JP2002148983A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device in which a warm-up time can be shortened to almost zero and excellent peeling performance at a nip part can be obtained even for a color image. SOLUTION: The fixing device which heats a thin heat belt having a conductive layer by induction with the magnetic field produced by a magnetic field producing means and fixes an unfixed toner image on a recording medium at the nip part formed between the heat belt and a pressure member provided opposite the heat belt is provide with a pressing member having an elastic layer inside the heat belt, and the pressing member is pressed against the pressure member across the heat belt to form the nip part for fixation.

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 for fixing an unfixed toner image with heat and pressure in an image forming apparatus such as a copying machine, a printer, a facsimile or the like employing an electrophotographic system. More particularly, the present invention relates to a fixing device using a belt-shaped member as a heating member.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine, a printer, or a facsimile which employs the above-mentioned electrophotographic system, at least a metal fixing device used for fixing an unfixed toner image by heating and pressing is used. A heating source such as a halogen lamp is provided inside a heating roll having a core made of, and the heating roll is heated from the inside,
A pressure roll is disposed so as to be in pressure contact with the heating roll,
The unfixed toner image is fixed on the recording medium by heat and pressure by passing the recording medium onto which the unfixed toner image has been transferred between the nip portions between the heating roll and the pressure roll, thereby obtaining a fixed image. Such a configuration is mainly used.

In the fixing device, the heating member can be instantaneously heated to a predetermined temperature from the viewpoint of energy saving and not to keep the user waiting when using the image forming apparatus. Uptime)
Is required, but the above-described method of heating the heating roll by a heating source such as a halogen lamp disposed inside the heating roll cannot be achieved for the following reasons.

That is, a heating roll as a heating member is
Because a pressure member such as a pressure roll is pressed against,
It is necessary to maintain rigidity higher than a predetermined value, and has a metal core having a certain thickness or more. Therefore, the heating roll is
The heat capacity cannot be reduced so much, and the halogen lamp as a heating source is provided inside the heating roll and heats the heating roll from the inside, so the heat is transferred to the surface of the heating roll. Since it takes time, the waiting time is inevitably increased. Further, since the halogen lamp for heating the heating roll usually has a glass tube, the halogen lamp itself also has a certain heat capacity, and it takes time to first warm the halogen lamp itself. .

For the above reasons, the above-mentioned conventional fixing device has a problem that it takes a long time to warm up and a waiting time becomes long. When a halogen lamp is used as a heating source, when a halogen lamp is turned ON / OFF, a so-called “current” flows transiently.
There is also the problem that the "flicker" phenomenon occurs.

Therefore, in recent years, as a heating means used in the fixing device, a heating means using an induction heating method instead of a halogen lamp has been studied. This is to apply a magnetic field generated by a magnetic field generating means to a heating member having a conductive layer to heat the heating member by an electromagnetic induction action. Is a very effective heating means for providing a fixing device with a short waiting time.

Further, the above-mentioned heating means such as a halogen lamp can be used only in a state in which a 360-degree surrounding is covered, such as inside of a heating roll. The means may be provided not only inside the heating member but also outside the heating member as long as the magnetic field can act on the heating member, and can be arranged at any position according to the configuration of the fixing device. That is, in the case of the heating means adopting the induction heating method, the heating means is disposed at an arbitrary position, and a magnetic field is applied only to a portion to be heated.
This has the advantage that only desired portions can be heated selectively and instantaneously.

As a fixing device employing the above-described induction heating method, there are, for example, those disclosed in Japanese Patent Application Laid-Open Nos. 2000-181258 and 2000-29332.

The fixing device disclosed in Japanese Patent Application Laid-Open No. 2000-181258 has a heating means having conductivity, a pressing means for pressing against the heating means, and a coil formed of a conductive wire to generate a magnetic field. A magnetic field generating means acting on the heating means, and a magnetic field blocking means for blocking a magnetic field generated by the magnetic field generating means, wherein the magnetic field generating means is sandwiched between the heating means and the magnetic field blocking means. It is arranged.

The fixing device disclosed in Japanese Patent Application Laid-Open No. 2000-181258 is an example in which a magnetic field generating means is arranged outside or inside a heating roll as a heating means having conductivity. As described above, since the magnetic field generating means can be arranged at an arbitrary position with respect to the heating roll as the heating member, the degree of freedom in designing the apparatus is increased. Further, when comparing a fixing device using a halogen lamp or the like as a heating source, since only the heating roll to be heated is selectively heated, the warm-up is about 10 to 30% faster.

[0011]

However, the prior art described above has the following problems. That is, in the case of the fixing device according to JP-A-2000-181258 or JP-A-2000-29332, the induction heating method is employed, and therefore, compared to the case where a heating source such as a halogen lamp is used. Although the warm-up time is faster, the heating roll itself has a certain heat capacity because it has a metal core thicker than a certain thickness to maintain rigidity. Has a problem that it has a limit and cannot achieve a warm-up time of 0 seconds.

On the other hand, JP-A-7-295411, JP-A-8-69190, or JP-A-11-38
As described in JP-A-827, a fixing device using an endless film as a fixing member has also been proposed.

An image heating apparatus according to the above-mentioned Japanese Patent Application Laid-Open No. 7-295411 has an image heating film provided with a metal film, an excitation coil provided on one side of the image heating film, and an excitation coil In the image heating device that heats the unfixed toner image carried on the recording material by the heat of the image heating film, the image heating film is heated by the magnetic flux generated by the heat of the image heating film.
The metal film has a low thermal conductive resin layer on a surface on the exciting coil side and a release resin layer on the other surface.

Further, the fixing device according to the above-mentioned Japanese Patent Application Laid-Open No. 8-69190 discloses a paper transport heating section, and a sheet pressing unfixed toner fed to the paper transport heating section together with the paper transport heating section in a predetermined manner. And a pressure roller section for holding with pressure, wherein the sheet transport heating section holds the belt-shaped heat-resistant endless thin body which is driven and driven from the outside from the inside, and the heat-resistant endless thin body. A metal support that maintains a state in contact with the pressure roller portion and guides the rotational movement thereof, and an induction heating coil that is provided opposite to the metal support with the heat-resistant endless thin body interposed therebetween. The induction heating coil is provided outside the pressure roller unit.

