Fixation device

Abstract

To provide a fixation device that can achieve stable temperature control even right after a heating start of a fixing member.SOLUTION: According to an embodiment, a fixation device has: a fixing member; a heat source; a non-contact temperature sensor; a contact temperature sensor; a memory; and a controller. The memory is configured to store an ordinary correction value for making a detection temperature of the non-contact temperature sensor approximate to an actual temperature of the fixing member, and an additional correction value to set in responce to an average value of the detection temperature of the non-contact temperature sensor in a first period from print processing including fixation processing starts to a prescribed time. The controller is configured to control the heat source on the basis of a value correcting the detection temperature of the non-contact temperature sensor using the additional correction value in addition to the ordinary correction value in the first period, and control the heat source on the basis of a value correcting the detection temperature of the non-contact temperature sensor using the ordinary correction value in a second period after the first period has gone by.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] Embodiments of the present invention relate to a fixing device.

Background Art

[0002] An image forming apparatus placed in a workplace or the like includes a fixing device that fixes a toner image on a print medium by applying heat and pressure to the print medium on which toner has been transferred. The fixing device has a temperature sensor that detects the temperature of the surface of the fixing member. The fixing device controls so that the temperature obtained as the surface of the fixing member from the detection signal of the temperature sensor becomes a target value. The temperature sensor used in the fixing device may be a non-contact sensor. The less expensive the non-contact temperature sensor is, the more difficult it is to directly detect the exact actual temperature of the surface of the fixing member. For this reason, the fixing device corrects the detected temperature of the non-contact temperature sensor with a preset steady correction value in order to approximate the detected temperature to the actual temperature of the surface of the fixing member.

[0003] However, the temperature obtained by correcting the detected temperature of the non-contact temperature sensor with a steady correction amount may be significantly lower than the actual temperature of the surface of the fixing member immediately after the start of heating of the fixing member. For this reason, in a fixing device using a non-contact temperature sensor, problems such as poor fixing may occur due to the surface temperature of the fixing member dropping significantly below the target value immediately after the start of heating of the fixing member.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The problem to be solved by the present invention is to provide a fixing device capable of realizing stable temperature control even immediately after the start of heating of the fixing member.

Means for Solving the Problems

[0006] According to an embodiment, a fixing device includes a fixing member, a heat source, a non-contact temperature sensor, a contact temperature sensor, a memory, and a controller. The fixing member is in contact with a medium onto which a developer image is transferred. The heat source supplies heat to the fixing member. The non-contact temperature sensor non-contactly detects the temperature of a region of the fixing member through which the medium passes. The contact temperature sensor detects the temperature at a detection portion that contacts a non-pass region of the fixing member where the medium does not pass. The memory stores a steady correction value for approximating the detected temperature of the non-contact temperature sensor to the actual temperature of the fixing member and an additional correction value set according to the average value of the detected temperatures of the non-contact temperature sensor in a first period from the start of printing processing including the fixing processing to a predetermined time. The controller controls the heat source based on a value obtained by correcting the detected temperature of the non-contact temperature sensor using the additional correction value in addition to the steady correction value in the first period, and controls the heat source based on a value obtained by correcting the detected temperature of the non-contact temperature sensor using the steady correction value in a second period after the first period has elapsed.

Brief Description of the Drawings

[0007]

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BEST MODE FOR CARRYING OUT THE INVENTION

[0008] Hereinafter, an image forming apparatus according to an embodiment will be described with reference to the drawings. FIG. 1 is a diagram for explaining a configuration example of an image forming apparatus 1 including a fixing device according to the embodiment. Further, FIG. 2 is a cross-sectional view showing a configuration example around a heat roller 71 in a fixing unit 21 of the configuration example shown in FIG. 1. The image forming apparatus 1 is, for example, a digital multi-function peripheral (MFP) that performs various processes such as image formation while conveying a recording medium such as a printing medium. The image forming apparatus 1 transfers a toner image formed by an electrophotographic method to a printing medium as a recording medium, and fixes the toner image on the printing medium with a fixing device.

[0009] The image forming apparatus 1 receives toner from a toner cartridge and prints an image on a printing medium with the received toner. The toner may be a single-color toner, or may be a color toner such as cyan, magenta, yellow, and black, for example. Further, the toner may be a decolorizing toner that decolorizes when heat is applied.

[0010] As shown in FIG. 1, the image forming apparatus 1 includes a housing 11, a communication interface 12, a controller (system controller) 13, a heater control circuit 14, a display device 15, an operation device 16, a plurality of paper trays 17, a paper discharge tray 18, a conveyance mechanism 19, an image forming mechanism 20, a fixing device 21, and a power conversion circuit 22.

[0011] The housing 11 is the main body of the image forming apparatus 1. The housing 11 houses the communication interface 12, the controller 13, the heater control circuit 14, the display device 15, the operation device 16, the plurality of paper trays 17, the paper discharge tray 18, the conveyance mechanism 19, the image forming mechanism 20, the fixing device 21, and the power conversion circuit 22.

[0012] The communication interface 12 is an interface for communicating with other devices connected through a network. The communication interface 12 is used for communication with external devices. The external devices are a user terminal that instructs a printing job, or a server as an external management device, etc. The communication interface 12 is composed of, for example, a LAN connector or the like. The communication interface 12 may perform wireless communication with other devices according to a standard such as Bluetooth (registered trademark) or Wi-fi (registered trademark).

[0013] The controller (system controller) 13 controls each part of the image forming apparatus 1 and executes data processing and the like. For example, the controller 13 is a computer including a processor, a memory, and various interfaces. The controller 13 controls each part and performs data processing by the processor executing a program stored in the memory. The controller 13 is connected to each part within the housing 11 through various internal interfaces.

[0014] The controller 13 generates a print job based on image data and the like received from an external device via the communication interface 12. The image data included in the print job is data indicating an image to be formed on the print medium P. The image data may be data for forming an image on one print medium P, or may be data for forming an image on a plurality of print media P. Further, the print job may include information indicating print conditions such as information indicating whether it is color printing or monochrome printing.

[0015] The controller 13 includes an engine controller that controls the operations of the conveyance mechanism 19, the image forming mechanism 20, and the fuser 21. For example, the controller 13 controls the conveyance of the print medium P by the conveyance mechanism 19. The controller 13 controls the formation of the developer image by the image forming mechanism 20 and the transfer of the developer image to the print medium P. The controller 13 controls the fixing of the developer image to the print medium P by the fuser 21. The controller 13 forms the image of the image data included in the print job on the print medium P by controlling the operations of the conveyance mechanism 19, the image forming mechanism 20, and the fuser 21.

[0016] Note that the image forming apparatus 1 may be configured to include an engine controller separately from the controller 13. For example, the image forming apparatus 1 may be provided with an engine controller for controlling at least one of the conveyance mechanism 19, the image forming mechanism 20, the fuser 21, etc. separately from the controller 13. The engine controller provided separately from the controller 13 may obtain information necessary for control from the controller 13.

[0017] The heater control circuit 14 is a temperature control device that controls the energization of a heater 73 (center heater 731 and side heater 732) provided in a fixing device 21 to be described later based on the control of the controller 13. The heater control circuit 14 generates a first energization power and a second communication power for energizing the heater 73 of the fixing device 21. The heater control circuit 14 supplies the first energization power to the center heater 731 and the second energization power to the side heater 732. A detailed description of the heater control circuit 14 will be given later.

[0018] The display device 15 includes a display that displays an image according to an image signal input from a display control unit such as the controller 13 or a graphic controller. For example, the display device 15 displays a setting screen for various settings of the image forming apparatus 1 on the display.

