JP2009025827A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device having improved heat generation efficiency by effectively using input electric power, even when using no core in a magnetic field generating means. <P>SOLUTION: The fixing device includes: a magnetic field generating means formed into a coil form from a conductive wire; a heating means composed of at least a conductive body having the form of a hollow cylinder or comprising an endless belt, held so as to be freely rotated, and heated by a magnetic field generated by a magnetic field generating means; a press-contact means disposed in press-contact with the heating means; and a temperature measuring means disposed in the heating means and measuring the temperature of the heating means. The magnetic field generating means is disposed outside the heating means. The temperature measuring means is disposed between the heat generating part of the heating means and the nip area in the rotating direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fixing device mounted on an image forming apparatus such as an electrostatic copying machine or a laser printer.

  2. Description of the Related Art Conventionally, a heating roller type fixing device includes a heating roller that heats a sheet carrying a developer image made of a powder developer, and a pressure roller that conveys the sheet while applying pressure. When the sheet passes through a fixing point which is a pressure contact portion (nip portion), the developer on the sheet is fused and pressure-fixed.

  As a heating source of the heating roller described above, a halogen lamp or the like is used and installed inside a metal roller. This roller is heated by radiant heat, and an elastic roller is pressed against the object to be fixed under pressure. In general, a system in which these rollers are rotated to pass an object to be fixed as described above, and various other systems such as a flash heating system, an oven heating system, and a hot plate heating system have been put into practical use.

  In recent years, a heating type fixing device using a cylindrical heat-resistant film material has been put into practical use. This fixing device has a heating body and a heat-resistant film that moves in close contact with the heating body, and a material to be heated is brought into close contact with the heating body through the film and moved together with the film to thereby heat the heating body. Energy is imparted to the object to be heated through a film.

  As fixing devices using the induction heating method, there are JP-A-9-258586, JP-A-8-76620, and the like.

  Japanese Patent Application Laid-Open No. 9-258586 is a system in which a coil is wound around a core provided along the rotation shaft of a fixing roller and an eddy current is passed through the roller to heat it.

Japanese Patent Laid-Open No. 8-76620 is an apparatus for fixing a recording medium in which a conductive film is heated and adhered by a magnetic field generating means, and a heating belt is sandwiched between a member that assembles the magnetic field generating means and a heating roller. Not forming a nip.
JP-A-9-258586 JP-A-8-76620

  However, the electromagnetic induction heating apparatus as described above has the following problems. That is, although a heating coil is used as the magnetic field generating means, the induction heating coil uses a core material in order to concentrate the magnetic flux at the fixing nip portion and its periphery. The core material is composed of iron or ferrite material. When iron is used as the core material, an eddy current is generated in the core material itself, so that the iron loss of the core material increases, the core generates heat, and the efficiency as a heating means is reduced. . In addition, since the core material generates heat, the temperature of the coil wound around the core material is increased, resulting in a problem that the heat resistance temperature of the coil is exceeded. In order to avoid such a problem, it is solved by using ferrite as a core material. That is, in the case of ferrite, it is possible to suppress the generation of eddy current in the core itself.

  However, when ferrite is used as the core material, if the roller temperature is maintained at a fixable temperature with the core inside the roller (about 180 ° C.), the Curie point temperature of the ferrite material is reached and the magnetic flux is reduced. There was a problem that it was impossible to concentrate.

  Accordingly, the present invention solves the above problems in a fixing device using an induction heating method, and can provide a fixing device that can effectively use input power and improve the heat generation efficiency of the device without using a core as a magnetic field generating means. provide.

  The fixing device according to the present invention includes a magnetic field generating means formed in a coil shape with a conductive wire and a hollow cylindrical or endless belt, and is rotatably supported by a magnetic field generated by the magnetic field generating means. The magnetic field comprising: a heating means configured to be at least composed of a conductor that generates heat; a pressure contact means that is in pressure contact with the heating means; and a temperature measurement means that is disposed inside the heating means and measures the temperature of the heating means. The generating means is arranged outside the heating means, and the temperature measuring means is arranged between the heating portion of the heating means and the nip region in the rotation direction.

