Fixing 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 installed in a workplace or the like includes a fixing device that fixes a toner image onto a print medium by applying heat and pressure to the print medium having toner transferred thereon. The fixing device has a temperature sensor that detects the temperature of the surface of a fixing member. The fixing device performs control such that the temperature obtained as the surface temperature of the fixing member from the detection signal of the temperature sensor reaches a target value. The temperature sensor used in the fixing device may be a non-contact sensor. For a cheaper non-contact temperature sensor, it is more difficult to directly detect the accurate actual temperature of the surface of the fixing member. For this reason, the fixing device corrects the temperature detected by the non-contact temperature sensor using a preset steady correction value to approximate the detected temperature to the actual temperature of the surface of the fixing member.

[0003] However, immediately after the start of heating of the fixing member, the temperature obtained by correcting the temperature detected by 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. Therefore, in a fixing device using a non-contact temperature sensor, problems such as fixing failure 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 Japanese Unexamined Patent Publication No. 2008-020630 SUMMARY OF THE INVENTION PROBLEM TO BE SOLVED BY THE INVENTION

[0005] The problem to be solved by the present invention is to provide a fixing device that can achieve stable temperature control even immediately after the start of heating of a fixing member. MEANS FOR SOLVING THE PROBLEM

[0006] According to the embodiment, the 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 the medium on which the developer image has been transferred. The heat source supplies heat to the fixing member. The non-contact temperature sensor non-contactly detects the temperature of the region through which the medium passes in the fixing member. The contact temperature sensor detects the temperature with a detection unit that contacts the non-pass region of the fixing member through which the medium does not pass. The memory stores a steady-state correction value for approximating the temperature detected by 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 temperature detected by the non-contact temperature sensor during a first period from the start of the printing process, including the fixing process, until a predetermined time. The controller controls the heat source based on a value obtained by correcting the temperature detected by 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 temperature detected by the non-contact temperature sensor using the steady-state correction value during a second period after the first period has elapsed. 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. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 shows an example of the configuration of an image forming apparatus including a fixing device according to an embodiment. [Figure 2] Figure 2 is a cross-sectional view showing an example of the configuration around the heat roller in a fixing device (fuser) included in an image forming apparatus according to the embodiment. [Figure 3] Figure 3 is a block diagram showing an example of the configuration of a control system in an image forming apparatus including a fixing device according to an embodiment. [Figure 4] Figure 4 shows the measurement results of the actual temperature of the heat roller surface when the image forming apparatus according to the embodiment performed continuous printing from a cold start without additional correction. [Figure 5] Figure 5 shows an example of calculating the average actual temperature of the heat roller surface during the first period from the measurement results shown in Figure 4. [Figure 6]Figure 6 shows an example of calculating the average actual temperature of the heat roller surface during the second period, after the first period has elapsed, based on the measurement results shown in Figure 4. [Figure 7] Figure 7 shows an example of calculating the difference value obtained by subtracting the average actual temperature of the heat roller surface during the first period shown in Figure 5 from the average actual temperature of the heat roller surface during the second period shown in Figure 6. [Figure 8] Figure 8 shows an example of the temperature conversion value of a non-contact temperature sensor when the image forming apparatus according to the embodiment performs continuous printing from a cold start without additional correction. [Figure 9] Figure 9 shows the average temperature conversion values ​​of the non-contact temperature sensor during the first period shown in Figure 8. [Figure 10] Figure 10 shows the average temperature conversion value of the non-contact temperature sensor during the second period shown in Figure 8. [Figure 11] Figure 11 shows the correlation between the temperature conversion value of a non-contact temperature sensor and the additional correction amount in an image forming apparatus including a fixing device according to the embodiment. [Figure 12] Figure 12 shows the measurement results of the actual temperature of the heat roller surface during the first period when the image forming apparatus according to the embodiment performed continuous printing with additional correction. [Figure 13] Figure 13 is a flowchart illustrating an example of continuous printing operation, including additional temperature correction, by an image forming apparatus including a fixing device according to the embodiment. [Modes for carrying out the invention]

[0008] The image forming apparatus according to this embodiment will be described below with reference to the drawings. Figure 1 is a diagram illustrating an example configuration of an image forming apparatus 1 including a fixing device according to an embodiment. Figure 2 is a cross-sectional view showing an example configuration of the area around the heat roller 71 in the fixing device 21 shown in Figure 1. Image forming apparatus 1 is a digital multifunction device (MFP: Multifunction Peripheral) that performs various processing such as image formation while transporting a recording medium such as a printing medium. Image forming apparatus 1 transfers a toner image formed by an electrophotographic method to a printing medium which serves as a recording medium, and fixes the toner image on the printing medium with a fuser.

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

[0010] As shown in Figure 1, the image forming apparatus 1 comprises a housing 11, a communication interface 12, a controller (system controller) 13, a heater control circuit 14, a display device 15, an operating device 16, multiple paper trays 17, an output tray 18, a transport mechanism 19, an image forming mechanism 20, a fuser 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 a communication interface 12, a controller 13, a heater control circuit 14, a display device 15, an operating device 16, multiple paper trays 17, an output tray 18, a transport mechanism 19, an image forming mechanism 20, a fuser 21, and a power conversion circuit 22.

