JP2008152247A - Fixing device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device making it possible to restrain excessive rise of the temperature of regions other than regions where sheets pass even if recording media having various sizes are used, and to provide an image forming device having the fixing device. <P>SOLUTION: A heat generation controlling member 46 is arranged facing the magnetic field generating unit 42 via a fixing belt 38 having a heat generation layer. The heat generation controlling member 46 has at least a temperature-sensitive magnetic material having a Curie temperature and controlling generation of heat of the heat generating layer by using the temperature-sensitive magnetic material of the heat generation controlling member 46, the material being magnetized or non-magnetized when the temperature thereof is near the Curie temperature of this material. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fixing device and an image forming apparatus.

As a fixing device of an image forming apparatus, a fixing device adopting an electromagnetic induction heating method has been proposed (see, for example, Patent Document 1). In this electromagnetic induction heating method, a magnetic field generated by an induction coil is applied to a rotating body having a conductive layer, and the rotating body is directly heated by an eddy current generated in the conductive layer.
JP 2001-176648 A

  An object of the present invention is to provide a fixing device that can suppress an excessive temperature rise in a non-sheet passing portion even when recording media of various sizes are used. Another object of the present invention is to provide an image forming apparatus provided with the fixing device.

The above problem is solved by the following means. That is,
The invention according to claim 1
A cylindrical first rotating body having a heat generating layer that generates heat by the action of a magnetic field;
A second rotating body in contact with the first rotating body;
A magnetic field generating means arranged to have a predetermined gap with respect to an inner peripheral surface or an outer peripheral surface of the first rotating body and generating the magnetic field;
A heat generation control member that is disposed to face the magnetic field generation means via the first rotating body, includes a temperature-sensitive magnetic material having a Curie point, and controls heat generation of the heat generation layer;
A fixing device.
Here, the Curie point is also referred to as a Curie point, a Curie temperature, or a Curie temperature, and indicates a temperature at which magnetism disappears and becomes a non-magnetic material (paramagnetic material) when the temperature is higher than this temperature. The temperature-sensitive magnetic material refers to a magnetic material that changes its magnetic characteristics with respect to a temperature change of the magnetic material.

The invention according to claim 2
2. The fixing device according to claim 1, wherein the Curie point is in a range not lower than a set temperature of the first rotating body and not higher than a heat resistant temperature of the first rotating body.
Here, the set temperature of the first rotating body means the surface temperature of the first rotating body when fixing is started. Further, the heat-resistant temperature is a temperature at which the constituent material of the first rotating body deteriorates to deteriorate the function and deform when continuously used.

The invention according to claim 3
The first rotating body is disposed through the first rotating body and the heat generation control member and opposed to the heat generation control member so as to face the magnetic field generating means, and includes a nonmagnetic metal material. The fixing device according to claim 1, comprising a nonmagnetic metal member.

The invention according to claim 4
The first rotating body and the heat generation control member are arranged in contact with each other through the first rotation body and the heat generation control member inside the first rotation body, and the magnetic field generation means is in contact with the heat generation control member. The fixing device according to claim 1, further comprising a nonmagnetic metal member that is disposed to face the nonmagnetic metal material.

The invention according to claim 5
The fixing device according to claim 1, wherein the heat generating layer is made of a nonmagnetic metal.

The invention according to claim 6
The fixing device according to claim 1, further comprising: a blocking unit configured to block an eddy current generated in the heat generation control member by electromagnetic induction from the magnetic field generation unit.

The invention according to claim 7 provides:
The fixing device according to claim 6, wherein the blocking unit is a slit or a notch provided in the heat generation control member.

The invention according to claim 8 provides:
2. The fixing device according to claim 1, further comprising: a drive transmission member that is provided at at least one of both axial ends of the first rotating body and that transmits rotational driving to the first rotating body.

  The invention according to claim 9 is the fixing device according to claim 1, wherein the heat generation control member is in contact with the first rotating body.

A tenth aspect of the present invention is the fixing device according to the first aspect, wherein the heat generation control member is not pressed and is in contact with the first rotating body.
Here, “non-pressing contact” indicates a state of contact with a contact surface without applying a large pressure, and the heat generation control member is in contact with the first rotating body at 0.1 to 200 N. Means that.

  The invention according to claim 11 is the fixing device according to claim 1, wherein the heat generation control member is not in contact with the first rotating body.

The invention according to claim 12 is the fixing device according to claim 1, wherein the heat generation control member is a non-heating element.
Here, the “non-heating element” means that the heat generation of eddy current loss due to electromagnetic induction is sufficiently small. In order to suppress the heat generation, the non-heat generating body may be structured to make it difficult to generate heat, and the member is 0.038 W / mm ² or less.

The invention according to claim 13 is:
The fixing device according to claim 1, wherein the temperature-sensitive magnetic material is a metal material.

The invention according to claim 14 is:
14. The fixing device according to claim 1, wherein the contact portion of the first rotating body is elastically deformed toward an inner peripheral surface when contacting the second rotating body. 15.

The invention according to claim 15 is:
A latent image carrier,
A latent image forming means for forming a latent image on the surface of the latent image holding member;
Developing means for developing the latent image into an image using an electrophotographic developer;
Transfer means for transferring the developed image to a transfer medium;
Fixing means for fixing the image on the transfer medium;
With
An image forming apparatus, wherein the fixing unit is the fixing device according to claim 1.

  According to the first aspect of the present invention, there is an effect that the temperature rise of the non-sheet passing portion in the first rotating body can be suppressed even when recording media of various sizes are used, as compared with the case where this configuration is not provided.

  According to the second aspect of the present invention, it is possible to prevent overheating at the time of fixing while preventing the fixing failure and preventing the deterioration of the first rotating body as compared with the case without this configuration.

  According to the invention which concerns on Claim 3, compared with the case where it does not have this structure, there exists an effect that the temperature rise of the 1st rotary body in the area | region which penetrated the magnetic flux (magnetic field) of the heat generation control member is reduced more.