  The fixing device according to the present invention includes a magnetic field generating means formed in a coil shape with a conductive wire and a hollow cylindrical or endless belt, and is rotatably supported by a magnetic field generated by the magnetic field generating means. The magnetic field comprising: a heating means configured to be at least composed of a conductor that generates heat; a pressure contact means that is in pressure contact with the heating means; and a temperature measurement means that is disposed inside the heating means and measures the temperature of the heating means. The generating means is arranged outside the heating means, and there are at least two temperature measuring means, one of which measures the temperature of the nip area, and the rest is the nip area from the heat generating portion of the heating means toward the rotation direction. It is characterized by being arranged between.

  According to the fixing device of the present invention, by not using the core, there is no core loss of the core, and by setting the heat generating magnetic field generating means at the optimum position, heat can be efficiently supplied to the heating roller. Can do. In addition, accurate temperature control can be performed by two thermistors, the heat capacity of the heating roller can be reduced, the start-up can be accelerated, and the speed of the fixing device can be increased and the energy can be saved.

  Hereinafter, a first embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a simplified diagram showing the overall configuration of the fixing device. The fixing device 1 includes a heating roller 2 (φ40 mm) and a pressure roller 3 (φ40). The pressure roller 3 is pressed against the heating roller 2 by a pressure mechanism (not shown) and is maintained to have a constant nip width. The heating roller 2 is a drive motor (not shown). The pressure roller 3 is driven to rotate in the direction of the arrow.

  On the circumference of the heating roller 2, a peeling claw 4 for peeling the paper P from the heating roller 3 on the downstream side in the rotational direction from the contact position (nip portion) between the heating roller 2 and the pressure roller 3, and the heating roller 2. A cleaning member 5 for removing dust such as offset toner and paper waste, a release agent application device 6 for applying an offset prevention release agent, and a thermistor 7 for detecting the temperature of the heating roller 2 are provided. .

The heating roller 2 is made of iron and has a thickness of 0.6 mm. The roller surface is coated with a release layer such as Teflon.
The pressure roller 3 is configured by covering the cored bar with silicon rubber, fluorine rubber or the like. When the paper P passes through a fixing point which is a pressure contact portion (nip portion) between the heating roller 2 and the pressure roller 3, the developer on the paper is fixed by fusing and pressing.

  As the heating principle, an induction heating device (magnetic field generating means) 9 is used. The induction heating device 9 includes an exciting coil 10 and is accommodated in the heating roller 2. The exciting coil 10 uses a linear 0.5 mm copper wire, and is configured as a litz wire in which a plurality of wires insulated from each other are bundled. By using a litz wire, the wire diameter can be made smaller than the penetration depth, and an alternating current can be effectively passed. In this embodiment, 15 pieces of φ0.5 mm are bundled. A heat-resistant polyimide amide is used for the coated wire of the coil.

  Magnetic flux and eddy current are generated in the heating roller so as to prevent changes in the magnetic field by magnetic flux generated by a high-frequency current applied to the exciting coil 10 from an excitation circuit (inverter circuit) (not shown). Heat is generated by this eddy current and heating roller resistance.

  Depending on the shape of the exciting coil 10, the vicinity of the nip of the heating roller 2 is heated. In this embodiment, a high frequency current having a frequency of 20 kHz and an output of 900 W was passed through the coil.

The surface temperature of the heating roller 2 was set to 180 ° C. The surface temperature is detected by the thermistor 7, and the heating roller 2 is heated by feedback control.
At this time, the heating roller 2 and the pressure roller 3 are rotating in order to make the temperature distribution of the entire roller uniform. A certain amount of heat is given to the entire roller surface by rotating the roller. When the surface temperature of the heating roller reaches 180 ° C., the copying operation starts, and the sheet P passes through a fixing point where the sheet P is a pressure contact portion (nip portion) between the heating roller 2 and the pressure roller 3. The above developer is fixed by fusion bonding. The current to the inverter circuit is supplied through a thermostat 8 which is a temperature fuse pressed against the surface of the heating roller. The thermostat 8 cuts off the current supplied to the circuit when the surface temperature of the heating roller 2 reaches a preset abnormal temperature.

