the toner, the fixing nip so that the leading end of the recording paper is sent out in the direction opposite to the winding direction. The curved state of is set. Further, conventionally, a fixing roller as a fixing means that has been generally used for OA equipment is made of silicone rubber which has good releasability to toner and has heat resistance and elasticity. Further, silicone oil was uniformly applied as a release agent on the silicone rubber from the viewpoints of ensuring releasability and improving durability, and the separation performance was maintained. Furthermore,
Some conventional fixing devices are provided with a separating claw to prevent a special paper type from being wrapped, but in this case, a releasing agent is applied to the surface of the fixing roller or the like. It has rarely had a fatal effect on the durability of the surface of the fixing roller or the like that is in sliding contact with the separation claw.

However, in recent years, an image forming apparatus using an oilless toner in which a releasing agent is not applied to a fixing roller or a fixing belt has been proposed, and this tendency is particularly noticeable in the fixing of a color image forming apparatus for fixing a color image. It is often used in equipment. Even in the image forming apparatus using such oilless toner, higher durability is required as the quality of the fixing device.

[0008]

By the way, in the case of an image forming apparatus using an oilless toner, the wax dispersed in the resin of the toner oozes out during the process of heating and pressurizing in the fixing step, and the releasing agent is released. It works as an agent. However, if the heating temperature, heating time, and pressure are not well balanced in this fixing process, the resin will be in a molten state before the wax oozes out, and the toner's adhesive force will act, causing the toner to become a fixing roller or fixing belt. However, there is a problem that the recording sheet is wound around the surface of the releasing layer of the fixing roller or the fixing belt.

Further, since the releasing agent is not applied, the surface of the fixing roller or the fixing belt is more disadvantageous to friction, and particularly the contact portion of the thermistor for temperature control or the separating claw is most likely to be damaged. . Here, there is a conflicting problem that if the contact pressure of the separation claw is increased because there is no margin for winding, the life will be further shortened. By the way, an example of an image forming apparatus using an oilless toner is disclosed in JP-A-11-133776. Here, a high-reliability fixing device which does not cause problems such as wrinkling of the release layer on the fixing roller, abrasion and deterioration due to friction, and deterioration of the release property while obtaining good releasing property and image quality is used. The purpose of the present invention is to obtain a conventional image forming apparatus.

Here, a structure provided with a release sheet is described as the recording paper separating means in the fixing device.
That is, the fixing device includes a release sheet having a contact width substantially equal to the axial length of the fixing roller, the release sheet is located downstream of the nip portion in the rotation direction of the fixing roller, and faces the rotation direction of the fixing roller. Direction and the tip and /
Alternatively, it is arranged so that the vicinity of the tip portion is in contact with the outer peripheral surface of the fixing roller. One of the problems of this conventional technique is that it is difficult to adjust the gap between the fixing roller and the release sheet. In this method, it is considered difficult to manage the assembling so that the gap of 0.5 mm or less does not change only with the component accuracy.

This publication describes that the release sheet, the surface of which is coated with a fluororesin, is arranged in contact with the fixing roller. However, the release sheet tip portion or the fixing sheet is fixed by long-term use. It is unavoidable that one of the roller surfaces becomes worn. Another problem is that it is difficult to separate a thin recording sheet immediately after the nip exit.

Looking at the drawings described in this publication, a flat recording sheet is brought into contact with the vicinity of the nip outlet, but it is difficult to shorten the distance between the release sheet and the nip outlet with this mechanism. is there. As a problem when the distance between the release sheet and the nip outlet cannot be shortened, if there is a solid image on the leading edge of thin paper and the white gap on the leading edge is small, the heat from the nip outlet to the contact position of the leading edge of the releasing sheet is There is a problem that the supply becomes excessive and the glossiness increases only at the leading edge of the image, and only the wound leading edge curls upward.

Based on the above problems, according to the present invention, firstly, it is easy to attach the tip of the release sheet sufficiently close to the exit side of the nip, and moreover, the fixing roller is irrespective of the kind of the recording material. It is an object of the present invention to provide a fixing device which has good separability of a recording material from a fixing belt and a fixing roller and a release sheet having sufficient durability.

Secondly, the tip of the recording material and the portion which tends to wind around the fixing belt on the release layer side due to the adhesive force of the toner following the same are locked by the tip of the release sheet to ensure reliable release, and the recording material can be separated. An object of the present invention is to provide a fixing device having good properties.

Thirdly, by performing image processing using the fixing device according to any one of claims 1 to 7, the recording material has good separability, and particularly, an image forming apparatus using an oilless toner. In addition, it is an object of the present invention to provide an image forming apparatus that can obtain good paper separability even with thin paper.

[0016]

In order to achieve the above object, the invention of claim 1 comprises a roller portion having an annular elastic layer, and an annular layer or roller portion integrally formed on the outer periphery of the roller portion. A release fixing layer formed by one of the endless belts formed separately on the outer surface of the endless belt, and the release fixing layer being heated by a heat source; A fixing unit for pressing the unfixed toner image on the recording material by heating and pressing the unfixed toner image carried on the recording material by the fixing nip formed by the rotary fixing unit and the pressing unit. In the apparatus, a release sheet is provided near the exit side of the fixing nip to release the recording material holding a toner image from the release layer, and the release sheet is a release layer that rotates integrally with the roller portion. Release layer with a curvature that follows the outer diameter shape Characterized in that it is mounted with a predetermined gap against. In this way, since the release sheet is attached with a shape having a curvature so as to follow the substantially outer diameter shape of the release layer that rotates integrally with the roller portion, the release sheet tip is attached sufficiently close to the exit side of the nip. However, the base side of the release sheet can be separated from the discharge path side of the recording material, and the attachment of the release sheet can be facilitated. Moreover, since the tip of the release sheet is mounted sufficiently close to the exit side of the nip, before the leading edge portion of the recording material, which has no toner, undergoes winding displacement at the portion affected by the adhesive force of the toner, Immediately, the front end of the recording material is locked by the front end of the release sheet, and the front end of the recording material and the portion which tends to be wound around the release layer side due to the adhesive force of the subsequent toner can be reliably released. Therefore, even if the recording material is thin paper, the recording material can be easily separated from the fixing roller or the fixing belt, which is the release layer side, regardless of the type of the recording material, and winding and fixing jam can be prevented.

Further, since the release sheet is attached to the fixing roller or the fixing belt on the release layer side with a predetermined gap, the release sheet is fixed to the fixing roller or fixing belt or the release sheet on the release layer side even after running. The durability can be improved and the separation of the recording material can be prevented from deteriorating. Furthermore,
Since the wrapping and the fixing jam can be prevented, the recording material does not remain inside the fixing unit due to the sham or the like, and it is possible to prevent the smoke and the burning which are easily caused when the recording material remains. In particular, it can be effectively used for an image forming apparatus using an oilless fixing device in which silicone oil as a release agent is not applied to a fixing roller or a fixing belt.