  According to the invention of claim 4, since the amount of heat transfer per unit time in the axial direction increases compared to the case without this configuration, the temperature increase in the non-sheet passing portion of the fixing belt itself is dispersed in the axial direction. As a result, the effect of suppressing the temperature rise can be obtained.

  According to the fifth aspect of the present invention, as compared with the case where the present configuration is not provided, sufficient heat generation can be obtained even if the thickness is reduced, so that it is possible to obtain a heat generation layer having a small heat capacity.

  According to the sixth aspect of the present invention, there is an effect that self-heating of the heat generation control member can be suppressed as compared with the case where this configuration is not provided.

  According to the seventh aspect of the present invention, the self-heating of the heat generation control member can be suppressed and the temperature movement in the axial direction of the heat generation control member can be suppressed as compared with the case where this configuration is not provided. It is possible to achieve this effect.

  According to the eighth aspect of the invention, as compared with the case where the present configuration is not provided, it is possible to suppress the fluctuation of the rotation speed due to the influence of the sliding resistance of the first rotating body, and to suppress paper wrinkles and fixing unevenness. Play.

  According to the ninth aspect of the present invention, there is an effect that it is possible to control the electromagnetic induction heat generation of the heat generation layer by the heat generation control member with high sensitivity as compared with the case where this configuration is not provided.

  According to the invention which concerns on Claim 10, compared with the case where it does not have this structure, since the sliding resistance of a 1st rotary body can be suppressed, there exists an effect that it becomes difficult to cause the lifetime reduction by wear.

  According to the eleventh aspect of the present invention, since the temperature does not decrease when the fixing device starts up because the first rotating body is not directly contacted as compared with the case where the present configuration is not provided, the fixing can be quickly achieved. It has the effect of being able to.

  According to the twelfth aspect of the present invention, since the self-heating of the heat generation control member is suppressed as compared with the case where this configuration is not provided, it is possible to perform the temperature control that reacts with high sensitivity by the temperature change of the first rotating body. Play.

  According to the thirteenth aspect of the present invention, since the heat capacity of the heat generation control member is smaller than in the case where this configuration is not provided, the temperature followability of the heat generation control member with respect to the temperature change of the first rotating body is increased and the sensitivity is improved. The reaction temperature can be controlled.

  According to the fourteenth aspect of the present invention, there is an effect that the sheet can be easily peeled off from the first rotating body after fixing as compared with the case where the present configuration is not provided.

  According to the fifteenth aspect of the present invention, there is an effect that a high-quality fixed image can be stably obtained over a long period of time, compared with the case where the present configuration is not provided.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In addition, the same code | symbol is provided to the member which has the substantially same function through all the drawings, and the overlapping description may be abbreviate | omitted.

  FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment. FIG. 2 is a schematic cross-sectional view illustrating the fixing device according to the embodiment. FIG. 3 is a schematic configuration diagram illustrating the fixing device according to the embodiment. FIG. 2 is a schematic cross-sectional view as seen from the axial direction of the fixing device. FIG. 3 is a schematic cross-sectional view taken along the line AA of FIG. 2, and is a schematic cross-sectional view seen from a direction orthogonal to the axial direction of the fixing device.

  As shown in FIG. 1, the image forming apparatus 100 according to the present embodiment includes a cylindrical photosensitive drum 10 that rotates in one direction (the direction of arrow A in FIG. 1). Around the photosensitive drum 10, a charging device 12 that charges the surface of the photosensitive drum 10 in order from the upstream side in the rotation direction of the photosensitive drum 10, and image light L is irradiated to the photosensitive drum 10 to irradiate the surface. An exposure device 14 that forms a latent image, a developing device 16 that includes developing devices 16A to 16D that selectively transfer toner to a latent image on the surface of the photosensitive drum 10 to form a toner image, and the photosensitive drum 10 An endless belt-shaped intermediate transfer body 18 that is supported so that the circumferential surface thereof can rotate, a cleaning device 20 that removes toner remaining on the photosensitive drum 10 after the transfer of the toner image, and the surface of the photosensitive drum 10 And a static elimination exposure device 22 for eliminating static electricity.

  Further, on the inner side of the intermediate transfer member 18, the transfer device 24 that primarily transfers the toner image formed on the surface of the photosensitive drum 10 to the intermediate transfer member 18, and two support rolls 26 </ b> A and 26 </ b> B perform secondary transfer. Therefore, the intermediate transfer body 18 is stretched so as to be able to circulate in one direction (the direction of arrow B in FIG. 1). At a position facing the transfer facing roll 28, there is a transfer roll 30 that secondarily transfers the toner image primarily transferred onto the outer peripheral surface of the intermediate transfer body 18 to the recording paper (recording medium) P via the intermediate transfer body 18. The recording paper P is fed in the direction of the arrow C to the press contact portion between the transfer facing roll 28 and the transfer roll 30. Then, the recording paper P on which the toner image is secondarily transferred on the surface at the press contact portion is conveyed in the direction of the arrow C as it is.

  A fixing device 32 that heats and melts the toner image on the surface of the recording paper P and fixes it on the recording paper P is disposed on the downstream side in the conveyance direction (arrow C direction) of the recording paper P. The recording paper P is a paper guide member. It is sent via 36. Further, a cleaning device 34 for removing toner remaining on the surface of the intermediate transfer body 18 is provided at a position along the downstream direction of the rotation of the intermediate transfer body 18 (arrow B direction).

  Next, the fixing device according to this embodiment will be described.

  As shown in FIGS. 2 and 3, the fixing device 32 according to the present embodiment includes an endless fixing belt 38 (first rotating body) that rotates in one direction (arrow D direction), and a peripheral surface of the fixing belt 38. The pressure roll 40 (second rotary body) that is pressed against the pressure belt 40 and rotates in one direction (the direction of arrow E) faces the outer peripheral surface opposite to the pressure contact surface between the pressure roll 40 of the fixing belt 38 and is spaced apart. And a magnetic field generation device 42 (magnetic field generation means) arranged in the same manner.

