JP2010002508A - Fixing belt used for fixing apparatus, the fixing apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing belt which is used for a fixing apparatus, having a self temperature control function, whose durability is improved, and which has a magnetic shunt alloy layer. <P>SOLUTION: The fixing belt 51 is used for the induction heating type fixing apparatus and is equipped with the magnetic shunt alloy layer 513, which shows ferromagnetism to generate heat, when temperature is under the Curie point, and loses magnetism to lower the calorific value, when the temperature is equal to or above the Curie point, and an elastic layer 512. The thickness of each of the layers is adjusted so that a neutral surface which is not tensioned and compressed exists within the elastic layer 512, when the belt moves in circulation. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a belt having a metal layer heated by an induction heating method, a fixing device using the belt, and an image forming apparatus including the fixing device, and more particularly to a technique for improving durability of the belt.

In recent years, among the fixing devices provided in electrophotographic and electrostatic recording image forming apparatuses, those using a heat source with a relatively high heat conversion efficiency and a compact induction heat generation method have emerged, and energy saving, space efficiency, and warm-up time have appeared. It is attracting attention from the viewpoint of shortening of
In particular, the heat capacity of the heat generating part can be designed to be considerably small by adopting a configuration in which the magnetic flux generated by flowing an alternating current through the exciting coil is guided to the conductive heat generating layer using a core material such as a ferrite core. Therefore, the warm-up time can be greatly shortened.

  However, since the heat does not easily move when the heat capacity of the heat generating portion becomes small, a portion where the recording sheet does not pass (hereinafter referred to as “non-sheet passing portion”) outside the fixing member in the width direction when a small-sized recording sheet having a small width is continuously used. )) Abnormally rises, causing thermal destruction and deterioration of peripheral members, and subsequently passing a wide recording sheet, high temperature offset occurs only on the outer side in the width direction, and uneven glossiness. There is a problem that occurs.

Therefore, in the fixing device, as a method of suppressing the temperature rise of the non-sheet passing portion, a technique for shielding only the magnetic flux to the non-sheet passing portion by moving the conductive member according to the sheet width, or a non-sheet passing by a demagnetizing coil. A technique for canceling only the magnetic flux to the part is known.
In the above fixing device, a magnetic shunt alloy having a Curie point slightly higher than the fixing temperature is used for the heat generating portion, so that when the temperature of the non-sheet passing portion rises to some extent, the non-sheet passing portion automatically There is a technique for suppressing an excessive temperature rise in the non-sheet passing portion by providing a self-temperature control function in which only the heat generating portion at the position loses magnetic rectification and the amount of heat generation is reduced.

On the other hand, the method using a fixing belt as a fixing member can be designed to have a considerably small heat capacity of the fixing belt, so that the warm-up time can be greatly shortened.
In order to heat such a fixing belt by an induction heating method while providing a self-temperature control function, a magnetic shunt alloy is used for another member that comes into contact with the fixing belt, such as a roller or a regulation plate, to generate heat. Thus, a method of indirectly heating the heat of another member by heat conduction, a method of directly heating by providing a magnetic shunt alloy layer in the fixing belt, and the like can be considered.

In particular, when a magnetic shunt alloy layer is provided in the fixing belt, the layer structure becomes more complex than in the past, so fatigue due to internal stress due to deformation such as bending tends to accumulate, and eventually local fracture occurs. Therefore, there is a problem that the life is shortened.
For example, as a conventional technique related to the life of a fixing belt, in Patent Document 1, in a belt having a metal layer, the strain when bending deformation occurs by sandwiching the metal layer between a base layer made of a synthetic resin and a clothing layer. An invention formed near a neutral axis that does not cause a crack is disclosed, and it is described that it is possible to reduce the distortion of the metal layer when bending deformation occurs, and to prevent the metal layer from being cracked or permanently deformed. .
JP 2004-70191 A

However, when fatigue due to internal stress associated with deformation such as bending accumulates in the fixing belt having a multilayer structure and causes local destruction, the metal layer is not necessarily destroyed first.
For example, a layer with a low modulus of elasticity is susceptible to ductile fracture, while a layer with a high modulus of elasticity is susceptible to brittle fracture with low toughness. In the elastic layer such as foamed silicone rubber to improve the property, if there are defective parts such as inhomogeneous strain or bubbles in the elastic layer, cracks will grow starting from the defective part during use In the case, cracks reach the belt surface, and the belt surface appears to wave, leading to a lifetime. In addition, silicon rubber has a drawback that it has a relatively low tear strength, which is a drag on the life of the fixing belt.

  The present invention relates to a fixing belt having a magnetic shunt alloy layer with improved durability, a fixing device including the fixing belt, and an image forming apparatus including the fixing device, which are used in a fixing device having a self-temperature control function. The purpose is to provide.

  In order to achieve the above object, a fixing belt according to the present invention is a circularly driven fixing belt used in an induction heating type fixing device, and exhibits heat and exhibits ferromagnetism at a temperature below the Curie point. In addition, the elastic layer has a magnetic shunt alloy layer that loses its magnetism and its calorific value is reduced when the temperature is higher than the Curie point. As described above, the thickness of each layer is adjusted.

In order to achieve the above object, a fixing device according to the present invention is a fixing device including the fixing belt.
In order to achieve the above object, an image forming apparatus according to the present invention is an image forming apparatus including the fixing device.
Here, the neutral plane refers to a plane where stress is minimized without being pulled or compressed when the belt rotates and bends.