Further, the fixing device according to the above-mentioned Japanese Patent Application Laid-Open No. 11-38827 discloses a first rotating member which is made of a conductive material and is driven to rotate, and a pressure is applied to the first rotating member. A second transfer member that is formed in a state where a developer image is formed between the transfer portions and passes through the member to be fixed, and a second transfer member that is provided on the first transfer member side; In a fixing device having induction heating means for concentrating induction heating of the contact portion of the first contact member and converting a developer image of a material to be fixed interposed in the contact portion into a fixed image, Storage means for storing calorific value data of the induction heating means corresponding to the type of the material to be fixed; detecting means for detecting the type of the material to be fixed conveyed to the transfer portion; The calorie data corresponding to the type of the detected material detected by the above is read out from the storage means. Depending on the amount of heat data read is obtained by configured to include a control means for controlling the induction heating means.

These fixing devices use a conductive film as a fixing member, and the heat capacity of the film itself is one unit with respect to a fixing roll of a fixing device of the same class.
By heating the film directly by induction heating, the film as the fixing member can be instantaneously raised to a desired temperature.

However, the fixing devices according to these proposals have the following problems, respectively.

First, in the case of the fixing device disclosed in JP-A-11-38827, if the fixing belt as the first rolling contact member is stopped, the fixing belt warms up instantaneously. Since the two rollers stretching the fixing belt inside take off heat of the belt, there is a problem that a waiting time occurs until the belt warms to a temperature necessary for fixing. I have. Further, the shape of the belt in the fixing nip is substantially linear because the belt is stretched over two rollers, so that the belt has a sharp change in curvature between the inside of the nip and the exit of the nip. For example, thin paper on which a large amount of toner has been transferred in a color image cannot be separated from the belt, which causes a problem of peeling failure.

Further, in the case of the fixing device disclosed in Japanese Patent Application Laid-Open No. 11-38827, since the fixing belt is stretched by two rolls, a complicated mechanism for controlling the deviation of the fixing belt is required. It also has the problem of becoming

In the case of the image heating apparatus disclosed in Japanese Patent Application Laid-Open No. 7-295411, although the image heating film can be instantaneously heated by the exciting coil, the guide member is an R-shaped rigid body. , The belt cannot follow the curvature of the R shape of the guide member, and furthermore, the bending direction of the belt cannot be reversed between the inside and outside of the nip,
In the case of thin paper or the like on which a large amount of toner has been transferred in a color image, the paper cannot be peeled from the image heating film, and there is a problem in that peeling failure occurs.

Further, in the case of the fixing device disclosed in Japanese Patent Application Laid-Open No. 8-69190, similarly to the above, there is no roll for stretching the belt-like heat-resistant endless thin body. Since the member that takes away heat inside is only a metal support, warm-up can be reduced. However, since the shape of the metal support is an R shape that conforms to the curvature of the belt-shaped heat-resistant endless thin body, peeling failure may occur on thin paper with a large amount of toner transferred on a color image. There is a problem that it occurs.

Accordingly, the present invention has been made to solve the above-mentioned problems of the prior art, and it is an object of the present invention to make it possible to make the warm-up time almost zero and to use color images. It is an object of the present invention to provide a fixing device capable of obtaining good peeling performance even with thin paper on which a large amount of toner is transferred.

[0023]

That is, according to a first aspect of the present invention, a thin heating belt having a conductive layer is induction-heated by a magnetic field generated by a magnetic field generating means, and is provided opposite to the heating belt. At the nip with the pressure member
In a fixing device for fixing an unfixed toner image on a recording medium, a pressing member having an elastic layer is provided inside the heating belt, and the pressing member is pressed against the pressing member via the heating belt, thereby fixing the image. Is formed so as to form a nip portion.

As a material for forming the conductive layer of the belt, for example, various materials such as copper, iron, aluminum, and nickel can be used. Among them, copper has a high conductivity, so that copper is thinned. By doing so, the resistance value per unit area can be set to a predetermined value, and the heat generation efficiency can be improved.

That is, if the strength and frequency of the magnetic field are constant, the heating value of the thin heating belt having the conductive layer is determined by the resistance value per unit area, and the conductivity of iron or nickel is relatively low. When using materials,
Unless the thickness of the conductive layer is set to a certain level (about 50 to 70 μm), a predetermined resistance value cannot be obtained. As described above, if the thickness of the conductive layer made of iron, nickel, or the like is increased to some extent, the rigidity of the heating belt itself is inevitably increased, and the heating belt loses flexibility. The heating belt has high rigidity,
When the flexibility is lost, a pressing member having an elastic layer is provided inside the heating belt, and the pressing member is pressed against the pressing member via the heating belt, thereby forming a nip portion for fixing. When forming, the heating belt is less likely to deform along the surface shape of the pressing member. As a result, in the nip formed between the heating belt and the pressing member, the pressure locally increases, or the pressure distribution becomes undesirably non-uniform. There is a possibility that a conveyance failure of the recording medium or a separation failure at the exit of the nip portion may occur.

To further explain, regarding the rigidity of the heating belt, for example, the physical property value (Young's modulus E) of polyimide used as the base material of the heating belt is determined by each manufacturer.
Although it depends on each type, it is about 2 to 6 Gpa. Incidentally, the Young's modulus E of nickel is 205 Gpa.
On the other hand, the physical property value (Young's modulus E) of copper is 123 Gp.
Since the thickness of the polyimide layer is, for example, 75 μm and the thickness of the conductive layer made of copper is about 5 μm, the rigidity (EI: I is effective by the cube of the thickness) is a. Is a contribution of at most 1 to 2%, and the rigidity of the heating belt is determined by a polyimide layer or the like as a base material.

As the pressure member, for example, a pressure roll is used. Even if the pressure roll does not have the elastic layer on the outer periphery of the metal core, the elastic layer may be used. It may have any.