  On the inner peripheral side of the fixing belt 38, the fixing member 44 that forms a contact portion with the pressure roll 40, and the magnetic field generator 42 are opposed to each other through the fixing belt 38 and are in contact with the inner peripheral surface of the fixing belt 38. And a support member 48 that supports the fixing member 44. The heat generation control member 46 is supported by a support member 48. At both ends of the fixing belt 38, drive transmission members 50 for transmitting the rotational power are provided in order to rotationally drive the fixing belt 38.

  Further, a peeling member 52 is provided on the downstream side of the contact portion between the fixing belt 38 and the pressure roll 40 in the conveyance direction (arrow F direction) of the recording paper P. The release member 52 includes a support portion 52A having one end fixedly supported and a release sheet 52B supported by the support member 52A. The release member 52B is disposed so that the front end of the release sheet 52B approaches or contacts the fixing belt 38.

  First, the fixing belt 38 will be described. As the fixing belt 38, for example, a base material and a belt in which a heat generation layer and a surface release layer are formed on the outer peripheral surface thereof can be applied.

As the base material, a material that has strength to support the thin heat generating layer, has heat resistance, penetrates the magnetic field (magnetic flux), and does not generate heat due to the action of the magnetic field or hardly generates heat can be appropriately selected. For example, a metal belt having a thickness of 30 to 200 μm (preferably 50 to 150 μm, more preferably 100 to 150 μm) (for example, nonmagnetic stainless steel as a nonmagnetic metal, soft magnetic material and hard magnetic material (for example, Fe, Ni) , Co, or an alloy thereof such as a belt made of a metal material such as Fe—Ni—Co or an Fe—Cr—Co alloy), a resin belt having a thickness of 60 to 200 μm (for example, a polyimide belt), or the like. .

The heat generation layer is a material that easily penetrates a magnetic field (magnetic flux) and easily generates heat by the action of the magnetic field, and has a heat capacity as small as possible.
When using a general-purpose power source with a frequency of 20 kHz to 100 kHz (which can be manufactured at a low cost when using a general-purpose power source) and thinning it to a heat generation layer of 50 μm or less, non-magnetic metal with a lower specific resistance is easier to induce by electromagnetic induction than magnetic metal. Become. On the other hand, if the thickness is 50 μm or more, the magnetic metal tends to generate heat. In general, a magnetic metal has a high specific resistance and a relative permeability of several tens to several thousand, so that an eddy current at the skin depth is difficult to flow. For example, the magnetic metal iron is 9.71, and nickel is 6.84 (each x10 ⁻⁸ Ωm). On the other hand, the low resistivity nonmagnetic metal silver is 1.59, copper is 1.67, aluminum is 2.7 (each x10 ⁻⁸ Ωm) and the resistivity is small, and the relative permeability is about 1. For this reason, heat generation tends to occur when the thickness is reduced. In particular, the nonmagnetic metal tends to generate heat when the thickness is 20 μm or less. Conversely, if the nonmagnetic metal is made thicker than this, it becomes difficult to generate heat, and although the eddy current flows, the specific resistance is small, so the amount of heat generated by eddy current loss decreases.
Specific examples of the heat generating layer include a heat generating layer containing a nonmagnetic metal material having a thickness of 2 μm to 20 μm (desirably 5 to 15 μm, a total heat capacity of the heat generating region, for example, 3 J / K or less). As the nonmagnetic metal material, copper, aluminum, and silver are desirable as described above.

  Examples of the surface release layer include a fluororesin layer having a thickness of 1 μm to 30 μm (for example, PFA layer: PFA: a layer of a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether).

  The fixing belt 38 is not limited to the above configuration, and a belt in which a heat generating layer is sandwiched between two base materials, specifically, a belt in which a heat generating layer (for example, copper) is sandwiched between two stainless steel base materials, for example, is also applied. obtain. Further, an elastic layer containing silicone rubber, fluorine rubber, fluorosilicone rubber, or the like may be provided between the base material and the heat generating layer or between the heat generating layer and the surface release layer.

  Further, the fixing belt 38 may be configured to have a small heat capacity (for example, a heat capacity of 5 J / K to 60 J / K, preferably 30 J / K or less) by reducing the thickness or selecting a constituent material.

  The diameter of the fixing belt 38 may be 20 to 50 mm, for example. Further, on the inner peripheral surface of the fixing belt 38, a film that is durable against sliding coated with a fluororesin is provided (for example, a film that is durable against sliding is provided only on the fixing member 44). ), A fluororesin or the like may be coated, or a lubricant (such as silicone oil) may be applied.

  Next, the pressure roll 40 will be described. In this embodiment, an example in which the pressure roll 40 is separated from the fixing belt 38 will be described below, but the fixing belt 38 and the pressure roll 40 may always be in contact with each other. The pressure roll 40 is arranged such that both ends thereof are pressed against the fixing member 44 by a spring member (not shown) through the fixing belt 38 with, for example, a total load 294N (30 kgf). On the other hand, during preliminary heating (heating until fixing is possible), the belt is moved away from the fixing belt 38 (see FIG. 4).

  The pressure roll 40 is, for example, a roll provided with a metal cylindrical core member 40A and an elastic layer 40B (for example, a silicone rubber layer, a fluorine rubber layer, etc.) provided on the surface of the core member 40A. Can be applied. Further, the pressure roll 40 may be provided with a surface release layer (fluororesin layer) on the outermost surface as necessary.

  Next, the heat generation control member 46 will be described. The heat generation control member 46 is configured to follow the inner peripheral surface of the fixing belt 38, is in contact with the inner peripheral surface of the fixing belt 38, and is disposed so as to face the magnetic field generator 42 through the fixing belt 38.