According to the configuration described in the means for solving the problem, since the neutral surface of the fixing belt exists in the elastic layer, even when the fixing belt runs on the roller peripheral surface, the stretching force acting on the elastic layer, As a result, the shrinkage force becomes small, and as a result, cracks hardly grow in the elastic layer.
Therefore, it is possible to improve the durability of a fixing belt having a magnetic shunt alloy layer used in a fixing device having a self-temperature control function.

Here, in the fixing belt, the fixing device, and the image forming apparatus, the fixing belt further includes a surface layer that is located on the outer peripheral side of the elastic layer and is in contact with the recording sheet, and the elastic modulus of the surface layer is increased. E ₁ , the layer thickness of the surface layer is T ₁ , the elastic modulus of the elastic layer is E ₂ , the layer thickness of the elastic layer is T ₂ , the elastic modulus of the magnetic shunt alloy layer is E ₃ , and the magnetic shunt alloy layer When the layer thickness is T ₃ ,

It can also be characterized by satisfying.
Accordingly, in the fixing belt having a three-layer structure in which the surface layer, the elastic layer, and the magnetic shunt alloy layer are laminated in this order from the outer peripheral side, the neutral surface can be present in the elastic layer, so that the elastic layer has cracks. It becomes difficult to grow.
Here, in the fixing belt, the fixing device, and the image forming apparatus, the fixing belt is further positioned on the outer peripheral side than the elastic layer, and includes a surface layer in contact with the recording sheet and an inner layer than the magnetic shunt alloy layer. And a metal layer made of a metal that is not a magnetic shunt alloy, the elastic modulus of the surface layer is E ₁ , the layer thickness of the surface layer is T ₁ , the elastic modulus of the elastic layer is E ₂ , The layer thickness of the elastic layer is T ₂ , the elastic modulus of the magnetic shunt alloy layer is E ₃ , the layer thickness of the magnetic shunt alloy layer is T ₃ , the elastic modulus of the metal layer is E ₄ , and the layer thickness of the metal layer is When T ₄

It can also be characterized by satisfying.
Accordingly, in the fixing belt having a four-layer structure in which the surface layer, the elastic layer, the magnetic shunt alloy layer, and the metal layer are laminated in this order from the outer peripheral side, the neutral surface can be present in the elastic layer. Cracks are difficult to grow.
Here, in the fixing belt, the fixing device, and the image forming apparatus, the fixing belt is further positioned on the outer peripheral side with respect to the elastic layer, the surface layer in contact with the recording sheet, and the inner peripheral side with respect to the surface layer. A first adhesive layer that adheres the surface layer and the elastic layer, and a second adhesive layer that is located on the inner peripheral side of the elastic layer and adheres the elastic layer and the magnetic shunt alloy layer. The elastic modulus of the surface layer is E ₁ , the layer thickness of the surface layer is T ₁ , the elastic modulus of the first adhesive layer is E ₂ , the layer thickness of the first adhesive layer is T ₂ , and the elastic layer E ₃ , the elastic layer thickness T ₃ , the second adhesive layer elastic modulus E ₄ , the second adhesive layer thickness T ₄ , and the magnetic shunt alloy layer elastic modulus E _5, the layer thickness of the magnetic shunt alloy layer when the T _5,

It can also be characterized by satisfying.
As a result, in the fixing belt having a five-layer structure in which the surface layer, the first adhesive layer, the elastic layer, the second adhesive layer, and the magnetic shunt alloy layer are laminated in this order from the outer peripheral side, the neutral surface is present in the elastic layer. This makes it difficult for cracks to grow in the elastic layer.
Here, in the fixing belt, the fixing device, and the image forming apparatus, the fixing belt is further positioned on the outer peripheral side with respect to the elastic layer, the surface layer in contact with the recording sheet, and the inner peripheral side with respect to the surface layer. A first adhesive layer that adheres the surface layer and the elastic layer, and a second adhesive layer that is located on the inner peripheral side of the elastic layer and adheres the elastic layer and the magnetic shunt alloy layer. A metal layer made of a metal that is not a magnetic shunt alloy and located on the inner peripheral side of the magnetic shunt alloy layer, wherein the elastic modulus of the surface layer is E ₁ , the layer thickness of the surface layer is T ₁ , The elastic modulus of one adhesive layer is E ₂ , the layer thickness of the first adhesive layer is T ₂ , the elastic modulus of the elastic layer is E ₃ , the layer thickness of the elastic layer is T ₃ , and the elastic modulus of the second adhesive layer E ₄ , the thickness of the second adhesive layer is T ₄ , the elastic modulus of the magnetic shunt alloy layer is E ₅ ,
When the layer thickness of the magnetic shunt alloy layer is T ₅ , the elastic modulus of the metal layer is E ₆ , and the layer thickness of the metal layer is T ₆ ,

It can also be characterized by satisfying.
Thus, in the fixing belt having a six-layer structure in which the surface layer, the first adhesive layer, the elastic layer, the second adhesive layer, the magnetic shunt alloy layer, and the metal layer are laminated in this order from the outer peripheral side, the neutral surface is placed in the elastic layer. Therefore, it is difficult for cracks to grow in the elastic layer.

[Embodiment 1]
<Overview>
Embodiment 1 of the present invention is an image forming apparatus including a fixing device that melts and fixes an unfixed image on a recording sheet using a heat source of an induction heat generation method, wherein the fixing belt has a multilayer structure, and is provided in an elastic layer. The life of the fixing belt is extended by adjusting the thickness of each layer of the fixing belt so that the neutral surface comes.

<Configuration>
FIG. 1 is a diagram illustrating an overall configuration of the image forming apparatus according to the first embodiment.
As shown in FIG. 1, an image forming apparatus 1 according to the present embodiment is a tandem color digital printer, and includes an image processing unit 3, a feeding unit 4, a fixing device 5, and a control unit 6, and a network (for example, in-house) When a print execution instruction is received from an in-house terminal device, a color image is formed on a recording sheet and output in accordance with the instruction.