  Next, the positional relationship between the induction heating device 9 and the heating roller 2 is shown in FIG. In the present embodiment, 15 wire rods having a wire diameter of 0.5 mm are bundled to form a litz wire, and the litz wire is formed as an excitation coil 10 having a total of 12 turns along the roller shape. The coil is wound in two layers along the roller circumference. The exciting coil is manufactured by using a coil winding machine, and is immersed in a heat-resistant impregnating agent and hardened to maintain the shape. The roller is fixed in a fixed distance from the roller by a holding member (not shown). In this embodiment, it is held by a holding member, but may be fixed using a bobbin or the like.

Next, FIG. 3 shows the relationship between the distance from the center point of the current flowing through the coil to the heating roller 2 and the distance between the center points of the current. The hatched portion shown in FIG. 3 shows a cross section of the coil area, and the center point of the current flowing in one direction (which may be considered as the center of gravity of the area) is at positions a and b, respectively. Let t be the shortest distance from the center points a and b to the heating roller 2. This is the length in the normal direction connecting the center points a and b and the heating roller 2. Also, let L be the length of the arc ab of the circle passing through the center points a and b from the same circle center as the heating roller 2. In order to efficiently heat the roller using the air-core coil, in this embodiment, the relationship between t and L is 2 × t ≦ L, and in order to further increase the heat generation efficiency to 90% or more,
3 × t ≦ L
The coil is arranged so that It has been experimentally clarified that the arrangement as described above reduces the components in which magnetic fluxes generated by the coils cancel each other, and generates heat efficiently. FIG. 4 shows an example in which the exciting coil 10 is arranged outside the heating roller 2. In this case, as in FIG. 3, the distance from the center point of the current flowing in one direction of the coil region cross section (which may be considered as the center of gravity of the region) to the outer peripheral surface of the heating roller is t, and the arc between the center points is When the length is L, in order to efficiently heat the roller, the relationship between t and L is set to 2 × t ≦ L, and the heat generation saturation amount is set to 90% or more.
3 × t ≦ L
The coil is arranged so that

  Conventionally, as shown in FIG. 5, the distance between the distance M and t in contact with the core material, not the distance from the current center of the coil, is related to heat generation. It has been found that the current center distance L is more important than the distance M in the coil.

  In FIG. 6, the amount of heat generated by the roller when the distance between t and L was changed was measured using a circuit actually driven at 20 kHz. Since the amount of current passed through one turn of the coil is constant at 50A peak, the heat generation amount decreases as the distance t from the roller increases. The amount of heat generation increases as L increases with the value of t. In particular, when L is small, the amount of heat generation decreases rapidly. FIG. 7 shows the results as a table. As can be seen here, the ratio of the calorific value of each t to the saturation value is less than 80%, x is 80-90%, and 90% or more is o. In this result, it is necessary to satisfy 2 × t ≦ L in order to obtain an efficiency of 80% or more of the saturation amount, and it is necessary to satisfy 3 × t ≦ L in order to obtain an efficiency of 90% or more. I understand that. Further, considering that the space occupied by the coil is made as small as possible, it was found from experimental values that 3 × t ≦ L. In this example, a calorific value of 900 W could be obtained.

  Next, a second embodiment according to the present invention will be described. Since the outline of the fixing device is the same as that of the first embodiment, the description thereof is omitted. FIG. 8 shows the positional relationship between the induction heating coil 20 and the heating roller 2. In this embodiment, 15 wire rods having a wire diameter of 0.5 mm are bundled to form a litz wire. The litz wire is used as an exciting coil having a total of 10 turns along the roller shape. In this embodiment, the coils are arranged so that the distances between the current centers of all the litz wires and the rollers are constant, as indicated by arrows, with the shortest distances between the current centers of the respective litz wires and the rollers.