  Further, the heat generation control member 46 is in contact with the inner peripheral surface of the fixing belt 38 in a non-pressing manner while maintaining the fixing belt 38 in a cylindrical shape by the spring member 48B of the supporting member 48 without contacting the supporting member main body 48A. Is arranged. In this embodiment, the heat generation control member 46 is in contact with the inner peripheral surface of the fixing belt 38 at 1N. Since no tension is applied to the belt, the belt shape does not change extremely even if the belt is brought into contact with the belt. If contact is made by applying a large tension, the sliding resistance increases, which may cause a reduction in the life due to wear. Further, since the sliding resistance is increased, the belt driving torque is increased, and a repeated twisting force is applied to the belt, which may cause problems such as cracking and buckling of the heat generating layer of the belt.

  The heat generation control member 46 includes a temperature-sensitive magnetic metal material having a Curie point. This Curie point is preferably in the range of not less than the set temperature of the fixing belt 38 and not more than the heat resistance temperature of the fixing belt 38. Specifically, for example, it is preferably 140 ° C. to 240 ° C., more preferably 150 ° C. ~ 230 ° C.

Further, the heat generation control member 46 itself is preferably a “non-heat generating body” that does not generate heat by the action of a magnetic field. If the non-heating element generates enough heat, when the fixing belt is heated by electromagnetic induction to the heat generation layer, magnetic flux due to electromagnetic induction acts on the “non-heating element” at the same time. If self-heating due to hysteresis loss is large, the temperature rises and unintentionally reaches the Curie temperature, and a temperature suppression effect may be manifested when not necessary. Since the “non-heating element” is a member necessary for suppressing the temperature of the fixing belt, an unintended temperature increase due to self-heating needs to be minimized. The “non-heating element” of the present embodiment is a member that has a sufficiently small self-heating with respect to the heat generation of the heat-generating layer, and makes it difficult for eddy current loss to occur when there is a problem in function development due to self-heating. For this purpose, a structure with slits or notches may be used. The slits and notches function as a blocking unit that blocks eddy current generated in the heat generation control member 46 due to electromagnetic induction from the magnetic field generator 42.

Specifically, for example, as shown in FIGS. 8 and 9, a slit 46 </ b> A is provided on the surface of the heat generation control member 46 so as to block a path through which eddy current flows. The slit 46A is formed by providing a groove on the surface along the width direction of the heat generation control member 46 (the circumferential direction of the fixing belt 38). The slits 46A are provided at predetermined intervals in the axial direction of the heat generation control member 46 (the rotational axis direction of the fixing belt 38). The slit 46A may be provided along the width direction of the heat generation control member 46 (the circumferential direction of the fixing belt 38), or may be provided inclined with respect to the width direction. By inserting a slit 46A on the surface of the heat generation control member 46, heat transfer (heat conduction) in the axial direction (rotation axis direction of the fixing belt 38) of the heat generation control member 46 can be suppressed. When the temperature of the non-sheet-passing portion 38 starts to rise, heat is transferred from the non-sheet-passing portion temperature rising region of the fixing belt to the opposing heat generation control member 46, and due to a decrease in the saturation magnetic flux density in the heat generation control member as the temperature rises, Heat generation in the heat generating layer of the fixing belt in the non-sheet passing portion region starts to be suppressed, and when the temperature rises to near the Curie point, the heat generation control member changes from magnetic to non-magnetic, and heat generation in the heat generating layer is further suppressed. At this time, if the heat in the high temperature portion of the non-sheet passing portion region in the heat generation control member 46 moves to the low temperature portion in the axial direction, the temperature in the non-sheet passing portion region decreases, and therefore heat is generated in the heat generating layer. As a result, the effect of suppressing the temperature rise in the non-sheet passing portion region of the fixing belt is reduced. The slit 46A is desirable in that it can also prevent this axial heat transfer.
Here, FIG. 8 is a schematic plan view showing the periphery of the heat generation control member of the fixing device according to another embodiment. FIG. 9 is a schematic side view showing the periphery of the heat generation control member of the fixing device according to another embodiment.

  In addition, temperature-sensitive magnetic materials are roughly classified into metal materials and oxide materials, but oxide materials (for example, ferrite, etc.) are difficult to thin (300 μm or less), are easy to break, and are difficult to handle. Further, since the heat capacity becomes large and the thermal conductivity is low, there may be a problem that the target heat generation control cannot be performed because the temperature change of the fixing belt cannot be followed with high sensitivity. In order to solve these problems, amorphous magnetic shunt steel, amorphous material, which is a metal material that can be easily and thinly molded at low cost, has good workability, flexibility, and high thermal conductivity. An alloy or the like is used. That is, it is a metal alloy material composed of Fe, Ni, Si, B, Nb, Cu, Zr, Co, Cr, V, Mn, Mo, etc., for example, Fe-Ni binary magnetic shunt steel or Fe-Ni- It is desirable to use Cr ternary shunt steel.

  The temperature-sensitive magnetic metal material is a ferromagnetic material, and when it is near the Curie point, the material becomes non-magnetic. By demagnetizing (paramagnetic) a ferromagnetic material having a relative permeability of at least several hundreds or more, the relative permeability approaches 1 and a change in magnetic flux density (magnetic field strength) occurs. A change that weakens the magnetic flux density and makes it difficult to generate heat can be given.

  Further, the skin depth of the conductor material made of metal is determined by the equation (1). When the skin depth is less than the thickness of the temperature-sensitive magnetic metal layer, the material should be made highly magnetically permeable by heat treatment, the frequency of the magnetic field generator 41 should be increased, or a material with a low specific resistance value should be selected. Can be realized. In the present embodiment, it is not essential that the skin depth is equal to or less than the thickness of the temperature-sensitive magnetic metal layer, but it is desirable that the skin depth is equal to or less than the thickness of the temperature-sensitive magnetic metal layer because the effect is further enhanced. In this case, the specific magnetic modulus of the temperature-sensitive magnetic metal material is selected according to the formula (1) according to at least the thickness of the heat generation control member 46 as long as it is less than the Curie point. In the case of a Ni-based magnetic shunt alloy, when the thickness of the heat generation control member 46 is 50 μm, the thickness is at least 5000 or more.

