JP6497134B2 - Fixing apparatus, image forming apparatus, and temperature control program - Google Patents

Description

  The present invention relates to a fixing device, an image forming apparatus, and a temperature control program.

  Patent Document 1 includes a fixing belt and a temperature-sensitive magnetic member movable toward the fixing belt, and the temperature-sensitive magnetic member is fixed to the fixing belt until the temperature of the temperature-sensitive magnetic member reaches a heating set temperature or higher. And a fixing device that heats the temperature-sensitive magnetic member toward the fixing belt after the temperature-sensitive magnetic member reaches a heating set temperature or more after being heated.

JP 2009-282413 A

  In the present invention, the endless member and the moving member are brought into contact with each other during the fixing process, as compared with the case where the temperature of the inner peripheral surface of the endless member is controlled by controlling the magnitude of the magnetic field at a predetermined change rate of the magnetic field. It is an object of the present invention to provide a fixing device, an image forming apparatus, and a temperature control program that can suppress temperature fluctuation of an endless member that occurs in some cases.

The fixing device according to claim 1 is a rotatable endless member that is heated by induction heating by a magnetic field, and that is heated by the induction heating and is movable in a direction in which the endless member is in contact with or separated from the inner peripheral surface of the endless member. A fixing device, wherein the temperature of the inner peripheral surface of the endless member is controlled to a target temperature by changing the magnetic field according to the temperature of the inner peripheral surface of the endless member, The rate of change of the magnetic field with respect to the temperature of the inner peripheral surface of the endless member when the moving member is in contact with the inner peripheral surface of the endless member during the fixing process by the member and the pressure member is determined by the moving member. The temperature of the inner peripheral surface of the endless member is controlled to a target temperature by making it smaller than the rate of change of the magnetic field with respect to the temperature of the inner peripheral surface of the endless member when moved to a position separated from the inner peripheral surface of the endless member. A control unit is provided.

The fixing device according to a second aspect is the fixing device according to the first aspect, wherein the control unit is configured to move the endless when the moving member is moved to a position separated from an inner circumferential surface of the endless member. Until the temperature of the inner peripheral surface of the member reaches a target temperature, control is performed by a normal change rate that is predetermined as the rate of change of the magnetic field with respect to the temperature of the inner peripheral surface of the endless member, and the moving member is controlled by the inner periphery of the endless member. if they are in contact with the surface, the temperature of the inner peripheral surface of the endless member is controlled by the rate of change is smaller than the change rate for the predetermined normal to reach the target temperature.

According to a third aspect of the present invention, there is provided the fixing device according to the first or second aspect, wherein the inner end of the endless member is moved when the moving member is moved to a position separated from the inner peripheral surface of the endless member. A coefficient of a first value indicating the rate of change of the magnetic field with respect to the temperature of the peripheral surface is set, and a second smaller than the coefficient of the first value when the moving member is in contact with the inner peripheral surface of the endless member. A setting unit that sets a coefficient of a value of the inner end of the endless member using the coefficient set by the setting unit and the difference between the temperature of the inner peripheral surface of the endless member and the target temperature . The peripheral surface temperature is controlled to the target temperature .

  A fixing device according to a fourth aspect of the present invention is the fixing device according to any one of the first to third aspects, further including a detection unit that detects a temperature of an inner peripheral surface of the endless member, and the control unit includes: Control is performed so that the temperature of the inner peripheral surface of the endless member detected by the detection unit becomes the target temperature.

The fixing device according to claim 5 is the fixing device according to any one of claims 1 to 4, wherein the control unit is configured such that the moving member is in contact with an inner peripheral surface of the endless member. And when the temperature of the inner peripheral surface of the endless member reaches the target temperature, the moving member has a lower rate of change of the magnetic field with respect to the temperature of the inner peripheral surface of the endless member. Return to the rate of change of the magnetic field with respect to the temperature when moved to a position away from.

  6. The image forming apparatus according to claim 6, wherein the image forming unit forms an image on a recording medium, and the image is fixed on the recording medium on which the image is formed by the image forming unit. A fixing device according to the item.

Temperature control program according to claim 7 moves, a rotatable endless member heated by induction heating by magnetic field, is heated by the induction heating, and toward or away from the inner peripheral surface of the endless member A temperature control program in a fixing device, wherein the temperature of the inner peripheral surface of the endless member is controlled to a target temperature by changing the magnetic field according to the temperature of the inner peripheral surface of the endless member. The rate of change of the magnetic field with respect to the temperature of the inner peripheral surface of the endless member when the moving member is in contact with the inner peripheral surface of the endless member during the fixing process by the endless member and the pressure member Less than the rate of change of the magnetic field with respect to the temperature of the inner peripheral surface of the endless member when the moving member is moved to a position separated from the inner peripheral surface of the endless member. Temperature To execute processing comprising controlling the temperature in the computer.

  According to the fixing device of the first aspect, the temperature of the inner peripheral surface of the endless member is controlled by controlling the magnitude of the magnetic field by the rate of change of the magnetic field when the moving member is separated from the inner peripheral surface of the endless member. Compared to the case, the temperature fluctuation of the endless member that occurs when the endless member and the moving member are brought into contact with each other during the fixing process can be suppressed.

  According to the fixing device of the second aspect, the endless member and the moving member are in contact with each other as compared with the case where the temperature of the inner peripheral surface of the endless member is controlled by controlling the magnitude of the magnetic field at a predetermined rate of change of the magnetic field. It is possible to suppress the temperature fluctuation of the endless member that occurs when the operation is performed.

  According to the fixing device of the third aspect, compared with a case where the temperature of the inner peripheral surface of the endless member is controlled using a coefficient when the moving member is separated from the inner peripheral surface of the endless member, the configuration is simple. Temperature fluctuation of the endless member that occurs when the endless member and the moving member are brought into contact with each other can be suppressed.

  According to the fixing device of the fourth aspect, it is possible to acquire the temperature of the endless member with higher accuracy than in the case where the detection unit is not provided.

  According to the fixing device of the fifth aspect, when the endless member and the moving member are in contact with each other, the inside of the endless member remains at a smaller rate of change than when the moving member is separated from the inner peripheral surface of the endless member. Compared with the case where the temperature of the peripheral surface is controlled, the temperature of the endless member can be controlled to the target temperature according to the temperature fluctuation of the temperature of the inner peripheral surface of the endless member.

  According to the image forming apparatus of the sixth aspect, the quality of the output image due to the temperature fluctuation of the fixing device as compared with the case where the fixing device according to any one of the first to fifth aspects is not provided. The decrease can be suppressed.