[0019] The operation device 16 supplies an operation signal corresponding to an operation on the operation device to the controller 13. The operation device is, for example, a touch sensor, a numeric keypad, a power key, various function keys, or a keyboard. The touch sensor acquires information indicating a specified position within a certain area. The touch sensor may be configured as a touch panel integrally with the display device 15. Note that the display device 15 and the operation device 16 may be provided on an operation panel as a user interface.

[0020] The power conversion circuit 22 supplies a DC voltage to each part in the image forming apparatus 1 using an AC voltage from an AC power source such as an external power source. For example, the power conversion circuit 22 generates a DC voltage Vdd and Vdc from the AC voltage of the AC power source AC. The power conversion circuit 22 supplies the DC voltage Vdd to the controller 13 and the DC power supply voltage Vdc to the heater control circuit 14. Further, the power conversion circuit 22 supplies a DC voltage necessary for image formation generated from the AC voltage of the AC power source AC to the image forming mechanism 20. The power conversion circuit 22 supplies a DC voltage necessary for conveying the print medium P generated from the AC voltage of the AC power source AC to the conveyance mechanism 19.

[0021] Next, the configuration of the conveyance system in the image forming apparatus 1 will be described. The plurality of paper trays 17 are cassettes that accommodate the print medium P. The paper trays 17 are configured to be able to supply the print medium P from the outside of the housing 11. For example, the paper tray 17 is configured to be pull-outable from the housing 11. The paper discharge tray 18 is a tray that supports the print medium P discharged from the image forming apparatus 1.

[0022] The conveyance mechanism 19 is a mechanism that conveys the print medium P within the image forming apparatus 1. As shown in FIG. 1, the conveyance mechanism 19 includes a plurality of conveyance paths. For example, the conveyance mechanism 19 includes a paper feed conveyance path 31 and a paper discharge conveyance path 32.

[0023] The paper feed conveyance path 31 and the paper discharge conveyance path 32 are each constituted by a plurality of motors, a plurality of rollers, and a plurality of guides. The plurality of motors rotate the shaft based on the control of the controller 13, thereby rotating the rollers interlocked with the rotation of the shaft. The plurality of rollers move the print medium P by rotating. The plurality of guides control the conveyance direction of the print medium P.

[0024] The paper feed conveyance path 31 takes in the print medium P from the paper tray 17 and supplies the taken-in print medium P to the image forming mechanism 20. The paper feed conveyance path 31 includes pickup rollers 33 corresponding to each paper tray. Each pickup roller 33 takes in the print medium P of the paper tray 17 into the paper feed conveyance path 31.

[0025] The paper discharge conveyance path 32 is a conveyance path for discharging the print medium P on which an image has been formed to the outside of the housing 11. The print medium P discharged by the paper discharge conveyance path 32 is supported by the paper discharge tray 18.

[0026] Next, the configuration of the image forming mechanism 20 in the image forming apparatus 1 will be described. The image forming mechanism 20 forms an image on the print medium P. The image forming mechanism 20 forms an image on the print medium P based on the print job generated by the controller 13. The image forming mechanism 20 includes a plurality of process units (image forming stations) 41, a plurality of exposure units 42, and a transfer mechanism 43. The image forming mechanism 20 includes an exposure unit 42 for each process unit 41. Since the plurality of process units 41 and the plurality of exposure units 42 may each have the same configuration, one process unit 41 and one exposure unit 42 will be described respectively.

[0027] First, the process unit 41 will be described. The process unit 41 forms a toner image. For example, the plurality of process units 41 are provided for each type of toner. For example, the plurality of process units 41 respectively correspond to color toners such as cyan, magenta, yellow, and black. Specifically, a toner cartridge having different color toners is connected to each process unit 41.

[0028] The toner cartridge includes a toner storage container and a toner delivery mechanism. The toner storage container is a container for storing toner. The toner delivery mechanism is a mechanism composed of a screw or the like for sending out the toner in the toner storage container.

[0029] The process unit 41 includes a photosensitive drum 51, a charger 52, a developing device 53, and the like. The photosensitive drum 51 is a photosensitive member including a cylindrical drum and a photosensitive layer formed on the outer peripheral surface of the drum. The photosensitive drum 51 rotates at a constant speed by a driving mechanism.

[0030] The charging charger 52 uniformly charges the surface of the photoreceptor drum 51. For example, the charging charger 52 applies a voltage (development bias voltage) to the photoreceptor drum 51 using a charging roller, thereby charging the photoreceptor drum 51 to a uniform negative potential (contrast potential). The charging roller rotates as the photoreceptor drum 51 rotates while applying a predetermined pressure to the photoreceptor drum 51.

[0031] The developing device 53 is a device that attaches toner to the photoreceptor drum 51. The developing device 53 includes a developer container, a stirring mechanism, a developing roller, a doctor blade, an auto toner control (ATC) sensor, and the like.

[0032] The developer container is a container that receives and stores the toner sent out from the toner cartridge. A carrier is stored in the developer container in advance. The toner sent out from the toner cartridge is stirred with the carrier by the stirring mechanism to form a developer in which the toner and the carrier are mixed. The carrier is stored in the developer container during the manufacture of the developing device 53.

[0033] The developing roller rotates in the developer container to attach the developer to its surface. The doctor blade is a member arranged at a predetermined interval from the surface of the developing roller. The doctor blade removes a part of the developer attached to the surface of the rotating developing roller. Thereby, a layer of developer with a thickness corresponding to the interval between the doctor blade and the surface of the developing roller is formed on the surface of the developing roller.

[0034] The ATC sensor is, for example, a magnetic flux sensor having a coil and detecting the voltage value generated in the coil. The detection voltage of the ATC sensor changes according to the density of the magnetic flux from the toner in the developer container. That is, the controller 13 determines the concentration ratio (toner concentration ratio) of the toner remaining in the developer container to the carrier based on the detection voltage of the ATC sensor. The controller 13 operates the motor that drives the feeding mechanism of the toner cartridge based on the toner concentration ratio to send the toner from the toner cartridge to the developer container of the developing device 53.

[0035] Next, the configuration of the exposure device 42 will be described. The exposure device 42 includes a plurality of light-emitting elements. The exposure device 42 forms a latent image on the photosensitive drum 51 by irradiating light from the light-emitting elements onto the charged photosensitive drum 51. The light-emitting elements are, for example, light-emitting diodes (LEDs) or the like. One light-emitting element is configured to irradiate light at a point on the photosensitive drum 51. The plurality of light-emitting elements are arranged in the main scanning direction, which is a direction parallel to the rotation axis of the photosensitive drum 51.

[0036] The exposure device 42 forms a latent image for one line on the photosensitive drum 51 by irradiating light onto the photosensitive drum 51 with a plurality of light-emitting elements arranged in the main scanning direction. Further, the exposure device 42 forms latent images for a plurality of lines by continuously irradiating light onto the rotating photosensitive drum 51.

[0037] In the above configuration, when light is irradiated from the exposure device 42 onto the surface of the photosensitive drum 51 charged by the charging charger 52, an electrostatic latent image is formed. When the layer of the developer formed on the surface of the developing roller approaches the surface of the photosensitive drum 51, the toner contained in the developer adheres to the latent image formed on the surface of the photosensitive drum 51. Thereby, a toner image is formed on the surface of the photosensitive drum 51.

[0038] Next, the configuration of the transfer mechanism 43 will be described. The transfer mechanism 43 is configured to transfer the toner image formed on the surface of the photosensitive drum 51 to the printing medium P. The transfer mechanism 43 transfers the toner image formed on the surface of the photosensitive drum 51 to the primary transfer belt 61, and transfers the toner image transferred to the primary transfer belt 61 to the printing medium P.