[0012] The communication interface 12 is an interface for communicating with other devices connected via a network. The communication interface 12 is used for communication with external devices. External devices include user terminals that issue print jobs, or servers that act as external management devices. The communication interface 12 is composed of, for example, a LAN connector. The communication interface 12 may also communicate wirelessly with other devices according to standards such as Bluetooth® or Wi-Fi®.

[0013] A controller (system controller) 13 executes control of each section of the image forming apparatus 1, data processing, and the like. For example, the controller 13 is a computer including a processor, a memory, and various interfaces. The controller 13 performs control of each section and data processing by causing the processor to execute a program stored in the memory. The controller 13 is connected to each section within the housing 11 via 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 representing an image to be formed on a print medium P. The image data may be data for forming an image on one print medium P, or may be data for forming images on a plurality of print media P. Further, the print job may include information indicating printing conditions, such as information indicating whether the printing is color printing or monochrome printing.

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

[0016] Note that the image forming apparatus 1 may be configured to include an engine controller separately from the controller 13. For example, in the image forming apparatus 1, an engine controller that controls at least one of the conveyance mechanism 19, the image forming mechanism 20, the fixing device 21, and the like may be provided separately from the controller 13. The engine controller provided separately from the controller 13 may be configured to acquire information necessary for control from the controller 13.

[0017] The heater control circuit 14 is a temperature control device that controls the supply of power to the heaters 73 (center heater 731 and side heaters 732) of the fuser 21, which will be described later, based on the control of the controller 13. The heater control circuit 14 generates a first energizing power and a second communication power to energize the heaters 73 of the fuser 21. The heater control circuit 14 supplies the first energizing power to the center heater 731 and the second energizing power to the side heaters 732. A detailed explanation of the heater control circuit 14 will be given later.

[0018] The display device 15 includes a display that displays an image in response to an image signal input from the controller 13 or a display control unit such as a graphics 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 operating device 16 supplies an operation signal to the controller 13 in accordance with the operation performed on the operating device. The operating device may be, 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 integrated with the display device 15. The display device 15 and the operating device 16 may be provided on an operation panel that serves as a user interface.

[0020] The power conversion circuit 22 supplies DC voltage to various parts of the image forming apparatus 1 using AC voltage from an AC power source such as an external power source. For example, the power conversion circuit 22 generates DC voltages Vdd and Vdc from the AC voltage of the AC power source. The power conversion circuit 22 supplies DC voltage Vdd to the controller 13 and DC power supply voltage Vdc to the heater control circuit 14. The power conversion circuit 22 also supplies the DC voltage necessary for image forming, generated from the AC voltage of the AC power source, to the image forming mechanism 20. The power conversion circuit 22 also supplies the DC voltage necessary for transporting the printing medium P, generated from the AC voltage of the AC power source, to the transport mechanism 19.

[0021] Next, the configuration of the transport system in the image forming apparatus 1 will be described. Each of the multiple paper trays 17 is a cassette that holds a print medium P. The paper trays 17 are configured to be able to receive the print medium P from outside the housing 11. For example, the paper trays 17 are configured to be able to be pulled out from the housing 11. The output tray 18 is a tray that supports the printing medium P discharged from the image forming apparatus 1.

[0022] The transport mechanism 19 is a mechanism for transporting the printing medium P within the image forming apparatus 1. As shown in Figure 1, the transport mechanism 19 has multiple transport paths. For example, the transport mechanism 19 has a paper feed transport path 31 and a paper discharge transport path 32.

[0023] The paper feed path 31 and the paper discharge path 32 are each composed of multiple motors, multiple rollers, and multiple guides. The multiple motors rotate their axes based on the control of the controller 13, thereby rotating the rollers that are linked to the rotation of the axes. The multiple rollers move the printing medium P by rotating. The multiple guides control the transport direction of the printing medium P.

[0024] The paper feed transport path 31 takes in the printing medium P from the paper tray 17 and supplies the taken printing medium P to the image forming mechanism 20. The paper feed transport path 31 is equipped with a pickup roller 33 corresponding to each paper tray. Each pickup roller 33 takes in the printing medium P from the paper tray 17 into the paper feed transport path 31.

[0025] The paper output transport path 32 is a transport path for discharging the printed medium P on which the image has been formed to the outside of the housing 11. The printed medium P discharged by the paper output transport path 32 is supported by the paper output 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 printing medium P. The image forming mechanism 20 forms an image on the printing medium P based on a print job generated by the controller 13. The image forming mechanism 20 comprises 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, each process unit 41 and exposure unit 42 will be described separately.

[0027] First, let's explain the process unit 41. The process unit 41 forms a toner image. For example, multiple process units 41 are provided for each type of toner. For example, multiple process units 41 correspond to color toners such as cyan, magenta, yellow, and black. Specifically, each process unit 41 is connected to a toner cartridge containing a different color toner.

[0028] A toner cartridge comprises a toner container and a toner dispensing mechanism. The toner container is a container that holds the toner. The toner dispensing mechanism is a mechanism consisting of a screw or the like that dispenses the toner from the toner container.

[0029] The process unit 41 includes a photoreceptor drum 51, a charger 52, and a developer 53, among other things. The photoreceptor drum 51 is a photoreceptor comprising a cylindrical drum and a photosensitive layer formed on the outer surface of the drum. The photoreceptor drum 51 rotates at a constant speed by a drive mechanism.