Further, as the pressing member, for example,
A pad member fixedly disposed inside the heating belt is used, and the pad member includes an elastic layer made of silicon rubber or the like and a support member made of a metal or the like that supports the elastic layer. Used. Further, as the pressing member, a roll-shaped pressing member that is rotatably disposed inside the heating belt and that is pressed against the pressing member may be used. For example, when the pressure roll does not have the elastic layer on the outer periphery of the metal core, it is preferable to use the roll-shaped pressing member having the elastic layer on the surface of the metal core. When the pressure roll has an elastic layer on the outer periphery of the metal core, even if it has an elastic layer on the surface of the metal core, it does not have the elastic layer. May be any.

Further, when a pad member composed of, for example, an elastic layer made of silicon rubber or the like and a supporting member made of metal or the like for supporting the elastic layer is used as the pressing member, the elastic layer is used. The thickness of the support member is set to be constant, and the pressure distribution in the nip portion is set as a target.The thickness of the elastic layer on the exit side of the nip portion is set to be thin, and the elastic layer on the exit side of the nip portion is relatively set. By setting the thickness of the nip portion to be large, the pressure distribution in the nip portion can be set asymmetrically so that the pressure on the outlet side of the nip portion increases along the moving direction of the heating belt.

Further, the invention according to claim 2 is configured such that the pressure distribution in the nip portion is set to be symmetrical along the moving direction of the heating belt.

Further, in the invention according to claim 3, the pressure distribution in the nip portion is asymmetrical between the inlet and the outlet of the nip portion, and the pressure distribution at the outlet portion is higher than the inlet portion. Is set.

Further, according to the present invention, a thin heating belt having a conductive layer is induction-heated by a magnetic field generated by a magnetic field generating means, and a pressure member provided opposite to the heating belt is provided. In the fixing device for fixing the unfixed toner image on the recording medium at the nip portion, by pressing the heating belt against the pressing member by the pressing member,
The curvature of the heating belt is reversed between the inside of the nip portion and the outside of the nip portion.

Further, according to a fifth aspect of the present invention, a thin heating belt having a conductive layer is induction-heated by a magnetic field generated by a magnetic field generating means, and a heating member is provided with a pressing member provided opposite to the heating belt. In a fixing device for fixing an unfixed toner image on a recording medium at a nip portion, the heating belt is a flexible belt including at least three layers of a base material layer, a conductive layer, and a surface release layer. It is configured as follows.

Further, according to the invention, a thin heating belt having a conductive layer is induction-heated by a magnetic field generated by a magnetic field generating means, and a pressure member provided opposite to the heating belt is provided. In the fixing device for fixing the unfixed toner image on the recording medium at the nip portion, by pressing the heating belt against the pressing member by the pressing member,
In the nip portion, the curvature of the heating belt is reversed.

According to a seventh aspect of the present invention, a thin heating belt having a conductive layer is induction-heated by a magnetic field generated by a magnetic field generating means, and a heating member is provided with a pressing member provided opposite to the heating belt. In a fixing device for fixing an unfixed toner image on a recording medium at a nip portion, a belt guide member for guiding an end of the heating belt is provided at both ends of the heating belt.

Further, according to the present invention, a thin heating belt having a conductive layer is induction-heated by a magnetic field generated by a magnetic field generating means, and a heating member is provided with a pressing member provided opposite to the heating belt. In a fixing device for fixing an unfixed toner image on a recording medium at a nip portion, a lubricant is interposed between the heating belt and the pressing member.

According to a ninth aspect of the present invention, a thin heating belt having a conductive layer is induction-heated by a magnetic field generated by a magnetic field generating means, and a pressing member provided opposite to the heating belt is provided. In the fixing device for fixing an unfixed toner image on a recording medium at the nip portion, a sheet material having good slidability is interposed between the heating belt and the pressing member.

Further, according to a tenth aspect of the present invention, a thin heating belt having a conductive layer is induction-heated by a magnetic field generated by a magnetic field generating means, and a heating member provided with a pressing member provided opposite to the heating belt. In a fixing device for fixing an unfixed toner image on a recording medium at a nip portion, a metal roll contacting a surface of the pressing member is provided in a non-sheet passing portion of the pressing member. .

According to the eleventh aspect of the present invention, a thin heating belt having conductivity is induction-heated by a magnetic field generated by a magnetic field generating means, and a heating member is provided with a pressing member provided opposite to the heating belt. In the fixing device for fixing the unfixed toner image on the recording medium at the nip portion,
A metal roll is provided in contact with the surface of the pressing member, and the metal roll is configured to be retractable with respect to the surface of the pressing member.

Further, according to a twelfth aspect of the present invention, a thin heating belt having a conductive layer is induction-heated by a magnetic field generated by a magnetic field generating means, and a heating member is provided with a pressing member provided opposite to the heating belt. In a fixing device for fixing an unfixed toner image on a recording medium at a nip portion, a magnetic core made of a ferromagnetic material or the like is provided inside the heating belt via a predetermined gap with the heating belt. Things.

According to a thirteenth aspect of the present invention, a thin heating belt having a conductive layer is induction-heated by a magnetic field generated by a magnetic field generating means, and a heating member is provided with a pressing member provided opposite to the heating belt. In a fixing device for fixing an unfixed toner image on a recording medium at a nip portion, an internal pressure roll having an elastic layer is provided inside the heating belt, and the internal pressure roll is externally applied via the heating belt. By pressing against the pressure roll, a nip portion for fixing is formed by deforming the internal pressure roll side into a concave shape.

[0042]

According to the present invention, a pressing member having an elastic layer is provided inside the heating belt, and the pressing member is pressed against the pressing member via the heating belt, thereby fixing the image. , The heat capacity of the heating member of the fixing device becomes extremely small, the warm-up time is shortened, and sufficient heating and pressurization can be performed in the nip portion. And good fixability can be obtained.

A pressing member is provided inside the heating belt, and a fixing nip portion is formed by the pressing member and the pressing member with the heating belt interposed therebetween, so that the curvature of the heating belt inside the nip portion can be reduced. Can be inverted with parts.

That is, inside the nip portion, the recording medium is wound around the pressing member in the same manner as the direction of the heating belt. At the exit portion of the nip portion, the heating belt changes its curvature rapidly, so that recording is performed. The media cannot keep up with the change in the curvature of the heating belt and moves away from the heating belt. Therefore, peeling failure does not occur even on thin paper on which a large amount of toner is loaded in a color image.