According to a second aspect of the invention, in the fixing device according to the first aspect, the rotary fixing means has a cored bar and a heater as a heat source inside the cored bar, and an elastic layer and an elastic layer on the outer periphery of the cored bar. It is characterized in that it is a fixing roller provided with overlapping release layers. Thus, the fixing nip can be formed by the elastic layer and the releasing layer of the fixing roller as the rotating fixing means and the pressing means, and the leading end of the recording material is separated from the fixing roller on the releasing layer side at the exit side of the nip. As a result, the fixing nip can be easily held in a curved shape, and in this respect, the recording material separability can be easily maintained.

According to a third aspect of the present invention, in the fixing device according to the first aspect, the rotary fixing means is arranged so as to face the roller portion and the roller portion including a cored bar and an elastic layer externally fitted to the cored bar. A heating roller having a heat source inside is provided, and an endless belt having a release layer is stretched between the heating roller and the heating roller. In this way, the fixing nip is formed by the heating roller as the rotary fixing means, the endless belt wound around the roller portion, and the pressing means, and the leading end of the recording material is formed on the release layer side at the exit side of the nip. It becomes easy to hold the fixing nip in a curved shape so that it can be separated from a certain endless belt, and also in this respect, the separation property of the recording material can be easily held, and winding and fixing jam can be prevented.

According to a fourth aspect of the present invention, in the fixing device according to any one of the first to third aspects, the pressurizing means comprises a cored bar and an elastic layer and a release layer which are stacked on the outer periphery of the cored bar. It is characterized by being a roller. In this way, the structure can be simplified by using the pressure roller as the pressure unit.

According to a fifth aspect of the present invention, in the fixing device according to any one of the first to third aspects, the distance between the leading edge position of the release sheet and the fixing nip outlet is preferably equal to the image leading edge blank width. Or less. As described above, the distance between the leading end position of the release sheet and the fixing nip outlet is preferably equal to or less than the white gap in the leading edge of the image. The tip of the recording material can be securely locked immediately to the tip of the recording material near the exit side of the nip before the tip part of the white spot width is wound and displaced due to the influence of the same adhesive force. Due to the adhesive force of the toner, the portion that tends to be wound around the release layer side can be reliably peeled off.

According to a sixth aspect of the present invention, in the fixing device according to any one of the first to fifth aspects, the edge ridge line facing the release layer that rotates integrally with the roller portion of the release sheet has the release line. It is characterized in that it is tapered so that the side close to the mold layer has an acute angle. In this way, since the side closer to the release layer is processed to have an acute angle, the leading end of the recording material can be immediately locked near the exit side of the nip, and the recording material separability can be reliably maintained.

According to a seventh aspect of the invention, in the fixing device according to any one of the first to sixth aspects, the surface roughness of the edge ridge line facing the release layer that rotates integrally with the roller portion of the release sheet. Is Ra: 0.2 μm or less. In this way, the side close to the release layer has an acute angle and the surface roughness of the edge ridge is Ra: 0.2 μm or less,
The separability of the recording material can be reliably maintained, and the durability of the fixing roller, the fixing belt, or the release sheet on the release layer side can be further improved.

According to an eighth aspect of the present invention, a heating roller having a heater as a heat source therein, a fixing roller having an elastic layer on the outer periphery of a core metal, and a releasing roller which is wound around the heating roller and the fixing roller. It is equipped with a fixing belt having a layer formed thereon and a pressure roller which is in pressure contact with the fixing roller with the fixing belt sandwiched between the core metal and an elastic layer and a release layer provided on the outer circumference of the core metal, and carries an unfixed toner image. A fixing device for fixing the recording material on the recording material by heating and pressurizing the recording material by a fixing nip formed by a fixing roller around which a fixing belt is wound and a pressure roller, and in the vicinity of the exit side of the fixing nip, The release sheet has a release sheet for releasing the recording paper holding the toner image from the fixing belt. The release sheet has a curvature along the substantially outer diameter shape of the fixing belt, and has a curvature with respect to the outer diameter of the fixing belt. Place Characterized in that mounted with clearance. As described above, the fixing nip can be formed in a curved shape by the pressing belt and the fixing belt formed on the heating roller as the rotation fixing means and the fixing roller provided with the elastic layer and having the release layer formed thereon. Yes, the curved fixing nip can displace the tip of the recording material at the exit side of the nip so as to separate it from the fixing belt, which is the release layer side, and discharge.
The recording material separability can be maintained.

Moreover, since the tip of the release sheet is mounted sufficiently close to the exit side of the nip, the tip end portion of the recording material, which has no toner, undergoes winding displacement at the portion affected by the adhesive force of the toner. Before that, the tip of the recording material is immediately locked by the tip of the peeling sheet, and the tip of the recording material and the portion which tends to be wound around the fixing belt on the release layer side can be reliably peeled by the adhesive force of the toner following the same. Therefore, even when the release layer side is the fixing belt, the recording material can be easily separated from the fixing belt, and winding and fixing jam can be prevented.

An image forming apparatus according to a ninth aspect of the present invention is a fixing device for heating and pressurizing an unfixed toner image carried on a recording material in an image forming section in an electrophotographic system. The fixing device according to the third aspect is provided. As described above, the image forming apparatus according to any one of claims 1 to 8.
By selectively adopting the fixing device according to any one of the above, it is possible to obtain the same effects as the adopted fixing device as an image forming apparatus, and it is possible to reliably maintain the recording material separability. In particular, the commerciality of the image forming apparatus can be improved as an image forming apparatus using an oilless toner that does not apply silicone oil as a release agent to the fixing roller or the fixing belt.

[0027]

DETAILED DESCRIPTION OF THE INVENTION An image forming apparatus equipped with a fixing device and an identification fixing device according to an embodiment of the present invention will be described below. FIG. 1 is a schematic diagram of a color copying machine 1 as an image forming apparatus equipped with a fixing device 10 according to a first embodiment of the present invention. The color copying machine 1 shown in FIG. 1 is compatible with color separation. Equipped with multiple photoconductors that can form images of different colors,
A multicolor image is formed by collectively transferring an image obtained by superimposing and transferring a toner image formed on each photoconductor onto an intermediate transfer body onto a recording sheet S as a recording material. Here, the fixing device 10
Can be installed in a conventionally known image forming apparatus as long as it does not deviate from the object of the present invention, and it goes without saying that not only the color copying machine 1 but also a color printer, a facsimile machine, a printing machine and the like not shown are included. Also, by using the fixing device 10 of the present invention, it is possible to improve the commercial property as an image forming apparatus that can reliably maintain the recording material separability.