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

[0031] The developer unit 53 is a device that deposits toner onto the photoreceptor drum 51. The developer unit 53 includes a developer container, an agitation mechanism, a developing roller, a doctor blade, an automatic toner control (ATC) sensor, and the like.

[0032] The developer container is a container that receives and stores the toner dispensed from the toner cartridge. A carrier is pre-packaged inside the developer container. The toner dispensed from the toner cartridge is mixed with the carrier by an agitation mechanism, forming a developer mixture of toner and carrier. The carrier is placed inside the developer container during the manufacturing of the developer unit 53.

[0033] The developing roller rotates within the developer container, thereby applying the developer to its surface. The doctor blade is a component positioned at a predetermined distance from the surface of the developing roller. The doctor blade removes a portion of the developer adhering to the surface of the rotating developing roller. This creates a layer of developer on the surface of the developing roller with a thickness corresponding to the distance between the doctor blade and the surface of the developing roller.

[0034] The ATC sensor is, for example, a magnetic flux sensor that has a coil and detects the voltage value generated in the coil. The voltage detected by the ATC sensor changes depending on the density of the magnetic flux from the toner in the developer container. That is, the controller 13 determines the density ratio of the toner remaining in the developer container to the carrier (toner density ratio) based on the voltage detected by the ATC sensor. Based on the toner density ratio, the controller 13 operates the motor that drives the toner cartridge delivery mechanism and delivers toner from the toner cartridge to the developer container of the developer unit 53.

[0035] Next, the configuration of the exposure unit 42 will be described. The exposure unit 42 is equipped with multiple light-emitting elements. The exposure unit 42 forms a latent image on the charged photoreceptor drum 51 by irradiating the photoreceptor drum 51 with light from the light-emitting elements. The light-emitting elements are, for example, light-emitting diodes (LEDs). Each light-emitting element is configured to irradiate light onto a single point on the photoreceptor drum 51. The multiple light-emitting elements are arranged in the main scanning direction, which is parallel to the rotation axis of the photoreceptor drum 51.

[0036] The exposure unit 42 forms a single line of latent image on the photoreceptor drum 51 by irradiating it with light using multiple light-emitting elements arranged in the main scanning direction. Furthermore, the exposure unit 42 forms multiple lines of latent image by continuously irradiating the rotating photoreceptor drum 51 with light.

[0037] In the above configuration, when light from the exposure unit 42 is shone onto the surface of the photoreceptor drum 51, which has been charged by the charging charger 52, an electrostatic latent image is formed. When the layer of developer formed on the surface of the developing roller comes into close proximity to the surface of the photoreceptor drum 51, the toner contained in the developer adheres to the latent image formed on the surface of the photoreceptor drum 51. As a result, a toner image is formed on the surface of the photoreceptor drum 51.

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

[0039] Furthermore, the transfer mechanism 43 includes, for example, a primary transfer belt 61, a secondary transfer opposing roller 62, and a plurality of primary transfer rollers 63 and secondary transfer rollers 64. In the configuration example shown in Figure 1, the primary transfer belt 61 is an endless belt wound around the secondary transfer opposing roller 62 and a plurality of winding rollers. The inner surface (inner circumferential surface) of the primary transfer belt 61 is in contact with the secondary transfer opposing roller 62 and the plurality of winding rollers, while the outer surface (outer circumferential surface) faces the photoreceptor 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 conveying direction. Multiple winding rollers are configured to rotate freely. Multiple winding rollers rotate in accordance with the movement of the primary transfer belt 61 by the secondary transfer opposing roller 62.

[0041] Multiple primary transfer rollers 63 are configured to bring the primary transfer belt 61 into contact with the photoreceptor drum 51 of the process unit 41. The multiple primary transfer rollers 63 are provided to correspond to the photoreceptor drums 51 of the multiple process units 41. Specifically, the multiple primary transfer rollers 63 are provided at positions (primary transfer positions) opposite each other, with the photoreceptor drum 51 and primary transfer belt 61 of the corresponding process unit 41 in between. The primary transfer rollers 63 contact the inner circumferential surface of the primary transfer belt 61, displacing the primary transfer belt 61 toward the photoreceptor drum 51. As a result, the primary transfer rollers 63 bring the outer circumferential surface of the primary transfer belt 61 into contact with the photoreceptor drum 51.

[0042] The secondary transfer roller 64 is positioned opposite the primary transfer belt 61 (secondary transfer position). The secondary transfer roller 64 contacts the outer circumferential surface of the primary transfer belt 61 and applies pressure. This forms a transfer nip where the secondary transfer roller 64 and the outer circumferential 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 circumferential surface of the primary transfer belt 61.

[0043] The secondary transfer roller 64 and the secondary transfer opposing roller 62 rotate to transport the printing medium P supplied from the paper feed transport path 31 while gripping it. This allows the printing medium P to pass through the transfer nip.

[0044] In the above configuration, when the outer surface of the primary transfer belt 61 comes into contact with the photoreceptor drum 51, the toner image formed on the surface of the photoreceptor drum is transferred to the outer surface of the primary transfer belt 61. If the image forming mechanism 20 includes a plurality of process units 41, the primary transfer belt 61 receives toner images from the photoreceptor drums 51 of the plurality of process units 41. The toner image transferred to the outer surface of the primary transfer belt 61 is transported by the primary transfer belt 61 to the transfer nip where the secondary transfer roller 64 and the outer surface of the primary transfer belt 61 are in close contact. If a printing medium P is present at the transfer nip, the toner image transferred to the outer surface of the primary transfer belt 61 is transferred to the printing medium P at the transfer nip.