  In a coil using a conventional core, magnetic flux is generated through the core, so that it is not affected by the arrangement of the coil. However, in the case of an air-core coil, the heat generation distribution changes depending on the shape and position of the coil. Moreover, as shown in FIG. 9, since the coil is composed of a litz wire, it is not necessarily a perfect circle and often deforms. For this reason, even if the distance between the outer shape of the coil and the roller is defined, the magnetic flux applied to the roller differs in the distance between the current center in the litz wire and the roller, so the magnetic flux changes and the heat generation distribution changes. . Therefore, as in the present embodiment, the distance between the current center in the litz wire and the roller is configured to be constant.

  By disposing the air-core coil as described above, the heat generation distribution on the roller surface can be made uniform. Further, by making the distance between the current center of all the litz wires and the roller constant, the magnetic flux can be efficiently applied to the roller. In this example, it was possible to generate heat efficiently without a core.

  Next, FIG. 10 shows a modification of the second embodiment. FIG. 10 is a simplified diagram showing the overall configuration of the fixing device. The fixing device has a fixing belt 30 formed of a conductor. In addition, a pressure roller 32 (φ30 mm) for forming a nip portion is provided on the side facing the air-core coil 31 via the fixing belt 30, and presses the fixing belt with a constant pressure. By controlling this pressing force, the nip length can be controlled.

  The fixing belt 30 is made of a conductor. As the conductor, a ferromagnetic metal such as nickel, iron, or stainless steel is used. A release layer (for example, fluororesin, silicone resin, silicone rubber) may be provided on the conductor surface layer. In this embodiment, a fluororesin coat is applied to an 80 μm nickel electroformed belt. In order to maintain the shape of the fixing belt 30, a holder 33 is provided on the upper side of the air-core coil.

  The pressure roller 31 is given a driving force by a motor (not shown) and is rotated in the direction of the arrow. Along with this rotation, the fixing belt 30 is driven by the frictional force with the pressure roller 31. When the paper P passes through a fixing point that is a pressure contact portion (nip portion) between the fixing belt 30 and the pressure roller 31, the developer on the paper is fused and pressed to be fixed. The pressure roller 31 may be a rigid roller or a roller provided with an elastic layer. In this embodiment, an elastic roller is used.

  In the second embodiment, since the conductor has a roller shape, the lines connecting the current centers of the litz wires are concentric with the cylindrical surface constituting the outer shape of the roller. This is because the distance between the center of the litz wire and the roller is kept constant. On the other hand, in this modified example, since a belt is used as the conductor, since the belt is not cylindrical in the nip portion, the distance between the center of the litz wire and the conductive member is constant. The line connecting the line centers deviates from the concentric circle on the cylindrical surface in the region near the nip and is on the inner side of the concentric circle. In other words, even if the line connecting the centers of the litz wires is not necessarily concentric, if the distance from the conductive member is kept constant, a constant amount of heat can be applied and good fixing performance can be obtained.

Furthermore, when the distance between the current center of the litz wire and the roller is kept constant (the distance is t), and the distance L between the current centers of the region flowing in one direction of the coil (distance L along the circumference), At least 2 × t ≦ L, and the optimum value is
3 × t ≦ L
It is also shown in the first embodiment that the calorific value is further increased. Also in this embodiment, the above relational expression is satisfied.

  Further, in both the first and second embodiments, the exciting coils 10 and 20 and the air-core coil 31 are arranged inside the heating roller 2, but the same effect can be obtained even if arranged outside the heating roller 2. Needless to say.

Next, a third embodiment according to the present invention will be described. FIG. 11 is a simplified diagram showing the overall configuration of the fixing device. The fixing device 40 includes a heating roller 2 (φ40 mm) and a pressure roller 3 (φ40 mm). The pressure roller 3 is pressed against the heating roller 2 by a pressure mechanism (not shown) and is maintained to have a constant nip width. The heating roller 2 is a drive motor (not shown). The pressure roller 3 is driven to rotate in the direction of the arrow.
The heating roller 2 is made of iron and has a thickness of 0.6 mm. The roller surface is coated with a release layer such as Teflon.