  The image processing section 3 is a part mainly responsible for image formation, and forms image toner images of yellow, magenta, cyan and black along with the intermediate transfer belt 11 circulating in the direction indicated by the arrow A. Units 3Y, 3M, 3C, and 3K are sequentially arranged, and an optical unit 10 including a light emitting element such as a laser diode is disposed below each image forming unit. In the image processing section 3, an image forming unit mainly composed of components having “Y” after the reference number generates an image of yellow toner, and similarly, “M” is added after the reference number. An image forming unit mainly composed of the constituent elements that are generated generates an image using magenta toner, an image forming unit mainly composed of the constituent elements that are suffixed with “C” generates an image formed using cyan toner, An image forming unit mainly composed of components having “K” after the reference number generates an image using black toner.

The image forming unit 3Y includes a photosensitive drum 31Y, and a charger 32Y, a developing device 33Y, a primary transfer roller 34Y, and a cleaner 35Y disposed around the photosensitive drum 31Y.
In generating an image using yellow toner, the charger 32Y uniformly charges the photosensitive drum 31Y, and the control unit 6 controls the laser beam L to the photosensitive drum 31Y uniformly charged by the optical unit 10. The electrostatic latent image is emitted to form an electrostatic latent image, and the developing device 33Y develops the formed electrostatic latent image with yellow toner, and the developed toner image is primarily transferred to the intermediate transfer belt 11 and primary transferred. Thereafter, the toner remaining on the photosensitive drum 31Y is removed by the cleaner 35Y.

The image forming units 3M, 3C, and 3K also have the same configuration as that of the image forming unit 3Y (the reference numerals are omitted in the drawing), and similarly generate images with toner of each color.
Each time the toner image primarily transferred to the intermediate transfer belt 11 passes through each of the image forming units, the respective colors are superimposed, and finally a full-color toner image is generated.
On the other hand, the feeding unit 4 is a part mainly responsible for transporting the recording sheet, and a paper feeding cassette 41 for storing the recording sheet S and a feeding roller 42 for feeding the stored recording sheet S one by one to the transporting path 43. And a timing roller pair 44 for timing to send out the fed recording sheet S and a secondary transfer roller 45, and the recording sheet S is conveyed to the secondary transfer position 46 and is generated on the intermediate transfer belt 11. The toner image is secondarily transferred to the recording sheet S at the secondary transfer position 46.

The fixing device 5 is a belt-type fixing device, and heats and pressurizes the recording sheet S on which the toner image is secondarily transferred, thereby fixing the toner image on the recording sheet S. The fixing device 5 will be described in detail below.
The recording sheet S after fixing is discharged to a discharge tray 72 by driving a discharge roller 71 and the like.
The control unit 6 is a controller that collectively controls the overall operation, temperature control, and the like of the image forming apparatus 1, and for each light-emitting element of the optical unit 10 for each image forming unit based on image data to be formed. A drive signal is generated, and the timing is adjusted so that the toner images of the respective colors are accurately superimposed in the primary transfer, or the toner images are accurately transferred to the recording sheet S in the secondary transfer.

FIG. 2 is a diagram schematically illustrating the configuration of the fixing device 5.
As shown in FIG. 2, the fixing device 5 includes a fixing belt 51, a fixing roller 52, a pressure roller 53, a fixed plate 54, and an exciting coil 55.
The fixing belt 51 is an endless belt that generates heat by guiding a magnetic flux generated by the exciting coil 55 to a built-in magnetic shunt alloy layer and serves as a heat source for fixing. In order from the outer peripheral surface in direct contact with the recording sheet S and the pressure roller 53, the surface layer made of a fluororesin or the like for improving the fine fixability and the recording sheet S at the time of fusion fixing An elastic layer made of foamed silicon rubber or the like for improving adhesion and improving fixability and a magnetic shunt alloy layer are laminated (see FIG. 3). Here, an adhesive layer or the like that joins the respective layers is usually omitted and is often not shown in the configuration diagram. Also in this embodiment, since the influence of the adhesive layer or the like joining the layers is small, the notation of the adhesive layer or the like is omitted, and the relational expression between the layers is derived. By the way, for example, between the surface layer and the elastic layer, and between the elastic layer and the magnetic shunt alloy layer, a method of joining with an adhesive layer is the mainstream, but the elastic modulus of the adhesive layer is in comparison with other layers. Since it is sufficiently small, a large error does not occur even if the adhesive layers between the surface layer and the elastic layer and between the elastic layer and the magnetic shunt alloy layer are not considered.

The fixing roller 52 is included in the inner periphery of the fixing belt 51, and is configured by laminating an elastic heat insulating layer such as silicon rubber or silicon sponge material on the outer periphery of a cylindrical steel or aluminum core shaft.
The pressure roller 53 is provided so as to apply a load to the fixing roller 52 via the fixing belt 51 so as to form a fixing nip between the pressure roller 53 and a core shaft such as a cylindrical steel or aluminum pipe. An elastic heat insulating layer such as silicon rubber and a release layer made of fluorine resin or the like are laminated on the outer periphery of the substrate.

  The fixing plate 54 is disposed in contact with the inner peripheral surface of the fixing belt 51 at a position not close to the fixing nip, and when the fixing belt is driven to circulate, the fixing plate 54 rubs against the fixing belt to regulate the rotation position of the fixing belt. The low-friction layer 541 on the side close to the fixing belt 51 and the low-resistance conductive layer 542 on the far side are provided to reduce friction caused by the rubbing between the fixing belt 51 and the fixing plate 54. And a laminated structure composed of at least two layers.