In the formula (1), δ: skin depth (m), ρ: specific resistance (Ωm), f: frequency (Hz), μ _r : relative permeability.

  The shape of the heat generation control member 46 has a thickness (for example, 20 to 300 μm), for example, a shape in which a portion corresponding to a range of a predetermined central angle of the cylinder (for example, 30 ° to 180 °) is cut out. There is no limit to this.

  Next, the fixing member 44 will be described. The fixing member 44 is formed of, for example, a rod-shaped member having an axial line in the axial direction (width direction) of the fixing belt 38 and resists the pressing force acting from the pressure roll 40. When the pressure roll 40 is pressed against the fixing member 44 via the fixing belt 38, the fixing belt 38 is deformed to the inner peripheral surface side. In this manner, the sheet is peeled from the fixing belt by applying the curvature of the fixing belt 38 at the downstream side of the contact portion between the pressure roll 40 and the fixing member 44 in the sheet conveying direction.

  Here, in order to obtain the sheet peeling performance, from the viewpoint of “whether the pressure roll 40 is pressed against the fixed pad 44 via the fixing belt 38, the fixing belt 38 can be elastically deformed to the inner peripheral surface side”. The fixing belt 38 is determined. Since a metal material is used for the fixing belt in this embodiment, the flexibility is determined by a layer made of a metal that determines the rigidity of the fixing belt 38, and the temperature-sensitive magnetic metal layer Determined by thickness.

  Further, whether or not the fixing belt 38 bends in the elastic deformation region to the inner side was investigated using a non-magnetic slenless hard material. As a result of evaluating the amount of deflection by applying a pressing force equal to or greater than the load applied to the fixing belt at the time of fixing, the non-magnetic slenless hard material hardly bent when the thickness of the hard material was 250 μm, but began to bend slightly at 200 μm. Sufficient bending occurred when the thickness of the non-magnetic slenless hard material was 150 μm, 125 μm, 100, and 75 μm. Accordingly, the metal layer of the fixing belt 38 is desirably 200 μm or less.

  As the material of the fixing member 44, heat-resistant resin or heat-resistant rubber is optimal. For example, PPS (polyphenylene sulfide) with glass fiber, phenol, polyimide, heat resistant resin such as liquid crystal polymer, and the like. Otherwise, aluminum is desirable as a metal with low specific heat and high thermal conductivity.

  Next, the support member 48 will be described. The support member 48 includes, for example, a support member main body 48A, a spring member 48B for supporting the heat generation control member 46, a support member main body 48A, and shafts 48C provided at both longitudinal ends of the main body 48A. .

The support member main body 48A and the shaft 48C may be made of a material having a deflection amount or less when the pressing force is received from the pressure roll 40, specifically, for example, a deflection amount of 0.5 mm or less. For example, the support member main body 48A can be made of, for example, a nonmagnetic metal material (eg, copper, aluminum, silver, nonmagnetic stainless steel). (Non-magnetic metal member). When the deflection due to the load applied to the shaft increases and the shaft rigidity becomes a problem, the structure may be made of a nonmagnetic metal and a member having a material having a Young's modulus such that the deflection is reduced. The thickness of the metal may be at least the skin depth of the formula (1).
When a magnetic metal material is used, the surface on the magnetic field generator 42 side is shielded with a low-resistance nonmagnetic metal (copper, aluminum, silver) having a skin depth or more, and the magnetic metal material is covered with the magnetic field generator. What is necessary is just to make it the structure where the magnetic flux from 41 does not reach. When magnetic flux reaches the magnetic metal material, Joule heat generation due to eddy current increases, resulting in an increase in useless loss.

  On the other hand, the spring member 48B is a connecting member between the heat generation control member 46 and the support member main body 48A, and directly supports the heat generation control member 46. The spring member 48B connects the heat generation control member 46 at both ends in the width direction.

Further, the spring member 48B is configured by, for example, a curved leaf spring (for example, a leaf spring made of metal, various elastomers, or the like). The heat generation control member 46 is supported by the spring member 48B, and even if the fixing belt 38 rotates eccentrically and the fixing belt 38 is displaced in the radial direction, the fixing belt 38 follows the displacement. The contact state is maintained on the inner peripheral surface of the.
Further, the heat generation control member 46 may also serve as the spring member 48B. In that case, the spring member and the heat generation control member may be formed integrally.

  Next, the drive transmission member 50 will be described. The drive transmission member 50 is a member for transmitting driving power for self-rotating the fixing belt 38. For example, the drive transmission member 50 is a flange portion 50A fitted inside the end portion of the fixing belt 38, and a cylinder having irregularities on the outer peripheral surface. And a gear portion 50B. The drive transmission member 50 can be made of, for example, a metal material, a resin material, or the like.

  The drive transmission member 50 is supported by the end portion of the fixing belt 38 by fitting the flange portion 50 </ b> A inside the end portion of the fixing belt 38. The gear portion 50B of the drive transmission member 50 is rotationally driven by a motor or the like (not shown), and the rotational power is transmitted to the fixing belt 38 so that the fixing belt 38 is self-rotated.

  The drive transmission members 50 are provided at both ends of the fixing belt 38 in the axial direction. However, the drive transmission members 50 are not limited to this, and may be provided only at one end of the fixing belt 38 in the axial direction. The drive transmission member 50 is supported by the end portion of the fixing belt 38 with the flange portion 50A fitted inside the end portion of the fixing belt 38. However, the present invention is not limited to this, and the fixing belt is provided inside the flange portion 50A. The drive transmission member 50 may be supported on the end portion of the fixing belt 38 by fitting the end portion thereof.

Next, the magnetic field generator 42 will be described. The magnetic field generator 42 is configured to follow the outer peripheral surface of the fixing belt 38, and is opposed to the heat generation control member 46 via the fixing belt 38, and a gap between the outer peripheral surface of the fixing belt 38 is, for example, 1 to 3 mm. It is arranged to be.
Further, in the magnetic field generator 42, an exciting coil (magnetic field generating means) 42 </ b> A that is wound a plurality of times is arranged along the axial direction of the fixing belt 38.