  According to the temperature control program of the seventh aspect, the temperature of the inner peripheral surface of the endless member is controlled by controlling the magnitude of the magnetic field by the rate of change of the magnetic field when the moving member is separated from the inner peripheral surface of the endless member. Compared with the case where it does, the temperature fluctuation of an endless member which arises when an endless member and a moving member are contacted during a fixing process can be suppressed.

1 is a configuration diagram illustrating an example of an image forming apparatus according to an embodiment. 1 is a cross-sectional view illustrating an example of a fixing device according to an embodiment. 1 is a cross-sectional view illustrating an example of a fixing device according to an embodiment. 1 is a cross-sectional view illustrating an example of a fixing device according to an embodiment. FIG. 3 is a cross-sectional view illustrating an example of a fixing belt according to an embodiment. It is explanatory drawing of the thermosensitive magnetic board used for the fixing device which concerns on embodiment, (A) is sectional drawing of a thermosensitive magnetic board, (B) is the model which showed the relationship between the magnetic permeability of a thermosensitive magnetic member, and temperature. FIG. It is a block diagram which shows an example of the temperature control apparatus contained in the control part which concerns on embodiment. FIG. 6 is a characteristic diagram illustrating an example of changes in temperature of a contact member and a fixing belt. FIG. 6 is a characteristic diagram illustrating an example of changes in temperature of a contact member and a fixing belt. FIG. 6 is a characteristic diagram illustrating an example of changes in temperature of a contact member and a fixing belt. It is a block diagram which shows an example of the computer which can implement | achieve a control part. It is a flowchart which shows an example of the flow of a process of temperature control.

  Hereinafter, an example of a fixing device according to an embodiment of the present invention and an image forming apparatus including the fixing device will be described in detail with reference to the drawings. The arrow V shown in the figure is the vertical direction and indicates the vertical direction of the apparatus, the arrow H is the horizontal direction and indicates the apparatus width (left and right of the apparatus), and the arrow D is the horizontal direction and the depth direction of the apparatus. Indicates.

  FIG. 1 shows an example of the configuration of an image forming apparatus 10 according to the first embodiment of the present invention. As shown in FIG. 1, the image forming apparatus 10 includes an image on which image formation is performed with toner (developer) of four colors of yellow (Y), magenta (M), cyan (C), and black (K). Image forming units 12 </ b> Y, 12 </ b> M, 12 </ b> C, and 12 </ b> K as an example of a forming unit are provided on the center side in the housing 11 of the image forming apparatus 10. Each of the image forming units 12Y to 12K is arranged so as to be inclined obliquely toward the lower left direction with respect to the apparatus width direction, and in the order of Y, M, C, and K from the upper right to the lower left in the apparatus width direction. It is arranged. Each of the image forming units 12Y to 12K has the same configuration except for the toner of each color to be accommodated. In the following description, when distinguishing each color of yellow, magenta, cyan, and black, it will be described with a symbol with Y, M, C, and K letters added after the number, but when it is not necessary to distinguish each color, The letters Y, M, C, and K after the numbers are omitted.

  Each image forming unit 12 has a main body portion constituted by s, a lower housing 13 and an upper housing 15. The lower housing 13 is provided with a developing roll 78, a conveying member 38, and a thin layer forming roll 24. The upper housing 15 has an image carrier 28, an exposure unit 70, a charging roll 72, a cleaning roll 68, and a cleaning. A blade 76 and a charge removal lamp 74 are provided.

  The image carrier 28 is driven to rotate in the direction of arrow B (counterclockwise direction in the figure). The charging roll 72 is for energizing the image holding member 28 during image formation while being driven and rotated to charge the image holding member 28 by contact with the outer peripheral surface of the image holding member 28. The exposure unit 70 irradiates the outer peripheral surface of the image carrier 28 with exposure light to form an electrostatic latent image, and the developing roller 78 develops the electrostatic latent image on the outer peripheral surface of the image carrier 28 with toner. belongs to. The neutralization lamp 74 is for irradiating the outer peripheral surface of the image carrier 28 after transfer with light, and the cleaning blade 76 is for cleaning the outer peripheral surface of the image carrier 28 after neutralization. Is. The cleaning roll 68 is for removing the external additive of the toner adhering to the outer peripheral surface of the charging roll 72 due to its rotation.

  Below the developing roll 78, a spiral (for example, a mixture of resin toner and metal carrier) supplied from a toner supply unit (not shown) is stirred (mixed) and supplied to the developing roll 78. Two conveying members 38 are provided. A thin layer forming roll 24 is provided opposite to the outer peripheral surface of the developing roll 78. The thin layer forming roll 24 is for regulating the amount of developer passing on the outer peripheral surface of the developing roll 78 to form a developer layer (thin layer) having a predetermined thickness on the developing roll 78. It is.

  A voltage is applied between the developing roller 78 and the image carrier 28 to form an electric field during development, and the developing roller 78 rotates the toner in the developer to the electrostatic latent image of the image carrier 28 while rotating. It is designed to move toward the statue.

  Next, above each of the image forming units 12Y to 12K, a transfer unit 14 that transfers a toner image (image) formed by each of the image forming units 12Y to 12K to a sheet member P as an example of a recording medium. Is provided. The transfer unit 14 is an endless intermediate transfer belt 16 and four primary transfer rolls arranged inside the intermediate transfer belt 16 for transferring the toner images of the image forming units 12Y to 12K to the intermediate transfer belt 16. 18Y, 18M, 18C, and 18K, and a secondary transfer roll 20 for transferring the toner image superimposed on the intermediate transfer belt 16 to the sheet member P.

  The intermediate transfer belt 16 is disposed opposite to the secondary transfer roll 20 and is wound around a drive roll 26 driven by a motor (not shown) and a support roll 22 that is rotatably supported. The intermediate transfer belt 16 is circulated and moved in the direction of arrow A (clockwise direction in the figure) by the rotation of the drive roll 26. Each of the primary transfer rolls 18Y to 18K is disposed so as to face an image carrier 28 described later of each of the image forming units 12Y to 12K with the intermediate transfer belt 16 interposed therebetween. A transfer voltage having a polarity opposite to the toner polarity (positive polarity as an example in the present embodiment) is applied to each of the primary transfer rolls 18Y to 18K. Further, a transfer voltage having a polarity opposite to the toner polarity is also applied to the secondary transfer roll 20. A cleaning device (not shown) for removing residual toner, paper dust, and the like on the intermediate transfer belt 16 is provided on the outer peripheral surface of the intermediate transfer belt 16 where the support roll 22 is provided.

