JP2016161637A - Fixing device, image forming apparatus, and temperature control program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a variation in temperature of an endless member that occurs when the endless member is in contact with a temperature-sensitive magnetic member.SOLUTION: When a fixing belt is heated while a contact member and an inner peripheral surface of the fixing belt are separated from each other and the temperature of the inner peripheral surface of the fixing belt is controlled to be a control temperature (310, 312), and the temperature of the contact member is within a predetermined temperature range (314, 316), the contact member and the inner peripheral surface of the fixing belt are brought into contact with each other (318). Thus, rapid transfer of heat can be suppressed in the contact member (152) and fixing belt (102).SELECTED DRAWING: Figure 13

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.

  Patent Document 2 includes a fixing belt and a temperature-sensitive magnetic member that can move toward the fixing belt. The fixing belt is moved at a first speed, and the temperature-sensitive magnetic member is moved toward the fixing belt. After that, a fixing device is disclosed in which the fixing belt is moved at a second speed higher than the first speed.

JP 2009-282413 A JP2013-020216A

  The present invention suppresses 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, as compared with a case where the moving member having a temperature outside the allowable range is brought into contact with the endless member. An object of the present invention is to provide a fixing device, an image forming apparatus, and a temperature control program.

  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. The moving member and the temperature of the inner peripheral surface of the endless member are controlled to a target temperature by controlling the magnitude of the magnetic field, and the moving member is moved to a position separated from the inner peripheral surface of the endless member in advance. When the temperature of the moving member during the fixing process by the endless member and the pressure member is within an allowable range determined according to the target temperature, the inner peripheral surface of the endless member is moved in the contact direction. And a control unit that performs control to contact the device.

  A fixing device according to a second aspect is the fixing device according to the first aspect, wherein a first detection unit that detects a temperature of an inner peripheral surface of the endless member, and a second detection unit that detects a temperature of the moving member; The control unit controls the magnitude of the magnetic field so that the temperature of the endless member detected by the first detection unit becomes the target temperature, and the second detection unit during the fixing process When the temperature of the moving member detected in step 1 is within the allowable range, the moving member is moved in the contact direction to contact the inner peripheral surface of the endless member.

  According to a third aspect of the present invention, in the fixing device according to the first or second aspect, the controller controls the temperature of the moving member to be within the allowable range before moving the moving member in the contact direction. When the temperature is predicted, and when the estimated time has elapsed, the moving member is moved in the contact direction so as to come into contact with the inner peripheral surface of the endless member.

  4. The image forming apparatus according to claim 4, wherein the image forming unit forms an image on a recording medium, and the image is fixed to the recording medium on which the image is formed by the image forming unit. A fixing device according to the item.

  A temperature control program according to claim 5 controls a computer to control a temperature of an inner peripheral surface of a rotatable endless member heated by induction heating by the magnetic field to a target temperature. In addition, a moving member that is heated by the induction heating and that is movable in a direction in which the endless member is brought into contact with or separated from the inner peripheral surface is moved in the separation direction in advance, and the endless member and the pressure member are used. A process including a control of moving the moving member in a contact direction to contact the inner peripheral surface of the endless member when the temperature of the moving member during the fixing process is within an allowable range determined according to the target temperature. Let it run.

  According to the fixing device of the first aspect, the temperature of the endless member generated when 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 moving member having a temperature outside the allowable range is brought into contact with the endless member. Variations can be suppressed.

  According to the fixing device of the second aspect, it is possible to acquire the temperatures of the endless member and the moving member with higher accuracy than when the first detection unit and the second detection unit are not provided.

  According to the fixing device of the third aspect, the endless member and the moving member can be obtained by a simple process as compared with the case where the moving member is brought into contact with the endless member without predicting the time until the moving member reaches the allowable range. Can be contacted.

  According to the image forming apparatus of the fourth 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 third aspects is not provided. The decrease can be suppressed.

  According to the temperature control program of claim 5, the endless member generated when the endless member and the moving member are brought into contact with each other during the fixing process is compared with the case where the moving member having a temperature outside the allowable range is brought into contact with the endless member. Temperature fluctuation can be suppressed.