Further, by providing an elastic layer on the pressing member, the toner can be fixed so as to enclose the toner, and the image quality is improved.

According to the sixth aspect of the present invention, for example, the portion of the pressing member that contacts the heating belt is a combination of an elastic layer and a non-elastic layer (supporting member), so that the inside of the nip portion is formed. It is possible to reverse the curvature of the heating belt, and by changing the curvature of the heating belt abruptly inside the nip portion, it becomes easier to separate the heating belt and the recording medium, and to the pressing member side during both-side fixing. It becomes possible to prevent the recording medium from being wound. In addition, since high pressure can be applied to the toner melted in the nip portion at the outlet of the nip portion, the toner enters between the fibers of the paper, and the fixing property can be improved.

Further, in the invention according to the seventh aspect, by providing edge guides at both ends of the heating belt, meandering and buckling of the heating belt can be prevented. Disappears, that is,
The heat capacity inside the heating belt can be reduced, and the warm-up can be shortened.

In the present invention, since the heating belt is not stretched in the fixing device, the driving source is provided on the pressure roll side, and the heating belt is driven by the driving source. If the slidability between the heating belt and the pressing member is poor, the pressing member acts as a brake, and the heating belt does not move at a predetermined speed, causing troubles such as image displacement and paper wrinkles. Therefore, in order to improve the slidability between the heating belt and the pressing member, a lubricant is interposed between the heating belt and the pressing member, or a sheet member having good slidability is interposed. By intervening, the heating belt does not delay with respect to the speed of the pressing member, and the above-described trouble can be prevented.

According to the tenth and eleventh aspects of the present invention, the temperature of the non-sheet passing portion rises, for example, when small-sized sheets are continuously passed. Therefore, by bringing a metal roll having good heat conductivity into contact with the pressing member and making it follow, the heat of the high-temperature portion in the non-sheet passing portion region is taken away, and the heat is transferred to a portion having a low temperature in the axial direction. I can do it. That is, it is possible to suppress the temperature rise in the non-sheet passing portion area during the continuous sheet passing of the small size, and to level the temperature distribution in the axial direction. Also,
By enabling retraction, when the pressurizing member such as the first in the morning is cold, or when the maximum size paper is used,
Since it can be kept away from the pressing member, as a result, the heat capacity on the pressing member side can be reduced, and the warm-up can be shortened.

Further, according to the twelfth aspect of the present invention, by providing a core made of a ferromagnetic material inside the heating belt, it is possible to efficiently collect magnetic flux and increase the power factor of the power supply. . Therefore, the frequency of the power supply can be reduced, which leads to downsizing and cost reduction of the power supply.

[0051]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment shown in the drawings.

Embodiment 1 First, the structure of a fixing device according to Embodiment 1 and members constituting the fixing device will be described.

The fixing device according to this embodiment aims at shortening the warm-up time and ensuring the performance of separating the recording medium, and as the fixing member, a flexible belt member having a small heat capacity is used. The belt-shaped member is used so as to minimize the number of members that take heat away from the belt-like member (there is no member disposed as much as possible). That is, a configuration in which only a pad member (pressing member) having an elastic layer forming a fixing nip portion is basically provided inside the belt-shaped member (heating belt) in opposition to the pressing member. Has adopted. Further, a method is used in which a conductive layer is provided on the belt-shaped member so that the belt-shaped member to be heated can be directly heated, and induction heating is performed by a magnetic field generated by a magnetic field generating unit.

FIG. 1 is a schematic configuration diagram showing a fixing device according to Embodiment 1 of the present invention.

In FIG. 1, reference numeral 1 denotes a heating belt as a heating and fixing member, and the heating belt 1 is constituted by an endless belt having a conductive layer. As shown in FIG. 2, the heating belt 1 has a base layer 2 made of a sheet member having high heat resistance, a conductive layer 3 laminated on the base layer 2, and an uppermost layer. Basically, at least three layers of the surface release layer 4 are provided. In this embodiment, the heating belt 1 has a diameter φ composed of a sheet-shaped base layer 2, a conductive layer 3, and a surface release layer 4.
A 30 mm endless belt is used.

The base layer 2 of the heating belt 1 is, for example,
10 to 100 μm in thickness, more preferably 50 to 10 in thickness
It is preferably a sheet having a high heat resistance of 0 μm (for example, 75 μm), for example, from a synthetic resin having a high heat resistance such as polyester, polyethylene terephthalate, polyether sulfone, polyether ketone, polysulfone, polyimide, polyimide amide, and polyamide. What is.

Further, in this embodiment, as shown in FIG. 3, the meandering of the heating belt 1 is regulated by abutting both ends of the heating belt 1 made of an endless belt against an edge guide 5. It is configured to be used. The edge guide 5 has a cylindrical portion 6 having an outer diameter slightly smaller than the inner diameter of the heating belt 1, a flange portion 7 provided at an end of the cylindrical portion 6, and a projection protruding outside the flange portion 7. A cylindrical or columnar holding portion 8 provided
It is composed of The edge guide 5 is fixed to both ends of the heating belt 1 so that the distance between the inner wall surfaces of the flange portions 7 is slightly longer than the length along the axial direction of the heating belt 1. Have been. Therefore, as the substrate layer 2, during the rotation of the heating belt 1,
In a portion other than the nip portion, it is necessary to maintain a circular shape with a diameter of 30 mm and to have a rigidity such that the heating belt 1 does not buckle or the like even when the end portion of the heating belt 1 abuts against the edge guide 5. Yes, for example, 50 μm thick
Is used.

The conductive layer 3 is a layer that generates heat by electromagnetic induction of a magnetic field generated by a magnetic field generating means to be described later. The conductive layer 3 is formed of a metal layer of iron, cobalt, nickel, copper, chromium, etc. in a thickness of about 1 to 50 μm. What was formed with the thickness of is used. However, in this embodiment, since the heating belt 1 needs to follow the shape of the nip portion inside a nip portion formed by a pad and a pressure roll described later,
It must be a flexible belt and the metal layer 3
It is preferable to make the layer as thin as possible.