[0039] Also, the transfer mechanism 43 includes, for example, a primary transfer belt 61, a secondary transfer opposing roller 62, a plurality of primary transfer rollers 63, and a secondary transfer roller 64. In the configuration example shown in FIG. 1, the primary transfer belt 61 is an endless belt wound around a secondary transfer opposing roller 62 and a plurality of winding rollers. The inner surface (inner peripheral surface) of the primary transfer belt 61 contacts the secondary transfer opposing roller 62 and the plurality of winding rollers, and the outer surface (outer peripheral surface) thereof faces the photosensitive drum 51 of the process unit 41.

[0040] The secondary transfer opposing roller 62 is rotated by a motor. By rotating, the secondary transfer opposing roller 62 conveys the primary transfer belt 61 in a predetermined conveyance direction. The plurality of winding rollers are configured to be rotatable freely. The plurality of winding rollers rotate according to the movement of the primary transfer belt 61 by the secondary transfer opposing roller 62.

[0041] The plurality of primary transfer rollers 63 are configured to bring the primary transfer belt 61 into contact with the photosensitive drum 51 of the process unit 41. The plurality of primary transfer rollers 63 are provided so as to correspond to the photosensitive drums 51 of the plurality of process units 41. Specifically, the plurality of primary transfer rollers 63 are provided at positions (primary transfer positions) facing each other with the photosensitive drum 51 of the corresponding process unit 41 and the primary transfer belt 61 interposed therebetween. The primary transfer roller 63 contacts the inner peripheral surface side of the primary transfer belt 61 and displaces the primary transfer belt 61 toward the photosensitive drum 51 side. Thereby, the outer peripheral surface of the primary transfer belt 61 is brought into contact with the photosensitive drum 51.

[0042] The secondary transfer roller 64 is provided at a position (secondary transfer position) facing the primary transfer belt 61. The secondary transfer roller 64 contacts the outer peripheral surface of the primary transfer belt 61 and applies pressure thereto. Thereby, a transfer nip is formed in which the secondary transfer roller 64 and the outer peripheral surface of the primary transfer belt 61 are in close contact. When the printing medium P passes through the transfer nip, the secondary transfer roller 64 presses the printing medium P passing through the transfer nip against the outer peripheral surface of the primary transfer belt 61.

[0043] The secondary transfer roller 64 and the secondary transfer counter roller 62 rotate to convey the print medium P supplied from the paper feed conveyance path 31 while sandwiching it. As a result, the print medium P passes through the transfer nip.

[0044] In the above configuration, when the outer peripheral surface of the primary transfer belt 61 contacts the photosensitive drum 51, the toner image formed on the surface of the photosensitive drum is transferred to the outer peripheral surface of the primary transfer belt 61. When the image forming mechanism 20 includes a plurality of process units 41, the primary transfer belt 61 receives the toner image from the photosensitive drums 51 of the plurality of process units 41. The toner image transferred to the outer peripheral surface of the primary transfer belt 61 is conveyed by the primary transfer belt 61 to the transfer nip where the secondary transfer roller 64 and the outer peripheral surface of the primary transfer belt 61 are in close contact. When the print medium P is present at the transfer nip, the toner image transferred to the outer peripheral surface of the primary transfer belt 61 is transferred to the print medium P at the transfer nip.

[0045] Next, the configuration of the fuser (fusing device) 21 in the image forming apparatus 1 will be described. The fuser 21 fixes the toner image to the print medium P onto which the toner image has been transferred. The fuser 21 operates based on the control of the controller 13. The fusing device according to the embodiment is assumed to be a device including the fuser 21, a heater control circuit 14, and a controller 13. The fuser 21 includes a fusing rotating body as a fixing member, a pressing member, a heating member (heat source), and a temperature sensor.

[0046] In the configuration example shown in FIG. 1, the fixing device 21 includes a heat roller 71, a press roller 72, a heater 73, non-contact temperature sensors 74 (741, 742), a contact temperature sensor 751, and the like. The heat roller 71 is an example of a fixing rotating body (fixing member). The press roller 72 is an example of a pressing member. The heater 73 is an example of a heat source. The heater 73 is, for example, a heater lamp. The fixing device 21 includes a heater 73 having a plurality of heat sources. In the configuration example shown in FIG. 2, the heater 73 has a heater (center heater) 731 which is an example of a first heat source and a heater (side heater) 732 which is an example of a second heat source. The heat sources (the first heat source and the second heat source) are not limited to heater lamps, and any device that heats the heat roller 71 is acceptable.

[0047] Further, the fixing device 21 has a plurality of non-contact temperature sensors 741, 742 as non-contact temperature sensors 74 and a contact temperature sensor 751. The non-contact temperature sensors 741 and 742 are non-contact type temperature sensors that detect the temperature of the detection site without contact. The non-contact temperature sensors 741, 742 are, for example, non-contact thermistors. The non-contact temperature sensor 741 is a first non-contact temperature sensor, and the non-contact temperature sensor 742 is a second non-contact temperature sensor.

[0048] In the configuration example shown in FIG. 2, the non-contact temperature sensor (first non-contact temperature sensor) 741 is a center temperature sensor that uses the center region (first region) C on the surface of the heat roller 71 as the detection site. The non-contact temperature sensor 741 outputs a detection signal indicating the temperature of the center region C without contacting the surface of the heat roller 71. The non-contact temperature sensor (second non-contact temperature sensor) 742 is a side temperature sensor that uses the side region S on the surface of the heat roller 71 as the detection site. The non-contact temperature sensor 742 outputs a detection signal indicating the temperature of the side region S without contacting the surface of the heat roller 71.

[0049] The contact temperature sensor 751 is a contact-type temperature sensor that detects the temperature of the detection site by the contact portion (detection portion) coming into contact with the detection site. The contact temperature sensor 751 is, for example, a contact thermistor. In the configuration example shown in FIG. 2, the contact temperature sensor 751 uses an end portion outside the passage region of the medium (non-paper-passing portion) on the surface of the heat roller 71 as the temperature detection site. The contact temperature sensor 751 is installed such that the contact portion contacts the end portion of the non-paper-passing portion of the heat roller 71.

[0050] The heat roller 71 is a fixing rotating body that rotates while being heated by the heater 73. The heat roller 71 has a metal mandrel formed in a hollow shape and an elastic layer formed on the outer periphery of the mandrel. The diameter of the heat roller 71 is, for example, φ30 mm. For example, the heat roller 71 is made of aluminum with a mandrel thickness of 0.65 mm. The peripheral speed of the heat roller 71 is, for example, 115 mm / s. The elastic layer is made of, for example, a fluororesin (tetrafluoroethylene resin). The values of the diameter of the heat roller 71, the thickness of the mandrel, the peripheral speed, and the raw material names of the mandrel and the elastic layer described above are examples and are not limited thereto.

[0051] The inside of the mandrel of the heat roller 71, which is formed in a hollow shape, is heated by the heater 73 as a heating member (heat source) disposed inside the mandrel. The heat applied to the inside of the mandrel is transmitted to the surface of the heat roller 71 (the surface of the elastic layer), which is the outside of the mandrel. Note that the fixing member may be configured as an endless belt.

[0052] As shown in FIG. 1, the press roller 72 is provided at a position facing the heat roller 71. The press roller 72 has a mandrel formed of metal with a predetermined outer diameter and an elastic layer formed on the outer periphery of the mandrel. The diameter of the press roller 72 is, for example, φ30 mm. The elastic layer of the press roller 72 is made of, for example, silicone rubber or fluororubber.

[0053] The press roller 72 applies pressure to the heat roller 71 due to the stress applied from the tension member. The pressure is, for example, 200 N. The diameter of the press roller 72, the value of the pressure, and the raw material name are examples and are not limited thereto. When pressure is applied from the press roller 72 to the heat roller 71, a nip (fixing nip) in which the press roller 72 and the heat roller 71 are in close contact is formed. The press roller 72 is rotated by a motor. By rotating, the press roller 72 moves the printing medium P that has entered the fixing nip and presses the printing medium P against the heat roller 71. Note that the heat roller 71 and the press roller 72 may each have a release layer on their surfaces.