In the color copying machine 1, the image forming section 1A is located at the central portion in the vertical direction, the sheet feeding section 1B is located below the image forming section 1A, and the original placing table 1C1 is provided above the image forming section 1A. Each of the scanning units 1C is arranged. The image forming portion 1A includes an intermediate transfer belt 2 having a horizontally extending surface.
Is arranged, and four sets of recording devices 9Y, 9M, 9C, and 9BK for forming an image of a color complementary to the color separation color are provided above the intermediate transfer belt 2.
Each recording device 9 is composed of the same constituent member.

That is, each recording device 9Y, 9M, 9C, 9B
The photoconductors 3Y, 3M, 3C, 3BK, which form the main part of K and which can carry images of toners of complementary colors (yellow, magenta, cyan, black), extend along the spreading surface of the intermediate transfer body 2. They are juxtaposed. Each photoconductor 3Y, 3M,
Each of 3C and 3BK is composed of a drum that can rotate in the same direction (counterclockwise in FIG. 1), and a charging device 4, a writing device 5, and a developing device that perform image forming processing in the rotation process are provided around the drum. 6, a primary transfer device 7, and a cleaning device 8 are arranged. It should be noted that, for example, targeting the photoconductor 3Y, the reference numeral of each device is attached with Y, and for other colors, the same reference numerals are attached to the same parts, and they are distinguished by the subscripts M, C, and BK. And

The intermediate transfer belt 2 includes a plurality of rollers 2A to 2A.
Each photoconductor 3Y, 3M, 3C, 3BK hung around 2C
It is provided with a structure capable of moving in the same direction at a time position of and. A roller 2C, which is different from the rollers 2A and 2B forming the stretched surface of the intermediate transfer belt 2, is provided at the downward position of the intermediate transfer belt 2 and is opposed to the secondary transfer device 20 with the intermediate transfer belt 2 interposed therebetween. In FIG. 1, reference numeral 11 indicates a cleaning device for the intermediate transfer belt 2. Two
The secondary transfer device 20 is wound around the charging drive roller 20A and the driven roller 20B to position the secondary transfer device 20.
A transfer belt 20C that is movable in the same direction as the intermediate transfer belt 2 at the next transfer position is provided.
Is charged by the charging drive roller 20A, it is possible to transfer the multicolor image superimposed on the intermediate transfer belt 2 or the carried single color image onto a recording sheet as a recording material.

At the secondary transfer position, the recording paper S is fed from the paper feeding unit 1B.
Are to be delivered. The paper feed unit 1B includes a plurality of paper feed cassettes 1B1 and a plurality of paper feed rollers 1 arranged in a conveyance path for a sheet fed from the paper feed cassette 1B1.
B2, a conveyance roller 1B3, and a registration roller 1B4 located in front of the secondary transfer position. In this embodiment, in addition to the transport path r of the recording paper S fed from the paper feed tray 1B1, the paper feed unit 1B feeds a type not stored in the paper feed cassette 1B1 toward the secondary transfer position. There is a configuration that can. In this configuration, a part of the wall surface of the image forming unit 1A can be raised and lowered to form a manual feed tray 1A1, and the manual feed tray 1A1 and the feeding roller 1A2 are provided. The conveying path r1 for the recording sheet S fed from the manual feed tray 1A1 merges in the middle of the conveying path r1 for the recording sheet S directed from the paper feed cassette 1B1 to the registration rollers 1B4, and is fed from any of the conveying paths. The recording paper S is also the registration roller 1B4
The registration timing is set by.

The document scanning unit 1C is provided with a scanner unit 1C2 which exposes and scans the document on the document placing table 1C1, and an automatic document feeding device 1C3 is arranged on the upper surface of the document placing table 1C1. There is. Automatic document feeder 1C3
Has a structure capable of reversing an original fed out on the original placing table 1C1 so that the front and back surfaces of the original can be scanned.

In the scanner section 1C2, the reflected light from the original document exposed and illuminated by the lamp 12 for exposing and scanning the original document on the original table 1C1 is reflected by the mirrors 13, 14 and 15 and reaches the imaging lens 16. This reflected light is formed by the imaging lens 1
The light is incident on the dichroic prism 17 from 6 and forms an image, and is split into light of three types of wavelengths, for example, red R, green G, and blue B. The separated light of each wavelength is incident on an individual light receiver, for example, CCD 18R, 18G, 18B. These CCDs 18R, 18G, 18B
Converts incident light into a digital signal and outputs the digital signal. The output is subjected to necessary processing in an image processing unit (not shown), and recording color information of each color, for example, recording of yellow Y, magenta M, cyan C, and black BK. It is converted into a color information signal for formation. A signal from an image processing unit (not shown) is input to the writing device 5.

Writing device 5 (5Y, 5M, 5C, 5B
K) indicates that the writing light is controlled by the image information obtained by scanning the document on the document table 1C1 or the image information output from the computer (not shown), and the writing light is transferred to the photoconductor 3 (3Y, 3M, 3C, 3BK). On the other hand, writing light according to image information is emitted to form an electrostatic latent image.

Photoreceptor 3 formed by writing device 5
The upper electrostatic latent image is subjected to visible image processing by the developing device 6 and is primarily transferred to the intermediate transfer belt 2. When the toner images of respective colors are superimposed and transferred onto the intermediate transfer belt 2, the secondary transfer device 20 collectively and secondarily transfers the toner images onto the recording paper S. An unfixed toner image carried on the surface of the recording sheet S secondarily transferred is fixed by a fixing device 10 described later. The recording paper S that has passed through the fixing device 10 is
The conveyance path switching claw 53 disposed on the rear side of the conveyance path switches the conveyance direction, and the conveyance path r3 toward the paper discharge tray 21 and the reverse conveyance path that reaches the registration roller 1B4 via the document reversing device 22. The transport direction is selected for RP.

Color copying machine 1 having the above-mentioned structure
Then, an electrostatic latent image is formed on the uniformly charged photoconductor 3 by exposing and scanning an original placed on the original placing table 1C1 or by image information from a computer, and an electrostatic latent image is formed. The image is the developing device 6 (6Y, 6M, 6C, 6
After the visible image processing is performed by BK), the toner image is primarily transferred to the intermediate transfer belt 2. The toner image transferred to the intermediate transfer belt 2 is directly transferred to the recording paper S fed from the paper feeding unit 1B in the case of a single color image, and the primary transfer is repeated in the case of a multicolor image. As a result, the toner images of the respective colors are superimposed and transferred, and then secondarily transferred to the recording paper collectively. The recording paper S after the secondary transfer is fed to the paper discharge tray 21 after the unfixed image is fixed by the fixing device 11 or reversed by the document reversing device 22 and again toward the registration roller 1B4.