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

[0046] In the configuration example shown in Figure 1, the fuser 21 includes a heat roller 71, a press roller 72, a heater 73, non-contact temperature sensors 74 (741, 742), and a contact temperature sensor 751. 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 fuser 21 includes a heater 73 having multiple heat sources. In the configuration example shown in Figure 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 (first heat source and second heat source) are not limited to heater lamps, but can be anything that heats the heat roller 71.

[0047] Furthermore, the fuser 21 has a plurality of non-contact temperature sensors 741, 742 and a contact temperature sensor 751, which serve as non-contact temperature sensors 74. Non-contact temperature sensors 741 and 742 are non-contact temperature sensors that detect the temperature of the detection area without contact. Non-contact temperature sensors 741 and 742 are, for example, non-contact thermistors. Non-contact temperature sensor 741 is the first non-contact temperature sensor, and non-contact temperature sensor 742 is the second non-contact temperature sensor.

[0048] In the configuration example shown in Figure 2, the non-contact temperature sensor (first non-contact temperature sensor) 741 is a center temperature sensor that detects the center region (first region) C on the surface of the heat roller 71. 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 detects the side region S on the surface of the heat roller 71. 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 a detection area by having its contact portion (detection portion) come into contact with the detection area. The contact temperature sensor 751 is, for example, a contact thermistor. In the configuration example shown in Figure 2, the contact temperature sensor 751 uses the edge of the heat roller 71 that is outside the medium passage area (non-paper passage area) as the temperature detection area. The contact temperature sensor 751 is installed so that its contact portion comes into contact with the edge of the heat roller 71 that is the non-paper passage area.

[0050] The heat roller 71 is a fixing rotating body that rotates while heated by the heater 73. The heat roller 71 has a hollow core made of metal and an elastic layer formed on the outer circumference of the core. The diameter of the heat roller 71 is, for example, φ30 mm. For example, the heat roller 71 is made of aluminum with a core 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, fluororesin (tetrafluoroethylene resin). The diameter of the heat roller 71, the thickness of the core, the peripheral speed, and the names of the raw materials for the core and elastic layer described above are examples and are not limited to these.

[0051] The heat roller 71 is heated on the inside of the core metal by a heater 73, which is a heating element (heat source) positioned inside the hollow core metal. The heat applied to the inside of the core metal is transferred to the surface of the heat roller 71 (the surface of the elastic layer), which is the outside of the core metal. The fixing member may be configured as an endless belt.

[0052] As shown in Figure 1, the press roller 72 is positioned opposite the heat roller 71. The press roller 72 has a core made of metal with a predetermined outer diameter and an elastic layer formed on the outer circumference of the core. The diameter of the press roller 72 is, for example, φ30 mm. The elastic layer 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 pressure value, and the name of the raw material are examples only and are not limited to these. The pressure applied from the press roller 72 to the heat roller 71 forms a nip (fixing nip) where the press roller 72 and the heat roller 71 are in close contact. The press roller 72 is rotated by a motor. As the press roller 72 rotates, it moves the printing medium P that has entered the fixing nip and presses the printing medium P against the heat roller 71. 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 that heats the heat roller 71. The heater 73 is composed of multiple heating elements that generate heat using electricity supplied from the heater control circuit 14. In the configuration example shown in Figures 1 and 2, the heater 73 in the fuser 21 has two heat sources (heating elements): a center heater 731 and a side heater 732. The center heater 731 and the side heater 732 can be any heat sources that heat the heat roller 71, which 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 equipped with halogen lamps.

[0055] In the configuration example shown in Figure 2, the fuser 21 has a center heater 731 and a side heater 732 as heaters 73. The center heater 731 is a first heat source that heats the central part (center region C) of the heat roller 71 in the direction of rotation axis. The side heater 732 is a second heat source that heats the peripheral part (side region S) of the heat roller 71 other than the central part in the direction of rotation axis. The printing medium P is transported in the transport direction F shown in Figure 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 through power supplied by the control of the controller 13. The power consumption of the center heater 731 and the side heater 732 is, for example, 600W. When the controller 13 performs a fixing process on a printing medium P that is narrow in the direction of rotation of the heat roller 71 (the transport direction F of the printing medium P), it heats the center area C of the heat roller 71. When the controller 13 heats the center area C of the heat roller 71, it activates the center heater 731 without activating the side heater 732 using the heater control circuit 14.

[0057] Furthermore, when the controller 13 performs a fixing process on a printing medium P that is wide in the direction of rotation of the heat roller 71 (the transport direction F of the printing medium P), it 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, it activates both the center heater 731 and the side heater 732 using the heater control circuit 14.