The exciting coil 55 faces the outer peripheral surface of the fixing belt 51 and is disposed at a position facing the fixing plate 54 with the fixing belt 51 interposed therebetween, and generates a magnetic flux toward the fixing belt 51 and the fixing plate 54.
As described above, the fixing device 5 according to the present embodiment includes the fixing roller 52 and the fixing plate 54 on the inner periphery of the fixing belt 51, as compared with the fixing belt 5 provided with two rollers on the inner periphery of the fixing belt. Since the belt length is extremely short, the heat capacity of the heat generating portion is small, which is very advantageous from the viewpoints of energy saving, space efficiency, and shortening of warm-up time.

The material and thickness of each layer will be described in detail below.
FIG. 3 is a diagram showing an outline of the layer structure from the center of the fixing roller 52 to the exciting coil 55.
As shown in FIG. 3, when viewed from the center of the fixing roller 52, there is an exciting coil 55 on the outermost side, and a fixing in which a surface layer 511, an elastic layer 512, and a magnetic shunt alloy layer 513 are laminated in that order. There is a belt 51, and a fixing plate 54 in which a low friction layer 541 and a low resistance conductive layer 542 are laminated in that order, and a fixing plate constituted by an elastic heat insulating layer 521 and a core shaft 522 inside the belt 51. A roller 52 is located. In addition, there is a gap between the exciting coil 55 and the fixing belt 51, the fixing belt 51 and the fixing plate 54 are in contact with each other, and there is also a gap between the fixing plate 54 and the fixing roller 52.

The material of the surface layer 511 is PFA in the present embodiment, and should be able to withstand use at the fixing temperature and have toner releasability. For example, silicon rubber, fluororubber, PFA, PTFE, Fluorine resins such as PEP and PFEP are preferred.
The film thickness of the surface layer 511 is 30 μm in the present embodiment, and is preferably about 5 to 100 μm and more preferably 5 to 50 μm practically from the viewpoint of durability and energy saving.

  The material of the elastic layer 512 is foamed silicon rubber in this embodiment, and must have heat resistance and elasticity. For example, the heat resistance of foamed silicon rubber, fluororubber, etc. that can withstand use depending on the fixing temperature. An elastomer can be used. Further, a filler may be mixed into the elastic layer 512 in order to improve thermal conductivity and reinforce. In consideration of processability and price, the filler is preferably silica, alumina, magnesium oxide, boron nitride, beryllium oxide, etc., and diamond, silver, copper, aluminum, marble, glass, etc. are characteristically used. There may be.

The film thickness of the elastic layer 512 is 0.62 to 1.04 mm in the present embodiment, and must be at least about 10 μm in order to obtain the necessary elastic force in the thickness direction. If it is too thick, the heat generated in the magnetic shunt alloy layer 513 is not easily transmitted to the recording sheet S, which is not desirable because the thermal efficiency is lowered.
Note that the range of the thickness of the elastic layer 512 in this embodiment is determined based on the predetermined conditions described later, based on the elastic modulus and the layer thickness of each layer constituting the fixing belt 51.

The thickness of the magnetic shunt alloy layer 513 is 15 μm in the present embodiment, and is preferably about 10 to 30 μm when a Ni—Fe alloy is used. In practice, the thickness of the magnetic shunt alloy layer 513 is 15 to ensure a certain degree of rigidity. 20 μm is more preferable.
Further, if the surface layer 511 and the magnetic shunt alloy layer 513 are too thick, the hardness of the belt itself becomes too high and leads to poor press contact.

Note that the thicknesses of the respective layers constituting the fixing belt 51 are determined not only within the above range but also based on predetermined conditions described later.
The material of the low friction layer 541 must have a sliding coefficient of friction when the fixing belt 51 is driven to circulate more than the low resistance conductive layer 542, and for example, PFA having heat resistance is preferable.
The thickness of the low friction layer 541 is 30 μm in the present embodiment, and is preferably about 5 to 100 μm and more preferably 5 to 50 μm practically from the viewpoint of durability and energy saving.

The material of the low-resistance conductive layer 542 is Cu in this embodiment, and any material can be used as long as it has high conductivity. However, the low-resistance conductive layer 542 must have a certain thickness and a low electric resistance value.
The thickness of the low resistance conductive layer 542 is 200 μm in this embodiment, preferably about 50 to 400 μm, and more preferably 100 to 300 μm practically.
Here, when the magnetic shunt alloy layer 513 is at a temperature lower than the Curie point, the magnetic shunt alloy layer 513 supplements the magnetic flux, and the magnetic shunt alloy layer 513 generates heat and is used for heat fixing.

  When the magnetic shunt alloy layer 513 reaches a temperature equal to or higher than the Curie point, the magnetic shunt alloy layer 513 that has lost its magnetism cannot supplement the magnetic flux, and the magnetic flux that has passed through the magnetic shunt alloy layer 513 is applied to the low resistance conductive layer 542. To reach. Since the low-resistance conductive layer 542 has a small resistance value, the amount of heat generated is small even when the magnetic flux reaches, but a reverse magnetic field is generated, so that an effect of canceling the original magnetic flux occurs. Therefore, the magnetic flux passing through the magnetic shunt alloy layer 513 decreases, and the amount of heat generated in the magnetic shunt alloy layer 513 decreases.

Based on the principle as described above, it is possible to suppress the temperature rise of the non-sheet passing portion when a small size recording sheet is thermally fixed.
The material of the elastic heat insulating layer 521 is a silicon sponge material in the present embodiment, and while holding the fixing belt 51 while insulating, at the same time, the deflection of the fixing belt 51 is allowed to ensure a nip width, and the paper discharge property, In addition, the separation property of the recording sheet S is improved. In addition, when the elastic heat insulating layer 521 has a two-layer structure of a rubber material and a sponge material, for example, high heat insulating properties and sufficient elasticity can be obtained relatively easily.