In this embodiment, as the conductive layer 3, copper having a high conductivity is deposited on the above-mentioned polyimide base layer 2 in a very thin thickness of about 5 μm so as to increase the heat generation efficiency. Is used.

Further, the surface release layer 4 is provided on the recording medium 9.
Since the layer is directly in contact with the unfixed toner image 10 transferred thereon, it is necessary to use a material having good releasability. As a material constituting the surface release layer 4, for example, tetrafluoroethylene perfluoroalkyl vinyl ether polymer (PFA), polytetrafluoroethylene (P
TFE), a silicon copolymer, or a composite layer thereof. The surface release layer 4 is formed by appropriately selecting one of these materials and providing the uppermost layer of the belt with a thickness of 1 to 50 μm. If the thickness of the surface release layer 4 is too small, the durability is poor in terms of abrasion resistance, and the life of the heating belt 1 is shortened. Conversely, if the thickness is too large, the heat capacity of the belt is large. This is undesirable because the warm-up will be long.

In this embodiment, in consideration of the balance between abrasion resistance and the heat capacity of the belt, a 10 μm-thick tetrafluoroethylene perfluoroalkyl vinyl ether polymer ( PFA)
Is used.

The heating belt 1 constructed as described above
Is provided with a pad member 12 as a pressing member having an elastic layer 11 of, for example, silicon rubber. In this embodiment, as the pad member 12, a silicone rubber 11 having a rubber hardness of 35 ° according to JIS-A
What is laminated | stacked on the rigid support member 13 which consists of metals, such as S and iron, or synthetic resin with high heat resistance, is used. The elastic layer 11 made of silicon rubber is, for example,
Those having a uniform thickness are used. The support member 13 of the pad member 12 is disposed in a state fixed to a frame of a fixing device (not shown). The elastic layer 11 is pressed against a surface of a pressure roll described later with a predetermined pressing force. It may be pressed toward the surface of the pressure roll by a biasing means such as a spring (not shown).

Then, the fixing device is provided with a pad member 12.
The pressing member 14
Is provided. The pressing member 14 forms a nip 15 by holding the heating belt 1 sandwiched between the pressing member 14 and the pad member 12, and the unfixed toner image 10 is transferred to the nip 15. By passing through the recording medium 9, the unfixed toner image 10 is fixed on the recording medium 9 by heat and pressure to form a fixed image.

In the present embodiment, the pressing member 14 is formed on the surface of a solid iron roll 16 having a diameter of 26 mm, and the release layer 17 is formed as a 30 μm-thick tetrafluoroethylene perfluoroalkyl vinyl ether polymer (PFA). ) Is used.

As shown in FIG. 1, the pressure roll 14 is provided with a metal roll 18 made of a metal such as aluminum or stainless steel having good heat conductivity so as to be able to be separated from and brought into contact with the pressure roll. When the temperature of the heating belt 1 and the pressure roll 14 is low, such as at the beginning of the morning when power supply to the fixing device is started, the metal roll 18 is stopped at a position away from the pressure roll 14. And in the fixing device,
For example, when the fixing device is used, for example, when the fixing process is continuously performed on the small-sized paper, the heating belt 1 is used.
When a temperature difference occurs in the pressure roll 14 along the axial direction, the metal roll 18 is brought into contact with the pressure roll 14. The metal roll 18
When the pressure roll 1 contacts the pressure roll 14,
4 and followers. In this embodiment,
As the metal roll 18, a solid roll made of aluminum having a diameter of 10 mm is used.

In this embodiment, the pressure roll 14
Is rotated by a driving unit (not shown) while being pressed against the pad member 12 via the heating belt 1 by a pressing unit (not shown).

The heating belt 1, which is a heating member, circulates following the rotation of the pressure roll 14. Therefore, in this embodiment, in order to improve the slidability between the heating belt 1 and the pad member 12, a sheet material having high friction resistance and good slidability, for example, a Teflon (registered trademark) resin is used. Improving slidability by interposing an impregnated glass fiber sheet (Chuo Kasei Kogyo: FGF400-4, etc.) and applying a release agent such as silicone oil as a lubricant to the inner surface of the heating belt 1 It is configured to be. By doing so, the driving torque during idle rotation of the pressure roll 14 during actual heating is approximately 6
It can be reduced from kg.cm to about 3 kg.cm. Therefore, the heating belt 1 follows the pressure roll 14 without slipping, and can circulate at a speed equal to the rotation speed of the pressure roll 14.

As described above, the heating belt 1 is provided at both ends in the axial direction as shown in FIG.
The movement in the axial direction is restricted by the edge guide 5, thereby preventing the heating belt 1 from meandering.

In this embodiment, a thin heating belt having a conductive layer is induction-heated by a magnetic field generated by a magnetic field generating means.

The magnetic field generating means 20 is a horizontally long member whose longitudinal direction is perpendicular to the rotation direction of the heating belt 1.
It is installed outside the heating belt 1 while maintaining a gap of about 5 mm to 2 mm. This magnetic field generating means 20
In this embodiment, the exciting coil 21 and the exciting coil 21
Formed by a coil support member 22 for holding the magnetic field, a core material 23 made of a ferromagnetic material provided at the center of the exciting coil 21, and magnetic field shielding means 24 provided on the opposite side of the heating belt 1 with respect to the exciting coil 21. Have been.

As the exciting coil 21, for example, a coil in which a predetermined number of litz wires, each of which is made up of 16 copper wires having a diameter of 0.5 mm and insulated from each other, are bundled and arranged in parallel, is used.

As shown in FIG. 4, an alternating current of a predetermined frequency is applied to the exciting coil 21 by an exciting circuit 25, thereby generating a fluctuating magnetic field H around the exciting coil 21. When the fluctuating magnetic field H crosses the conductive layer 3 of the heating belt 1, an eddy current B is generated in the conductive layer 3 of the heating belt 1 by an electromagnetic induction action so as to generate a magnetic field that hinders the change of the magnetic field H. Exciting coil 21
Is, for example, 10 to 50 k
Hz, in this embodiment, the frequency of the alternating current is set to 30 kHz. Then, the eddy current B flows through the conductive layer 3 of the heating belt 1 so that
Joule heat is generated by electric power (W = IR ² ) proportional to the resistance of the conductive layer 3 to heat the heating belt 1 as a heating member.