[0054] The heater 73 is a heat source for heating the heat roller 71. The heater 73 is composed of heating elements as a plurality of heat sources that generate heat by the electric power supplied from the heater control circuit 14. In the configuration example shown in FIGS. 1 and 2, the heater 73 in the fixing device 21 has a center heater 731 and a side heater 732 as two heat sources (heating elements). The center heater 731 and the side heater 732 may be heat sources that heat the heat roller 71 that can be controlled by the controller 13 and the heater control circuit 14. For example, the center heater 731 and the side heater 732 are halogen lamp heaters including halogen lamps.

[0055] In the configuration example shown in FIG. 2, the fixing device 21 has a center heater 731 and a side heater 732 as the heater 73. The center heater 731 is a first heat source that heats the central portion (center region C) in the rotation axis direction of the heat roller 71. The side heater 732 is a second heat source that heats the peripheral portion (side region S) other than the central portion in the rotation axis direction of the heat roller 71. The printing medium P is conveyed in the conveyance direction F shown in FIG. 2. For example, the center region C and the side region S are set according to the size of the medium used as the printing medium P.

[0056] The center heater 731 and the side heater 732 generate heat by the electric power supplied under the control of the controller 13, respectively. The power consumption of the center heater 731 and the side heater 732 is, for example, 600 W. When the controller 13 performs the fixing process on the narrow-width printing medium P in the rotational axis direction of the heat roller 71 (the conveyance direction F of the printing medium P), the controller 13 heats the center region C of the heat roller 71. When the controller 13 heats the center region C of the heat roller 71, the controller 13 operates the center heater 731 without operating the side heater 732 by the heater control circuit 14.

[0057] Further, when the controller 13 performs the fixing process on the wide-width printing medium P in the rotational axis direction of the heat roller 71 (the conveyance direction F of the printing medium P), the controller 13 heats the entire heat roller 71 (both the center region C and the side region S). When the controller 13 heats the entire heat roller 71, the controller 13 operates both the center heater 731 and the side heater 732 by the heater control circuit 14.

[0058] In the configuration example shown in FIG. 2, the non-contact temperature sensors 741 and 742 are arranged in parallel with the rotational axis of the heat roller 71. The non-contact temperature sensor 741 detects the temperature of the center region (the central portion when divided into three in the rotational axis direction) C in the rotational axis direction of the heat roller 71. The non-contact temperature sensor 741 is installed so as to face the detection site in the center region C on the surface of the heat roller 71. Further, the non-contact temperature sensor 741 is arranged so that the distance (gap, width) Gap to the surface of the heat roller 71 is within the allowable range.

[0059] Further, the non-contact temperature sensor 742 detects the temperature of the side region (any side portion when divided into three in the rotational axis direction) S in the rotational axis direction of the heat roller 71. The non-contact temperature sensor 742 is installed so as to face the detection site in the side region S on the surface of the heat roller 71. The non-contact temperature sensor 742 is installed so that the distance (gap, width) Gap to the surface of the heat roller 71 is the allowable width.

[0060] The contact temperature sensor 751 detects the temperature of the surface of the heat roller 71 when the contact part contacts the surface of the heat roller 71. In the configuration example shown in FIG. 2, the contact temperature sensor 751 is installed such that the contact part contacts an end part (non-paper-passing part) other than the region (paper-passing part) where a recording medium such as paper passes (contacts) in the heat roller 71. The contact temperature sensor 751 detects a temperature for correcting the temperatures detected by the non-contact temperature sensors 741 and 742.

[0061] The non-contact temperature sensors 741, 742, and the contact temperature sensor 751 each supply a detection signal indicating the detection result of the temperature to the controller 13. The controller 13 corrects the detected temperature of the non-contact temperature sensor 741 with a correction value for approximating the detected temperature to the actual temperature of the detection site. By this correction process, the controller 13 specifies the temperature of the center region C of the heat roller 71 which is the detection site of the non-contact temperature sensor 741. For example, when heating the center region C of the heat roller 71, the controller 13 controls the power supply to the center heater 731 while referring to the temperature of the center region C specified by the correction process.

[0062] The controller 13 corrects the detected temperature (detection signal) of the non-contact temperature sensor 742 with a correction value for approximating the detected temperature to the actual temperature of the detection site. By this correction process, the controller 13 specifies the temperature of the side region S of the heat roller 71. When heating the entire heat roller 71, the controller 13 controls the side heater 732 based on the temperature of the side region S specified by the correction process together with the control of the center heater 731.

[0063] The heat roller 71 and the press roller 72 apply heat and pressure controlled within a predetermined temperature range to the print medium P passing through the fixing nip. The toner on the print medium P is fixed on the surface of the print medium P by the heat from the heat roller 71 and the pressure from the heat roller 71 and the press roller 72. Thereby, the toner image is fixed on the print medium P that has passed through the fixing nip. The print medium P that has passed through the fixing nip is introduced into the paper discharge conveyance path 32 and discharged to the outside of the housing 11.

[0064] Next, the configuration of the control system in the image forming apparatus 1 according to the embodiment will be described. FIG. 3 is a block diagram showing a configuration example of the control system in the image forming apparatus 1. As shown in FIG. 3, in the image forming apparatus 1, a communication interface 12, a heater control circuit 14, a display device 15, an operation device 16, a conveyance mechanism 19, an image forming mechanism 20, a fixing device 21, etc. are connected to a controller (system controller) 13.

[0065] The controller 13 includes a processor 81, a ROM (Read Only Memory) 82, a RAM (Random Access Memory) 83, and a data memory 84. The controller 13 constitutes a computer by the processor 81, the ROM 82, the RAM 83, and the data memory 84. Further, the controller 13 may be provided with an ASIC or the like which is a processor for image processing.

[0066] The processor 81 corresponds to the central part of the computer as the controller 13. The processor 81 controls each part of the image forming apparatus 1 according to an operating system or an application program. The processor 81 is, for example, a CPU (Central Processing Unit).

[0067] ROM 82 and RAM 83 correspond to the main memory part of the computer as the controller 13. ROM 82 is a non-volatile memory area, and RAM 83 is a volatile memory area. ROM 82 stores the operating system or application programs. ROM 82 stores the control data necessary for the processor 81 to execute the processes for controlling each part. RAM 83 is used as a work area where data is appropriately rewritten by the processor 81. RAM 83 has, for example, a work area for storing image data.

[0068] The data memory 84 is composed of a rewritable non-volatile memory. The data memory 84 corresponds to the auxiliary storage part of the computer as the controller 13. The data memory 84 is composed of a storage device such as, for example, EEPROM (registered trademark) (Electric Erasable Programmable Read-Only Memory), HDD (Hard Disc Drive), or SSD (Solid State Drive).

[0069] The data memory 84 stores data such as setting data used by the processor 81 to perform various processes. The data memory 84 stores the data generated by the processes executed by the processor 81. The data memory 84 may store an application program. The data memory 84 stores correction values (steady correction values and additional correction values), which will be described later, for correcting the detected temperatures of the non-contact temperature sensors 741 and 742 to actual temperatures. Further, the data memory 84 may store information (for example, a correlation formula) indicating the correlation between the detected temperatures of the non-contact temperature sensors 741 and 742 and the additional correction values, which will be described later.

[0070] The controller 13 controls the image forming mechanism 20. For example, the controller 13 controls each process unit 41, the exposure device 42, and the transfer mechanism 43. For example, the controller 13 controls the on / off of charging for the charger 52 of each process unit 41. The controller 13 controls the on / off of the laser light irradiated on the photosensitive drum 51 for the exposure device 42 of each process unit 41. Thereby, an electrostatic latent image is formed on the photosensitive drum 51.