[0058] In the configuration example shown in Figure 2, the non-contact temperature sensors 741 and 742 are arranged parallel to the rotation axis of the heat roller 71. The non-contact temperature sensor 741 detects the temperature of the center region C (the central part when the heat roller 71 is divided into three sections in the direction of rotation) in the direction of rotation axis of the heat roller 71. The non-contact temperature sensor 741 is installed so as to face the detection area in the center region C on the surface of the heat roller 71. Furthermore, the non-contact temperature sensor 741 is positioned so that the distance (gap, width) Gap to the surface of the heat roller 71 is within an acceptable range.

[0059] Furthermore, the non-contact temperature sensor 742 detects the temperature of the side region S (any side portion when the heat roller 71 is divided into three sections in the direction of rotation) in the direction of rotation axis of the heat roller 71. The non-contact temperature sensor 742 is installed so as to face the detection area 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 within the allowable width.

[0060] The contact temperature sensor 751 detects the surface temperature of the heat roller 71 by having its contact portion contact the surface of the heat roller 71. In the configuration example shown in Figure 2, the contact temperature sensor 751 is installed so that its contact portion contacts the edge (non-paper-feeding portion) of the heat roller 71 other than the area (paper-feeding portion) through which a recording medium such as paper passes (contacts). The contact temperature sensor 751 detects a temperature to correct the temperature detected by the non-contact temperature sensor 741 and the non-contact temperature sensor 742.

[0061] The non-contact temperature sensors 741 and 742 and the contact temperature sensor 751 each supply a detection signal indicating the temperature detection result to the controller 13. The controller 13 corrects the temperature detected by the non-contact temperature sensor 741 using a correction value to approximate the actual temperature of the detection area. Through this correction process, the controller 13 identifies the temperature of the center region C of the heat roller 71, which is the detection area 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 identified by the correction process.

[0062] The controller 13 corrects the temperature detected by the non-contact temperature sensor 742 (detection signal) using a correction value to approximate the actual temperature of the detected area. Through this correction process, the controller 13 identifies the temperature of the side region S of the heat roller 71. When heating the entire heat roller 71, the controller 13 controls the center heater 731 and the side heater 732 based on the temperature of the side region S identified in the correction process.

[0063] The heat roller 71 and press roller 72 apply heat and pressure controlled within a predetermined temperature range to the printing medium P as it passes through the fuser nip. The toner on the printing medium P is fixed to the surface of the printing medium P by the heat from the heat roller 71 and the pressure from the heat roller 71 and press roller 72. As a result, a toner image is fixed to the printing medium P as it passes through the fuser nip. The printing medium P that has passed through the fuser nip is introduced into the paper discharge 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 this embodiment will be described. Figure 3 is a block diagram showing an example of the control system configuration in the image forming apparatus 1. As shown in Figure 3, the image forming apparatus 1 connects a communication interface 12, a heater control circuit 14, a display device 15, an operating device 16, a transport mechanism 19, an image forming mechanism 20, and a fuser 21, etc., to a controller (system controller) 13.

[0065] The controller 13 includes a processor 81, ROM (Read Only Memory) 82, RAM (Random Access Memory) 83, and data memory 84. The controller 13, along with the processor 81, ROM 82, RAM 83, and data memory 84, constitutes a computer. The controller 13 may also include an ASIC, such as an image processing processor.

[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 the operating system or application program. The processor 81 is, for example, a CPU (Central Processing Unit).

[0067] ROM 82 and RAM 83 correspond to the main memory portion of the computer acting 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 control data necessary for the processor 81 to perform processing to control each part. RAM 83 is used as a work area where data is rewritten as appropriate by the processor 81. RAM 83 has a work area for storing, for example, image data.

[0068] The data memory 84 is composed of rewritable non-volatile memory. The data memory 84 corresponds to the auxiliary storage portion of the computer acting as the controller 13. The data memory 84 is composed of storage devices such as EEPROM (Electric Erasable Programmable Read-Only Memory), HDD (Hard Disk Drive), or SSD (Solid State Drive).

[0069] The data memory 84 stores data such as configuration data used by the processor 81 when performing various processes. The data memory 84 also stores data generated by processes executed by the processor 81. The data memory 84 may also store application programs. The data memory 84 stores correction values ​​(steady-state correction values ​​and additional correction values) described later for correcting the detected temperatures of the non-contact temperature sensors 741 and 742 to actual temperatures. The data memory 84 may also store information (for example, a correlation formula) showing the correlation between the detected temperatures of the non-contact temperature sensors 741 and 742 and the additional correction values ​​described later.

[0070] The controller 13 controls the image forming mechanism 20. For example, the controller 13 controls each process unit 41, the exposure unit 42, and the transfer mechanism 43. For example, the controller 13 controls the on / off switching of the charger 52 of each process unit 41. The controller 13 controls the on / off switching of the laser light that irradiates the photoreceptor drum 51 to the exposure unit 42 of each process unit 41. As a result, an electrostatic latent image is formed on the photoreceptor drum 51.

[0071] Furthermore, the controller 13 controls the on / off switching of the development bias for the developer unit 53 of each process unit 41. As a result, the electrostatic latent image on the photoreceptor drum 51 is developed by the toner supplied from the developer unit 53, and a toner image is formed on the photoreceptor drum 51. The controller 13 controls the primary transfer bias for the transfer mechanism 43 at each primary transfer position. The toner image on the photoreceptor drum 51 is transferred to the primary transfer belt 61 at the primary transfer position. In addition, the controller 13 controls the secondary transfer bias for the transfer mechanism 43 at the secondary transfer position. As a result, the toner image on the primary transfer belt 61 is transferred to the printing medium P.