Next, a first embodiment of the fixing device 10 used in the color copying machine 1 as the image forming apparatus of the present invention will be described. As shown in FIGS. 1 and 2, the fixing device 10 is a roller-type fixing device using an oilless toner in which WAX as a release agent is dispersed internally in a resin base material. The fixing device 10 contacts a fixing roller 25 as a rotary fixing means, a pressure roller 26 as a pressure means for forming a nip N by pressing the fixing roller 25, and an upper end side portion of the fixing roller 25. The fixing roller 25 includes a cleaning roller 27 that removes paper pieces and the like on the surface of the fixing roller 25, and a release sheet 28 that faces the fixing roller 25 on the nip outlet g side. The rollers 25, 26, 27 are pivotally attached to a fixing device base frame 29 fixed to a part of the wall surface of the image forming unit 1A, and the release sheet 28 is a guide member on the fixing device base frame 29 side as described later. 30 (see FIGS. 4 and 5). A conveyance guide member 31 is attached to a portion of the base frame 29 for the fixing device facing the end of the secondary transfer device 9, and a recording paper carrying an unfixed toner image is fixed by the fixing roller 25 and the pressure roller 26. Guide to the nip N to be formed.

As shown in FIG. 3, a fixing roller 25 as a rotary fixing means has a cored bar 251 forming a roller part, an elastic layer 252 fitted on the cored bar 251 and a release member integrally joined to such a roller part. And layer 253. Here, the fixing roller 25 is formed to have a diameter of φ60 as an example, and is formed into an annular shape from a heat-resistant elastic material such as foamed silicone rubber or liquid silicone rubber in order to obtain a nip width L0 on the outer periphery of the Fe cored bar 251. Elastic layer 252. The silicone rubber elastic layer 252 includes a release layer 253 formed as an annular layer so as to wrap the surface layer and integrally bond the layer.
The release layer 253 is formed of a heat resistant resin having both strength and releasability. In the core metal 251 of the fixing roller 25, a halogen heater 254 for accelerating the temperature rise of the fixing roller is arranged.

As shown in FIG. 2, a thermistor 32 is slidably attached to the surface of the fixing roller 25, and a temperature control unit 19 which is a part of an image processing unit (not shown) fixes the temperature based on the detected temperature information. The surface temperature of the roller 25 is controlled to a predetermined fixing temperature. The release layer 253 shown in FIG. 3 is made of a material having heat resistance and a small surface energy. For example, silicone resin, fluororesin such as polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkylvinylether copolymer ( Polymer resins such as PFA) and tetrafluoroethylene-hexafluoropropylene copolymer (FEP) are used as the heat resistant tube.

The surface hardness of the fixing roller 25 is Aske 30.
It is about 50 Hs.

As shown in FIG. 3, the pressure roller 26 is
A heat-resistant elastic layer 262 made of fluorine-based rubber, silicone rubber or the like, and a surface release layer 263 forming an endless pressure face Fc made of fluorine-based resin are provided on the outer periphery of the e or Al cored bar 261. In this embodiment, in order to improve the peeling property between the recording paper and the toner, the surface hardness of the pressure roller 26 is set to the fixing roller 25.
A fixing nip N having a nip width L0, which is harder than the other, is abutted between the fixing belt 33 and the pressure roller 26, and both ends thereof are curved downward. In this embodiment, the thickness of the elastic layer 262 of the pressure roller 26 is 0.5 to 2 mm.
And its surface hardness is Asker C70-90H
s. A halogen heater 264 for accelerating the temperature rise of the pressure roller is provided in the pressure roller 26. As shown in FIG. 2, a thermistor 33 is slidably attached to the surface of the pressure roller 26, and a temperature control unit 19 forming a part of an image processing unit (not shown) detects the temperature information based on the detected temperature information. The surface temperature of is controlled to a predetermined fixing temperature.

As shown in FIG. 2, the journal 261 ′ at the end of the pressure roller 26, which is integral with the core metal 261 of the pressure roller 26, is displaceable in the vertical direction, which is the direction of contact and separation with the fixing roller 25, and the fixing device base frame 29. Be pivoted to. That is, the journal 261 'is supported by the lever 34 via the pivot portion 265 that pivotally supports the journal 261', and the lever 34 is attached to the fixing device base frame 29 by the base shaft 341.
Is fixed to the fixing device base frame 29 by a tension spring 35, one end of which is locked to the fixing device base frame 29, and thereby elastically receives an upward pulling force. The tension spring 35 causes the pressure roller 26 to come into pressure contact with the fixing roller 25.

The fixing device 10 has a rotary drive system (not shown), and the rotary drive system transmits the rotary drive force to the pressure roller 26 by a transmission means (not shown). In addition to this, the rotational driving force may be transmitted to the fixing roller 25 in some cases. As shown in FIGS. 2 and 3, the fixing roller 25
A release sheet 28 for preventing the recording paper from being wound around the fixing roller 25 is provided on the nip outlet side g of the sheet. 4 and 5
As shown in, the outer diameter of the paper transport portion of the fixing roller 25 is
Here, it is φ60, and there are φ30 journals (portions integrated with both ends of the core metal 251) 251 ′ at both ends thereof.
The φ30 journal 251 ′ is supported by the bearing portion 301 of the guide member 30 via a bearing (not shown).

The pair of guide members 30 have a bilaterally symmetrical shape, and the bearing portion 301 for pivotally supporting the journal 251 'of the fixing roller 25 and its one end are provided with a bracket 36 on the fixing device base frame 29 side. Wall 302 fixed by
And a sheet receiving portion 303 extending from the other end of the bearing portion 301. The pair of left and right guide members 30 has a part of the mounting wall 302 fixed to the fixing device base frame 29 side via a bracket 36, so that the fixing roller 25
It is configured so that it does not rotate when is rotated. The sheet receiving portion 303 has a thick plate shape, and the bearing portion 3
A curved sheet groove 304 is formed by maintaining a gap j between the other side surface f1 of 01 and the upper opening.

As shown in FIGS. 5A and 5B, by inserting the release sheet 28 along the sheet grooves 304 of the pair of left and right guide members 30, the release sheet 28 is attached to the fixing roller 25. It can be attached to a predetermined position with high accuracy. The gap j between the sheet grooves 304 has the same width as the thickness of the release sheet 28. A screw hole 305 is formed on the upper end side of the sheet receiving portion 303, and the release sheet 2 inserted and supported in the sheet groove 304 is formed here.
A screw for tightening the seat 8 is screwed. The release sheet 28 is a sheet member having a thickness of about 0.1 to 0.2 mm, and is formed of a material such as a heat resistant resin sheet or a metal thin film sheet.

The release sheet 28 has a straight portion 282 and a portion near the outer periphery of the fixing roller 25 at the tip thereof, which maintains a predetermined gap d with respect to the release layer and has a substantially outer diameter of the release layer. A curved portion 283 having a curvature and extending so as to follow the shape and extending, and a tip portion 281 at the tip of the curved portion 283 are provided. The tip portion 281 is located at a position separated from the nip exit end of the fixing roller 25 by a predetermined distance L1. by the way,
Generally, the distance from the leading edge of the recording paper S as a recording material to the leading edge position of the image is called "leading edge blank width". When the paper is discharged from the nip outlet g, The recording paper S does not wind around the fixing roller 25.