[0071] Also, the controller 13 controls the on / off of the developing bias for the developing device 53 of each process unit 41. Thereby, the electrostatic latent image on the photosensitive drum 51 is developed by the toner supplied from the developing device 53, and a toner image is formed on the photosensitive drum 51. The controller 13 controls the primary transfer bias at each primary transfer position for the transfer mechanism 43. The toner image on the photosensitive drum 51 is transferred to the primary transfer belt 61 at the primary transfer position. Further, the controller 13 controls the secondary transfer bias at the secondary transfer position for the transfer mechanism 43. Thereby, the toner image on the primary transfer belt 61 is transferred to the print medium P.

[0072] Also, the controller 13 controls the fixing device including the fixing unit 21. The controller 13 controls the operations of the center heater 731 and the side heater 732 by the heater control circuit 14 according to the detection results of the non-contact temperature sensor 741 and the non-contact temperature sensor 742. The heater control circuit 14 operates according to the control instruction from the controller 13 to control the energization to the center heater 731 and the side heater 732. Note that part or all of the configuration of the heater control circuit 14 described later may be a configuration included in the controller 13.

[0073] The heater control circuit 14 controls the energization of the center heater 731 and the side heater 732 so that the surface of the heat roller 71 reaches the set target temperature. For example, the controller 13 sets a target value (control target) for the heater control circuit 14. The controller 13 calculates (estimates) the actual temperature of the surface of the heat roller 71 by correcting the detected temperatures of the non-contact temperature sensors 741 and 742 using a steady correction value and an additional correction value.

[0074] The steady correction value is a correction value for approximating the detected temperature of the non-contact temperature sensor 74 (741, 742) to the actual temperature of the surface of the heat roller 71 when the temperature of the heat roller 71 is in a stable state. The steady correction value is set according to the difference value between the detected temperatures of the non-contact temperature sensors 741 and 742 and the detected temperature of the contact temperature sensor 751. For example, the steady correction value is set as the difference value between the detected temperatures of the non-contact temperature sensors 741 and 742 and the detected temperature of the contact temperature sensor 751 with the surface of the heat roller 71 at a predetermined temperature. The additional correction value is used for additional correction performed in the first period from the start of printing to a predetermined time when continuous printing is executed from a cold start. The additional correction value and the additional correction using the additional correction value will be described in detail later.

[0075] The heater control circuit 14 controls the power supply to the center heater 731, which is the heat source (first heat source), so that the center region (first region) C of the heat roller 71 reaches the target value. The controller 13 calculates (estimates) the actual temperature of the center region C by correcting the detected temperature of the non-contact temperature sensor 741 using a correction value described later. The heater control circuit 14 turns the power supply to the center heater 731 on and off so that the actual temperature of the center region C calculated using the correction value reaches the target value.

[0076] Further, the heater control circuit 14 controls the power supply to the side heater 732, which is the heat source (second heat source), so that the side region (second region) S of the heat roller 71 reaches the target value. The controller 13 calculates (estimates) the actual temperature of the side region S by correcting the detected temperature of the non-contact temperature sensor 742 using a correction value described later. The heater control circuit 14 turns on and off the power supply to the side heater 732 so that the actual temperature of the side region S calculated using the correction value reaches the target value.

[0077] Further, when the temperature of the center region C of the heat roller 71 reaches the set high-temperature stop temperature of the center, the heater control circuit 14 cuts off the power supply to the center heater 731. When the temperature of the side region S of the heat roller 71 reaches the set high-temperature stop temperature of the side, the heater control circuit 14 cuts off the power supply to the side heater 732. The heater control circuit 14 sets and corrects the high-temperature stop temperature of the center and the high-temperature stop temperature of the side by the controller 13.

[0078] Next, the temperature control of the heat roller 71 in the fixing device 21 of the image forming apparatus 1 according to the embodiment will be described. FIG. 4 is a diagram showing an example of measurement results of measuring the actual temperature of the surface of the heat roller 71 when continuous printing is performed from a cold start without additional correction. In the measurement results shown in FIG. 4, it is assumed that the recording medium used for continuous printing is paper with a basis weight of 60 to 90 g / m2. Also, the control target temperature (target value) is set to 150°C. However, since there is a delay (time constant) in temperature detection, it is assumed that the actual temperature is slightly higher than the target value and is stably controlled. Further, a cold start means starting printing without a break after the heat roller 71 rises from a state where it is at a predetermined temperature (for example, 40 degrees or less). Also, additional correction means correcting the detected temperatures of the non-contact temperature sensors 741 and 742, which are non-contact temperature sensors, using an additional correction value described later.

[0079] When continuous printing is executed without additional correction, the controller 13 controls the heater 73 so that the value obtained by correcting the detected temperatures of the non-contact temperature sensors 741 and 742 with the steady correction value becomes the target value. Here, it is assumed that the controller 13 controls the center heater 731 so that the value obtained by correcting the detected temperature of the non-contact temperature sensor 741 with the steady correction value becomes the target value. Also, FIG. 4 shows the measurement results of the surface temperature of the center region C of the heat roller 71 actually measured with a thermocouple.

[0080] FIG. 4 shows the measurement results of the actual temperature of the center region C when the distance (hereinafter, gap) between the non-contact temperature sensor 741 and the surface of the heat roller 71 is different. In FIG. 4, the curve H shows the measurement results of the actual temperature when the gap is the upper limit value (the upper limit value of the allowable range of the gap). The curve L shows the measurement results of the actual temperature when the gap is the lower limit value (the lower limit value of the allowable range of the gap). The curve C shows the measurement results of the actual temperature when the gap is the center value (for example, the intermediate value between the upper limit value and the lower limit value).

[0081] According to the measurement results shown in FIG. 4, the variation tendency of the measurement results is different between the period from the start of printing to 30 seconds (the first period) and the period after 30 seconds from the start of printing (the second period). In the second period, the actual temperature of the surface of the heat roller 71 is stably controlled around a certain value (about 153 ° C.). In the first period, the actual temperature of the surface of the heat roller 71 is unstable at a lower temperature than in the second period. Furthermore, in the first period, the actual temperature of the surface of the heat roller 71 varies greatly depending on the gap, and the temperature becomes lower as the gap increases (on the lower limit side).

[0082] FIG. 5 is a diagram showing an example in which the average value of the actual temperature of the surface of the heat roller 71 in the first period (the period from the start of printing to 30 seconds) is calculated from the measurement results shown in FIG. 4. In FIG. 5, Gap_Ha represents the average value of the actual temperature of the surface of the heat roller 71 in the first period when the gap is at the upper limit value. Gap_La represents the average value of the actual temperature of the surface of the heat roller 71 in the first period when the gap is at the lower limit value. Gap_Ca represents the average value of the actual temperature of the surface of the heat roller 71 in the first period when the gap is at the center value. As shown in FIG. 5, the average value of the actual temperature of the surface of the heat roller 71 decreases as the gap increases.

[0083] FIG. 6 is a diagram showing an example in which the average value of the actual temperature of the surface of the heat roller 71 in the second period (the period after 30 seconds have elapsed since the start of printing) is calculated from the measurement results shown in FIG. 4. In FIG. 6, Gap_Hb represents the average value of the actual temperature of the surface of the heat roller 71 in the second period when the gap is at the upper limit value. Gap_Lb represents the average value of the actual temperature of the surface of the heat roller 71 in the second period when the gap is at the lower limit value. Gap_Cb represents the average value of the actual temperature of the surface of the heat roller 71 in the second period when the gap is at the center value. As shown in FIG. 6, in the second period, the variation of the average value of the actual temperature of the surface of the heat roller 71 due to the gap is small.