[0072] Furthermore, the controller 13 controls the fixing device, including the fuser 21. The controller 13 controls the operation of the center heater 731 and the side heaters 732 by the heater control circuit 14 according to the detection results of the non-contact temperature sensors 741 and 742. The heater control circuit 14 controls the supply of power to the center heater 731 and the side heaters 732 by operating in response to control instructions from the controller 13. Note that some or all of the components of the heater control circuit 14, which will be described later, may be included in the controller 13.

[0073] The heater control circuit 14 controls the supply of power to the center heater 731 and the side heater 732 so that the surface of the heat roller 71 reaches a 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 temperatures detected by the non-contact temperature sensors 741 and 742 using a steady-state correction value and an additional correction value.

[0074] The steady-state correction value is a correction value used to approximate the temperature detected by the non-contact temperature sensors 74 (741, 742) to the actual temperature of the heat roller 71 when the temperature of the heat roller 71 is stable. The steady-state correction value is set according to the difference between the temperature detected by the non-contact temperature sensors 741 and 742 and the temperature detected by the contact temperature sensor 751. For example, the steady-state correction value is set by the difference between the temperature detected by the non-contact temperature sensors 741 and 742 and the temperature detected by the contact temperature sensor 751 when the surface of the heat roller 71 is at a predetermined temperature. In addition, the additional correction value is used for additional correction performed during the first period from the start of printing to a predetermined time when performing continuous printing from a cold start. The additional correction value and the additional correction using the additional correction value will be explained 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 temperature detected by 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] Furthermore, the heater control circuit 14 controls the power supply to the side heater 732, which is a 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 temperature detected by the non-contact temperature sensor 742 using a correction value described later. The heater control circuit 14 turns the power supply to the side heater 732 on and off so that the actual temperature of the side region S calculated using the correction value reaches the target value.

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

[0078] Next, the temperature control of the heat roller 71 in the fuser 21 of the image forming apparatus 1 according to this embodiment will be described. Figure 4 shows an example of measurement results of the actual surface temperature of the heat roller 71 when continuous printing is performed from a cold start without any additional correction. In the measurement results shown in Figure 4, the recording medium used for continuous printing is assumed to be paper with a basis weight of 60-90 g / m2. The target temperature (target value) is set to 150°C, but since there is a delay (time constant) in temperature detection, it is assumed that the actual temperature will be slightly higher than the target value and be stably controlled. Cold start means that printing will begin immediately after the heat roller 71 has risen from a predetermined temperature (e.g., 40°C or lower). Additional correction means correcting the detected temperature of the non-contact temperature sensors 741 and 742, which are non-contact temperature sensors, using the additional correction value described later.

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

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

[0081] As shown in Figure 4, the measurement results differ in their fluctuation trends between the first period (up to 30 seconds from the start of printing) and the period after 30 seconds from the start of printing (second period). In the second period, the actual temperature of the heat roller 71 surface is stably controlled around a constant value (approximately 153°C). In the first period, the actual temperature of the heat roller 71 surface is lower and more unstable than in the second period. Furthermore, in the first period, the actual temperature of the heat roller 71 surface varies greatly depending on the gap, with the temperature decreasing as the gap increases (towards the lower limit).

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

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

[0084] Figure 7 shows the difference between the average actual surface temperature of the heat roller 71 during the second period and the average actual surface temperature of the heat roller 71 during the first period. In Figure 7, Gap_Hc represents the difference 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. Gap_Lc represents the difference obtained by subtracting the average value La in the first period from the average value La in the second period when the gap is at the lower limit. Gap_Cc represents the difference obtained by subtracting the average value Ca in the first period from the average value Ca in the first period from the average value Cb in the second period when the gap is at the center value.

[0085] As shown in Figure 7, the average actual temperature in the first period is lower than the average 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 to be lower than the target value with only the steady-state correction control. Therefore, in the first period, additional correction control is necessary in addition to the steady-state correction control. The additional correction control implemented in the first period should be one that corrects the difference between the actual temperature in the second period and the actual temperature in the first period.

[0086] The amount of correction to be corrected as additional correction control (additional correction value) is set according to the difference value, for example, as shown in Figure 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 an acceptable range. Therefore, according to the example shown in Figure 7, the difference value for setting the additional correction value is the 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) fluctuates depending on the size of the gap. The correlation between the additional correction amount and the temperature conversion value is set using the temperature conversion value of the non-contact temperature sensors 74 and the difference value shown in Figure 7. In the image forming apparatus 1, the controller 13 can acquire 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 sensors, the controller 13 sets the additional correction value from the temperature conversion values ​​of the non-contact temperature sensors 741 and 742.

[0088] Figure 8 shows 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 Figure 8, the recording medium used for continuous printing is assumed to be paper with a basis weight of 60-90 g / m2. Also, in Figure 8, the non-contact temperature sensor 74 is assumed to be the non-contact temperature sensor 741 facing the center region C.