  On the other hand, below the image forming unit 12, a paper feeding unit 46 in which the sheet member P is stored is provided. A sheet conveyance path 50 through which the sheet member P is conveyed is provided vertically upward from the left end of the sheet feeding unit 46. In the sheet conveyance path 50, a delivery roll 48 that sends out the sheet member P from the sheet feeding unit 46, a conveyance roll 52 that is composed of a pair of rolls that convey the sheet member P, and an image transfer timing on the intermediate transfer belt 16. And a pair of positioning rolls 54 that match the conveyance timing of the sheet member P are provided. The sheet members P sequentially sent out from the paper supply unit 46 by the delivery roll 48 are conveyed to the secondary transfer position of the intermediate transfer belt 16 by the alignment roll 54 via the paper conveyance path 50.

  A fixing device 100 is provided on the downstream side (upper side) of the secondary transfer roll 20 on the paper conveyance path 50. The fixing device 100 is for fixing the toner image transferred to the sheet member P by heating and pressing the sheet member P to the sheet member P. Details of the fixing device 100 will be described later.

  A pair of discharge rollers 66 for discharging the fixed sheet member P to the outside of the housing 11 is provided on the downstream side of the fixing device 100 on the paper conveyance path 50, and is discharged by the discharge rollers 66. The sheet member P is discharged to a discharge portion 67 formed on the upper surface of the housing 11. In the housing 11, an apparatus control unit 36 that performs drive control of each unit of the image forming apparatus 10 is provided above the transfer unit 14 (details will be described later).

Next, an image forming operation of the image forming apparatus 10 will be described.
When each unit of the image forming apparatus 10 is activated, the image data subjected to the image processing by the apparatus control unit 36 is converted into color material gradation data of each color and sequentially output to the exposure unit 70. The exposure unit 70 emits each exposure light according to the color material gradation data of each color, and exposes the outer peripheral surface of each image carrier 28 charged by the charging roll 72. Thereby, an electrostatic latent image is formed on the outer peripheral surface of each image carrier 28.

  The electrostatic latent image formed on the outer peripheral surface of each image carrier 28 is developed with toner images (development) of each color of yellow (Y), magenta (M), cyan (C), and black (K) by the developing roller 78, respectively. Developed as an agent image). The toner images of the respective colors sequentially formed on the image holders 28 of the image forming units 12Y to 12K are sequentially multiplex-transferred onto the intermediate transfer belt 16 by the four primary transfer rolls 18Y to 18K.

  The toner images of the respective colors transferred onto the intermediate transfer belt 16 are secondarily transferred by the secondary transfer roll 20 onto the sheet member P conveyed from the paper supply unit 46. Then, the toner images of the respective colors on the sheet member P are fixed by the fixing device 100, and the fixed sheet member P is discharged to the discharge unit 67 by the discharge roll 66.

  Residual toner, paper dust, and the like are removed from the outer peripheral surface of the image carrier 28 after the primary transfer of the toner image by the cleaning blade 76.

Next, the fixing device 100 will be described.
2 to 4 show an example of the fixing device 100. Although details will be described later, in FIG. 2, the pressure roll 104 (an example of a pressure member) has been moved to a non-pressure position that is separated from the fixing belt 102, and the contact member 152 has an inner circumference of the fixing belt 102. An example of the state moved to the separation position which is separated from the surface is shown. Further, in FIG. 3, the pressure roll 104 is moved to a pressure position where the pressure roller 104 is in contact with the fixing belt 102 and presses the fixing belt 102, and the contact member 152 is separated from the inner peripheral surface of the fixing belt 102. An example of the state moved to is shown. Further, in FIG. 4, the pressure roller 104 is moved to a pressure position where it contacts the fixing belt 102 and presses the fixing belt 102, and the contact position where the contact member 152 contacts the inner peripheral surface of the fixing belt 102. An example of the state moved to is shown.

  As shown in FIGS. 2 to 4, the fixing device 100 includes a housing 120 in which openings 120 </ b> A and 120 </ b> B for entering or discharging the sheet member P are formed. Inside the housing 120 is provided an endless fixing belt 102 (an example of an endless member) that can be rotated in the direction of arrow E by driving a motor (not shown). A bobbin 108 made of an insulating material is disposed at a position facing a part of the outer peripheral surface of the fixing belt 102.

  The bobbin 108 has a circular arc shape that follows the outer peripheral surface of the fixing belt 102 when viewed from the rotation axis direction of the fixing belt 102 (in this embodiment, the same direction as the apparatus depth direction), and is opposite to the fixing belt 102. A convex portion 108A is formed on the center side in the circumferential direction of the side surface. The interval between the bobbin 108 and the fixing belt 102 is about 1 to 3 mm. An excitation coil 110 (an example of a magnetic field generating member) that generates a magnetic field HA by energization is wound around the bobbin 108 a plurality of times along the surface around the convex portion 108A. A magnetic core 112 formed in an arc shape following the arc shape of the bobbin 108 is disposed at a position facing the excitation coil 110, and the magnetic core 112 is supported by the bobbin 108 or the excitation coil 110.

  FIG. 5 shows an example of the configuration of the fixing belt 102. The fixing belt 102 includes a base layer 124, a heat generation layer 126, an elastic layer 128, and a release layer 130 that are arranged from the inside toward the outside, and these are laminated and integrated. For example, the fixing belt 102 has a diameter of 30 mm and a width direction length of 370 mm.

  The base layer 124 has a strength to support the heat generating layer 126, has heat resistance, and can appropriately select a material that penetrates the magnetic field (magnetic flux) and does not generate heat or hardly generates heat due to the action of the magnetic field. In the present embodiment, a heat resistant resin (polyimide) having a thickness of 80 μm is used as an example of the base layer 124. The heat generating layer 126 is made of a metal material that generates heat by electromagnetic induction. Further, the heat generating layer 126 is configured to be thinner than the skin depth, which is a thickness that allows the magnetic field HA to enter, in order to penetrate the magnetic flux of the magnetic field HA. In the present embodiment, copper having a thickness of 10 μm is used as an example of the heat generating layer 126. The elastic layer 128 is made of silicon rubber or fluorine rubber from the viewpoint of obtaining elasticity and heat resistance. In the present embodiment, 200 μm thick silicon rubber is used as the elastic layer 128. The release layer 130 is provided to make it easier to peel the sheet member P from the fixing belt 102. In the present embodiment, as an example of the release layer 130, a 30 μm thick ethylene tetrafluoride / perfluoroalkoxyethylene copolymer resin (PFA) is used.

  As shown in FIG. 2 to FIG. 4, inside the fixing belt 102, an area that does not face the exciting coil 110 in the radial direction, and an area on the discharge side of the sheet member P (an upper area in the figure). Is provided with a temperature detection sensor 134 for detecting the temperature of the inner peripheral surface of the fixing belt 102. Further, the fixing belt 102 is supported in contact with the inner peripheral surface of the fixing belt 102 so as to face the fixing belt 102 on the inner side so as to face the bobbin 108 with the fixing belt 102 interposed therebetween. A contact member 152 (an example of a moving member) having a circular arc plate shape in cross section is provided.