An excitation circuit (not shown) that supplies an alternating current to the excitation coil 42A is connected to the excitation coil 42A. On the surface of the exciting coil 42A, a magnetic member 42B is disposed so as to extend along the length direction (the axial direction of the fixing belt 38). The magnetic member 42B is formed by inserting the exciting coil 42A and the fixing belt 38 with the heat generation control member 46, which is a magnetic material, and can form a magnetic path to suppress the leakage magnetic field, improve the magnetic coupling, and improve the power factor. It is like that. The magnetic member 42B is preferably a ferromagnetic material, and for example, a ferromagnetic metal material typified by iron, nickel, chromium, manganese, or an alloy thereof, or an oxide thereof may be used. Loss and hysteresis loss may be reduced. When the eddy current loss is large, a slit or notch may be formed so that the eddy current does not flow easily, or the thin plate shape may be laminated like a silicon steel plate.
For example, examples of the material having small eddy current loss and hysteresis loss include soft ferrite and oxide-based soft magnetic metal materials.

  The output of the magnetic field generator 42 is generated, for example, within a range in which the magnetic flux (magnetic field) generates heat while penetrating the heat generating layer of the fixing belt 38 and is less than the Curie point so that the magnetic flux (magnetic field) hardly penetrates the heat generation control member 46 and does not generate heat. Is called.

  The magnetic field generator 42 may be provided on the inner peripheral surface side of the fixing belt 38 with a predetermined gap. In this case, the heat generation control member 46 is provided in contact with the outer peripheral surface of the fixing belt 38.

  Hereinafter, the operation of the image forming apparatus 100 according to the present embodiment will be described.

  First, the surface of the photosensitive drum 10 is charged by the charging device 12, and then the image light L is irradiated from the exposure device 14 to form a latent image due to the difference in electrostatic potential on the surface of the photosensitive drum 10. Then, the rotation of the photosensitive drum 10 in the direction of arrow A moves to a position facing one developing device 16A of the developing device 16, and the toner of the first color is transferred from the developing device 16A to the surface of the photosensitive drum 10. A toner image is formed. The toner image is conveyed to a position facing the intermediate transfer member 18 by the rotation of the photosensitive drum 10 in the direction of arrow A, and is electrostatically primarily transferred onto the surface of the intermediate transfer member 18 by the transfer device 24.

  On the other hand, the toner remaining on the surface of the photosensitive drum 10 after the primary transfer is removed by the cleaning device 20, and the cleaned surface of the photosensitive drum 10 is potentialally initialized by the charge eliminating exposure device 22, and again with the charging device 12. Move to the opposite position.

  Thereafter, the three developing devices 16B, 16C, and 16D of the developing device 16 sequentially move to positions facing the photosensitive drum 10, and similarly, the second, third, and fourth color toner images are sequentially formed, and the four colors are changed. When they overlap, they are transferred onto the surface of the intermediate transfer member 18 in a lump.

  The toner image superimposed on the intermediate transfer body 18 is conveyed to a position where the transfer roll 30 and the transfer counter roll 28 face each other by the circular movement of the intermediate transfer body 18 in the direction of arrow B, and is fed to the recording paper P that has been fed. Touched. A transfer bias voltage is applied between the transfer roll 30 and the intermediate transfer member 18, and the toner image is secondarily transferred onto the surface of the recording paper P.

  The recording paper P holding the unfixed toner image is conveyed to the fixing device 32 via the paper guide member 36.

Next, the operation of the fixing device 32 according to the present embodiment will be described.
First, in the fixing device 32, for example, at the same time when the toner image forming operation in the image forming device 100 is started (of course, there may be a time lag. The same applies hereinafter), and the fixing belt 38 and the pressure roll. The drive transmission member 50 is rotationally driven by a motor (not shown) while being separated from the motor 40 (see FIG. 4), and accordingly, the fixing belt 38 is rotationally driven in the direction of arrow D at a peripheral speed of 200 mm / sec, for example.

  The fixing belt 38 is driven to rotate, and an alternating current is supplied from an excitation circuit (not shown) to the excitation coil 42A included in the magnetic field generator 42. When an alternating current is supplied to the exciting coil 42A, a magnetic flux (magnetic field) repeatedly generates and disappears around the exciting coil 42A. When this magnetic flux (magnetic field) crosses the heat generating layer of the fixing belt 38, an eddy current is generated in the heat generating layer so that a magnetic field that hinders the change of the magnetic field is generated, and the skin resistance of the heat generating layer and the current flowing through the heat generating layer Heat is generated in proportion to the square (see FIG. 5A). Here, the two-dot chain line in FIG. 5 indicates the main magnetic flux.

  Thereby, the fixing belt 38 is heated to a set temperature (for example, 150 ° C.) in about 10 seconds by the heat generation layer.

  Next, in a state where the pressure roll 40 is pressed against the fixing belt 38, the recording paper P sent to the fixing device is sent to a contact portion between the fixing belt 38 and the pressure roll 40, and is generated by a heating element. Heated and pressed by the heated fixing belt 38 and the pressure roll 40, the toner image is melt-pressed on the surface of the recording paper P, and the toner image is fixed on the surface of the recording paper P.

  Here, when fixing with the fixing belt 38 and the pressure roll 40, if the recording paper P having a small size smaller than the fixing area width (axial length) of the fixing belt 38 is continuously fixed, the passing through the fixing belt 38 is performed. Heat is consumed in the paper portion, whereas heat is not consumed in the non-sheet passing portion. For this reason, the temperature rises at the non-sheet passing portion of the fixing belt 38.