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

[0090] Figure 9 shows the average temperature conversion value of the non-contact temperature sensor 741 during the first period, which is the period from the start of printing (start of continuous printing) as shown in Figure 8 up to 30 seconds. Figure 10 shows the average temperature conversion value of the non-contact temperature sensor 741 during the second period, which is from 30 seconds after the start of printing as shown in Figure 8. As shown in Figures 9 and 10, the average temperature conversion value of the non-contact temperature sensor 741 differs for each gap, becoming lower as the gap increases. Furthermore, the average temperature conversion value of the non-contact temperature sensor 741 is lower in the first period than in the second period for any gap. Moreover, the difference between the average temperature conversion value of the non-contact temperature sensor 741 between the first and second periods increases as the gap increases.

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

[0092] The additional correction value when the gap between the non-contact temperature sensor 741 and the surface of the heat roller 71 is at the upper limit corresponds to the difference value Gap_Hc shown in Figure 7. Furthermore, the temperature conversion value of the non-contact temperature sensor 741 when the gap is at the upper limit is determined from the measurement results shown in Figure 9. In Figure 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 Figure 11, the additional correction values ​​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 are plotted.

[0093] The three points plotted based on the correspondence between the temperature conversion value of the non-contact temperature sensor 741 and the additional correction value for each gap show a linear correlation, as shown in Figure 11. According to the correlation shown in Figure 11, the controller 13 can identify the additional correction value from the temperature conversion value of the non-contact temperature sensor 741, which 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 Figure 11 can be expressed as a correlation equation.

[0094] For example, the data memory 84, which functions as memory, stores a correlation formula that shows the correlation between the temperature conversion value of the non-contact temperature sensor 741 and the additional correction value. When the controller 13 obtains the temperature conversion value of the non-contact temperature sensor 741 during the first period, it calculates the average value of the temperature conversion value of the non-contact temperature sensor 741 during the first period. The controller 13 identifies the additional correction value from the average value of the temperature conversion value of the non-contact temperature sensor 741 during the first period using the correlation formula stored in the data memory 84. Based on this result, the controller 13 saves (updates) the additional correction value to be added to the steady-state correction value during the first period in the data memory 84.

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

[0096] The measurement results shown in Figure 12 indicate that, during the first period, the actual temperature of the surface of the heat roller 71 is controlled to reach the target value, similar to the second period shown in Figure 4. This indicates that the actual temperature of the surface of the heat roller 71 during the first period is corrected to reach the target value by additional correction using an additional correction value. Furthermore, the measurement results shown in Figure 12 show that, 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, which fluctuates depending on the gap between the non-contact temperature sensor 741 and the heat roller 71. Therefore, the fuser (fusing device) 21 according to this embodiment can accurately control the actual temperature of the surface of the heat roller 71 during the first period to reach the target value by additional correction.

[0097] In the above description with reference to Figures 4 to 12, temperature control of the center region C was explained, but temperature control of the side region S can be performed in the same manner. In other words, in the image forming apparatus including the fixing device according to the embodiment, an 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 described above.

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

[0099] In other words, the image forming apparatus according to the embodiment corrects the temperature conversion values ​​of the non-contact temperature sensors 741 and 742 during the first period using a steady correction value and an additional correction value, respectively. As a result, the image forming apparatus according to the embodiment can accurately control the center region C and the side region S to target values ​​even during the first period (immediately after the start of heating of the heat roller 71) when performing contact printing from a cold start.

[0100] Furthermore, the above explanation with reference to Figures 4 to 12 described an example of measurement results when continuous printing is performed using a recording medium (paper) with a basis weight of 60 to 90 g / m2. However, the amount of heat absorbed by the heat roller 71 differs depending on the type of recording medium. In the first period, when the heat roller 71 and press roller 72 are not sufficiently heated, the amount of heat absorbed by the recording medium (paper) greatly affects temperature control. For this reason, the additional correction value in the first period when performing continuous printing from a cold start may be set for each type of recording medium. In this case, the data memory 84 stores the additional correction value for each type of recording medium. When performing continuous printing from a cold start, the controller 13 performs temperature control in the first period using the additional correction value according to the type of recording medium and a steady-state correction value.

[0101] For example, the data memory 84 stores a correlation formula for each type of recording medium that shows the correlation between the additional correction value described above and the temperature conversion value of the non-contact temperature sensor. When continuous printing is performed from a cold start, the controller 13 calculates the average value of the temperature conversion value of the non-contact temperature sensor during the first period. The controller 13 can then set (update) the additional correction value, which is identified from the average value of the temperature conversion value of the non-contact temperature sensor using the correlation formula for each type of recording medium, for each type of recording medium.

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

[0103] First, the controller 13 turns on the power to the fuser unit 21 in response to user instructions (ACT 10). When the power to the fuser unit 21 is turned on, the controller 13 obtains the temperature detected by the contact temperature sensor 751. The controller 13 checks whether the temperature detected by the contact temperature sensor 751 (contact temperature) when the power is turned on is 40 degrees or less (ACT 11).

[0104] If the temperature detected by the contact temperature sensor 751 exceeds 40 degrees (ACT11, NO), the controller 13 omits the additional temperature correction using an additional correction value. When the additional temperature correction is omitted, the controller 13 switches to the normal control state. When printing is performed in the normal control state, the controller 13 controls the temperature of the heat roller 71 by correcting the temperature detected by the non-contact temperature sensors 74 (741, 742) using a constant correction value.