  FIG. 6A shows an example of a part of the contact member 152. The contact member 152 includes a temperature-sensitive magnetic plate 114 that is a temperature-sensitive magnetic member arranged in layers, and a substrate 154 that is arranged in layers inside the temperature-sensitive magnetic plate 114. The temperature-sensitive magnetic plate 114 is disposed to face the exciting coil 110 with the fixing belt 102 interposed therebetween in the apparatus width direction.

  FIG. 6B shows an example of the temperature sensitive characteristic of the temperature sensitive magnetic plate 114. The temperature-sensitive magnetic plate 114 is a temperature-sensitive magnetic plate 114 whose magnetic permeability begins to decrease continuously from a magnetic permeability change start temperature in a temperature range not lower than the fixing (heating) set temperature of the fixing belt 102 and not higher than the heat resistance temperature of the fixing belt 102. It is made of a material having characteristics. In this embodiment, a 300 μm thick iron-nickel alloy (Fe—Ni) is used as the temperature sensitive layer 115. The magnetic permeability change start temperature is a temperature at which the magnetic permeability (measured in accordance with JIS C2531) starts to decrease, and refers to a point at which the penetration amount of the magnetic flux of the magnetic field starts to change. Further, the permeability change start temperature is different from the Curie point, and is preferably set at 150 ° C. to 230 ° C.

  The substrate 154 holds heat generated by the temperature-sensitive magnetic plate 114 and conducts the held heat in the depth direction of the apparatus. Thereby, the temperature distribution in the apparatus depth direction of the temperature-sensitive magnetic plate 114 is made uniform, and the local temperature rise is suppressed. In addition, when the temperature of the temperature-sensitive magnetic plate 114 rises and the magnetic permeability decreases above the permeability change start temperature, the magnetic flux penetrating the fixing belt 102 is reduced, and the amount of heat generated by the fixing belt 102 is suppressed. It is like that. In the present embodiment, aluminum having a thickness of 400 μm is used as the substrate 154.

  As shown in FIGS. 2 to 4, a temperature detection sensor 135 that detects the temperature of the temperature-sensitive magnetic plate 114 is disposed below the temperature-sensitive magnetic plate 114. In addition, a base member 118 formed by bending an aluminum plate is provided inside the contact member 152. The base member 118 extends in the depth direction of the apparatus and does not penetrate the magnetic flux of the magnetic field HA. The upper end supports the upper end of the contact member 152, and the lower end supports the lower end of the contact member 152. It has become. Further, the other end of the rod 184 is held at a portion between the upper end and the lower end of the base member 118. A frame 158 that supports the base member 118 is attached to the base member 118 so that the base member 118 is moved in the apparatus width direction.

  The frame 158 is disposed on the opposite side of the contact member 152 with the base member 118 interposed therebetween. Further, the frame 158 includes a main body member 160 extending in the apparatus depth direction, an upper support member 162 that supports the upper side of the base member 118, and a lower support member 164 that supports the lower side of the base member 118. Has been.

  The main body member 160 is formed to extend in the apparatus depth direction using a metal material (for example, a steel material), and both ends of the main body member 160 in the apparatus depth direction are fixed to the housing 120. An upper support member 162 is attached to the upper surface 160B of the main body member 160, and a lower support member 164 is attached to the lower surface 160C of the main body member 160.

  A coil spring 170 is attached to the lower support member 164, and the lower side of the contact member 152 is movable toward the inner peripheral surface of the fixing belt 102 via the base member 118 by the biasing force of the coil spring 170. . Further, the upper support member 162 is attached with a coil spring 166, and the upper side of the contact member 152 is movable toward the inner peripheral surface of the fixing belt 102 via the base member 118 by the biasing force of the coil spring 166. Yes.

  On the other hand, inside the main body member 160, a pull-in mechanism 180 that pulls the base member 118 toward the main body member 160 and separates the contact member 152 from the inner peripheral surface of the fixing belt 102 is provided.

  The retracting mechanism 180 includes an eccentric cam 182 whose axial direction is the apparatus depth direction, and a rod 184 whose proximal end is in contact with the peripheral surface of the eccentric cam 182 and whose distal end is in contact with the base member 118. A plurality (for example, two) of eccentric cams 182 and rods 184 are arranged at intervals in the apparatus depth direction. Both ends of the shaft portion 182A of the eccentric cam 182 are rotatably supported by the housing 120, and a rotational force is transmitted to the shaft portion 182A from a driving member 183 (see FIG. 7 or FIG. 11, for example, a stepping motor). It has become so. One end of the rod 184 is pressed against the outer peripheral surface of the eccentric cam 182 by the biasing force of the coil spring 186, and the other end of the rod 184 is held by the base member 118.

  Therefore, when the eccentric cam 182 is rotated, the rod 184 is moved in the longitudinal direction of the rod 184, and the base member 118 is moved in the apparatus width direction. Further, the movement of the base member 118 causes the contact member 152 to come into contact with the inner peripheral surface of the fixing belt 102 (see FIG. 4), and the contact member 152 to move away from the inner peripheral surface of the fixing belt 102 (see FIG. 4). (See FIG. 2).

  In the present embodiment, the driving member 183 outputs information indicating the positions of the separation position and the contact position of the contact member 152.

  On the other hand, on the side opposite to the side on which the base member 118 is disposed in the main body member 160, a pressing pad 132 that fixes the fixing belt 102 between the pressing roll 104 is fixed. In the present embodiment, a liquid crystal polymer is used as a material constituting the pressing pad 132.

  The pressure roll 104 includes a cored bar 104A made of a metal such as aluminum, and a sponge elastic layer 104B of foamed silicon rubber having a thickness of 5 mm that is covered with the cored bar 104A. The pressure roll 104 is provided with a release layer (not shown) made of carbon tetrafluoride ethylene / perfluoroalkoxyethylene copolymer resin (PFA) containing carbon having a thickness of 50 μm outside the sponge elastic layer 104B. ing.

  The cored bar 104A of the pressure roll 104 is moved in the apparatus width direction by a retract mechanism (not shown). The pressure roll 104 is in contact with the fixing belt 102 by the movement of the metal core 104A to press the fixing belt 102 (see FIGS. 3 and 4), and in the non-pressing position (see FIG. 3) away from the fixing belt 102. 2). Further, rotational force from a motor (not shown) is transmitted to the core metal 104A of the pressure roll 104 so that the pressure roll 104 rotates in the direction of arrow F shown in FIG. 4 (the direction opposite to the direction of arrow E). It has become.