  The pressure roller 3 is configured by covering the cored bar with silicon rubber, fluorine rubber or the like. When the paper P passes through a fixing point which is a pressure contact portion (nip portion) between the heating roller 2 and the pressure roller 3, the developer on the paper is fixed by fusing and pressing.

  As a heating principle, an induction heating device (magnetic field generating means) 41 is used. The induction heating device 41 includes an exciting coil 42 and is disposed outside the heating roller 2. The exciting coil 42 uses a linear 0.5 mm copper wire, and is configured as a litz wire in which a plurality of wires insulated from each other are bundled. By using a litz wire, the wire diameter can be made smaller than the penetration depth, and an alternating current can be effectively passed. In this embodiment, 15 pieces of φ0.5 mm are bundled. A heat-resistant polyimide amide is used for the coated wire of the coil. Further, the outer side of the heating roller 2 is wound 12 turns along the circumference. The exciting coil 42 is formed of an air-core coil that does not use a core or the like that concentrates magnetic flux. In this embodiment, an air-core coil is used, but the coil may be formed using a core material as shown in FIG.

  The reason why the exciting coil 42 is arranged on the outside is that it is easier and more accurate than the arrangement on the inside in the assembly process. Moreover, if it arrange | positions inside the heating roller 2, the radiant heat from the heating roller 2 will remain inside, and the temperature rise of the exciting coil 42 will be promoted. Therefore, it is necessary to reduce the current flowing through the coil. If the exciting coil 42 is arranged outside as in the present embodiment, the temperature rise of the coil can be suppressed, the life of the exciting coil 42 is extended, and the heat resistance temperature of the insulating coating of the exciting coil 42 is also increased compared to the case where it is arranged inside. Can be handled with low materials.

  In addition, when a coil wound around the core 43 is used as the magnetic field generating means as shown in FIG. 12, if it is disposed inside the heating roller, the core temperature rises due to the radiant heat in the roller, and exceeds the Curie point temperature of the core. There was a phenomenon that the characteristics dropped significantly. When placed on the outside, the temperature of the core material does not exceed the Curie point because the temperature can be easily controlled and the heat dissipation of the core material is easy to take.

  The excitation coil 42 generates a magnetic flux and an eddy current in the heating roller so as to prevent a change in the magnetic field by a magnetic flux generated by a high frequency current applied to the excitation coil 42 from an excitation circuit (inverter circuit) (not shown). Heat is generated by this eddy current and heating roller resistance. In this embodiment, a high frequency current having a frequency of 20 kHz and an output of 900 W was passed through the coil.

  The surface temperature of the heating roller 92 was set to 180 ° C. The surface temperature is detected by a thermistor 99 disposed inside the roller, and the heating roller 2 is heated by feedback control. At this time, the heating roller 2 and the pressure roller 3 are rotating. A certain amount of heat is given to the entire roller surface by rotating the roller. When the surface temperature of the heating roller reaches 180 ° C., the copying operation starts, and the sheet P passes through a fixing point where the sheet P is a pressure contact portion (nip portion) between the heating roller 2 and the pressure roller 3. The above developer is fixed by fusion bonding.

  In the present embodiment, the position of the thermistor 7 is arranged inside the heating roller 2 in a region from the facing portion of the rotating magnetic field generating means 41 to the nip portion. Accordingly, the temperature of the thermistor 7 can accurately grasp the temperature of the nip portion when the fixing material passes through the nip portion. In FIG. 13, the position of the thermistor 7 is arranged at the entrance of the nip portion. Even in this case, the same effect can be obtained.