1 is a configuration diagram illustrating an example of an image forming apparatus according to a first embodiment. 1 is a cross-sectional view illustrating an example of a fixing device according to a first embodiment. 1 is a cross-sectional view illustrating an example of a fixing device according to a first embodiment. 1 is a cross-sectional view illustrating an example of a fixing device according to a first embodiment. FIG. 3 is a cross-sectional view illustrating an example of a fixing belt according to the first embodiment. It is explanatory drawing of the temperature-sensitive magnetic board used for the fixing apparatus which concerns on 1st Embodiment, (A) is sectional drawing of a temperature-sensitive magnetic board, (B) shows the relationship between the magnetic permeability of a temperature-sensitive magnetic member, and temperature. It is a schematic diagram. It is a block diagram which shows an example of the temperature control apparatus contained in the control part which concerns on 1st 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 a relationship between a temperature fluctuation of the fixing belt and a temperature of the temperature-sensitive magnetic plate. 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 a temperature maintenance control part. It is a flowchart which shows an example of the flow of a process of a temperature fluctuation suppression control part. It is a flowchart which shows an example of the flow of a temperature determination process. 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 the control part which concerns on 2nd Embodiment. It is a flowchart which shows an example of the flow of the temperature determination process which concerns on 2nd Embodiment. It is a characteristic view which shows an example of transition of the temperature of the contact member and fixing belt which concern on 2nd Embodiment.

  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.

(First embodiment)
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 examples of the forming unit are provided on the center side in the housing 11 of the image forming apparatus 10. Each of the image forming units 12 </ b> Y to 12 </ b> K is arranged to be inclined obliquely toward the lower left direction with respect to 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. 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, a control unit 36 that controls driving 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 image processing by the control unit 36 is converted into color material gradation data for 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 an endless member) is moved to a non-pressure position that is separated from the fixing belt 102, and the contact member 152 is an inner peripheral surface of the fixing belt 102. An example of a state in which it has been moved to a separated position 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, polyimide having a thickness of 60 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).

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

  FIG. 7 shows an example of the temperature control device 200 included in the control unit 36. The temperature control device 200 includes a temperature fluctuation suppression control unit 202 and a temperature maintenance control unit 204. A temperature detection sensor 134 that detects the temperature of the inner peripheral surface of the fixing belt 102 and a temperature detection sensor 135 that detects the temperature of the temperature-sensitive magnetic plate 114 are connected to the temperature fluctuation suppression control unit 202. In addition, a drive member 183 for rotating the eccentric cam 182 is connected to the temperature fluctuation suppression control unit 202. A temperature detection sensor 134 and an excitation coil 110 are connected to the temperature maintenance control unit 204.

  The temperature maintenance control unit 204 executes temperature control so that the temperature of the fixing belt 102 becomes a control temperature as a predetermined target temperature. In this embodiment, the temperature maintenance control unit 204 executes temperature control so that the temperature Ta of the inner peripheral surface of the fixing belt 102 becomes a predetermined control temperature Ts. In the present embodiment, the temperature maintenance control unit 204 supplies electric power, that is, alternating current to the exciting coil 110, and generation and disappearance of the magnetic field HA are repeated 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.

  Further, the temperature maintenance control unit 204 detects the temperature Ta of the inner peripheral surface of the fixing belt 102 that has been heated by the temperature detection sensor 134, and when the temperature is equal to or higher than the control temperature Ts (for example, 170 degrees Celsius) as the target temperature. The supply of alternating current to the exciting coil 110 is restricted (for example, the supply is stopped). Further, when the temperature Ta of the inner peripheral surface of the fixing belt 102 is lower than the control temperature Ts, supply of alternating current to the exciting coil 110 is increased (for example, supply is resumed). As a result, the temperature Ta of the inner peripheral surface of the fixing belt 102 is maintained at a predetermined control temperature Ts.

  The temperature fluctuation suppression control unit 202 executes control for suppressing temperature fluctuation when the temperature Ta of the inner peripheral surface of the fixing belt 102 is controlled to the control temperature Ts. In this embodiment, the temperature fluctuation suppression control unit 202 controls the rotation of the eccentric cam 182 and suppresses the temperature fluctuation by bringing the heated temperature-sensitive magnetic plate 114 into and out of contact with the fixing belt 102. That is, the magnetic field HA generated by the supply of alternating current to the exciting coil 110 penetrates to the temperature-sensitive magnetic plate 114, and the temperature-sensitive magnetic plate 114 generates heat. In this case, the contact member 152 including the generated heat-sensitive magnetic plate 114 is moved from the separated position (FIG. 3) to the contact position (FIG. 4) by the rotation of the eccentric cam 182. As a result, the contact member 152 and the inner peripheral surface of the fixing belt 102 come into contact with each other, so that heat is supplied from the temperature-sensitive magnetic plate 114 to the fixing belt 102 and the contact member 152 moves to the separated position. Thus, the temperature drop of the fixing belt 102 is suppressed.