[0084] FIG. 7 is a diagram showing the difference value between the average value of the actual temperature of the surface of the heat roller 71 in the second period and the average value of the actual temperature of the surface of the heat roller 71 in the first period. In FIG. 7, Gap_Hc represents the difference value obtained by subtracting the average value Ha in the first period from the average value Hb in the second period when the gap is at the upper limit value. Gap_Lc represents the difference value obtained by subtracting the average value La in the first period from the average value Lb of the actual temperature in the second period when the gap is at the lower limit value. Gap_Cc represents the difference value obtained by subtracting the average value Ca of the actual temperature in the first period from the average value Cb of the actual temperature in the second period when the gap is at the center value.

[0085] As shown in FIG. 7, the average value of the actual temperature in the first period is smaller than the average value of the actual temperature in the second period regardless of the gap size. This indicates that in the first period, the actual temperature of the heat roller is controlled lower than the target value only by the correction control with the steady correction value. Therefore, in the first period, in addition to the correction control with the steady correction value, additional correction control is required. The additional correction control to be performed in the first period may be any correction that corrects the difference value between the actual temperature in the second period and the actual temperature in the first period.

[0086] The correction amount (additional correction value) to be corrected as the additional correction control is set according to, for example, the difference value as shown in FIG. 7. The non-contact temperature sensors 741 and 742 are installed so that the gap, which is the distance from the surface of the heat roller 71, is within the allowable range. Therefore, according to the example shown in FIG. 7, the difference value for setting the additional correction value is a value from the difference value Gap_Hc at the upper limit of the gap to the difference value Gap_Lc at the lower limit of the gap.

[0087] The temperature conversion value (detected temperature) obtained from the detection signals of the non-contact temperature sensors 74 (741, 742) varies according to the gap size. Using the temperature conversion value of the non-contact temperature sensor 74 and the difference value as shown in FIG. 7, the correlation between the additional correction amount and the temperature conversion value is set. In the image forming apparatus 1, the controller 13 can acquire the temperature conversion values of the non-contact temperature sensors 741 and 742. The controller 13 sets the additional correction value from the temperature conversion values of the non-contact temperature sensors 741 and 742 based on the correlation between the additional correction amount and the temperature conversion value of the non-contact temperature sensor.

[0088] FIG. 8 is a diagram showing an example of the temperature conversion value of the non-contact temperature sensor 74 (741) when continuous printing is performed from a cold start without additional correction. However, in FIG. 8, the recording medium used for continuous printing is paper with a basis weight of 60 to 90 g / m2. Also, in FIG. 8, the non-contact temperature sensor 74 is assumed to be the non-contact temperature sensor 741 facing the center region C.

[0089] When performing continuous printing without additional correction, the controller 13 controls the center heater 731 so that the temperature obtained by correcting the detected temperature of the temperature sensor 741 with a steady correction value becomes the target value. In the example shown in FIG. 8, the curve H shows the transition of the temperature conversion value of the non-contact temperature sensor 741 whose gap is the upper limit value. The curve L shows the transition of the temperature conversion value of the non-contact temperature sensor 741 whose gap is the lower limit value. The curve C shows the transition of the temperature conversion value of the non-contact temperature sensor 741 when the gap is the center value.

[0090] FIG. 9 is a diagram showing the average value of the temperature conversion value of the non-contact temperature sensor 741 in the first period, which is the period from the start of printing (start of continuous printing) shown in FIG. 8 to 30 seconds. Further, FIG. 10 is a diagram showing the average value of the temperature conversion value of the non-contact temperature sensor 741 in the second period after 30 seconds from the start of printing shown in FIG. 8. As shown in FIGS. 9 and 10, the average value of the temperature conversion value of the non-contact temperature sensor 741 differs for each gap, and the larger the gap, the lower it becomes. Also, the average value of the temperature conversion value of the non-contact temperature sensor 741 is lower in the first period than in the second period for any gap. Furthermore, the larger the gap of the non-contact temperature sensor 741, the larger the difference between the first period and the second period becomes.

[0091] FIG. 11 is a diagram showing the correlation between the temperature conversion value of the non-contact temperature sensor 741 and the additional correction amount in the first period. The correlation shown in FIG. 11 is obtained based on the measurement results shown in FIG. 7 and the measurement results shown in FIG. 9. The average value of the actual temperature in the first period becomes the average value in the second period by adding the difference value shown in FIG. 7. In other words, the difference value shown in FIG. 7 corresponds to the additional correction value in the first period based on the measurement results shown in FIG. 4.

[0092] When the gap between the non-contact temperature sensor 741 and the surface of the heat roller 71 is at the upper limit, the additional correction value corresponds to the difference value Gap_Hc shown in FIG. 7. Further, the temperature conversion value of the non-contact temperature sensor 741 with the gap at the upper limit is specified from the measurement results shown in FIG. 9. In FIG. 11, the additional correction value corresponding to the temperature conversion value of the non-contact temperature sensor 741 when the gap is at the upper limit is plotted. Similarly, in FIG. 11, the additional correction value corresponding to the temperature conversion value of the non-contact temperature sensor 741 when the gap is at the center value and the lower limit is plotted.

[0093] As shown in FIG. 11, the three points plotted based on the correspondence between the temperature conversion value and the additional correction value of the non-contact temperature sensor 741 for each gap show a correlation such that they form a linear function. According to the correlation shown in FIG. 11, the controller 13 can specify the additional correction value from the temperature conversion value of the non-contact temperature sensor 741 that changes according to the gap. If the additional correction amount is "y" and the temperature conversion value of the non-contact temperature sensor 741 is "x", the correlation shown in FIG. 11 can be represented by a correlation formula (correlation relationship formula).

[0094] For example, the data memory 84 as a memory stores a correlation formula showing the correlation between the temperature conversion value and the additional correction value of the non-contact temperature sensor 741. When the controller 13 acquires the temperature conversion value of the non-contact temperature sensor 741 in the first period, it calculates the average value of the temperature conversion values of the non-contact temperature sensor 741 in the first period. The controller 13 specifies the additional correction value from the average value of the temperature conversion values of the non-contact temperature sensor 741 in the first period according to the correlation formula stored in the data memory 84. As a result, the controller 13 stores (updates) in the data memory 84 the additional correction value to be added to the steady correction value in the first period.

[0095] FIG. 12 is a diagram showing an example of the measurement results of the actual temperature of the surface of the heat roller 71 in the first period when continuous printing is performed from a cold start with additional correction. In FIG. 12, curve H shows the measurement result of the actual temperature of the center region C in the first period when the gap between the non-contact temperature sensor 741 and the heat roller 71 is at the upper limit value. Curve L shows the measurement result of the actual temperature of the center region C in the first period when the gap is at the lower limit value. Curve C shows the measurement result of the actual temperature of the center region C in the first period when the gap is at the center value.

[0096] The measurement results shown in FIG. 12 indicate that in the first period, the actual temperature of the surface of the heat roller 71 is controlled to reach the target value in the same manner as in the second period shown in FIG. 4. This indicates that through additional correction with the additional correction value, the actual temperature of the surface of the heat roller 71 in the first period is corrected to reach the target value. Also, in the measurement results shown in FIG. 12, regardless of the gap, the actual temperature of the surface of the heat roller 71 is controlled to reach the target value. This is because the additional correction value is set according to the temperature conversion value of the non-contact temperature sensor 741 that varies depending on the gap between the non-contact temperature sensor 741 and the heat roller 71. Therefore, the fixing device (fixing apparatus) 21 according to the present embodiment can accurately control the actual temperature of the surface of the heat roller 71 to the target value by additional correction in the first period.