The thickness of the elastic heat insulating layer 521 is 10 mm in the present embodiment, and when a silicon sponge material is used, it is preferably 2 to 15 mm, more preferably 8 to 12 mm.
Further, the hardness of the elastic heat insulating layer 521 is preferably 20 to 60 degrees, more preferably 30 to 50 degrees in a hardness Asker rubber hardness meter.
The material of the core shaft 522 is aluminum in this embodiment, and a heat-resistant molded pipe such as steel or PPS (polyphenylene sulfide) can be used as long as the strength can be secured. However, it is preferable to use a non-magnetic material so that the core shaft 522 does not generate heat due to the leaked magnetic flux.

The thickness of the core shaft 522 is 10 mm in diameter in the present embodiment.
FIG. 4 is a diagram showing an outline of the layer structure of the pressure roller 53.
As shown in FIG. 4, the pressure roller 53 has a release layer 531, an elastic heat insulating layer 532, and a core shaft 533 stacked in order from the outer peripheral side.
The material of the release layer 531 is a fluororesin such as PTFE or PFA in this embodiment, and may be any material that enhances the surface release properties.

The thickness of the release layer 531 is 20 μm in this embodiment, and is preferably about 10 to 50 μm when a fluororesin is used.
The material and thickness of the elastic heat insulating layer 532 are the same as those of the elastic heat insulating layer 521 of the fixing roller 52.
The material and thickness of the core shaft 533 are the same as those of the core shaft 522 of the fixing roller 52.

<Method for Determining the Thickness of Each Layer Constructing Fixing Belt 51>
When the fixing belt 51 passes through the fixing nip, the maximum bending stress is generated, and fatigue due to internal stress due to deformation such as bending accumulates. It is presumed that this will lead to a complete destruction.
The elastic layer 512 in the fixing belt 51 is made of foamed silicon rubber or the like. If the elastic layer 512 has a defective portion such as inhomogeneous strain or bubbles, a crack grows starting from the defective portion during use. In some cases, cracks reach the surface of the belt, and the belt surface appears to wave, leading to a life. Silicone rubber has a disadvantage that it has a relatively low tear strength. May be the weakest part.

On the other hand, there is generally a neutral surface within the belt that is driven to rotate, where there is no tension or compression when the belt rotates and bends, and the stress is minimized. The stress increases as the distance increases.
Therefore, in the present embodiment, the thickness of each layer of the fixing belt 51 is adjusted so that the elastic layer 512 has a neutral surface, and the stress acting on the elastic layer 512 is minimized, so that the vicinity of the elastic layer 512 is obtained. The fatigue of the fixing belt 51 is reduced by suppressing the fatigue due to the internal stress of the fixing belt 51, thereby extending the life of the fixing belt 51.

  When the elastic modulus and thickness of each layer are expressed by (Ei, Ti) for a belt laminated in n layers (2 = <n), the distance y from the upper surface of the belt to the neutral surface is expressed by the following equation ( It is given by Equation 1).

  Therefore, in order to make the neutral plane exist in the m-th layer (m = <n) from the upper surface, the following equation (Equation 2) may be satisfied.

In order to apply Equation 2 to the fixing belt 51 so that the elastic layer 512 has a neutral surface, 2 is applied from the upper surface of the belt laminated on the three layers of the surface layer 511, the elastic layer 512, and the magnetic shunt alloy layer 513. There must be a neutral plane in the second layer.
Here, although it seems that the thickness of each layer is determined vaguely, it seems that it is impossible to gather at first glance because there are innumerable combinations, but in reality, each layer other than the elastic layer 512 has severe restrictions, Since the thickness is inevitably determined in order for each to exhibit its original performance, the thickness of each layer other than the elastic layer 512 is determined in advance, and the elastic layer 512 is determined using Equations 1 and 2. Determine the layer thickness.

The elastic modulus and layer thickness of the surface layer 511 are (E ₁ , T ₁ ), the elastic modulus and layer thickness of the elastic layer 512 are (E ₂ , T ₂ ), and the elastic modulus and layer thickness of the magnetic shunt alloy layer 513 are Is (E ₃ , T ₃ ), Equation 1 is expanded into the following equation (Equation 3).

Here, the elastic modulus E ₂ of the elastic layer 512 is sufficiently small, sufficiently small in comparison section E ₂ T ₂ are other terms, numbers 3 Ignoring this is rewritten to the equation (4).

  Substituting Equation 4 into Equation 2 yields Equation 5.

  Equations 6 and 7 are obtained by solving the inequality of Equation 5.

Therefore, the range of _{T 2} are expressed by the following equation (8).

  Table 1 below shows a list of the elastic modulus and layer thickness of each layer of the fixing belt 51 obtained using Equation 8.

[Modification 1]
<Overview>
Modification 1 differs from Embodiment 1 only in a part of the fixing belt, and a metal layer is further laminated on the fixing plate side of the fixing belt, and the thickness of the elastic layer is set so that the neutral surface comes within the elastic layer. It has been changed.