It is desirable to use a heat-resistant non-magnetic material for the coil support member 22, for example, heat-resistant glass or heat-resistant resin such as polycarbonate.

The magnetic field shielding means 24 includes:
Magnetic materials such as iron, cobalt, nickel, and ferrite are used. The magnetic field shielding means 24 collects magnetic flux generated by the exciting coil 21 to form a magnetic path, and enables efficient heating, and at the same time, the magnetic flux leaks out of the fixing device and peripheral members become improper. This is for preventing the heating to be performed in a proper manner.

At the center of the exciting coil 21,
A core 23 made of ferromagnetic ferrite or the like is provided. With this configuration, the excitation coil 21
Can efficiently collect the magnetic flux generated in the above, and the heating efficiency can be increased. Therefore, the excitation coil 21
To reduce the frequency of the high-frequency power supply that applies alternating current to the
It is possible to reduce the number of turns of the exciting coil 21, and it is possible to reduce the size of the power supply, the size of the exciting coil 21, and the cost.

With the above configuration, in the fixing device according to this embodiment, the warm-up time can be made almost zero, good fixability can be obtained, and defective peeling can be achieved as follows. This can be reliably prevented from occurring.

That is, in the fixing device according to this embodiment, as shown in FIG.
/ S at a process speed of / s. Further, the heating belt 1 is in pressure contact with the pressure roll 14, and circulates at a speed of 100 mm / s, which is equal to the moving speed of the pressure roll 14.

In the fixing device, as shown in FIG. 1, the recording medium 9 onto which the unfixed toner 10 has been transferred is transferred to the heating belt 1 and the pressure roll 1 by a transfer device (not shown).
4 while the recording medium 9 passes through the nip portion 15 formed between the heating belt 1 and the heating belt 1.
The toner image 10 is fixed on the recording medium 9 by being heated and pressed by the pressure roller 14 and the pressure roller 14.

At this time, in the fixing device, the heating belt 1
Is controlled at about 180 ° C. to 200 ° C. at the entrance of the nip 15 during the fixing operation by the frequency of the high-frequency current flowing through the exciting coil 21 and the like.

In the fixing device according to this embodiment, at the same time as the image forming signal is input, the pressing roll 14 starts rotating and a high-frequency current is applied to the exciting coil 21. When power of, for example, 700 W is applied to the excitation coil 21 as active power, the temperature of the heating belt 1 reaches a fixing temperature from room temperature in about 2 seconds due to induction heating. That is, the warm-up is completed within the time required for the recording paper 9 to move from the paper feed tray to the fixing device. Therefore, in the fixing device, the fixing process can be performed without making the user wait.

Now, in the nip portion 15 of the fixing device,
When the recording medium 9 on which a large amount of toner such as a color solid image has been transferred enters thin paper of about 0 gms, the attractive force between the toner and the release layer 4 on the surface of the heating belt 1 increases. Usually, it is difficult to peel off the recording medium 9 from the surface of the heating belt 1. However, in the configuration of this embodiment, the shape of the heating belt 1 is convex outside the nip portion 15, whereas it is concave inside the nip portion 15. That is, the nip 15
Inside, the direction of the recording medium 9 is the direction of winding around the pressure roll 14, and at the exit of the nip portion 15, the direction of the heating belt 1 changes rapidly from a concave shape to a convex shape. Due to the strain (rigidity) of the recording medium 9 itself, the medium 9 cannot keep up with a sudden change in the shape of the heating belt 1 and is naturally separated from the heating belt 1. Therefore, in the fixing device according to this embodiment, it is possible to reliably prevent the problem of the peeling failure of the recording medium 9 from occurring.

When the small-sized recording medium 9 is continuously fixed, the temperatures of the heating belt 1, the pad member 12, the pressure roll 14, and the like in the non-sheet passing area increase. By bringing the metal roll 18 provided on the roll 14 side into contact with the surface of the pressure roll 14, the heat of the high-temperature portion of the pressure roll 14 can be absorbed by the metal roll 18, and the heat can be absorbed by the low-temperature portion. , The temperature distribution in the axial direction moves in a direction of decreasing, and the temperature of the pressure roll 14 and the temperature of the heating belt 1 can be prevented from becoming higher than a certain temperature.

Further, the fixing device according to the first embodiment
Since the elastic layer 11 is provided on the heating member 1 side of the nip portion 15 with the heating belt 1 having a thickness of 65 μm therebetween, an effect of wrapping and fixing the toner at the time of fixing can be obtained, and good color image quality can be obtained. Further, in order to obtain better color image quality, several tens of μm is provided between the conductive layer of the heating belt and the release layer.
Although an elastic layer of silicon rubber or the like may be provided, it is inevitable that the warm-up time becomes long.

Second Embodiment FIG. 5 shows a second embodiment of the present invention. The same parts as those in the first embodiment are denoted by the same reference numerals and described. , The pressure distribution in the nip is asymmetric at the inlet and the outlet of the nip, and the pressure at the outlet is set to be asymmetric such that the pressure at the outlet is higher than the inlet.

In the second embodiment, the heating belt is pressed against the pressing member by the pressing member, so that the bending direction of the heating belt is reversed inside the nip portion.

Further, in the third embodiment, a magnetic core made of a ferromagnetic material or the like is provided inside the heating belt via a predetermined gap with the heating belt.

That is, in the second embodiment, the basic parts are the same as those in the first embodiment, and only different parts will be described.

The magnetic field generating means 20 is composed of an exciting coil 21 composed of 16 litz wires bundled with each other and having a diameter of 0.5 mm and insulated from each other, a ferrite or the like having an E-shaped cross section covering the exciting coil 21. It is made of a magnetic core 30 made of a ferromagnetic material, and is provided with a gap of about 0.5 to 2.0 mm from the heating belt 1.

The second magnetic core 31 is provided inside the heating belt 1 with a gap of about 1 mm to 4 mm from the heating belt 1. With this configuration, leakage of magnetic flux is reduced, and efficient heating becomes possible. Therefore, the power supply frequency can be reduced, and the power supply can be reduced in size and cost.