Next, the device control unit 36 will be described.
The apparatus control unit 36 performs drive control of each unit of the image forming apparatus 10. The device control unit 36 includes a temperature control device 200 (an example of a control unit) that controls the temperature of the fixing belt 102.

  FIG. 7 shows an example of the temperature control device 200 included in the device control unit 36. The temperature control device 200 includes a coefficient setting unit 202 (an example of a setting unit) and a target temperature control unit 206. A drive member 183 that rotates the eccentric cam 182 is connected to the coefficient setting unit 202 in order to acquire information indicating the position of the contact member 152. A temperature detection sensor 134 and an excitation coil 110 are connected to the target temperature control unit 206.

  The target temperature control unit 206 performs temperature control so that the temperature of the fixing belt 102 becomes the target temperature. The target temperature control unit 206 supplies electric power (for example, alternating current) to the exciting coil 110 and repeats generation and extinction of the magnetic field HA around the exciting coil 110. When the magnetic field HA crosses the heat generating layer 126 (see FIG. 5) of the fixing belt 102, an eddy current is generated in the heat generating layer 126 so as to generate a magnetic field that prevents the magnetic field HA from changing. As a result, the heat generating layer 126 generates heat, and the fixing belt 102 is heated.

  In the present embodiment, a case will be described in which the target temperature control unit 206 executes temperature control so that the temperature Ta of the inner peripheral surface of the fixing belt 102 becomes a predetermined target temperature Ts. The target temperature control unit 206 supplies power to the exciting coil 110 according to the temperature difference of the temperature Ta of the inner peripheral surface of the fixing belt 102 with respect to the target temperature Ts. Target temperature control unit 206 includes a storage area 208 for storing information indicating power temperature coefficient K. The power temperature coefficient K is a proportional constant indicating power / temperature, and is an example of the rate of change of the magnetic field HA for causing the contact member 152 and the fixing belt 102 to generate heat.

The target temperature control unit 206 indicates each of the power temperature coefficient K stored in the storage area 208, a predetermined target temperature Ts, and the temperature Ta of the inner peripheral surface of the fixing belt 102 detected by the temperature detection sensor 134. Using the information, the supply power I supplied to the exciting coil is calculated. An example of calculating the supplied power I is shown by the following arithmetic expression.
I = K · (Ts-Ta)

  Therefore, when the temperature Ta of the inner peripheral surface of the fixing belt 102 is equal to or higher than the target temperature Ts, the supply of alternating current to the exciting coil 110 is limited (for example, the supply is stopped). In addition, when the temperature Ta of the inner peripheral surface of the fixing belt 102 is lower than the target temperature Ts, the supply of alternating current to the exciting coil 110 is increased (for example, the supply is resumed). In this way, the temperature Ta of the inner peripheral surface of the fixing belt 102 is controlled to the target temperature Ts by the control by the target temperature control unit 206.

  In the above arithmetic expression, a constant may be added to the temperature difference of the temperature Ta of the inner peripheral surface of the fixing belt 102 with respect to the target temperature Ts. By adding a constant in the above arithmetic expression, even when the target temperature Ts and the temperature Ta of the inner peripheral surface of the fixing belt 102 are the same, a current determined by the constant can be supplied to the exciting coil 110.

  The power temperature coefficient K is set by the coefficient setting unit 202. The coefficient setting unit 202 includes a coefficient output unit 204 to which the driving member 183 is connected. The coefficient output unit 204 has a first coefficient k1 as a first value coefficient and a second value coefficient smaller than the first coefficient k1 depending on the position of the contact member 152 that is in contact with and away from the inner peripheral surface of the fixing belt 102. One of the second coefficients k2 is stored in the storage area 208 of the target temperature control unit 206. In the present embodiment, the power temperature coefficient K when the contact member 152 is moved to the separated position is used as the first coefficient k1, and the power temperature coefficient K when the contact member 152 is moved to the contact position is the second coefficient k2. Used as That is, the contact member 152 is moved to the separation position (FIG. 3) and the contact position (FIG. 4) by the rotation of the eccentric cam 182 by the drive member 183. Information indicating the positions of the separation position and the contact position is output by the driving member 183. The coefficient output unit 204 outputs the first coefficient k1 when the contact member 152 is moved to the separation position, and outputs the second coefficient k2 when the contact member 152 is moved to the contact position. Accordingly, the rate of change of the magnetic field HA when the contact member 152 is separated from the inner peripheral surface of the fixing belt 102 is determined by the first coefficient k1, and the contact member 152 is in contact with the inner peripheral surface of the fixing belt 102. The rate of change of the magnetic field HA is determined by the second coefficient k2.

  By the way, when the contact member 152 and the inner peripheral surface of the fixing belt 102 are brought into contact with each other, the temperature of the contact member 152 (temperature Tb of the temperature-sensitive magnetic plate 114) and the temperature of the fixing belt 102 (temperature Ta of the inner peripheral surface). Is different, heat is transferred between the contact member 152 and the fixing belt 102. Specifically, when the temperature Ta of the inner peripheral surface of the fixing belt 102 is controlled to the target temperature Ts, if the temperature Tb of the thermosensitive magnetic plate 114 is higher than the temperature Ta of the inner peripheral surface of the fixing belt 102, Heat is supplied from the contact member 152 to the fixing belt 102, and the temperature Ta of the inner peripheral surface of the fixing belt 102 rises. When the temperature Tb of the temperature-sensitive magnetic plate 114 is lower than the temperature Ta of the inner peripheral surface of the fixing belt 102, the heat of the fixing belt 102 is taken away by the contact member 152, and the temperature Ta of the inner peripheral surface of the fixing belt 102 decreases. To do. As described above, when the contact member 152 and the fixing belt 102 come into contact with each other in a state where the temperature Tb of the temperature-sensitive magnetic plate 114 and the temperature Ta of the inner peripheral surface of the fixing belt 102 are different, the temperature fluctuation of the fixing belt 102 occurs. Occurs.

  In addition, since the fixing belt 102 includes a plurality of layers, the temperature of the inner peripheral surface of the fixing belt 102 and the temperature (surface temperature) of the outer peripheral surface of the fixing belt 102 may be different.

  FIG. 8 shows an example of changes in the temperatures of the contact member 152 and the fixing belt 102. In FIG. 8, the temperature characteristic of the inner peripheral surface of the fixing belt 102 is indicated by a curve 234, and the temperature characteristic of the temperature (surface temperature) of the outer peripheral surface of the fixing belt 102 is indicated by a curve 232. In FIG. 8, the characteristic of the power I supplied to the exciting coil 110 is indicated by a curve 236 (dotted line). In FIG. 8, the temperature of the temperature-sensitive magnetic plate 114 when the contact member 152 and the inner peripheral surface of the fixing belt 102 are contacted from a separated state is indicated by a point 230.