Then, at the moment when the leading edge of the image is discharged from the nip outlet g, an adhesive force acts on the fixing roller 25, and the recording paper S is pulled up to the fixing roller 25 side and wound around. There is. In order to prevent the recording paper S from being wrapped around, the distance L1 from the leading end of the release sheet 28 and the nip outlet g, that is, the nip outlet g of the nip N.
If the distance L1 to the side end is less than the leading edge blank width, the recording sheet S does not wind around the fixing roller 25 and the release sheet 2
The sheet is separated relatively easily by 8, and then conveyed by the sheet discharge rollers 38 and 39 and discharged onto the sheet discharge tray 21. Since the leading edge blank width in the fixing device 10 of FIG. 1 is set to, for example, 3 mm, the leading end portion 281 of the release sheet 28 is assembled so that the distance L1 from the nip outlet end is 3 mm or less.

If the release sheet 28 remains normal,
The tip portion 281 also has the same thickness as other portions,
As shown in FIG. 6, the tip portion 2 of the release sheet 28 here
The edge ridge line facing the peeling layer 253 at 81 is formed as an edge portion e having an acute angle θ. Therefore, the tip portion 281
When the sheet has the same thickness as the other portions, the leading edge of the recording sheet is easily caught, but here, the leading edge 28 of the release sheet 28 is used.
Since 1 forms the ridge edge e, even if the thin recording paper is ejected from the nip outlet g while being wound around the fixing roller 25, the ridge edge e reliably separates the leading edge of the recording paper and It can function away from the 25 side.

The surface roughness of the edge portion e is Ra: 0.
It is formed with a thickness of 2 μm or less. For this reason, the separability of the recording material can be reliably maintained, and the durability of the fixing roller 25 on the release layer 253 side can be further improved. Further, the surface of the release sheet 28 may be coated with a thin film of fluororesin,
In this case, even if the release sheet 28 contacts the fixing roller 25 on the release layer 253 side, it is possible to reduce the damage to the fixing roller 25. Further, the release layer 253 of the release sheet 28 and the fixing roller 25 shown in FIGS.
And are separated from each other by a predetermined gap d. Ideally, the gap d is preferably 50 μm or less so as not to enter the gap between the fixing roller 25 and the release sheet 28 even if the thinnest paper that can be passed through is completely wrapped around the release sheet 2.
It is practically difficult to adjust it to 50 μm or less because of the straightness of the tip end of 8 and the shake when the fixing roller 25 rotates.

If the gap d is narrowed, another problem is that when the fixing roller 25 and the release sheet 28 are in contact with each other or in a position very close to each other, heat is taken from the fixing roller 25 to lower the surface temperature of the fixing roller 25. There is a concern that it will end up. In this embodiment, the pair of left and right guide members 3 in FIG.
0 is used and the gap d is preferably set to about 0.5 mm in consideration of component accuracy. Next, the process of fixing the unfixed toner image t forming the multicolor image or the carried single color image on the intermediate transfer belt 2 onto the recording paper S by the fixing roller 25 and the pressure roller 26 will be described. To do.

The toner image t on the recording paper S reaching the fixing device 10 is heated to a low viscosity state by the fixing roller 25, and further, the recording paper S is pressed by the pressure roller 15.
Permeates into the fibers of. After that, when the toner cools and solidifies, the toner and the paper fibers are firmly fixed. However, at this time, if the temperature of the toner layer at the time of separation from the fixing roller 25 is equal to or lower than the softening temperature Ts, the resin of the toner does not sufficiently soften and accordingly does not penetrate into the fibers of the recording paper S. Sufficient fixing strength cannot be obtained.

On the other hand, if the surface temperature of the toner layer at the time of separation from the fixing roller 25 is equal to or higher than the outflow start temperature Tf, the resin viscosity of the toner becomes too low and the fibers of the recording paper S sufficiently permeate. Although the releasability of the fixing roller 25 from the releasing layer 253 is deteriorated, a problem such as offset to the fixing roller 25 or winding of recording paper around the fixing roller 25 occurs, so that the surface of the toner layer after fixing is fixed. The control temperature of the fixing temperature is determined so that the temperature is in the range of Ts to Tf, and it is desirable that the control system has a small temperature deviation in a region near the center thereof.

Even when thin paper to thick paper are fixed at the same fixing temperature, the toner layer surface temperature after fixing is higher for thin paper and lower for thick paper because the heat capacities of the papers themselves are different. As a result, the adhesive force between the toner layer surface and the surface of the fixing roller 25 becomes large even if the offset phenomenon does not occur in thin paper passing, and it becomes difficult to separate immediately after passing through the nip. It is wound around along the curvature of and is taken. Depending on the size of the adhesive force, if the tip is peeled off even a little, it will be pulled downward by the weight of that part and it will not wind up, but from some places the tip will not peel off and will be wrapped around as it is.
It is known that the adhesive force changes due to environmental changes, changes in the amount of adhered toner, changes in the temperature of the fixing roller 25, and the like. In particular, the phenomenon of thin paper wrapping around the fixing roller will be described.

The recording paper S is composed of a fixing roller 25 and a pressure roller 1.
After being sandwiched by the nip constituted by 5, the toner image is fixed to the recording paper S under the action of heat and pressure. The nip shape when the fixing roller 25 and the pressure roller 26 are in pressure contact is determined by the relationship between the rubber layer thickness and the rubber hardness of the fixing roller 25, and the rubber layer thickness and the rubber hardness of the pressure roller 26.

In one embodiment, the fixing roller 25 has an outer diameter of φ60, the thickness of the Si rubber is 2 mm, and the JISA hardness of the rubber layer is 20 degrees.
6 is an outer diameter of φ60, the thickness of the Si rubber is 2 mm, and the J of the rubber layer is
The ISA hardness is 30 degrees, and in each case, a PFA tube having a thickness of 50 μm is provided on the outermost layer. In this roller combination, when the adhesive force between the surface of the toner layer and the surface of the fixing roller 25 is almost negligible, the discharge angle of the recording paper S at the nip outlet is slightly downward from the horizontal. The discharge angle of the recording paper S at the nip exit g is preferably a little downward in consideration of stable transportability, but if it is made too downward, the first side of the double-sided fixed image is placed on the pressure roller 26 side when fixing the second side. Since there is a possibility of wrapping around, care must be taken when designing the fixing roller 25 and pressure roller 26 configurations.