  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, that is, the temperature Tb of the temperature-sensitive magnetic plate 114, and the temperature of the fixing belt 102, that is, the inner peripheral surface of the fixing belt 102 are measured. If the temperature Ta is different, heat is exchanged 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 control temperature Ts, 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 increases. 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 (dotted line), and the temperature characteristic of the thermosensitive magnetic plate 114 is indicated by a curve 230 (dashed line). Further, the temperature characteristic of the temperature (surface temperature) of the outer peripheral surface of the fixing belt 102 is shown by a curve 232 (solid line). In FIG. 8, the supply characteristic of the power supplied to the exciting coil 110 is shown by a curve 236 (two-dot chain line). Also, the conveyance timing of the sheet member P conveyed to the fixing device 100, that is, the fixing belt 102 in order to fix the toner images of the respective colors is indicated by a rectangular waveform 238.

  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, since the fixing belt 102 and the contact member 152 are separated from each other, the temperature of the fixing belt 102 rises earlier than the temperature-sensitive magnetic plate 114. When the temperature Ta of the fixing belt 102 reaches the control temperature Ts or a preset fixing temperature when the power is turned on (time t1), the supply of alternating current to the exciting coil 110 is suppressed. When the temperature of the fixing belt 102 is controlled to the control temperature Ts (time t2), the conveyance of the sheet member P is started.

  The temperature of the temperature-sensitive magnetic plate 114 rises in a state where the fixing belt 102 and the contact member 152 are separated from each other. For example, when the temperature becomes equal to or higher than the control temperature Ts (time t3), The contact member 152 is brought into contact. In this case, since the temperature Tb of the temperature-sensitive magnetic plate 114 is higher than the temperature of the inner peripheral surface of the fixing belt 102, heat is supplied from the contact member 152 to the inner peripheral surface of the fixing belt 102, and the fixing belt 102 is kept in a thermal equilibrium state. The temperature of the inner peripheral surface of the rises sharply. At this time, the temperature Ta of the inner peripheral surface of the fixing belt 102 has a temperature change width 240 that changes in the temperature increasing direction. On the other hand, when the temperature of the inner peripheral surface of the fixing belt 102 rises sharply, the supply of alternating current to the exciting coil 110 may be stopped in order to suppress the temperature rise. However, since the heat supply does not reach the outer peripheral surface of the fixing belt 102 and the temperature (surface temperature) does not rise, the heat generation is stopped by stopping the supply of alternating current to the exciting coil 110, and the alternating current to the exciting coil 110 is stopped. The temperature decreases until the supply of current is resumed (time t4). At this time, the temperature of the outer peripheral surface of the fixing belt 102 has a temperature change width 242 that changes in the temperature decreasing direction. As described above, even when the temperature Ta of the inner peripheral surface of the fixing belt 102 is detected and the temperature control is performed so that the temperature becomes the control temperature Ts, the outer peripheral surface (surface of the fixing belt 102). ) May change.

  On the other hand, even when the fixing belt 102 and the contact member 152 are brought into contact with each other when the temperature Tb of the temperature-sensitive magnetic plate 114 is lower than the temperature of the inner peripheral surface of the fixing belt 102, the temperature of the fixing belt 102 may be changed.

  FIG. 9 shows the temperature of the contact member 152 and the fixing belt 102 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 lower than the temperature of the inner peripheral surface of the fixing belt 102. An example of the transition is shown. As shown in FIG. 9, 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 lower than the temperature of the inner peripheral surface of the fixing belt 102, the inner surface of the fixing belt 102 Heat is supplied to the contact member 152, that is, heat is taken away from the fixing belt 102, and the temperature of the inner peripheral surface of the fixing belt 102 rapidly decreases while the temperature of the outer peripheral surface of the fixing belt 102 increases. This is because when the temperature of the inner peripheral surface of the fixing belt 102 is low, the supply of alternating current to the exciting coil 110 is restarted or increased, and the temperature of the fixing belt 102 is increased.