  When the image forming apparatus 10 is turned on, the temperature of the inner and outer peripheral surfaces of the fixing belt 102 increases, and the temperature of the temperature-sensitive magnetic plate 114 also increases. When the power is turned on, the fixing belt 102 and the contact member 152 are separated from each other, and the temperature of the fixing belt 102 rises earlier than the temperature-sensitive magnetic plate 114. Then, the temperature Ta of the inner peripheral surface of the fixing belt 102 is controlled to the target temperature Ts, the conveyance of the sheet member P is started, and the fixing process is started. During this fixing process, the contact member 152 is moved to the contact position at a timing such as when the temperature Ta of the inner peripheral surface of the fixing belt 102 decreases or when a predetermined time has elapsed since the fixing process started. Thus, the fixing belt 102 and the contact member 152 are brought into contact with each other. As a result, the contact member 152 and the inner peripheral surface of the fixing belt 102 are brought into contact with each other, heat is supplied from the contact member 152 including the temperature-sensitive magnetic plate 114 to the fixing belt 102, and the temperature decrease of the fixing belt 102 is suppressed. The

  However, as shown in FIG. 8, when the temperature Tb (point 230) of the thermosensitive magnetic plate 114 is lower than the temperature Ta of the inner peripheral surface of the fixing belt 102, the contact member 152 is brought into contact with the inner peripheral surface of the fixing belt 102. (Time t1), the temperature Ta of the inner peripheral surface of the fixing belt 102 drops sharply. That is, heat is removed from the fixing belt 102 by supplying heat from the inner peripheral surface of the fixing belt 102 to the contact member 152, and the temperature Ta of the inner peripheral surface of the fixing belt 102 rapidly decreases. On the other hand, the temperature of the outer peripheral surface of the fixing belt 102 rises. This is because a sudden temperature change occurs on the inner peripheral surface of the fixing belt 102 due to the contact of the contact member 152, whereas the sharp temperature change has little influence on the outer peripheral surface and is supplied according to the temperature change sharply. It is conceivable that heat is promoted by the power I supplied to the exciting coil 110 and the temperature rises.

  Therefore, in this embodiment, when the temperature Ta of the inner peripheral surface of the fixing belt 102 is controlled to the target temperature Ts during the fixing process, and the contact member 152 and the inner peripheral surface of the fixing belt 102 are in contact with each other, the fixing belt. Control for suppressing temperature fluctuations on the outer peripheral surface 102 is executed. That is, the coefficient setting unit 202 sets the normal first coefficient k1 as the power temperature coefficient K when the contact member 152 and the inner peripheral surface of the fixing belt 102 are separated from each other. On the other hand, when the contact member 152 and the inner peripheral surface of the fixing belt 102 are in contact with each other, the coefficient setting unit 202 sets a second coefficient k2 smaller than the first coefficient k1 as the power temperature coefficient K. Therefore, when the contact member 152 and the inner peripheral surface of the fixing belt 102 are in contact with each other, the supply power I having the suppressed characteristic 237 is supplied to the exciting coil 110 and the temperature (surface temperature) of the outer peripheral surface of the fixing belt 102 is supplied. ) Has a characteristic 233 in which a sharp rise is suppressed. That is, by changing the power temperature coefficient K from the first coefficient k1 to the second coefficient k2, the sensitivity of the power I supplied to the exciting coil 110 with respect to the change in the temperature Ta of the inner peripheral surface of the fixing belt 102 is reduced. Thereby, when the contact member 152 and the inner peripheral surface of the fixing belt 102 are in contact with each other, the temperature variation can be suppressed on the outer peripheral surface of the fixing belt 102 as compared with the temperature variation due to the normal first coefficient k1. .

  In the present embodiment, when the contact member 152 and the inner peripheral surface of the fixing belt 102 are in contact during the fixing process, the second coefficient k2 set as the power temperature coefficient K is returned to the first coefficient k1. be able to. The time when the power temperature coefficient K is returned from the second coefficient k2 to the first coefficient k1 is preferably the time when the temperature Ta of the inner peripheral surface of the fixing belt 102 reaches the target temperature Ts and is controlled. Further, it may be a time when a predetermined time has passed as a time when the temperature Ta of the inner peripheral surface of the fixing belt 102 reaches the target temperature Ts and is controlled. By returning to the first coefficient k1, it is possible to quickly cope with the temperature change of the inner peripheral surface of the fixing belt 102 during the fixing process.

  FIG. 9 shows an example of the transition of the temperature of each part when the power temperature coefficient K is set to the second coefficient k2 and then returned to the first coefficient k1 during the fixing process. As shown in FIG. 9, the supplied power I after the power temperature coefficient K is set to the first coefficient k1 (time t1) becomes the suppressed characteristic 237, and the temperature (surface temperature) of the outer peripheral surface of the fixing belt 102 is reduced. The temperature has a characteristic 233 in which a sharp rise is suppressed. When the power temperature coefficient K is returned from the second coefficient k2 to the first coefficient k1 (time t2), the temperature Ta of the inner peripheral surface of the fixing belt 102 becomes a temperature characteristic according to the curve 234 by the first coefficient k1, and the fixing is performed. The outer peripheral surface of the belt 102 has a temperature characteristic according to the curve 232.

  Although the case where the temperature Tb (point 230) of the temperature-sensitive magnetic plate 114 is lower than the temperature Ta of the inner peripheral surface of the fixing belt 102 has been described above, the temperature Tb (point 230) of the temperature-sensitive magnetic plate 114 is fixed. The same applies to the case where the temperature is higher than the temperature Ta of the inner peripheral surface of the belt 102.

  FIG. 10 shows an example of the transition of the temperature of each part when the fixing belt 102 and the contact member 152 are brought into contact when the temperature Tb of the temperature-sensitive magnetic plate 114 is higher than the temperature Ta of the inner peripheral surface of the fixing belt 102. Has been. As shown in FIG. 10, when the temperature Tb (point 230) of the temperature-sensitive magnetic plate 114 is higher than the temperature of the inner peripheral surface of the fixing belt 102, if the fixing belt 102 and the contact member 152 are brought into contact with each other, the contact member 152 Heat is supplied to the inner peripheral surface of the fixing belt 102, and the temperature of the inner peripheral surface of the fixing belt 102 rapidly increases, while the temperature of the outer peripheral surface of the fixing belt 102 decreases.