FIG. 7 is a schematic diagram of a color copying machine 1a as an image forming apparatus equipped with a fixing device 10a according to the second embodiment of the present invention. The color copying machine 1a shown in FIG. The color copying machine 1 is different from the color copying machine 1 in that the intermediate transfer using the intermediate transfer body is not performed, and the direct transfer to the recording paper S is performed, and the other configurations are almost the same. Here, duplicate description will be omitted, the same reference numerals will be given to the same portions, and a subscript a will be given to a portion that requires distinction of overlapping members for the sake of clarity. Color copier 1
a is provided with a plurality of photoconductors capable of forming an image of a color corresponding to color separation, and multi-colored by sequentially transferring the toner images formed on the respective photoconductors to a recording sheet S as a recording material in a multi-layered manner. Adopt a configuration capable of forming an image.

Here, the color copying machine 1a includes the image forming unit 1
Aa is located at the central portion in the vertical direction, and the paper feeding unit 1 is provided on the side thereof.
Ba and a document scanning unit 1Ca are arranged above the image forming unit 1Aa. The image forming unit 1Aa has a pair of driving rollers 2Aa and 2Ba and a transfer belt 2a which is stretched between them and has a horizontally extending surface. The transfer belt 2a has a registration roller 1B4a at its entrance end and an unfixed toner image t on the recording paper S at its exit end.
It is provided so as to face the fixing device 4a for fixing the. Note that the recording paper S for the fixing device 10a is provided on the lower side of the transfer belt 2a.
A cleaning device (not shown) that cleans the paper dust or the developer adhering to the surface of the transfer belt 2a that has been conveyed is provided. Above the transfer belt 2a, four sets of recording devices 9aBK, 9aC _, 9aM _{, and} 9aY for forming an image of a color complementary to the color separation color are provided. Each recording device 9a has four sets of recording devices 9BK and 9BK shown in FIG.
Since the same configurations as C _, 9M _{, and} 9Y are adopted, redundant description will be omitted here.

[0058] Each recording device 9a, for example, a recording apparatus 9aC for cyan has a drum-shaped photoreceptor _{3 C,} the photoreceptor 3
Around and C, a charger 4C, the laser beam emitting device _{5 C} by exposure position, a developing device 6C, a transfer charger 7
C and the like are provided in order. The uniformly charged photoreceptor onto 3C by a charger 4 _C, by exposure to a laser beam emitting device 5C, the latent image of the cyan light image is formed,
A visible image is formed by the development by the developing device 6C. The recording paper S fed from the paper feed unit 1Ba, for example, a paper feed cassette by the paper feed roller 1B2a, has its leading end aligned by the registration roller 1B4a, and is sent to the transfer belt 2a at the same timing. The recording paper S conveyed by the transfer belt 2a is formed by the photoconductors 3BK, 3C _, 3 having visible images formed thereon.
M _, 3Y are sequentially sent to transfer chargers 7BK, 7C _,
The visible image is transferred by the action of 7M _and 7Y.

The recording paper S on which the visible image is transferred is sent to a fixing device 10a described later, and the unfixed toner image t is heated and pressed by the device to be fixed, and then the paper is ejected by a paper ejection roller 38 to a paper ejection tray 21. Is ejected. At one end of the transfer belt 2a in the stretching direction, that is, at the end on the side opposite to the paper feeding unit 20 in FIG.
The fixing device 4 is provided, and at the other end, that is, in the vicinity of the sheet feeding unit 20, the paper dust or the developer attached to the surface of the transfer belt 24 after the conveyance of the recording sheet S to the fixing device 4 is finished is cleaned. A cleaning device (not shown) is provided. The recording sheet S separated from the transfer belt 2a is conveyed by the conveyance guide member 49.
The unfixed toner image t carried on the recording paper S is fixed by being guided by the reference numerals 1, 492. Then, the recording sheet S that has been fixed
Is discharged toward the discharge tray 27 by the discharge rollers 23.

The fixing device 10a used in such a color copying machine 1a will be described. Here, the fixing device 10a does not violate the object of the present invention, that is, the fixing device 10a here.
a is also mounted on the color copying machine 1a which is a conventionally known image forming apparatus using an oilless toner which does not apply silicone oil as a releasing agent to the fixing belt 40, but is not limited to this, and a color printer (not shown), The present invention can be applied to a facsimile machine, a printing machine, and the like, and by using the fixing device 10a of the present invention, it is possible to improve the commercial property as an image forming apparatus that can reliably maintain the recording material separability.

As shown in FIG. 7 and FIG. 8, the image forming apparatus has a fixing roller 41 as a roller portion provided as a rotating and fixing means facing each other, a heating roller 42, and an endless belt stretched between both rollers. And the fixing belt 40. Further, a pressure roller 43 having an endless pressure surface Fc and a tension roller 44 for applying a tension to the fixing belt 40 are provided as a pressure means for forming the nip N by pressing against the fixing belt 40, and further, the fixing belt 40. It has a release sheet 28a opposite to. The fixing device 10a heats the fixing belt 40 by the heating roller 42, rotates the fixing belt 40 in the arrow direction D (see FIG. 8), and in the nip N formed by the fixing belt 33 and the pressure roller 34, the recording material The non-fixed toner image t carried on S is melted by heating and fixed on the recording material S. Here, the fixing roller 31, the heating roller 32, and the pressure roller 34 are pivotally attached to the fixing device base frame 45 fixed to the transport unit U side, and their respective rotation axes are arranged in parallel with each other.

The base material of the fixing belt 40 is made of heat resistant resin. Materials for the heat resistant resin include polyimide, polyamide imide, polyether ketone (PEE)
K) etc. are used. The thickness of the base material is preferably 30 to 100 μm from the viewpoint of balance between heat conduction and strength. Since the surface of the fixing belt 33 is brought into pressure contact with the recording material S and the unfixed toner image t, a surface layer excellent in releasability and heat resistance is required. (See Figure 8)
Is covered. An elastic layer made of heat-resistant rubber such as silicone rubber or fluororubber having a thickness of 100 to 300 μm is provided under the surface release layer in order to obtain image uniformity.

The heating roller 42 has a diameter of φ20 to φ30.
Formed of Al or Fe and has a wall thickness of t = 0.3 to
It is formed so as to form a thin metal roller of 1.0 mm, and has a halogen heater 47 as a heat source inside. The temperature of the heating roller 32 is detected by the temperature control element 46, and the detected temperature information is output to the image processing unit 48, and the heating roller 42 is controlled to have a preset constant temperature. It plays the role of heating to the required temperature.

The heating roller 42 also serves as a tension roller, and is stretched in the direction of the broken line arrow P1 in the drawing by a tension spring or the like (not shown). The fixing roller 41 has a diameter of φ20 to φ30, and is provided with an elastic layer 412 formed of a heat resistant elastic body such as foamed silicone rubber or liquid silicone rubber on the outer periphery of the Fe cored bar 411 to obtain a nip width L. . The elastic layer 412 has a thickness of 3
It is about 6 mm. The surface hardness of the fixing roller 41 is As.
kerC is about 30 to 50 Hs.