  Therefore, in the present embodiment, when the temperature variation suppression control unit 202 controls the temperature Ta of the inner peripheral surface of the fixing belt 102 to the control temperature Ts, control for suppressing temperature variation is executed. In other words, the temperature fluctuation suppression control unit 202 has a temperature Tb of the temperature-sensitive magnetic plate 114 that is not more than the temperature Ta of the inner peripheral surface of the fixing belt 102 and within a temperature range as an allowable range that is not less than a predetermined threshold Tth from the control temperature Ts. When (Tth ≦ Tb ≦ Ta), the contact member 152 and the inner peripheral surface of the fixing belt 102 are brought into contact with each other. Note that the threshold value Tth is the control temperature Ts, the thermal resistance from the fixing belt 102 to the sheet member P, the processing amount (productivity) of the sheet member P to be fixed by the fixing device 100, and the heat conduction of the fixing belt 102. It can be experimentally determined from the values of heat rate and heat capacity, and thermal resistance when the temperature-sensitive magnetic plate 114 and the fixing belt 102 are in contact with each other. By doing in this way, the temperature fluctuation of the fixing belt 102 can be suppressed as compared with the case where the timing of contacting the fixing belt 102 and the contact member 152 is not taken into consideration.

  FIG. 10 shows characteristics obtained by experimentally determining the relationship between the temperature fluctuation of the outer peripheral surface of the fixing belt 102 and the temperature Tb of the temperature-sensitive magnetic plate 114. In FIG. 10, when the temperature fluctuation value is set to the vertical axis, the temperature Tb of the temperature-sensitive magnetic plate 114 is set to the horizontal axis, and the temperature Ta of the inner peripheral surface of the fixing belt 102 is controlled to the control temperature Ts, the contact member. A temperature fluctuation characteristic of the outer peripheral surface of the fixing belt 102 that occurs when 152 is brought into contact with the inner peripheral surface of the fixing belt 102 is indicated by a curve 250 (solid line). In addition, a temperature fluctuation characteristic of the inner peripheral surface of the fixing belt 102 that occurs when the contact member 152 and the inner peripheral surface of the fixing belt 102 are brought into contact with each other is indicated by a curve 252 (dashed line).

  As shown in FIG. 10, the contact member 152 and the inner peripheral surface of the fixing belt 102 are in contact with each other, the temperature-sensitive magnetic plate 114 is less than the temperature Tmin, and the temperature on the outer peripheral surface of the fixing belt 102 increases ( It was found that when the temperature fluctuates beyond the fluctuation value Eg on the positive side, fixing failure of the toner image (so-called gloss unevenness) occurs. Further, the contact member 152 and the inner peripheral surface of the fixing belt 102 are brought into contact with each other, the temperature-sensitive magnetic plate 114 exceeds the temperature Tmax, and the fluctuation value is on the side where the temperature of the outer peripheral surface of the fixing belt 102 decreases (minus side). It has been found that the toner image is poorly fixed even when the temperature fluctuates beyond Ec. It was also found that the temperature Tmax of the temperature-sensitive magnetic plate 114 is the same as or close to the control temperature Ts. Therefore, it is preferable that the fixing belt 102 and the contact member 152 are brought into contact with each other when the temperature fluctuation value of the outer peripheral surface of the fixing belt 102 is within the range of the fluctuation values Eg to Ec. As a result, the temperature range from the temperature Tmin of the temperature-sensitive magnetic plate 114 corresponding to the variation value Eg to the temperature Tmax of the temperature-sensitive magnetic plate 114 corresponding to the variation value Ec changes between the contact member 152 and the inner peripheral surface of the fixing belt 102. The temperature range is preferable for contact, and the threshold value Tth for the control temperature Ts can be obtained using this temperature range.

  A preferable temperature range for bringing the contact member 152 into contact with the inner peripheral surface of the fixing belt 102 is not limited to the temperature range from the temperature Tmin to the temperature Tmax of the temperature-sensitive magnetic plate 114. For example, a plurality of stages may be defined as the toner image fixing quality, and a temperature range corresponding to each of the plurality of stages of fixing quality may be determined.

  In the above description, the threshold value Tth is obtained as the lower limit value for the control temperature Ts. However, the threshold value as the upper limit value for the control temperature Ts may be obtained. In this case, the temperature range (allowable range) can be determined by the upper limit value and the lower limit value for the control temperature Ts.

  Further, the temperature range determined with respect to the control temperature Ts may be determined from a temperature gradient due to temperature fluctuations on the inner peripheral surface of the fixing belt 102.