  When the contact member 152 and the inner peripheral surface of the fixing belt 102 are in contact with each other (the time t1), the coefficient setting unit 202 sets the second coefficient k2 smaller than the first coefficient k1 as the power temperature coefficient K, thereby exciting the coefficient. The coil 110 is supplied with a supply power I having a characteristic 237 in which fluctuations are suppressed. As a result, the temperature of the outer peripheral surface of the fixing belt 102 (surface temperature) becomes a characteristic 233 in which a steep decrease is suppressed, and the outer peripheral surface of the fixing belt 102 is compared with the temperature fluctuation due to the normal first coefficient k1. , Temperature fluctuation can be suppressed. Further, for example, when the temperature Ta of the inner peripheral surface of the fixing belt 102 reaches the target temperature Ts and is controlled (time t2), by returning to the first coefficient k1, the inside of the fixing belt 102 during the fixing process. It is possible to respond quickly to changes in the temperature of the peripheral surface.

  The first coefficient k1 and the second coefficient k2 are the target temperature Ts, the thermal resistance from the fixing belt 102 to the sheet member P, and the processing amount (productivity) per unit time of the sheet member P to be fixed by the fixing device 100. It can be determined experimentally from the values of thermal conductivity and heat capacity of the fixing belt 102 and thermal resistance when the temperature-sensitive magnetic plate 114 and the fixing belt 102 are in contact with each other.

  The device control unit 36 including the temperature control device 200 described above can be realized by a computer.

  In FIG. 11, an example of a computer capable of realizing the device control unit 36 including the temperature control device 200 is shown as a computer 201. The computer 201 includes a CPU 210, a memory 212, a nonvolatile storage unit 214, and an input / output port (I / O) 222, which are connected to each other via a bus 224. The I / O 222 rotates the AD converter 226 connected to the temperature detection sensor 134, the AD converter 228 connected to the temperature detection sensor 135, the driver 230 connected to the excitation coil 110, and the eccentric cam 182. The driver 232 connected to the drive member 183 and the driver 234 connected to the various mechanism drive units 101 of the image forming apparatus 10 are also connected.

  The storage unit 214 can be realized by an HDD (Hard Disk Drive), a flash memory, or the like. In the storage unit 214 as a recording medium, a temperature control program 215 and a basic operation control program 220 for causing the computer 201 to function as the device control unit 36 are stored. The temperature control program 215 includes a target temperature control process 217 and a coefficient setting process 219. The storage unit 214 stores various data 221 such as information indicating the first coefficient k1, the second coefficient k2, and the target temperature Ts. The CPU 210 reads out each of the temperature control program 215 and the basic operation control program 220 from the storage unit 214, expands it in the memory 212, and executes each process.

  When processing by the temperature control program 215 is executed, a storage area 208 for storing information indicating the power temperature coefficient K is secured in the memory 212.

  The basic operation control program 220 is a program for controlling the image forming operation of the image forming apparatus 10. That is, the CPU 210 controls the various mechanism driving units 101 of the image forming apparatus 10 for performing the image forming operation of the image forming apparatus 10 by executing the basic operation control program 220. Accordingly, the computer 201 that has executed the basic operation control program 220 functions as the device control unit 36 that executes the basic operation of the image forming apparatus 10. When the computer 201 executes the basic operation control program 220 and functions as the apparatus control unit 36, the image forming operation of the image forming apparatus 10 is executed as described above.

  The temperature control program 215 is a program for executing temperature control of the fixing belt 102. The CPU 210 executes the target temperature control process 217 and the coefficient setting process 219 by executing the temperature control program 215. The CPU 210 operates as the temperature control device 200 shown in FIG. 7 by executing the temperature control program 215. That is, the apparatus control unit 36 is realized by the computer 201, and the computer 201 is operated as the temperature control apparatus 200 shown in FIG. 7 by executing the temperature control program 215. Further, the CPU 210 operates as the target temperature control unit 206 shown in FIG. 7 by executing the target temperature control process 217 included in the temperature control program 215. Further, the CPU 210 operates as the coefficient setting unit 202 illustrated in FIG. 7 by executing the coefficient setting process 219 included in the temperature control program 215.

  Next, the operation of the computer 201 functioning as the device control unit 36 including the temperature control device 200 will be described.

  FIG. 12 shows an example of the processing flow of the temperature control device 200. The CPU 210 periodically executes the processing routine shown in FIG.

  First, in step 300, information indicating the temperature Ta of the inner peripheral surface of the fixing belt 102 detected by the temperature detection sensor 134 is acquired. In the next step 302, the information indicating the separation position (FIG. 3) or the contact position (FIG. 4) of the contact member 152 output from the drive member 183 is discriminated to thereby determine the inner peripheral surface of the contact member 152 and the fixing belt 102. Is separated from each other. If the contact member 152 is in the separated position, an affirmative determination is made in step 302, and the process proceeds to step 308. In step 308, the first coefficient k1 at the normal time is set as the power temperature coefficient K. That is, the CPU 210 acquires the first coefficient k1 from the data 221 and stores it in the storage area 208 secured in the memory 212.

  Next, in step 310, the supplied power I is calculated according to the above arithmetic expression. That is, the CPU 210 acquires the target temperature Ts from the data 221, acquires the power temperature coefficient K stored in the storage area 208, and detects the temperature Ta of the inner peripheral surface of the fixing belt 102 detected by the temperature detection sensor 134. To get. Here, the first coefficient k1 is acquired as the power temperature coefficient K. Then, using each information indicating the target temperature Ts, the power temperature coefficient K, and the temperature Ta of the inner peripheral surface of the fixing belt 102, the supply power I is calculated according to an arithmetic expression. In the next step 312, the supply power I calculated in step 310 is supplied to the exciting coil 110. That is, when the CPU 210 outputs information indicating the supply power I calculated in step 310 to the driver 230, the driver 230 supplies the supply power I to the excitation coil 110.

  On the other hand, if the contact member 152 is in the contact position, a negative determination is made in step 302, and the process proceeds to step 304. In step 304, it is determined whether or not the temperature Ta of the inner peripheral surface of the fixing belt 102 has reached the target temperature Ts. In step 304, it may be determined whether or not the temperature Ta of the inner peripheral surface of the fixing belt 102 is included in a temperature range that is predetermined with respect to the target temperature Ts. When an affirmative determination is made in step 304, the process proceeds to step 308, and the first coefficient k1 is set as the power temperature coefficient K. On the other hand, if a negative determination is made in step 304, the process proceeds to step 306. In step 306, the power coefficient K is set to a second coefficient k2 smaller than the normal first coefficient k1. That is, the CPU 210 acquires the second coefficient k2 from the data 221 and stores it in the storage area 208 secured in the memory 212, and the process proceeds to step 310. In step 310 in this case, the supply power I smaller than the value of the first coefficient k1 is calculated by the second coefficient k2 as the power temperature coefficient K and supplied to the exciting coil 110.