  When the temperature of the non-sheet passing portion of the fixing belt 38 is near the Curie point of the temperature-sensitive magnetic metal material constituting the heat generating control member 46, the heat generating control member 46 that overlaps (is in contact with) the non-sheet passing portion of the fixing belt 38. This region is demagnetized. As a result, a difference in magnetic flux density (magnetic field strength) occurs between the paper passing area, which is a magnetically maintained area, and the non-magnetic (paramagnetic) non-passing area. Less heat is generated in the heat generating layer. Thus, the heat generation control member 46 controls the heat generation of the heat generation layer of the fixing belt 38.

  Further, when the heat generation control member 46 is demagnetized (relative permeability approaches 1), the magnetic flux (magnetic field) easily penetrates as can be seen from the equation (1). At this time, as shown in FIG. 5B, the supporting member main body 48A made of a nonmagnetic metal material (silver, copper, aluminum, etc.) having a low specific resistance value (having a thickness equal to or greater than the skin depth) When present, magnetic flux (magnetic field) mainly causes eddy currents to flow through the support member main body 48 </ b> A, and heat generation due to eddy current loss flowing through the heat generating layer of the fixing belt 38 is further suppressed. Further, the magnetic flux (magnetic field) penetrating the heat generation control member 46 reaches the support member main body 48 </ b> A made of a nonmagnetic metal material and returns to the magnetic field generator 42. In addition, the support member main body 48 </ b> A is provided in contact with the heat generation control member 46 together with the fixing belt 38, so that heat energy is not taken away from the fixing belt 38.

Further, the support material main body 48A may be constituted by a structure of a low specific resistance nonmagnetic metal member 48D made of aluminum, copper or silver and a support 48F. For example, as shown in FIG. 7, a configuration in which a curved plate-like nonmagnetic metal member 48D is also provided so as to be interposed between the heat generation control member 46 and the support 48F. The low specific resistance nonmagnetic metal member 48D is a member for suppressing heat generation due to eddy current loss flowing in the heat generating layer of the fixing belt 38 as described above, and the support 48F supports the load from the pressure roll 40. It is desirable to have a rigidity with little bending. Further, when the nonmagnetic metal member 48D is brought into contact with the heat generation control member 46 together with the fixing belt 38, the main heat transfer between the fixing belt 38 and the nonmagnetic metal member 48D is the heat via the heat generation control member 46. It becomes conduction and the amount of heat transfer per unit time increases. As a result, since the amount of heat transfer per unit time in the axial direction increases, a temperature rise suppression effect can be obtained by dispersing the temperature rise of the non-sheet passing portion of the fixing belt 38 in the axial direction.
Here, FIG. 7 is a schematic sectional view showing the periphery of the heat generation control member and the support member of the fixing device according to another embodiment.

  On the other hand, at the time of fixing by the fixing belt 38 and the pressure roll 40, the fixing belt 38 is brought into non-pressing contact with the heat generation control member 46 having a shape following the shape of the inner peripheral surface thereof, rotates while being supported, and slides. While suppressing the dynamic resistance, it suppresses the vibration due to the fixing member mark of the fixing belt and the electromagnetic force (the repulsive force between the magnetic field from the coil and the reaction magnetic field created by the eddy current flowing in the heat generating layer in the direction to prevent it) Force is applied in the direction away from the coil), the distance between the belt and the coil is kept stable, and the belt shape is maintained and fixing is performed.

  When the recording paper P is sent out from the contact portion between the fixing belt 38 and the pressure roll 40, the recording paper P tries to go straight in the feeding direction due to its rigidity, and the leading end is peeled off from the fixing belt 38 that is bent. The release member 52 (release sheet 52B) enters between the leading edge of the recording paper P and the fixing belt 38, and the recording paper P is released from the surface of the fixing belt 38.

  As described above, the toner image is formed on the recording paper P, and fixing is performed.

  In the present embodiment, the fixing belt 38 is in contact with the heat generation control member 46 having a shape following the shape of the inner peripheral surface thereof in a non-pressing manner and is rotated while being supported. Without being limited thereto, as shown in FIG. 6, the fixing belt 38 and the heat generation control member may be disposed so as not to contact each other. In this embodiment, the heat energy of the fixing belt 38 is prevented from moving to the heat generation control member 46.

(Test example)
Hereinafter, test examples of the fixing device according to the embodiment will be described.

-Test Example 1
First, the following evaluation was performed using the fixing device according to the above-described embodiment (see FIGS. 1, 2, and 6). Each member used the following. Also,

Fixing belt: 10 μm thick copper layer (heating layer) and 30 μm thick PFA layer (PFA: tetrafluoroethylene and perfluoro) on the outer peripheral surface of a polyimide resin base material having a diameter of 30 mm, a width of 370 mm, and a thickness of 60 μm A belt constructed by sequentially laminating an alkyl vinyl ether copolymer) (heat-resistant temperature of about 240 ° C.)
Pressurizing roll: A pressurizing roll having an outer diameter of 28 mm and a length of 355 mm is a roll having a structure in which a 5 mm sponge elastic layer and a 30 μm PFA layer as a surface release layer are sequentially laminated on a slender core mandrel having a diameter of 18 mm.
Heat generation control member: Curved plate shape obtained by cutting a portion corresponding to a central angle of 160 ° of a cylinder having a thickness of 150 μm, a length of 340 mm, and a diameter of 30 mm, and a maximum relative permeability of 10,000 or more (ratio of processing increase) A hard material having a magnetic permeability of about 400 was softened by heat treatment by annealing, and the material was made high in permeability). The material was composed of Fe-Ni alloy MS-220 made by Neomax Material at a Curie temperature of 215 to 230 ° C. Heat generation control member.
・ Distance between fixing belt and heat generation control member:
In the configuration of FIG. 2, the contact is made, but in the configuration of FIG. In the configuration of FIG. 6, the distance between the fixing belt and the heat generation control member is approximately 1 mm. A circular arc having a radius of 14 mm (angle corresponding to 160 °) is non-contacted with the fixing belt so as to be approximately concentric.
In the case of the configuration of FIG. 6, in this test example, the warm-up time (rise time) is 6 to 8 seconds and the start-up preparation can be completed in a very short time. Can be provided. The warm-up time in the configuration of FIG. 2 requires 11 to 13 seconds.
Support member body: Support member body made of non-magnetic metal aluminum

-Evaluation-
In each of the configurations of FIGS. 2 and 6, recording paper (paper of size B5 is used under the conditions of a control temperature of 160 to 170 ° C. and a process speed of 170 mm / s within the output 1100 W to 400 W of the apparatus that generates the magnetic field. The paper is fed with one short side of the paper as the leading edge), basis weight 98 gsm: Fuji Xerox JD paper), the image is continuously fixed 1000 sheets, and the temperature of the fixing belt passing part and non-passing part is set. Each was measured.