Further, the pad member 12 provided inside the heating belt 1 includes a portion of the elastic layer 11 and a rigid support member 13. For example, as the elastic layer 11, silicone rubber having a rubber hardness of 35 ° is used, and the elastic layer 1
Adjacent to 1, a pad portion 32 having rigidity is used on the downstream side in the running direction of the recording medium 9. Pad part 3 with rigidity
As 2, for example, a metal having good heat conductivity such as aluminum may be used, or a heat-resistant resin or the like which does not easily remove heat may be used. The former has the effect of improving the temperature distribution in the axial direction, and the latter does not hinder the reduction of warm-up because it is difficult to remove heat from the heating belt 1.

The pressure member 14 is provided with an elastic layer 33 having a thickness of about 0.1 to 2 mm. At this time, the shape of the fixing nip portion 15 is convex upward on the pad portion made of the elastic layer 11 on the entrance side, and convex downward on the rigid pad portion 32 on the exit side. The pad member 12 is thus
With the stepped configuration, the bending direction of the heating belt 1 can be changed in the nip portion 15, and
As shown in FIG. 6, the pressure distribution inside
The outlet side is asymmetrical with a higher height, and at the moment this high pressure comes out of the nip portion 15, it is released at once,
Separation of the recording medium 9 from the heating belt 1 is further facilitated.

Further, even during the double-side fixing, a high pressure can be applied on the outlet side in the nip portion 15 to distort the elastic layer 33 on the pressure roll 14 side.
The winding of the paper 9 around the fourth side can be prevented.

Further, since a high pressure is applied on the outlet side of the nip portion 15, the toner melted in the nip portion 15 enters between the fibers of the paper 9 and the fixing property is improved.

The other configuration and operation are the same as those of the first embodiment, and the description is omitted.

Third Embodiment FIG. 7 shows a third embodiment of the present invention. The same portions as those in the first embodiment are denoted by the same reference numerals and described. A thin heating belt having a conductive layer is induction-heated by a magnetic field generated by a magnetic field generating means, and a nip portion between the heating belt and a pressing member provided opposite to the heating belt is used to form an unfixed toner image on a recording medium. In the fixing device for fixing, an internal pressure roll having an elastic layer is provided inside the heating belt, and the internal pressure roll is pressed against an external pressure roll via the heating belt to thereby form the internal pressure roll. It is configured to form a nip portion for fixing whose side is deformed into a concave shape.

That is, the third embodiment proposes a fixing device for realizing self-stripping without using a peeling means in a belt-type fixing device utilizing an electromagnetic induction effect.

A heating belt 1 serving as a heating member includes, in order from the inside of the belt, a base layer 2 (thickness of 10 μm) made of polyimide or the like and a conductive layer 3 (thickness of several μm) made of copper or the like.
m), and a release layer 4 (thickness of several μm) made of a fluororesin or the like is formed on the outermost side. An elastic layer (thickness: 10 μm) made of silicon rubber, fluorine rubber, or the like may be provided between the conductive layer 3 and the release layer 4.

Further, as described above, this fixing device is characterized in that the conductive layer 3 is formed of a thin layer having a thickness of several μm. By making the thickness of the conductive layer 3 very thin, the heating belt 1 can be freely deformed. As shown in FIG. 7, the heating belt 1 serves as a pressing member disposed inside the heating belt 1. The nip portion 15 can be formed by deforming the internal pressure roll 40 into a concave shape. According to the configuration of the nip portion 15, the nip portion 1
By recovering the distortion of the internal pressure roll 40 in No. 5 at the exit B of the nip portion 15, a self-stripping method, which is a method of peeling the paper, can be adopted. Can be prevented from being damaged. However, if such a nip portion 15 is to be formed by a heating belt having a metal conductive layer having a thickness of several tens of μm, an entrance portion A of the nip portion 15 is required.
Since the metal conductive layer is broken at the exit portion B of the nip portion 15, a crack is generated, and the metal layer becomes unusable. As a result, in a heating belt having a metal conductive layer having a thickness of several tens of micrometers, the self-stripping method cannot be adopted, and a peeling claw must be provided.

In order to form the nip 15 as described above, an elastic material such as fluoro rubber is used as the surface material of the internal pressure roll 40, and an internal material such as fluororesin is used as the surface material of the external pressure roll 14. A material harder than the pressure roll 40 may be used.

The heating belt 1 is kept from contacting the surrounding members as much as possible except at the nip portion 15 so that heat is not taken from the heating belt by the surrounding members. In the present invention, since the heating belt 1 having a very thin thickness is used as the heat generating member, it is necessary to prevent the internal heating roll 40 having a large heat capacity from contacting the heating belt 1. Therefore, as shown in FIG. 7, a belt support member 41 is disposed between the heating belt 1 and the internal heating roll 40. Here, the heating belt 1 is not stretched by the belt support member 41, and is in a state where both are not in contact with each other as much as possible. As a material of the belt supporting member 41, a liquid crystal polymer or a phenol resin having a small heat capacity and heat resistance and having no problem in strength is used.

The coil assembly 20 is supported by a holder (not shown), and is fixed to the frame of the fixing device with a predetermined gap between the coil assembly 20 and the heating belt 1.

Further, the external pressure member 14 can be kept at a uniform temperature in the axial direction by contacting a metal roll 18 made of aluminum or the like having good thermal conductivity.

The other configuration and operation are the same as those of the first embodiment, and the description is omitted.

[0104]

As described above, according to the present invention, a thin endless belt having a conductive layer is used as a heating member without tension, a tension roll is not provided inside the belt, and a nip is provided. Since a small heat capacity pad is used to form the belt, the heat capacity inside the belt can be minimized as much as possible, and the belt itself, which is the object to be heated, can be directly heated by induction heating, so that the warm-up time is minimized. It can approach 0 seconds.

Further, since the fixing nip is formed by a pad having an elastic layer and a flexible belt is used, the belt follows the shape of the pad in the nip, that is, the inside of the nip and the portion other than the nip. Since the curvature can be changed between portions and the inside of the nip, the thin recording material on which a large amount of toner is loaded can be easily separated. Further, the image can be improved because the effect of the elastic layer can fix the toner so as to enclose the toner.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a fixing device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional configuration diagram illustrating a heating belt used in the fixing device according to the first embodiment of the present invention.