<Configuration>
In the first modification, the fixing belt 51 of the first embodiment is replaced with a fixing belt 56, and other components are the same as those of the first embodiment.
Similar to the fixing belt 51 of the first embodiment, the fixing belt 56 is an endless belt that generates heat by guiding a magnetic flux generated by the exciting coil 55 to a built-in magnetic shunt alloy layer and serves as a heat source for fixing. The surface layer, the elastic layer, the magnetic shunt alloy layer, and the metal layer are laminated. Here, as in the first embodiment, the adhesive layer that joins the respective layers has a small influence on the adhesive layer that joins the respective layers even in the first modification. The relationship between each layer is derived. Incidentally, a method of joining with a magnetic shunt alloy layer and a metal layer by heat or pressure is the mainstream. FIG. 5 is a diagram showing an outline of the layer structure from the center of the fixing roller 52 to the exciting coil 55 in the first modification.

In the first modification, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
The layer structure of FIG. 5 is the same as that of the first embodiment except that the fixing belt 51 in the layer structure of FIG. 3 of the first embodiment is replaced with the fixing belt 56.
In the fixing belt 56, a surface layer 511, an elastic layer 561, a magnetic shunt alloy layer 513, and a metal layer 562 are laminated in order from the side close to the exciting coil 55.

The material of the elastic layer 561 is the same as that of the elastic layer 512 of the first embodiment.
The film thickness of the elastic layer 561 is 2.5 to 3.33 mm in this modification, and this range is based on the predetermined conditions described later based on the elastic modulus and layer thickness of each layer constituting the fixing belt 56. It has been decided.
The material of the metal layer 562 is Cu in this embodiment, and any material having high conductivity such as aluminum or stainless steel may be used. However, the metal layer 562 must have a certain thickness and a low electric resistance value.

The thickness of the metal layer 562 is 15 μm in the present embodiment, and is preferably about 10 to 30 μm when Cu is used, and more preferably 15 to 20 μm practically.
<Method for Determining the Thickness of Each Layer Constructing Fixing Belt 56>
In order to apply Formula 2 to the fixing belt 56 so that the neutral surface comes to the elastic layer 561, a belt laminated on four layers of the surface layer 511, the elastic layer 561, the magnetic shunt alloy layer 513, and the metal layer 562. A neutral plane must be present in the second layer from the top surface of the substrate.

  Here, as in the first embodiment, even if the thickness of each layer is determined vaguely, it seems that it cannot be collected at first glance because there are innumerable combinations, but in reality, each layer other than the elastic layer 561 In the first embodiment, each of the restrictions is severe, and the thickness is inevitably determined in order to exhibit the original performance. Therefore, the thickness of each layer other than the elastic layer 561 is determined in advance, and the first embodiment is used. The thickness of the elastic layer 561 is determined using Equations 1 and 2.

The elastic modulus and layer thickness of the surface layer 511 are (E ₁ , T ₁ ), the elastic modulus and layer thickness of the elastic layer 561 are (E ₂ , T ₂ ), and the elastic modulus and layer thickness of the magnetic shunt alloy layer 513 are Is (E ₃ , T ₃ ), and the elastic modulus and layer thickness of the metal layer 562 are (E ₄ , T ₄ ), then Equation 1 is developed into the following equation (Equation 9).

Here, the elastic modulus E ₂ of the elastic layer 561 is sufficiently small, sufficiently small in comparison section E ₂ T ₂ are other terms, numbers 9 Ignoring this is rewritten to the number 10.

  Expression 11 is obtained by substituting Expression 10 into Expression 2.

  Equations 12 and 13 are obtained by solving the inequality of Equation 11.

Therefore, the range of _{T 2} are expressed by the following equation (equation 14).

  Table 2 below shows a list of elastic moduli and layer thicknesses of the respective layers of the fixing belt 56 obtained using Equation 14.

In the first embodiment and the first modification, the relational expression is considered without considering the adhesive layer that joins the surface layer and the elastic layer and the adhesive layer that joins the elastic layer and the magnetic shunt alloy layer. However, the relational expression may be derived in consideration of these adhesive layers. Details are described in Modification 2 and Modification 3.
[Modification 2]
In Modification 2, the adhesive layer that joins the surface layer and the elastic layer in Embodiment 1 is defined as the first adhesive layer, and the adhesive layer that joins the elastic layer and the magnetic shunt alloy layer is the first adhesive layer. A layer structure including a first adhesive layer and a second adhesive layer is defined as one adhesive layer.

FIG. 6 is a diagram showing an outline of the layer structure from the center of the fixing roller 52 to the exciting coil 55 in the second modification.
In the second modification, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
The layer structure of FIG. 6 is the same as that of the first embodiment except that the fixing belt 51 in the layer structure of FIG. 3 of the first embodiment is replaced with the fixing belt 57.

  The fixing belt 57 is substantially the same as the fixing belt 51 of the first embodiment, and in order to more accurately prescribe the relational expression for determining the thickness of each layer, the fixing belt 57 includes a surface layer and an elastic layer. An adhesive layer that joins the elastic layer and the magnetic shunt alloy layer, and a surface layer 511, a first adhesive layer 571, and an elastic layer in order from the side closer to the exciting coil 55. A layer 512, a second adhesive layer 572, and a magnetic shunt alloy layer 513 are laminated.

<Method for Determining the Thickness of Each Layer Constructing Fixing Belt 57>
In order to apply Equation 2 to the fixing belt 57 so that the elastic layer 512 has a neutral surface, the surface layer 511, the first adhesive layer 571, the elastic layer 512, the second adhesive layer 572, and the magnetic shunt alloy layer 513. The neutral plane must be present in the third layer from the upper surface of the belt laminated in the five layers.
Here, as in the first embodiment, even if the thickness of each layer is determined vaguely, it seems that it cannot be collected at first glance because there are an infinite number of combinations, but in reality, each layer other than the elastic layer 512 In the first embodiment, the respective restrictions are severe, and the thickness is inevitably determined in order to exhibit the original performance of each. Therefore, the thickness of each layer other than the elastic layer 512 is determined in advance, and the first embodiment The thickness of the elastic layer 512 is determined using Equations 1 and 2.