  That is, the temperature fluctuation of the fixing belt 102 that occurs when the contact member 152 and the fixing belt 102 come into contact depends on the heat transfer between the contact member 152 and the fixing belt 102. The temperature fluctuation of the fixing belt 102 due to the heat transfer includes a control temperature Ts, a thermal resistance from the fixing belt 102 to the sheet member P, a processing amount (productivity) per unit time of the sheet member P to be fixed by the fixing device 100, The temperature of the inner peripheral surface of the fixing belt 102 changes in accordance with a physical quantity determined from each value of the thermal conductivity and heat capacity of the fixing belt 102 and the thermal resistance when the temperature-sensitive magnetic plate 114 and the fixing belt 102 are in contact with each other. It appears to appear in the temperature gradient due to fluctuations.

  Therefore, a temperature gradient in which the temperature of the inner peripheral surface of the fixing belt 102 fluctuates sharply increases or decreases is set to a temperature range corresponding to the temperature fluctuation of the fixing belt 102 that causes poor fixing. For example, the temperature gradient 241 due to a steep rise in the inner peripheral surface of the fixing belt 102 shown in FIG. The upper limit temperature of the contact member 152 is set as a positive threshold. Further, the temperature gradient 241 due to the steep descent of the inner peripheral surface of the fixing belt 102 shown in FIG. The lower limit temperature of 152 is set as a negative threshold value. The temperature range is determined from the upper and lower thresholds. In the fixing device 100 of the present embodiment, as an example of the temperature gradient 241, when the positive temperature gradient 241 is 6.8 degrees Celsius / second or more, the negative temperature gradient 241 is −5.8 degrees Celsius / second. Experimental results have been obtained in the following cases that may result in poor fixing.

  The 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 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. The storage unit 214 as a recording medium stores a temperature maintenance control program 216, a temperature fluctuation suppression control program 218, and a basic operation control program 220 for causing the computer 201 to function as the control unit 36. The CPU 210 reads out each of the temperature maintenance control program 216, the temperature fluctuation suppression control program 218, and the basic operation control program 220 from the storage unit 214, expands it in the memory 212, and executes each process.

  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 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 control unit 36, the image forming operation of the image forming apparatus 10 is executed as described above.

  The temperature maintenance control program 216 is a program for executing temperature control of the fixing belt 102. The CPU 210 operates as the temperature maintenance control unit 204 shown in FIG. 7 by executing the temperature maintenance control program 216. That is, the control unit 36 is realized by the computer 201, and the computer 201 is operated as the temperature maintenance control unit 204 (FIG. 7) by executing the temperature maintenance control program 216. The temperature fluctuation suppression control program 218 is a program for executing control for suppressing temperature fluctuation of the fixing belt 102. The CPU 210 operates as the temperature fluctuation suppression control unit 202 shown in FIG. 7 by executing the temperature fluctuation suppression control program 218. When the computer 201 executes the processes of the temperature maintenance control program 216 and the temperature fluctuation suppression control program 218, the computer 201 functions as the temperature control device 200 shown in FIG.

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

  FIG. 12 shows an example of the processing flow of the temperature maintenance control unit 204 included in 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, it is determined whether or not the temperature Ta of the inner peripheral surface of the fixing belt 102 is the same as the control temperature Ts. When the temperature Ta of the inner peripheral surface of the fixing belt 102 is the same as the control temperature Ts (Ts = Ta), the process proceeds to step 306 and the supply of alternating current to the exciting coil 110 is maintained. In step 302, an approximate temperature between the temperature Ta of the inner peripheral surface of the fixing belt 102 and a predetermined minute temperature range with respect to the control temperature Ts may be determined as the same temperature. When the temperature Ta of the inner peripheral surface of the fixing belt 102 exceeds the control temperature Ts (Ts <Ta), the process proceeds to step 304, and the supply of alternating current to the exciting coil 110 is limited or stopped. . When the temperature Ta of the inner peripheral surface of the fixing belt 102 is lower than the control temperature Ts (Ts> Ta), the process proceeds to step 308 and the supply of alternating current to the exciting coil 110 is increased or maintained. Thus, the CPU 210 controls the supply of alternating current to the exciting coil 110 so that the temperature Ta of the inner peripheral surface of the fixing belt 102 is maintained at the control temperature Ts.

  FIG. 13 shows an example of the processing flow of the temperature fluctuation suppression control unit 202 included in the temperature control device 200. The CPU 210 periodically executes the processing routine shown in FIG.