FIG. 3 is a configuration diagram showing a support structure of a heating belt.

FIG. 4 is an explanatory diagram illustrating a heating principle of the heating belt.

FIG. 5 is a configuration diagram illustrating a fixing device according to a second embodiment of the present invention.

FIG. 6 is a graph showing a pressure distribution in a nip portion of a fixing device according to a second embodiment of the present invention.

FIG. 7 is a configuration diagram illustrating a fixing device according to a third embodiment of the present invention.

[Explanation of symbols]

1: heating belt, 2: base material layer, 3: conductive layer, 4: surface release layer, 5: edge guide, 12: pad member, 14: pressure roll, 20: magnetic field generating means.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuyoshi Ito 430 Green Tech Nakaicho, Nakai-cho, Ashigara-gun, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. Inside Fuji Xerox Co., Ltd. (72) Inventor Yasuhiro Uehara 430 Green Tech Nakanaka, Nakai-machi, Ashigara-kami, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. F-term in Xerox Corporation (reference) 2H033 AA02 AA16 AA30 BA11 BA12 BB28 BB33 BB34 BE03 BE06 3K059 AA08 AB00 AB19 AB20 AB22 AC10 AC51 AC73 AD03 AD07 AD28 CD52 CD54 CD66 CD75 CD77

Claims (13)

[Claims] 1. A thin heating belt having a conductive layer is induction-heated by a magnetic field generated by a magnetic field generating means, and a nip portion between the heating belt and a pressing member provided opposite to the heating belt determines an undetermined state on a recording medium. In a fixing device for fixing a toner image, a pressing member having an elastic layer is provided inside the heating belt, and the pressing member is pressed against the pressing member via the heating belt, thereby forming a nip portion for fixing. A fixing device comprising: a fixing device; 2. The fixing device according to claim 1, wherein a pressure distribution in the nip is set to be symmetrical along a moving direction of the heating belt. 3. The pressure distribution in the nip portion is asymmetric at the inlet and the outlet of the nip portion, and the pressure at the outlet portion is higher than that at the inlet portion.
The fixing device as described in the above. 4. A thin heating belt having a conductive layer is induction-heated by a magnetic field generated by a magnetic field generating means, and a nip portion between the heating belt and a pressing member provided opposite to the heating belt determines an undetermined state on a recording medium. In the fixing device for fixing the toner image, the heating belt is pressed against the pressing member by the pressing member, so that the bending direction of the heating belt is reversed between the inside of the nip portion and the outside of the nip portion. The fixing device according to claim 1, wherein: 5. A thin heating belt having a conductive layer is induction-heated by a magnetic field generated by a magnetic field generating means, and a nip portion between the heating belt and a pressing member provided opposite to the heating belt determines an undetermined state on a recording medium. The fixing device for fixing a toner image, wherein the heating belt is a flexible belt including at least three layers of a base material layer, a conductive layer, and a surface release layer. 5. The fixing device according to item 4. 6. A thin heating belt having a conductive layer is induction-heated by a magnetic field generated by a magnetic field generating means, and a nip portion between the heating belt and a pressing member provided opposite to the heating belt determines an undetermined state on a recording medium. 2. A fixing device for fixing a toner image, wherein a heating belt is pressed against a pressing member by the pressing member, whereby a bending direction of the heating belt is reversed inside the nip portion. The fixing device as described in the above. 7. A thin heating belt having a conductive layer is induction-heated by a magnetic field generated by a magnetic field generating means, and a nip portion between the heating belt and a pressing member provided opposite to the heating belt determines an undetermined state on a recording medium. 2. The fixing device according to claim 1, wherein a belt guide member that guides an end of the heating belt is provided at both ends of the heating belt. 8. A thin heating belt having a conductive layer is induction-heated by a magnetic field generated by a magnetic field generating means, and a nip portion between the heating belt and a pressing member provided opposite to the heating belt determines an undetermined state on a recording medium. 2. The fixing device according to claim 1, wherein a lubricant is interposed between the heating belt and the pressing member in the fixing device for fixing the toner image. 9. A thin heating belt having a conductive layer is induction-heated by a magnetic field generated by a magnetic field generating means, and a nip portion between the heating belt and a pressing member provided opposite to the heating belt determines an undetermined state on a recording medium. 2. The fixing device according to claim 1, wherein a sheet material having good slidability is interposed between the heating belt and the pressing member. 10. A thin heating belt having a conductive layer,
In a fixing device that performs induction heating by a magnetic field generated by a magnetic field generating means and fixes an unfixed toner image on a recording medium at a nip portion between the heating belt and a pressing member provided opposite to the heating belt, 2. The fixing device according to claim 1, further comprising a metal roll that contacts a surface of the pressing member. 11. A thin heating belt having a conductive layer,
In a fixing device for performing induction heating by a magnetic field generated by a magnetic field generating means and fixing an unfixed toner image on a recording medium at a nip portion between the heating belt and a pressing member provided opposite to the heating belt, 2. The fixing device according to claim 1, wherein a metal roll that contacts the surface of the pressure member is provided in the non-paper passing portion, and the metal roll is configured to be able to contact and separate from the surface of the pressure member. 12. A thin heating belt having a conductive layer,
In a fixing device for performing induction heating by a magnetic field generated by a magnetic field generating means and fixing an unfixed toner image on a recording medium at a nip portion between the heating belt and a pressing member provided opposite to the heating belt, 2. The fixing device according to claim 1, further comprising a magnetic core made of a ferromagnetic material or the like provided between the heating belt and a predetermined gap. 13. A thin heating belt having a conductive layer,
In a fixing device for performing induction heating by a magnetic field generated by a magnetic field generating means and fixing an unfixed toner image on a recording medium at a nip portion between the heating belt and a pressing member provided opposite to the heating belt, An internal pressure roll having an elastic layer is provided, and the internal pressure roll is pressed against an external pressure roll via a heating belt, thereby fixing the internal pressure roll side to a concave shape. A nip portion formed by the fixing device.