  As described above, in the present embodiment, the contact member 152 and the inner peripheral surface of the fixing belt 102 are separated from each other during the fixing process in which the temperature Ta of the inner peripheral surface of the fixing belt 102 is controlled to the target temperature Ts. In this case, the supply power I calculated using the normal first coefficient k1 is supplied to the exciting coil 110. Thereby, it is possible to quickly cope with a temperature change of the inner peripheral surface of the fixing belt 102 with respect to the target temperature Ts.

  In the present embodiment, when the contact member 152 and the inner peripheral surface of the fixing belt 102 are in contact with each other, the supply power I calculated using the second coefficient k2 instead of the first coefficient k1 is supplied to the excitation coil 110. Supplied. As a result, the influence of the steep temperature fluctuation generated on the inner peripheral surface of the fixing belt 102 is suppressed, and the temperature fluctuation on the outer peripheral surface of the fixing belt 102 can be suppressed.

  Furthermore, in this embodiment, when the contact member 152 and the inner peripheral surface of the fixing belt 102 are in contact with each other and the second coefficient k2 is set, the temperature Ta of the inner peripheral surface of the fixing belt 102 is the target temperature Ts. Is reached, the power temperature coefficient K is returned to the first coefficient k1. As a result, it is possible to quickly return to a state in which the temperature change of the inner peripheral surface of the fixing belt 102 with respect to the target temperature Ts can be dealt with.

  In the above embodiment, the preferable power temperature coefficient K when the contact member 152 and the inner peripheral surface of the fixing belt 102 are brought into contact with each other is not limited to one second coefficient k2, and a plurality of coefficients are determined. Also good. For example, a temperature difference between the target temperature Ts and the temperature of the inner peripheral surface of the fixing belt 102 may be determined in stages, and a coefficient corresponding to each stage may be used as the power temperature coefficient.

  In the above embodiment, the case where the second coefficient k2 smaller than the first coefficient k1 is set as the power temperature coefficient K when the contact member 152 and the inner peripheral surface of the fixing belt 102 are in contact with each other has been described. The present invention is not limited to this. For example, when the contact member 152 and the inner peripheral surface of the fixing belt 102 are in contact with each other, the temperature fluctuation amount of the inner peripheral surface of the fixing belt 102 is acquired, and the acquired temperature fluctuation amount exceeds a predetermined fluctuation amount. Alternatively, the second coefficient k2 may be set. In this case, the predetermined fluctuation amount may be applied by separately determining each of the upper limit value and the lower limit value.

  Although the present invention has been described in detail with respect to specific embodiments, the present invention is not limited to such embodiments, and various other embodiments can be taken within the scope of the present invention. .

  In each of the above embodiments, the processing performed by executing the program stored in the storage unit 214 has been described. However, the processing of the program may be realized by hardware.

  Further, the processing in each of the above embodiments may be stored and distributed as a program in a storage medium such as an optical disk.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Image forming unit (an example of an image forming part)
36 Device control unit 100 Fixing device 102 Fixing belt (an example of an endless member)
110 Excitation coil (an example of a magnetic field generator)
134 Temperature detection sensor (an example of a detection unit)
135 Temperature detection sensor 152 Contact member (an example of a moving member)
200 Temperature controller (an example of a control unit)
202 Coefficient setting unit (an example of a setting unit)
206 Target temperature controller

Claims (7)

A rotatable endless member heated by induction heating with a magnetic field;
A moving member that is heated by the induction heating and is movable in a direction in which the endless member is in contact with or separated from the inner peripheral surface;
A fixing device in which the temperature of the inner peripheral surface of the endless member is controlled to a target temperature by changing the magnetic field according to the temperature of the inner peripheral surface of the endless member,
The rate of change of the magnetic field with respect to the temperature of the inner peripheral surface of the endless member when the moving member is in contact with the inner peripheral surface of the endless member during the fixing process by the endless member and the pressure member The temperature of the inner peripheral surface of the endless member is made smaller than the rate of change of the magnetic field with respect to the temperature of the inner peripheral surface of the endless member when the member is moved to a position separated from the inner peripheral surface of the endless member. A fixing device comprising a control unit for controlling the operation. When the moving member is moved to a position separated from the inner peripheral surface of the endless member, the control unit is configured to change the inner periphery of the endless member until the temperature of the inner peripheral surface of the endless member reaches a target temperature. When the moving member is in contact with the inner peripheral surface of the endless member, the temperature of the inner peripheral surface of the endless member is controlled by a normal change rate determined in advance as the rate of change of the magnetic field with respect to the surface temperature. The fixing device according to claim 1, wherein the fixing device is controlled with a change rate smaller than the predetermined normal change rate until the temperature reaches a target temperature. When the moving member is moved to a position separated from the inner peripheral surface of the endless member, a coefficient of a first value indicating a rate of change of the magnetic field with respect to the temperature of the inner peripheral surface of the endless member is set, and the movement A setting unit that sets a second value coefficient smaller than the first value coefficient when the member is in contact with the inner peripheral surface of the endless member;
The control unit controls the temperature of the inner peripheral surface of the endless member to a target temperature using the coefficient set by the setting unit and the difference between the temperature of the inner peripheral surface of the endless member and the target temperature. The fixing device according to claim 1 or 2. Including a detector for detecting the temperature of the inner peripheral surface of the endless member,
The fixing device according to claim 1, wherein the control unit controls the temperature of the inner peripheral surface of the endless member detected by the detection unit to be the target temperature. The controller is configured to reduce the endless member when the moving member is in contact with the inner peripheral surface of the endless member and when the temperature of the inner peripheral surface of the endless member reaches the target temperature . The rate of change of the magnetic field with respect to the temperature of the inner peripheral surface is returned to the rate of change of the magnetic field with respect to the temperature when the moving member is moved to a position separated from the inner peripheral surface of the endless member. The fixing device according to claim 1. An image forming unit for forming an image on a recording medium;
The fixing device according to any one of claims 1 to 5, wherein an image is fixed on a recording medium on which an image is formed by the image forming unit.
An image forming apparatus comprising: Comprising a rotatable endless member heated by induction heating by magnetic field, it is heated by the induction heating, and the a movable member movable toward or away from the inner peripheral surface of the endless member, wherein A temperature control program in a fixing device in which the temperature of the inner peripheral surface of the endless member is controlled to a target temperature by changing the magnetic field according to the temperature of the inner peripheral surface of the endless member,
The rate of change of the magnetic field with respect to the temperature of the inner peripheral surface of the endless member when the moving member is in contact with the inner peripheral surface of the endless member during the fixing process by the endless member and the pressure member The temperature of the inner peripheral surface of the endless member is made smaller than the rate of change of the magnetic field with respect to the temperature of the inner peripheral surface of the endless member when the member is moved to a position separated from the inner peripheral surface of the endless member. A temperature control program for causing a computer to execute a process including controlling.