The pressure roller 43 comprises a heat-resistant elastic layer 432 made of fluorine-based rubber, silicone rubber or the like on the outer periphery of a core bar 431 made of Fe or Al, and a surface release layer 34 made of fluorine-based resin.
3 is formed. In this embodiment, the recording material S
In order to improve the releasability of the toner and the toner, the surface hardness of the pressure roller 43 is made harder than that of the fixing roller 41, and the fixing belt 42 is
The pressure roller 43 and the pressure roller 43 contact each other to form a fixing nip N having a nip width L in which both ends are curved downward. In this embodiment, the thickness of the elastic layer 432 of the pressure roller 43 is about 0.5 to 2 mm, and the surface hardness is A.
It is skerC70-90Hs. It is desirable to provide a halogen heater 434 in the pressure roller 43 to accelerate the temperature rise of the pressure roller.

The fixing device 10a has a rotary drive system (not shown), and the rotary drive system transmits the rotary drive force to the pressure roller 43 by a transmission means (not shown). In addition to this, the rotational driving force may be transmitted to the fixing roller 41 in some cases. Such a fixing device 10a is provided with the fixing belt 4
A nip N having a nip width L2, which is constituted by a portion where 0 is in contact with the fixing roller 41 in a wound state and an abutting portion of the pressure roller 43, is held. Therefore, the nip N reduces the crushing of the image, and the stable feeding property and fixing property are obtained.

Here, the release sheet 28 is provided on the release surface of the fixing belt 40 which comes into contact with the fixing roller 41 in a wound state.
a is placed opposite. The release sheet 28a here is formed in the same manner as the release sheet 28 of FIG. 1, and includes a straight portion 282, a curved portion 283, and a tip portion 281. The release sheet 28a is similar to the release sheet 28 of FIG. 1, and has a pair of left and right guide members pivotally supporting the fixing roller 41 (see FIG. 5A,
It is supported by the bracket 36 on the fixing device base frame 29 side via the reference numeral 304 in (b)), and the duplicated description is omitted.

The tip portion 281 of the release sheet 28a is located at a position separated by a predetermined distance L1 from the nip outlet end of the nip N formed by the fixing belt 40 and the pressure roller 43, which are in contact with each other while being wound around the fixing roller 41. Will be deployed. Further, the configuration of the tip portion 281 of the release sheet 28a is as shown in FIG.
The same structure as that of the release sheet 28 of FIG.

Also in this case, the distance L1 from the end on the nip outlet g side is set to be equal to or less than the leading edge blank width as in the release sheet 28 of FIG. 1, and the recording paper S is wound around the fixing belt 40. It is separated relatively easily by the release sheet 28, and then conveyed by the paper discharge rollers 38 and discharged to the paper discharge tray 21.

The release sheet 28 in FIG. 2 is supposed to be supported by the bracket 36 on the fixing device base frame 29 side through a pair of left and right guide members (see reference numeral 30 in FIGS. 5A and 5B). Instead of this, it may be configured as shown in FIGS. Here, the upper end connecting portion 501 is fixed to the downward surface of the base frame 29 side for the fixing device 10b, and the L-shaped bracket 50 having the same length as the fixing roller 25 side is provided. The L-shaped bracket 50 is provided with a sheet receiving portion 502 at the lower end thereof in a continuous manner in the longitudinal direction X. The sheet receiving portion 502 is formed with a surface fe with which the upper end of the release sheet 28a can abut. Therefore, after the release sheet 28a is overlaid on the surface fe, the backing plate 51 is overlaid from the outside, and the upper end of the release sheet 28a is fastened to the sheet receiving portion 502 with a plurality of screws 52 via the backing plate 51. Can be reliably supported. The fixing device 10 of FIG. 2 has a pair of left and right guide members (see FIG. 5A).
Instead of (see reference numeral 30 in (b)), the fixing device 10b using the L-shaped bracket 50 in FIGS. 9 and 10 can also obtain the same effect.

In the fixing device 10 used in the color copying machine 1, the pressure applying means presses the pressure roller 26 having the endless pressure surface Fc on the side of the fixing roller 25, which is the rotary fixing means, and presses it against the fixing nip. Although N is formed, instead of this, as shown in FIG. 11, a pressure belt 60 having a pressure-applying means having an endless pressure-applying surface Fc and a pressure roller 61 having one end thereof fitted externally are provided. The fixing device 10c in which the fixing nip N is formed by the driven roller 62 which fits the end may be configured. In this fixing device 10c, the pressure roller 61 presses the pressure belt 60 against the fixing roller 25 to form the fixing nip N. Instead of the driven roller 62 here, a belt running guide (not shown) having an arcuate sliding contact surface that slidably contacts the inner peripheral surface of the pressure belt 60 may be used to simplify the apparatus. The fixing device 10c using these pressurizing means has the same configuration as the fixing device 10 of FIG. 1 except for the pressurizing means, so that the same effect as the fixing device 10 of FIG. 1 can be obtained.

Although the color copying machines 1 and 1a have been described above as the image forming apparatus, the present invention is not limited to this, and the present invention may be applied to a single color copying machine, a facsimile, a printer, or the like. Similar effects can be obtained in these cases as well.

[0073]

As described above, according to the invention of claim 1, since the release sheet is attached with a shape having a curvature so as to follow the substantially outer diameter shape of the release layer which rotates integrally with the roller portion, the release sheet is attached. Even if the tip is attached sufficiently close to the exit side of the nip, the base side of the release sheet can be separated from the discharge path side of the recording material, and the release sheet can be easily attached. Moreover,
For example, even when the recording material is thin paper, the recording material can be easily separated from the fixing roller or the fixing belt, which is the release layer side, regardless of the type of the recording material, and winding and fixing jam can be prevented.

Further, since the release sheet is attached to the fixing roller or the fixing belt on the release layer side with a predetermined gap, the release sheet is fixed to the fixing roller or the fixing belt or the release sheet on the release layer side even after running. The durability can be improved and the separation of the recording material can be prevented from deteriorating.

According to the second aspect of the invention, the fixing nip can be formed by the elastic layer and the releasing layer of the fixing roller as the rotating fixing means and the pressing means, and the leading end of the recording material is located on the releasing layer side at the exit side of the nip. It becomes easy to hold the fixing nip in a curved shape so that it can be separated from the fixing roller, and in this respect, the recording material separability can be easily held.

According to the third aspect of the present invention, the fixing nip is formed by the heating roller as the rotary fixing means, the endless belt wound around the roller portion, and the pressing means, and the leading end of the recording material at the exit side of the nip. It becomes easy to hold the fixing nip in a curved shape so that it can be separated from the endless belt, which is the release layer side. In this respect, the recording material separability can be easily maintained, and winding and fixing jam can be prevented. .