  FIG. 14 and FIG. 15 show the heat distribution by the air-core coil and the temperature change of the heating roller surface temperature for one heating roller. FIG. 14 shows the temperature change from the nip outlet. Since there is no heat source from the nip outlet to the vicinity of the exciting coil, there is almost no temperature rise. After that, when reaching the lower part of the exciting coil (left side), heat is applied and the temperature starts to rise. Thereafter, at the center of the exciting coil, as can be seen from the heat distribution diagram of FIG. 15, the heat generation is close to 0, and therefore the temperature rise is only the heat conduction from the side at the center of the exciting coil. After that, the temperature rises when passing through the lower part of the exciting coil (right side). This operation is repeated until the fixing temperature reaches 180 ° C. and the warm-up operation is finished.

  As shown in FIG. 14, the temperature immediately before the fixing material enters the nip portion can be grasped in a region A of the graph representing the temperature. In the case of this embodiment, since the roller is locally heated and the roller is rotated, the temperature change is large outside the region A, and the temperature of the nip portion is not shown. Therefore, in order to accurately grasp the temperature of the nip portion, it is necessary to arrange the thermistor 7 in the region A. The region A indicates a region from the point heated to a predetermined temperature by the exciting coil 10 to the nip region. This is the difference from the conventional halogen lamp. Further, when the heating roller 2 is thick, the temperature inside the roller is maintained even in the latter half of the nip region, and therefore can be measured in the latter half of the nip region. Moreover, since the thermistor 7 is arranged on the inner side, it is not affected by the magnetic flux generated by the exciting coil arranged on the outer side of the roller, so that there is little noise and there is a magnetic flux shielding effect.

  By arranging the thermistor 7 at a position corresponding to the region A in FIG. 14 as described above, an accurate temperature can be grasped and the magnetic flux from the exciting coil is not affected. This makes it possible to reduce the heat capacity of the roller.

  Next, a fourth embodiment according to the present invention will be described. A schematic diagram of the fixing device is shown in FIG. In the description of the schematic diagram of the fixing device, the same parts as those of the third embodiment are omitted. 16 differs from the third embodiment in that there are thermistors 50 and 51 as thermistors that are temperature detecting means, and the thermistor 50 is disposed at a position facing the induction heating device 41 via the heating roller 2. ing. On the other hand, the thermistor 51 is disposed in the nip portion which is a contact point between the heating roller 2 and the pressure roller 3. The thermistors 50 and 51 and the induction heating device 41 are controlled by a CPU (not shown).

  In the conventional halogen lamp type, the nip portion could not be measured, but when the induction heating device 41 is arranged outside the heating roller 2 as in this embodiment, the thermistors 50 and 51 can be arranged inside the heating roller 2. It is possible to measure the temperature of the nip roller immediately before the fixing material passes through the nip. Thereby, the temperature drop when the fixing material passes can be detected by the thermistor, and offset or the like can be prevented. In this embodiment, since the thermistor 50 is further arranged at a position facing the coil, a control method for increasing the temperature at the nip portion by detecting the temperature difference between the locally heated portion and the nip portion. Used.

  An example of control is shown in FIGS. When the fixing material does not pass through or when the fixing device is started up, the temperature of the heating roller only needs to be kept at a certain temperature, and therefore control is performed using only the temperature detection of the thermistor 50. For example, as shown in FIG. 16, it is determined whether or not the fixing device is started up (ST1). If it is during the start-up operation of the fixing device, the process proceeds to ST3 to be described later. In the case of NO, it is determined whether or not it is on standby (ST2). If YES, the process proceeds to ST3, and if NO, the process proceeds to the fixing device operation routine of ST7 (FIG. 18).