  First, in step 310, the positional relationship between the contact member 152 and the fixing belt 102 is determined. That is, the rotational position of the drive member 183 is acquired, and it is determined whether the contact member 152 is moved to the separated position (FIG. 3) or the contact position (FIG. 4) by the eccentric cam 182. Thus, the positional relationship between the contact member 152 and the fixing belt 102 is determined. In the next step 312, it is determined whether the positional relationship between the contact member 152 and the fixing belt 102 is separated from the determination result in step 310. If a negative determination is made in step 312, this processing routine is terminated as it is. If an affirmative determination is made, the process proceeds to step 314.

  In step 314, a temperature determination process (details will be described later) for determining whether the contact member 152 is movable is executed. In the temperature determination process, a temperature determination flag indicating that the temperature Tb of the temperature-sensitive magnetic plate 114 is a temperature at which the contact member 152 can be moved is set or reset. In the next step 316, it is determined whether or not the contact member 152 is movable from the determination result (temperature determination flag) in step 314. If the temperature determination flag has been reset and a negative determination is made in step 316, the present processing routine is terminated. On the other hand, if the temperature determination flag is set and an affirmative determination is made, the process proceeds to step 318. In step 318, a movement process for moving the contact member 152 from the separated position to the contact position is executed. That is, the eccentric cam 182 is rotated by rotating the driving member 183, and the contact member 152 is moved from the separated position (FIG. 3) to the contact position (FIG. 4).

  FIG. 14 shows an example of the flow of the temperature determination process. The CPU 210 executes a processing routine shown in FIG. 14 as the processing in step 314 shown in FIG.

  First, in step 320, information indicating a predetermined temperature range To with respect to a control temperature Ts that is preferably contacted between the fixing belt 102 and the contact member 152 is acquired. In step 320, the lower limit temperature of the temperature range To is obtained as the threshold value Tth (= Ts−To).

  Next, in step 322, information indicating the temperature Ta (first temperature) of the inner peripheral surface of the fixing belt 102 detected by the temperature detection sensor 134 is acquired. In the next step 324, the information is detected by the temperature detection sensor 135. Information indicating the temperature Tb (second temperature) of the temperature-sensitive magnetic plate 114 is acquired.

  Next, in step 326, it is determined whether or not the temperature Tb of the temperature-sensitive magnetic plate 114 is included in the temperature range To (Tth ≦ Tb ≦ Ta). When the temperature Tb of the temperature-sensitive magnetic plate 114 is included in the temperature range To (Tth ≦ Tb ≦ Ta), the temperature Tb of the temperature-sensitive magnetic plate 114 is a temperature at which the fixing belt 102 and the contact member 152 can be brought into contact with each other. The temperature is determined to be present, and a temperature determination flag is set as a determination result. On the other hand, when the temperature Tb of the temperature-sensitive magnetic plate 114 is not included in the temperature range To, the temperature determination flag is reset as a determination result.

  FIG. 15 shows an example of the temperature transition of the temperature Tb of the temperature-sensitive magnetic plate 114 and the temperature of the fixing belt 102 when the temperature is controlled by the temperature control device 200 according to the present embodiment. The image forming apparatus 10 is turned on, the temperature of the fixing belt 102 is controlled to the control temperature Ts, and the conveyance of the sheet member P is started (time t2). When the temperature Tb of the temperature-sensitive magnetic plate 114 falls within the temperature range (Tth ≦ Tb ≦ Ta), the fixing belt 102 and the contact member 152 are brought into contact (time t3). Even when the fixing belt 102 and the contact member 152 are brought into contact with each other when the temperature Tb of the temperature-sensitive magnetic plate 114 is within the temperature range, a fixing defect does not occur due to temperature fluctuation of the fixing belt 102.

  As described above, in this embodiment, when the temperature Ta of the inner peripheral surface of the fixing belt 102 is controlled to the control temperature Ts, the temperature Tb of the thermosensitive magnetic plate 114 is within the temperature range (Tth ≦ Tb ≦ Ta), the contact member 152 and the inner peripheral surface of the fixing belt 102 are brought into contact with each other. Since the contact member 152 and the fixing belt 102 are in contact with each other when the temperature Tb of the temperature-sensitive magnetic plate 114 is within the temperature range, the contact member 152 moves from the separated position to the contact position, and the inner periphery of the contact member 152 and the fixing belt 102. Temperature unevenness that occurs in the fixing belt 102 when the surface comes into contact is suppressed. Accordingly, the temperature fluctuation of the fixing belt 102 can be suppressed as compared with the case where the timing of bringing the fixing belt 102 into contact with the contact member 152 is not considered.