The elastic modulus and layer thickness of the surface layer 511 are (E ₁ , T ₁ ), the elastic modulus and layer thickness of the first adhesive layer 571 are (E ₂ , T ₂ ), and the elastic modulus and layer thickness of the elastic layer 512 are (E ₃ , T ₃ ), the elastic modulus and layer thickness of the second adhesive layer 572 (E ₄ , T ₄ ), and the elastic modulus and layer thickness of the magnetic shunt alloy layer 513 (E ₅ , T ₅ ). Then, Equation 1 is expanded into the following equation (Equation 15).

Since the elastic modulus _{E 3} of the elastic modulus _{E 2} and the elastic layer 512 of the first adhesive layer 571 and the elastic modulus _{E 4} of the second adhesive layer 572 is sufficiently _small, term and _E 3 of the E 2 _{T 2} T The terms ₃ and E ₄ T ₄ are sufficiently smaller than the other terms, and if this is ignored, Equation 15 is rewritten as Equation 16.

  Expression 17 is obtained by substituting Expression 16 into Expression 2.

  Equations 18 and 19 are obtained by solving the inequality of Equation 17.

Accordingly, the scope of _{T 3} is represented by the following equation (Equation 20).

[Modification 3]
In Modification 3, the adhesive layer that joins the surface layer and the elastic layer in Modification 1 is defined as the first adhesive layer, and the adhesive layer that joins the elastic layer and the magnetic shunt alloy layer is the first adhesive layer. A layer structure including a first adhesive layer and a second adhesive layer is defined as an adhesive layer.
FIG. 7 is a diagram showing an outline of the layer structure from the center of the fixing roller 52 to the exciting coil 55 in the third modification.

In the third modification, the same components as those in the first modification are denoted by the same reference numerals, and the description thereof is omitted.
The layer structure of FIG. 7 is the same as that of Modification 1 except that the fixing belt 56 in the layer structure of FIG. 5 of Modification 1 is replaced with the fixing belt 58.
The fixing belt 58 is substantially the same as the fixing belt 56 of the first modification. In order to more accurately define the relational expression for determining the thickness of each layer, the fixing belt 58 is provided between the surface layer and the elastic layer. , An adhesive layer that joins between the elastic layer and the magnetic shunt alloy layer, the surface layer 511, the first adhesive layer 581, and the elastic layer in order from the side closer to the exciting coil 55 561, a second adhesive layer 582, a magnetic shunt alloy layer 513, and a metal layer 562 are laminated.

<Method for Determining the Thickness of Each Layer Constructing Fixing Belt 58>
In order to apply Equation 2 to the fixing belt 58 so that the elastic layer 561 has a neutral surface, the surface layer 511, the first adhesive layer 581, the elastic layer 561, the second adhesive layer 582, and the magnetic shunt alloy layer 513. The neutral plane must be present in the third layer from the top surface of the belt laminated to the six metal layers 562.

  Here, as in the first modification, it seems that the thickness of each layer is determined vaguely, but there seems to be an infinite number of combinations. Since the restrictions are strict and the thickness is inevitably determined in order to exhibit the original performance of each, the thickness of each layer other than the elastic layer 561 is determined in advance, and The layer thickness of the elastic layer 561 is determined using Equations 1 and 2.

The elastic modulus and layer thickness of the surface layer 511 are (E ₁ , T ₁ ), the elastic modulus and layer thickness of the first adhesive layer 581 are (E ₂ , T ₂ ), and the elastic modulus and layer thickness of the elastic layer 561 are (E ₃ , T ₃ ), the elastic modulus and layer thickness of the first adhesive layer 581 (E ₄ , T ₄ ), and the elastic modulus and layer thickness of the magnetic shunt alloy layer 513 (E ₅ , T ₅ ). Assuming that the elastic modulus and the layer thickness of the metal layer 562 are (E ₆ , T ₆ ), Equation 1 is developed into the following equation (Equation 21).

Since the elastic modulus _{E 2} and the elastic modulus _{E 3} of the elastic layer 561 of the first adhesive layer 571 and the elastic modulus _{E 4} of the second adhesive layer 572 is sufficiently _small, term and _E 3 of the E 2 _{T 2} T The terms ₃ and E ₄ T ₄ are sufficiently smaller than the other terms, and if this is ignored, Equation 21 is rewritten as Equation 22.

  Substituting Equation 22 into Equation 2 yields Equation 23.

  Equations 24 and 25 are obtained by solving the inequality of Equation 23.

Accordingly, the scope of _{T 3} is represented by the following formula (number 26).

<Summary>
As described above, according to the fixing device of Embodiment 1, Modification 1, Modification 2, and Modification 3, and the image forming apparatus including the fixing device, the fixing device having the self-temperature control function is used. Since the durability of the fixing belt having the magnetic shunt alloy layer can be improved, maintenance opportunities can be reduced, and resource saving can also be achieved.

The present invention can be widely applied to the technical field of an image forming apparatus including a fixing device.
According to the present invention, the life of the fixing belt can be extended, and its industrial utility value is extremely high.