In ST3, when the standby temperature is set to 150 ° C., temperature detection is performed using the thermistor 50 (ST6), and the temperature is maintained at 150 ° C. (ST5).
Next, when the material to be fixed is passed, in the fixing device operation routine (ST7), first, the thermistor 50 is used (ST9) to detect the surface temperature of the heating roller 2 (ST10), and a predetermined fixable temperature. Heat until it reaches 180 ° C. in this embodiment (ST11). Thereafter, the temperature difference is detected using the thermistor 50 and the thermistor 51 (ST12), and the heat generation amount is varied. That is, when the fixing material passes, the heating roller temperature is controlled to 180 ° C. This temperature is detected by the thermistor 50. On the other hand, in the nip region, the temperature decreases when the fixing material passes. The thermistor 51 is used for this temperature detection. When this temperature difference is large, that is, when the pressure roller temperature is low, when OHP or thick paper is passed as a fixing material, the temperature is lower than when normal paper is passed. Therefore, the temperature difference between the thermistor 50 and the thermistor 51 is detected (ST13). If the temperature difference is large, the heating amount of the magnetic field generating means is increased. If the temperature difference is small, the heating amount is increased. There is a control table to reduce (ST14). Thereafter, it is determined whether or not the fixing operation has been completed. If NO, the process returns to ST12. If YES, the fixing apparatus operating routine is terminated. In the induction heating coil of the present embodiment, the amount of heat generation can be varied step by step, so that the above control can be performed at low cost. Thereby, the fixing temperature can be kept constant regardless of the type of the object to be heated. Further, it does not depend on the pressure roller temperature.

  Thereby, good fixing performance can be obtained. Further, since the temperature ripple can be reduced, the fixing performance can be obtained even if the heat capacity of the roller is reduced, and the rise time can be shortened.

1 is a cross-sectional view of a fixing device according to a first embodiment of the present invention. The figure which showed the positional relationship of an induction heating apparatus and a heating roller. The figure which showed the positional relationship of the current center and heating roller which flow in an exciting coil. The figure which showed the positional relationship at the time of arrange | positioning the induction heating apparatus outside the heating roller. The figure which showed the positional relationship of a core material and a heating roller. The figure which showed the change of the emitted-heat amount when t and L are made into parameters. FIG. FIG. 6 is a cross-sectional view of a fixing device according to a second embodiment of the present invention. The enlarged view of an exciting coil and a heating roller. The figure which showed the modification of the 2nd Example of this invention. FIG. 6 is a cross-sectional view of a fixing device according to a third embodiment of the present invention. FIG. 6 is a cross-sectional view of a fixing device according to a third embodiment of the present invention. The figure which showed the 3rd Example which has arranged the thermistor in the nip vicinity. The figure which showed the change of the surface temperature of a heating roller. The figure which showed the heat_generation | fever distribution on the surface of a heating roller by a magnetic field generation means. Sectional drawing of the fixing device which concerns on the 4th Example of this invention. The flowchart figure which showed an example of control of a 4th Example. The figure which showed the operation routine of the fixing device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixing device 2 Heating roller 3 Pressure roller 4 Peeling claw 5 Release agent application device 6 Cleaning member 7 Thermistor 8 Thermostat 9 Induction heating device 10 Excitation coil 20 Excitation coil 30 Fixing belt 31 Air core coil 32 Pressure roller 33 Holder 40 Fixing Device 41 Induction heating device 42 Excitation coil 43 Core material 44 Coil 50 Thermistor 51 Thermistor

Claims (2)

A magnetic field generating means formed in a coil shape by a conductive wire;
A heating means constituted by at least a conductor, which is constituted by a hollow cylindrical shape or an endless belt and is rotatably supported and generates heat by a magnetic field generated by the magnetic field generation means,
A pressure contact means for pressure contact with the heating means;
And a temperature measuring means for measuring the temperature of the heating means, wherein the magnetic field generating means is arranged outside the heating means, and the temperature measuring means generates heat from the heating means. A fixing device which is disposed between a portion and a nip region in a rotation direction. A magnetic field generating means formed in a coil shape by a conductive wire;
A heating means constituted by at least a conductor, which is constituted by a hollow cylindrical shape or an endless belt and is rotatably supported and generates heat by a magnetic field generated by the magnetic field generation means,
A pressure contact means for pressure contact with the heating means;
A temperature measuring means arranged inside the heating means and measuring the temperature of the heating means, the magnetic field generating means is arranged outside the heating means, and there are at least two temperature measuring means, One of them measures the temperature of the nip region, and the rest is arranged between the heating portion of the heating means and the nip region in the rotation direction.

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