According to the fourth aspect of the invention, the structure can be simplified by using the pressure roller as the pressure means.

According to the invention of claim 5, the distance between the tip position of the release sheet and the fixing nip outlet is preferably equal to or less than the white gap in the image leading edge, so that the toner is melted at the leading edge of the recording material. Image that does not receive adhesive force Before the tip part of the leading edge of the blank area is wound and displaced due to the effect of the adhesive force, the tip of the recording material can be securely locked immediately on the tip of the recording material near the exit side of the nip. The tip of the recording material and the subsequent adhesive force of the toner can surely peel off the portion that tends to wind around the release layer side.

According to the sixth aspect of the present invention, since the side close to the release layer is processed so as to form an acute angle, the tip of the recording material can be surely locked immediately near the exit side of the nip, and the recording material separability is ensured. Can be held at

In the invention according to claim 7, the side closer to the release layer has an acute angle, and the surface roughness of the edge ridge is Ra: 0.2 μm.
Since it is m or less, the separability of the recording material can be surely maintained, and the durability of the fixing roller, the fixing belt or the release sheet on the release layer side can be further improved.

According to an eighth aspect of the present invention, a fixing nip is formed between a heating roller as a rotary fixing means and a fixing roller having an elastic layer and a releasing belt formed on the fixing belt and a pressing means. It can be formed into a curved shape, and the curved fixing nip can be displaced so that the leading end of the recording material is separated from the fixing belt which is the release layer side at the exit side of the nip, and the recording material can be separated.

An image forming apparatus according to a ninth aspect of the present invention selectively adopts the fixing device according to any one of the first to eighth aspects, and thereby, the image forming apparatus has the same effect as the adopted fixing device. In the same manner as above, the recording material separability can be surely maintained, and in particular, the image forming apparatus using an oilless toner which does not apply silicone oil as a releasing agent to the fixing roller or the fixing belt has a commercial property. Can be improved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a color copying machine including a fixing device as an embodiment of the present invention.

FIG. 2 is an enlarged schematic configuration diagram of a fixing device used in the color copying machine of FIG.

3 is an enlarged schematic configuration diagram of a fixing roller and a pressure roller used in the fixing device of FIG.

4 is an exploded perspective view of a fixing roller, a release sheet and a guide member used in the fixing device of FIG.

5A and 5B are enlarged side views of a guide member used in the fixing device of FIG. 2, where FIG. 5A shows a release sheet before attachment and FIG. 5B shows a release sheet after attachment.

FIG. 6 is an enlarged partial sectional view of the tip of a release sheet used in the fixing device of FIG.

FIG. 7 is a schematic configuration diagram of a color copying machine incorporating a fixing device as another embodiment of the present invention.

8 is an enlarged schematic configuration diagram of a fixing device used in the color copying machine of FIG.

FIG. 9 is a side view of a main part of an L-shaped bracket and a release sheet used in a fixing device as another embodiment of the present invention.

FIG. 10 is a configuration diagram of a main part of the fixing device in FIG. 9 in plan view.

FIG. 11 is a side view of a main part of a fixing roller and a pressing unit used in a fixing device as another embodiment of the present invention.

[Explanation of symbols]

1 color copier 25 fixing roller 252 annular elastic layer 253 Release layer 254 heat source 28 Release sheet 40 endless belt 401 Release layer 41 Fixing roller (roller part) 42 Belt fixing means d Predetermined gap to the release layer g Exit side 25r, 41r Roller part Fc Endless pressure surface Pm pressurizing means N fixing nip S recording paper (recording material)

Continued front page    F term (reference) 2H033 AA16 BA11 BA12 BA20 BA21                       BB03 BB04 BB13 BB15 BB18                       BB29 BB30                 3F053 AA19 LA02 LB01

Claims (9)

[Claims] 1. A mold release comprising a roller portion having an annular elastic layer, and either an annular layer integrally formed on the outer periphery of the roller portion or an endless belt externally fitted to the roller portion separately. A rotary fixing means formed by heating the release layer with a heat source; and a pressing means for pressing an endless pressing surface against the rotary fixing means, the rotary fixing means and the pressing means A fixing device that heats and presses an unfixed toner image carried on a recording material by the fixing nip formed in 1. to fix the toner image on the recording material, the recording material holding the toner image near the exit side of the fixing nip. A release sheet for releasing from the release layer,
The fixing device is characterized in that the release sheet has a curvature so as to follow a substantially outer diameter shape of a release layer that rotates integrally with the roller portion, and is attached to the release layer with a predetermined gap. 2. A fixing roller comprising a cored bar and a heater as a heat source inside the cored bar, and an elastic layer and a release layer stacked on the outer periphery of the cored bar. The fixing device according to claim 1. 3. The rotation fixing means comprises a roller portion composed of a cored bar and an elastic layer externally fitted to the cored bar, and a heating roller disposed opposite to the roller part and having a heat source inside thereof. The fixing device according to claim 1, wherein an endless belt having a release layer is stretched between the heating roller and the heating roller. 4. The fixing roller according to claim 1, wherein the pressing means is a pressing roller in which an elastic layer and a release layer are provided on an outer periphery of a cored bar. apparatus. 5. The distance between the position of the leading edge of the release sheet and the exit of the fixing nip is desirably equal to or less than the blank width of the leading edge of the image, or less.
The fixing device according to any one of 1. 6. The edge ridge line of the release sheet, which faces the release layer that rotates integrally with the roller portion, has a taper shape processed so that the side close to the release layer has an acute angle. The fixing device according to claim 1. 7. The surface roughness of the edge ridge line facing the release layer that rotates integrally with the roller portion of the release sheet is Ra:
7. The thickness is 0.2 .mu.m or less.
The image fixing device described in any one of 1. 8. A heating roller having a heater as a heat source inside, a fixing roller having an elastic layer on the outer periphery of a core metal, and a release layer formed by stretching the heating roller and the fixing roller. Equipped with a fixing belt and a pressure roller that is pressed against the fixing roller with the fixing belt sandwiched and has an elastic layer and a release layer on the outer circumference of the core, fixing the recording material carrying the unfixed toner image. A fixing device for fixing on a recording material by heating and pressing by a fixing nip formed by a fixing roller around which a belt is wound around and a pressure roller, wherein a toner image is held near the exit side of the fixing nip. The release sheet has a release sheet that separates the recording paper from the fixing belt. The release sheet has a curvature along the substantially outer diameter of the fixing belt and has a predetermined gap with respect to the outer diameter of the fixing belt. Installed Fixing apparatus characterized by being. 9. A fixing device according to any one of claims 1 to 8 is provided as a fixing device for heating and pressing an unfixed toner image carried on a recording material in an image forming section in an electrophotographic system. An image forming apparatus characterized by the above.