  Further, since the temperature unevenness generated in the fixing belt 102 is suppressed, it is possible to provide the fixing device 100 that can suppress fixing failure. Further, the image forming apparatus 10 including the fixing device 100 described above suppresses temperature unevenness that occurs in the fixing belt 102, so that deterioration in output image quality due to temperature unevenness of the fixing belt 102 is suppressed.

(Second Embodiment)
Next, a second embodiment will be described. In addition, since 2nd Embodiment is the structure similar to 1st Embodiment, it attaches | subjects the same code | symbol about the same structure, and abbreviate | omits description. In the second embodiment, the timing at which the contact member 152 and the fixing belt 102 are brought into contact is predicted, and the contact member 152 and the fixing belt 102 are brought into contact at the timing of the prediction result.

  In FIG. 16, an example of a computer capable of realizing the control unit 36 including the temperature control device 200 according to the present embodiment is shown as a computer 201. A computer 201 illustrated in FIG. 16 includes a timer 223 connected to the I / O 222. The timer 223 may be configured by hardware, or may function as a timer by software. Note that the computer 201 shown in FIG. 16 is obtained by adding a timer 223 to the computer 201 shown in FIG.

  FIG. 17 shows an example of the flow of temperature determination processing according to the present embodiment. The CPU 210 executes a processing routine shown in FIG. 17 as the processing of step 314 shown in FIG.

  First, in step 320, information indicating the temperature range To is acquired, and in step 322, information indicating the temperature Ta of the inner peripheral surface of the fixing belt 102 is acquired. Next, in step 330, information indicating the temperatures Tb1 to Tbn of the plurality of temperature-sensitive magnetic plates 114 detected continuously by the temperature detection sensor 135 is acquired. In the next step 332, using the temperatures Tb1 to Tbn of the plurality of temperature-sensitive magnetic plates 114 acquired in step 330, the temperature characteristics of the temperature-sensitive magnetic plate 114 whose temperature changes are obtained. Next, in step 334, using the temperature characteristic of the temperature-sensitive magnetic plate 114 obtained in step 332, a time tx until the temperature Tb of the temperature-sensitive magnetic plate 114 is in the temperature range is predicted and calculated. The predicted time tx is set in the timer 223 at step 336.

  In the next step 338, a negative determination is repeated until the time measured by the timer 223 has passed the time tx. When the time by the timer 223 has passed the time tx, an affirmative determination is made, and the process proceeds to step 340. In step 340, the temperature determination flag is set or reset. That is, in step 340, instead of determining whether the temperature Tb of the temperature-sensitive magnetic plate 114 is included in the temperature range To (Tth ≦ Tb ≦ Ta), the elapsed time by the timer 223 is set to the time tx as a determination process. It is determined whether or not it has elapsed. That is, the temperature determination flag is reset as a determination result until the elapsed time by the timer 223 has passed the time tx, and when the elapsed time by the timer 223 has passed the time tx, the temperature determination flag is set as the determination result. When the temperature determination flag is set, a movement process for moving the contact member 152 from the separated position to the contact position is executed (step 318 shown in FIG. 13).

  Note that in the determination process of step 340, information indicating the temperature Ta of the inner peripheral surface of the fixing belt 102 is further acquired, and the determination is made when the temperature Ta of the inner peripheral surface of the fixing belt 102 is controlled to the control temperature Ts. You may make it do.