1 is a diagram illustrating an overall configuration of an image forming apparatus according to Embodiment 1. FIG. 2 is a diagram schematically illustrating a configuration of a fixing device 5. FIG. 2 is a diagram showing an outline of a layer structure from the center of the fixing roller 52 to an exciting coil 55. FIG. 3 is a diagram showing an outline of a layer structure of a pressure roller 53. FIG. 10 is a diagram showing an outline of a layer structure from the center of a fixing roller 52 to an exciting coil 55 in Modification 1. FIG. 10 is a diagram showing an outline of a layer structure from the center of a fixing roller 52 to an exciting coil 55 in Modification 2. FIG. 10 is a diagram showing an outline of a layer structure from the center of a fixing roller 52 to an exciting coil 55 in Modification 3. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 3 Image process part 4 Feeding part 5 Fixing apparatus 6 Control part 10 Optical part 11 Intermediate transfer belt 3Y, 3M, 3C, 3K Image forming unit 31Y, 31M, 31C, 31K Photosensitive drum 32Y, 32M, 32C , 32K Charger 33Y, 33M, 33C, 33K Developer 34Y, 34M, 34C, 34K Primary transfer roller 35Y, 35M, 35C, 35K Cleaner 41 Paper feed cassette 42 Feeding roller 43 Conveyance path 44 Timing roller pair 45 Secondary transfer Roller 46 Secondary transfer position 51 Fixing belt 52 Fixing roller 53 Pressure roller 54 Fixed plate 55 Excitation coil 56 Fixed plate 57 Fixing belt 58 Fixing belt 71 Discharge roller 72 Discharge tray 511 Surface layer 512 Elastic layer 513 Magnetic shunt alloy layer 521 Elastic heat insulation layer 52 Core shaft 531 release layer 532 elastic thermal insulation layer 533 core shaft 541 low-friction layer 542 low-resistance conductive layer 561 elastic layer 562 metal layer 571 first adhesive layer 572 second adhesive layer 581 first adhesive layer 582 second adhesive layer

Claims (7)

A fixing belt that is used in an induction heating type fixing device and is driven in a circular manner,
A magnetic shunt alloy layer that exhibits ferromagnetism at a temperature lower than the Curie point and generates heat, loses magnetism at a temperature equal to or higher than the Curie point, and the amount of heat generation decreases,
With an elastic layer,
A fixing belt, wherein the thickness of each layer is adjusted so that a neutral surface that is not tensioned or compressed exists in the elastic layer during the circular motion. The fixing belt further includes:
Located on the outer peripheral side of the elastic layer, comprising a surface layer in contact with the recording sheet,
E _{1 is} the elastic modulus of the surface layer,
The layer thickness of the surface layer is T ₁ ,
E _{2 is} the elastic modulus of the elastic layer,
The thickness of the elastic layer is T ₂ ,
The elastic modulus of the magnetic shunt alloy layer is E ₃ ,
When the layer thickness of the magnetic shunt alloy layer and T _3,

The fixing belt according to claim 1, wherein: The fixing belt further includes
A surface layer located on the outer peripheral side of the elastic layer and in contact with the recording sheet;
A metal layer that is located on the inner peripheral side of the magnetic shunt alloy layer and made of a metal that is not a magnetic shunt alloy;
E _{1 is} the elastic modulus of the surface layer,
The layer thickness of the surface layer is T ₁ ,
E _{2 is} the elastic modulus of the elastic layer,
The thickness of the elastic layer is T ₂ ,
The elastic modulus of the magnetic shunt alloy layer is E ₃ ,
The layer thickness of the magnetic shunt alloy layer is T ₃ ,
The elastic modulus of the metal layer is E ₄ ,
When the layer thickness of the metal layer and T _4,

The fixing belt according to claim 1, wherein: The fixing belt further includes
A surface layer located on the outer peripheral side of the elastic layer and in contact with the recording sheet;
A first adhesive layer located on the inner peripheral side of the surface layer and bonding the surface layer and the elastic layer;
A second adhesive layer that is located on the inner peripheral side of the elastic layer and bonds the elastic layer and the magnetic shunt alloy layer;
E _{1 is} the elastic modulus of the surface layer,
The layer thickness of the surface layer is T ₁ ,
The elastic modulus of the first adhesive layer is E ₂ ,
The layer thickness of the first adhesive layer is T ₂ ,
E _{3 is} the elastic modulus of the elastic layer,
The layer thickness of the elastic layer is T ₃ ,
The elastic modulus of the second adhesive layer is E ₄ ,
The layer thickness of the second adhesive layer is T ₄ ,
The elastic modulus of the magnetic shunt alloy layer is E ₅ ,
When the layer thickness of the magnetic shunt alloy layer and T _5,

The fixing belt according to claim 1, wherein: The fixing belt further includes
A surface layer located on the outer peripheral side of the elastic layer and in contact with the recording sheet;
A first adhesive layer located on the inner peripheral side of the surface layer and bonding the surface layer and the elastic layer;
A second adhesive layer that is located on the inner peripheral side of the elastic layer and bonds the elastic layer and the magnetic shunt alloy layer;
A metal layer that is located on the inner peripheral side of the magnetic shunt alloy layer and made of a metal that is not a magnetic shunt alloy;
E _{1 is} the elastic modulus of the surface layer,
The layer thickness of the surface layer is T ₁ ,
The elastic modulus of the first adhesive layer is E ₂ ,
The layer thickness of the first adhesive layer is T ₂ ,
E _{3 is} the elastic modulus of the elastic layer,
The layer thickness of the elastic layer is T ₃ ,
The elastic modulus of the second adhesive layer is E ₄ ,
The layer thickness of the second adhesive layer is T ₄ ,
The elastic modulus of the magnetic shunt alloy layer is E ₅ ,
The layer thickness of the magnetic shunt alloy layer is T ₅ ,
E _{6 is} the elastic modulus of the metal layer,
When the layer thickness of the metal layer and T _6,

The fixing belt according to claim 1, wherein:   A fixing device comprising the fixing belt according to claim 1.   An image forming apparatus comprising the fixing device according to claim 6.

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