[0097] In the above description with reference to FIGS. 4 to 12, the temperature control of the center region C has been described, but the temperature control of the side region S can be implemented in the same manner. That is, in the image forming apparatus including the fixing device according to the embodiment, the additional correction value for the temperature conversion value of the non-contact temperature sensor 742 provided in the side region S can also be set in the same manner as the above description.

[0098] The data memory 84 stores the fixed correction value and the additional correction value set for the center area C (the first non-contact temperature sensor 741), and the fixed correction value and the additional correction value set for the side area S (the second non-contact temperature sensor 742). The controller 13 controls the center heater 731 with the fixed correction value and the additional correction value for the center area C, and controls the side heater 732 with the fixed correction value and the additional correction value for the side area S. As a result, the heat roller 71 is controlled so that the temperatures of the center area C and the side area S reach the target value according to the temperature additionally corrected in the first period.

[0099] That is, the image forming apparatus according to the embodiment corrects the temperature conversion values of the non-contact temperature sensors 741 and 742 in the first period by using the fixed correction value and the additional correction value, respectively. Thereby, the image forming apparatus according to the embodiment can accurately control the center area C and the side area S to the target value even in the case of contact printing from cold start and in the first period (immediately after the start of heating of the heat roller 71).

[0100] In addition, in the above description with reference to FIGS. 4 to 12, examples of measurement results in the case of performing continuous printing using a recording medium (paper) having a basis weight of 60 to 90 g / m2 were referred to. However, the amount of heat taken away by the heat roller 71 varies depending on the type of the recording medium. In the first period when the heat roller 71 and the press roller 72 are not sufficiently heated, the amount of heat taken away by the recording medium (paper) greatly affects the temperature control. Therefore, the additional correction value in the first period when performing continuous printing from cold start may be set for each type of the recording medium. In this case, the data memory 84 stores the additional correction value for each type of the recording medium. When performing continuous printing from cold start, the controller 13 performs temperature control using the additional correction value corresponding to the type of the recording medium and the fixed correction value in the first period.

[0101] For example, the data memory 84 stores, for each type of recording medium, a correlation formula indicating the correlation between the additional correction value as described above and the temperature conversion value of the non-contact temperature sensor. When continuously printing from a cold start, the controller 13 calculates the average value of the temperature conversion values of the non-contact temperature sensor in the first period. The controller 13 may set (update) for each type of recording medium the additional correction value specified from the average value of the temperature conversion values of the non-contact temperature sensor using the correlation formula for each type of recording medium.

[0102] Next, the operation of continuous printing including additional temperature correction by the image forming apparatus 1 having the fixing device 21 as the fixing device according to the embodiment will be described. FIG. 13 is a flowchart for explaining an operation example of continuous printing including additional temperature correction by the image forming apparatus 1 having the fixing device 21 as the fixing device according to the embodiment. For example, the controller 13 performs correction control of the temperature in the fixing device 21 by the processor 81 executing a program for additional temperature correction. The program executed by the processor 81 shall be stored in a non-volatile memory such as the ROM 82 or the data memory 84.

[0103] First, the controller 13 turns on the power of the fixing device 21 in response to a user instruction or the like (ACT10). When the controller 13 turns on the power of the fixing device 21, it acquires the temperature detected by the contact temperature sensor 751. The controller 13 checks whether the detected temperature (contact temperature) of the contact temperature sensor 751 when the power is turned on is 40 degrees or less (ACT11).

[0104] When the detected temperature of the contact temperature sensor 751 exceeds 40 degrees (ACT11, NO), the controller 13 omits the additional temperature correction by the additional correction value. When omitting the additional temperature correction, the controller 13 shifts to the normal control state. When executing printing in the normal control state, the controller 13 controls the temperature of the heat roller 71 by correcting the detected temperature of the non-contact temperature sensors 74 (741, 742) with the steady correction value.

[0105] When the detected temperature of the contact temperature sensor 751 is 40 degrees or less (ACT11, YES), the controller 13 shifts to the ready state (printable state) by executing a warm-up operation (ACT12). When the controller 13 shifts to the ready state, it determines whether to execute printing (continuous printing) (ACT13). For example, when the power is turned on in response to a continuous printing execution instruction by the user, the controller 13 determines to execute continuous printing from a cold start. When the controller 13 determines not to execute printing (ACT13, NO), it omits the additional temperature correction by the additional correction value and shifts to the normal control state.

[0106] When the controller 13 determines to execute printing (ACT13, YES), it performs additional correction for the detected temperature of the non-contact temperature sensor 74 (ACT14). The controller 13 executes a printing process including a fixing process on the printing medium while performing temperature control of the heat roller 71 based on the temperature corrected by the correction process including the additional correction.

[0107] That is, the controller 13 sets a steady correction value stored in the data memory 84 and an additional correction amount corresponding to the recording medium to be used for printing. The controller 13 performs a correction process of correcting the temperature conversion value of the detection signal in the non-contact temperature sensor 74 with a correction value obtained by adding the additional correction value to the steady correction value. The controller 13 executes the printing operation while controlling the power supply to the heater 73 so that the temperature obtained by correcting the temperature conversion value of the non-contact temperature sensor 74 becomes the target value.

[0108] For example, when the passing area of the printing medium used for printing is the center area C of the heating roller 71, the controller 13 executes temperature control of the center area C. When performing temperature control of the center area C, the controller 13 sets a steady correction value and an additional correction value for the non-contact temperature sensor 741. The controller 13 corrects the temperature conversion value of the non-contact temperature sensor 741 with a correction value obtained by adding the additional correction value to the steady correction value. The controller 13 controls the power supply to the center heater 731 so that the temperature obtained by correcting the temperature conversion value of the non-contact temperature sensor 741 becomes the target value, which is the control temperature of the center area C.

[0109] When the passing areas of the medium used for printing are the center area C and the side area S, the controller 13 executes temperature control of the side area S together with the temperature control of the center area C. In this case, the controller 13 sets a steady correction value and an additional correction value for each of the non-contact temperature sensors 741 and 742. The controller 13 corrects the temperature conversion values of the non-contact temperature sensors 741 and 742 with correction values obtained by adding the additional correction value to the steady correction value for each. As the temperature control of the center area C, the controller 13 controls the power supply to the center heater 731 so that the temperature obtained by correcting the temperature conversion value of the non-contact temperature sensor 741 becomes the target value. As the temperature control of the side area S, the controller 13 controls the power supply to the side heater 732 so that the temperature obtained by correcting the temperature conversion value of the non-contact temperature sensor 742 becomes the target value.

[0110] Also, while continuously executing printing in the first period, the controller 13 stores temperature information including the temperature conversion value of the non-contact temperature sensor 74 in the RAM 83 (or the data memory 84) (ACT16). The controller 13 monitors whether 30 seconds (the first period), which is a predetermined time from the start of printing, has elapsed while executing the processes of ACT14 - 16 (ACT17). If continuous printing ends before 30 seconds (the first period) have elapsed since the start of printing (ACT17, NO), the controller 13 shifts to the normal control state with no additional correction required (no additional correction).

[0111] When a predetermined time (30 seconds) has elapsed during continuous printing from a cold start (ACT17, NO), the controller 13 disables the additional correction by the additional correction value and shifts to the second period (ACT18). When the controller 13 disables the additional correction and shifts to the second period, it continues to execute continuous printing in the normal control state.

[0112] Also, when the continuous printing is executed during a predetermined time (30 seconds) from the start of printing (the first period) (ACT17, NO), the controller 13 executes an update process for updating the additional correction amount (ACT19 - 21). However, the update process for updating the additional correction amount may be executed in parallel with the operation of continuous printing in the normal control state. Also, the update process for updating the additional correction amount may be executed at a predetermined timing (for example, after the end of continuous printing, or at regular intervals).