  FIG. 18 shows an example of the temperature transition of the temperature Tb of the temperature-sensitive magnetic plate 114 and the temperature of the fixing belt 102 when the temperature is controlled by the temperature control apparatus 200 according to the present embodiment. The image forming apparatus 10 is powered on, and the temperatures of the plurality of temperature-sensitive magnetic plates 114 are acquired while the temperature Tb of the temperature-sensitive magnetic plate 114 is increasing. In the example of FIG. 18, the temperatures Tb1 and Tb2 of the temperature-sensitive magnetic plate 114 indicated by points Dt1 and Dt2 and the respective times are acquired. The temperature characteristics of the temperature-sensitive magnetic plate 114 are obtained using each of the temperature and time at the points Dt1 and Dt2. In this embodiment, as the temperature characteristics of the temperature-sensitive magnetic plate 114, the temperature change rate of the temperature-sensitive magnetic plate 114, which is the rate of temperature increase with respect to the time of the points Dt1 and Dt2, is obtained. Using the temperature change rate of the temperature-sensitive magnetic plate 114, the time Tx until the temperature Tb of the temperature-sensitive magnetic plate 114 falls within the temperature range (Tth ≦ Tb ≦ Ta), that is, the threshold Tth or more is obtained. When the time tx has elapsed, the fixing belt 102 and the contact member 152 are brought into contact with each other (time t3) assuming that the temperature Tb of the temperature-sensitive magnetic plate 114 is within the temperature range (Tth ≦ Tb ≦ Ta). Even when the fixing belt 102 and the contact member 152 are brought into contact with each other when the temperature Tb of the temperature-sensitive magnetic plate 114 is within the temperature range, a fixing defect does not occur due to temperature fluctuation of the fixing belt 102.

  As described above, in this embodiment, when the temperature Ta of the inner peripheral surface of the fixing belt 102 is controlled to the control temperature Ts, the temperature Tb of the temperature-sensitive magnetic plate 114 is predicted to be within the temperature range. The contact member 152 and the inner peripheral surface of the fixing belt 102 are brought into contact with each other while managing the time to be performed. Therefore, as compared with the case where the temperature Tb of the temperature-sensitive magnetic plate 114 reaching the temperature range is detected and the fixing belt 102 and the contact member 152 are brought into contact with each other, the temperature fluctuation of the fixing belt 102 can be caused by simple processing based on time management. Can be suppressed.

  In addition, since the temperature unevenness generated in the fixing belt 102 is suppressed by simple processing based on time management for the contact between the contact member 152 and the inner peripheral surface of the fixing belt 102, the fixing device 100 can suppress fixing failure with a simple configuration. Can be provided. Further, in the image forming apparatus 10, since the temperature unevenness generated in the fixing belt 102 is suppressed by the fixing device 100 having the above-described simple configuration, the quality of the output image due to the temperature unevenness of the fixing belt 102 can be reduced with the simple configuration. It is suppressed.

  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 a CD-ROM.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Image forming unit (an example of an image forming part)
36 Control part (an example of a control part)
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 (example of first detection unit)
135 Temperature detection sensor (example of second detection unit)
152 Contact member (an example of a moving member)
200 Temperature controller (an example of a control unit)
202 Temperature fluctuation suppression control unit 204 Temperature maintenance control unit

Claims (5)

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;
The temperature of the inner peripheral surface of the endless member is controlled to a target temperature by controlling the magnitude of the magnetic field, and the moving member is moved in advance to a position separated from the inner peripheral surface of the endless member, Control that moves the moving member in the contact direction to contact the inner peripheral surface of the endless member when the temperature of the moving member during the fixing process by the member and the pressure member is within an allowable range determined according to the target temperature A control unit for performing
A fixing device. A first detector for detecting the temperature of the inner peripheral surface of the endless member;
A second detector for detecting the temperature of the moving member;
Including
The control unit controls the magnitude of the magnetic field so that the temperature of the endless member detected by the first detection unit becomes the target temperature, and is detected by the second detection unit during the fixing process. The fixing device according to claim 1, wherein when the temperature of the moving member is within the allowable range, the moving member is moved in a contact direction to be brought into contact with an inner peripheral surface of the endless member. The control unit predicts the time when the temperature of the moving member becomes the temperature of the allowable range before moving the moving member in the contact direction, and contacts the moving member when the predicted time has elapsed. The fixing device according to claim 1, wherein the fixing device is controlled so as to move in a direction and contact with an inner peripheral surface of the endless member. An image forming unit for forming an image on a recording medium;
The fixing device according to any one of claims 1 to 3, wherein the image is fixed on a recording medium on which an image is formed by the image forming unit.
An image forming apparatus comprising: On the computer,
The computer controls the temperature of the inner peripheral surface of a rotatable endless member heated by induction heating by the magnetic field by controlling the magnitude of the magnetic field, and is heated by the induction heating, and the endless member A moving member that can move in a direction in which it is in contact with and away from the inner peripheral surface is moved in the separation direction in advance, and the temperature of the moving member during the fixing process by the endless member and the pressure member is the target temperature. A temperature control program for executing processing including moving the moving member in the contact direction and bringing it into contact with the inner peripheral surface of the endless member in the case of an allowable range determined according to.

Images