  As a result, the temperature at the sheet passing portion of the fixing belt was 160 to 170 ° C., whereas the temperature at the non-sheet passing portion was suppressed to 230 ° C. or less.

-Comparative Example 1-
Evaluation was performed in the same manner as in Test Example 1 except that no temperature control member was provided.

  As a result, the temperature of the non-sheet passing portion exceeded 235 ° C., which is the heat resistance temperature of the fixing belt, before the image was fixed to 100 sheets continuously.

  Therefore, as a temperature uniformizing means for suppressing the temperature rise in the non-sheet passing portion, a heat pipe having a diameter of φ12.7 mm was placed in contact with the pressure roll and evaluated in the same manner. About 400 sheets, the temperature of the non-sheet passing portion reached 235 ° C. which is the heat resistance temperature of the fixing belt.

  From the results of the above test examples, in this test example, even when a recording medium of various sizes such as a small size is used, the temperature rise of the non-sheet passing portion in the fixing belt is suppressed and overheating is performed. It can be seen that is prevented.

1 is a schematic configuration diagram illustrating an image forming apparatus according to an exemplary embodiment. 1 is a schematic cross-sectional view illustrating a fixing device according to an exemplary embodiment. 1 is a schematic cross-sectional view illustrating a fixing device according to an exemplary embodiment. FIG. 3 is a schematic cross-sectional view illustrating a state in which the fixing belt and the pressure roll are separated from each other in the fixing device according to the exemplary embodiment. FIG. 3 is a schematic cross-sectional view schematically showing a main magnet penetrating a fixing belt in the fixing device according to the present embodiment. It is a schematic sectional drawing which shows the fixing device which concerns on this other embodiment. FIG. 10 is a schematic cross-sectional view showing the periphery of a heat generation control member and a support member of a fixing device according to another embodiment. FIG. 6 is a schematic plan view showing the vicinity of a heat generation control member of a fixing device according to another embodiment. FIG. 6 is a schematic side view showing the vicinity of a heat generation control member of a fixing device according to another embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Photosensitive drum 12 Charging apparatus 14 Exposure apparatus 16 Development apparatus 18 Intermediate transfer body 20 Cleaning apparatus 22 Static elimination exposure apparatus 24 Transfer apparatus 26A, 26B Support roll 28 Transfer opposing roll 30 Transfer roll 32 Fixing apparatus 34 Cleaning apparatus 36 Paper guide member 38 Fixing belt 40 Pressure roll 42 Magnetic field generator 44 Fixing member 46 Heat generation control member 48 Support member 48A Support member main body 48B Spring member 48C Shaft 48D Nonmagnetic metal member 50 Drive transmission member 52 Peeling member 100 Image forming apparatus P Recording paper

Claims (15)

A cylindrical first rotating body having a heat generating layer that generates heat by the action of a magnetic field;
A second rotating body in contact with the first rotating body;
A magnetic field generating means arranged to have a predetermined gap with respect to an inner peripheral surface or an outer peripheral surface of the first rotating body and generating the magnetic field;
A heat generation control member that is disposed to face the magnetic field generation means via the first rotating body, includes a temperature-sensitive magnetic material having a Curie point, and controls heat generation of the heat generation layer. A fixing device characterized.   The fixing device according to claim 1, wherein the Curie point is in a range not less than a set temperature of the first rotating body and not more than a heat resistant temperature of the first rotating body.   The first rotating body is disposed through the first rotating body and the heat generation control member and opposed to the heat generation control member so as to face the magnetic field generating means, and includes a nonmagnetic metal material. The fixing device according to claim 1, comprising a nonmagnetic metal member.   The first rotating body and the heat generation control member are arranged in contact with each other through the first rotation body and the heat generation control member inside the first rotation body, and the magnetic field generation means is in contact with the heat generation control member. The fixing device according to claim 1, further comprising a nonmagnetic metal member that is disposed so as to face the nonmagnetic metal material.   The fixing device according to claim 1, wherein the heat generating layer is made of a nonmagnetic metal.   The fixing device according to claim 1, further comprising: a blocking unit configured to block an eddy current generated in the heat generation control member by an electromagnetic induction action from the magnetic field generation unit.   The fixing device according to claim 6, wherein the blocking unit is a slit or a notch provided in the heat generation control member.   The fixing device according to claim 1, further comprising: a drive transmission member that is provided on at least one of both axial ends of the first rotating body and transmits a rotational drive to the first rotating body.   The fixing device according to claim 1, wherein the heat generation control member is in contact with the first rotating body.   The fixing device according to claim 1, wherein the heat generation control member is in non-pressing contact with the first rotating body.   The fixing device according to claim 1, wherein the heat generation control member is not in contact with the first rotating body.   The fixing device according to claim 1, wherein the heat generation control member is a non-heat generating member.   The fixing device according to claim 1, wherein the temperature-sensitive magnetic material is a metal material.   The fixing device according to claim 1, wherein a contact portion of the first rotating body is elastically deformed toward an inner peripheral surface when contacting the second rotating body. A latent image carrier,
A latent image forming means for forming a latent image on the surface of the latent image holding member;
Developing means for developing the latent image into an image using an electrophotographic developer;
Transfer means for transferring the developed image to a transfer medium;
Fixing means for fixing the image on the transfer medium;
With
The image forming apparatus, wherein the fixing unit is the fixing device according to claim 1.

Images