[0113] In the update process of the additional correction amount, the controller 13 calculates the average value of the temperature conversion values of the non-contact temperature sensors 741 and 742 in the first period stored in the RAM 83 or the data memory 84 (ACT19). When the controller 13 calculates the average value of the temperature conversion values, it specifies an additional correction value corresponding to the average value of the temperature conversion values based on a correlation formula according to the type of the recording medium used for printing (ACT20). When the controller 13 specifies the additional correction value, it updates the additional correction value corresponding to the type of the recording medium stored in the data memory 84 with the specified additional correction value (ACT21).

[0114] As described above, the fixing device (image forming apparatus) according to the embodiment corrects the temperature conversion value of the non-contact temperature sensor with a steady correction value and an additional correction value during the first period up to a predetermined time in continuous printing from the start of printing. The fixing device controls the heater with the temperature corrected by the steady correction value and the additional correction value during the first period, and controls the heater with the temperature corrected by the steady correction value during the second period after the first period has elapsed. Thereby, the fixing device according to the embodiment can stably control the temperature of the heat roller to the target value without significantly decreasing the temperature of the heat roller even during the first period.

[0115] Although some embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalent scope thereof.

[0116] Hereinafter, fixing devices according to embodiments will be listed. [1] A fixing member with which the medium onto which the developer image has been transferred comes into contact, A heat source that supplies heat to the fixing member, A non-contact temperature sensor that non-contact detects the temperature of the region through which the medium passes in the fixing member, A contact temperature sensor that detects the temperature with a detection unit that contacts a non-passage region in the fixing member where the medium does not pass, A memory that stores a steady correction value for approximating the detected temperature of the non-contact temperature sensor to the actual temperature of the fixing member, and an additional correction value set according to the average value of the detected temperature of the non-contact temperature sensor in a first period from the start of printing processing including fixing processing to a predetermined time, A controller that controls the heat source based on a value obtained by correcting the detected temperature of the non-contact temperature sensor using the additional correction value in addition to the steady correction value in the first period, and controls the heat source based on a value obtained by correcting the detected temperature of the non-contact temperature sensor using the steady correction value in a second period after the first period has elapsed, A fixing device having the above. [2] The additional correction value is set according to the difference between the actual temperature of the fixing member measured in the first period and the actual temperature of the fixing member measured in the second period when the heat source is controlled without correction by the additional correction value. The fixing device according to [1]. [3] The memory stores an additional correction value for each type of medium used in the printing process. The controller controls the heat source based on a value obtained by correcting the detected temperature of the non-contact temperature sensor by using, in addition to the steady correction amount in the first period, an additional correction value corresponding to the type of medium used for the printing process. The fixing device according to [1]. [4] Based on a correlation relationship indicating an additional correction value corresponding to the detected temperature of the non-contact temperature sensor, the controller updates the additional correction value stored in the memory with an additional correction value specified from the detected temperature of the non-contact temperature sensor detected in the first period. The fixing device according to [1]. [5] Based on a correlation relationship indicating an additional correction value corresponding to the average value of the detected temperatures of the non-contact temperature sensor, the controller updates the additional correction value stored in the memory with an additional correction value specified from the average value of the detected temperatures of the non-contact temperature sensor in the first period. The fixing device according to [4]. [6] The memory stores a correlation formula indicating an additional correction value corresponding to the average value of the detected temperatures of the non-contact temperature sensor. The controller calculates an additional correction amount corresponding to the average value of the detected temperatures of the non-contact temperature sensor detected in the first period by using the correlation formula. The fixing device according to [5]. [7] The memory stores the additional correction value for each type of medium used for the printing process. Based on the correlation relationship for each type of medium used for the printing process, the controller updates the additional correction amount for the type of medium used for the printing process with an additional correction value specified from the detected temperature of the non-contact temperature sensor detected in the first period. The fixing device according to [4]. [8] The controller updates the additional correction amount for the type of medium used in the printing process by an additional correction value specified from the average value of the detected temperature of the non-contact temperature sensor detected in the first period based on the correlation for each type of medium used in the printing process. The fixing device according to [7]. [9] The memory stores a correlation formula indicating an additional correction value corresponding to the average value of the detected temperature of the non-contact temperature sensor for each type of medium used in the printing process. The controller calculates an additional correction amount for the type of medium used in the printing process according to the average value of the detected temperature of the non-contact temperature sensor detected in the first period using the correlation formula for the type of medium used in the printing process. The fixing device according to [8].

[10] The heat source includes a first heat source that supplies heat to a first region of the fixing member and a second heat source that supplies heat to a second region of the fixing member. The non-contact temperature sensor includes a first non-contact temperature sensor that non-contact detects the temperature of the first region of the fixing member and a second non-contact temperature sensor that non-contact detects the temperature of the second region of the fixing member. The memory stores an additional correction amount for the first non-contact temperature sensor and an additional correction amount for the second non-contact temperature sensor. In the first period, the controller controls the first heat source with a value obtained by correcting the temperature conversion value of the first non-contact temperature sensor using an additional correction value for the first non-contact temperature sensor, and controls the second heat source with a value obtained by correcting the temperature conversion value of the second non-contact temperature sensor using an additional correction value for the second non-contact temperature sensor. The fixing device according to [1].

Explanation of Signs

[0117] 1... Image forming apparatus 12... Communication interface 13... Controller 14... Heater control circuit 21…Fixing device (fixing apparatus), 71…Heat roller (fixing member), 72…Press roller, 73…Heater (heat source), 731…Center heater (first heat source), 732…Side heater (second heat source), 74…Temperature sensor, 741…Non-contact temperature sensor (first non-contact temperature sensor, center temperature sensor), 742…Non-contact temperature sensor (second non-contact temperature sensor, side temperature sensor), 751…Contact temperature sensor (end temperature sensor), 81…Processor, 82…ROM, 83…RAM, 84…Data memory (memory).

Claims

1. a fixing member that comes into contact with the medium to which the developer image has been transferred; a heat source that supplies heat to the fixing member; a non-contact temperature sensor that detects the temperature of a region of the fixing member through which the medium passes in a non-contact manner; a contact temperature sensor that detects temperature using a detection portion that contacts a non-passage area of ​​the fixing member where the medium does not pass; a memory that stores a steady-state correction value for approximating the temperature detected by the non-contact temperature sensor to an actual temperature of the fixing member, and an additional correction value that is set according to an average value of the temperature detected by the non-contact temperature sensor during a first period from the start of a printing process including a fixing process to a predetermined time; a controller that controls the heat source based on a value obtained by correcting the detected temperature of the non-contact temperature sensor using the additional correction value in addition to the steady-state correction value during the first period, and controls the heat source based on a value obtained by correcting the detected temperature of the non-contact temperature sensor using the steady-state correction value during a second period after the first period has elapsed; A fixing device having the same.

2. the additional correction value is set according to a difference between an actual temperature of the fixing member measured in the first period and an actual temperature of the fixing member measured in the second period when the heat source is controlled without correction using the additional correction value. The fixing device according to claim 1 .

3. the memory stores an additional correction value for each type of medium used in the printing process; the controller controls the heat source based on a value obtained by correcting the temperature detected by the non-contact temperature sensor using an additional correction value corresponding to a type of medium used in a printing process in addition to the steady correction amount during the first period. The fixing device according to claim 1 .

4. the controller updates the additional correction value stored in the memory with an additional correction value specified from the average value of the detected temperature of the non-contact temperature sensor during the first period based on a correlation indicating an additional correction value corresponding to the average value of the detected temperature of the non-contact temperature sensor; The fixing device according to claim 1 .

5. the memory stores a correlation equation indicating an additional correction value corresponding to an average value of the detected temperature of the non-contact temperature sensor; the controller calculates an additional correction amount according to an average value of the detected temperatures of the non-contact temperature sensor detected in the first period by using the correlation equation; The fixing device according to claim 4 .

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