[0105] If the temperature detected by the contact temperature sensor 751 is 40 degrees or lower (ACT11, YES), the controller 13 performs a warm-up operation to transition to a ready state (printable state) (ACT12). Once the controller 13 transitions to the ready state, it decides whether or not to perform printing (continuous printing) (ACT13). For example, if the power is turned on in response to a user's instruction to perform continuous printing, the controller 13 decides to perform continuous printing from a cold start. If the controller 13 decides not to perform printing (ACT13, NO), it omits the additional temperature correction using the additional correction value and transitions to the normal control state.

[0106] If the controller 13 determines that it is time to print (ACT13, YES), it performs an additional correction to the temperature detected by the non-contact temperature sensor 74 (ACT14). Based on the temperature corrected by the correction process, including the additional correction, the controller 13 performs the printing process, including the fixing process on the printing medium, while controlling the temperature of the heat roller 71 (ACT15).

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

[0108] For example, if the area through which the printing medium used for printing passes is the center area C of the heat roller 71, the controller 13 performs temperature control of the center area C. When performing temperature control of the center area C, the controller 13 sets a steady-state 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-state 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 printing medium passes through a center area C and a side area S, the controller 13 performs temperature control of both the center area C and the side area S. In this case, the controller 13 sets a steady-state 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 a correction value obtained by adding the additional correction value to the steady-state correction value. For 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 reaches the target value. For 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 reaches the target value.

[0110] Furthermore, while continuous printing is being performed 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 data memory 84) (ACT 16). While executing the processes of ACT14-16, the controller 13 monitors whether 30 seconds (first period) have elapsed since the start of printing (ACT17). If continuous printing is completed before 30 seconds (first period) have elapsed since the start of printing (ACT17, NO), the controller 13 returns to the normal control state, indicating that no additional correction is needed (no additional correction).

[0111] If a predetermined time (30 seconds) elapses during continuous printing from a cold start (ACT17, NO), the controller 13 disables the additional correction based on the additional correction value and moves to the second period (ACT18). After disabling the additional correction and moving to the second period, the controller 13 continues to perform continuous printing in the normal control state.

[0112] Furthermore, if continuous printing is performed within a predetermined time (30 seconds) from the start of printing (first period) (ACT17, NO), the controller 13 performs an update process to update the additional correction amount (ACT19-21). However, the update process to update the additional correction amount may be performed in parallel with the operation of continuous printing in the normal control state. Also, the update process to update the additional correction amount may be performed at predetermined timings (for example, after the completion of continuous printing, or at predetermined intervals).

[0113] In the process of updating 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 during the first period, which are stored in the RAM 83 or data memory 84 (ACT 19). Once the controller 13 has calculated the average value of the temperature conversion values, it identifies an additional correction value corresponding to the average value of the temperature conversion values ​​based on a correlation formula corresponding to the type of recording medium used for printing (ACT 20). Once the controller 13 has identified the additional correction value, it updates the additional correction value corresponding to the type of recording medium stored in the data memory 84 using the identified additional correction value (ACT 21).

[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 a first period of continuous printing from the start of printing until a predetermined time. The fixing device controls the heater with the temperature corrected with the steady correction value and the additional correction value during the first period, and controls the heater with the temperature corrected with the steady correction value during the second period after the first period has elapsed. As a result, the fixing device according to the embodiment can stably control the temperature of the heat roller to the target value without the temperature of the heat roller dropping significantly even during the first period.

[0115] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents.

[0116] The fixing devices according to the embodiment are listed below. [1] A fixing member in contact with the medium on 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 the region through which the medium passes in the fixing member without contact, A contact temperature sensor that detects temperature at a detection unit that contacts a non-passing region in 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 the actual temperature of the fixing member, and an additional correction value set according to the average value of the temperature detected by the non-contact temperature sensor during a first period from the start of the printing process, including the fixing process, to a predetermined time, A controller that controls the heat source based on a value obtained by correcting the temperature detected by 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 temperature detected by the non-contact temperature sensor using the steady-state correction value during the second period after the first period has elapsed, A fixing device having the following features. [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. [1] Fixing device as described above. [3] The memory stores additional correction values ​​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 the type of medium used for printing in addition to the steady-state correction amount during the first period. [1] Fixing device as described above. [4] The controller updates the additional correction value stored in the memory based on a correlation that indicates an additional correction value corresponding to the temperature detected by the non-contact temperature sensor, using an additional correction value identified from the temperature detected by the non-contact temperature sensor during the first period. [1] Fixing device as described above. [5] The controller updates the additional correction value stored in the memory based on a correlation that indicates an additional correction value corresponding to the average value of the temperature detected by the non-contact temperature sensor during the first period, using an additional correction value identified from the average value of the temperature detected by the non-contact temperature sensor during the first period. [4] Fixing device as described above. [6] The memory stores a correlation formula that indicates an additional correction value corresponding to the average value of the temperature detected by the non-contact temperature sensor. The controller calculates an additional correction amount corresponding to the average value of the detected temperature of the non-contact temperature sensor detected during the first period using the correlation formula. [5] Fixing device as described above. [7] The memory stores the additional correction values ​​for each type of medium used in the printing process. The controller updates the additional correction amount for the type of medium used in the printing process based on the correlation for each type of medium used in the printing process, using an additional correction value determined from the temperature detected by the non-contact temperature sensor detected during the first period. [4] Fixing device as described above. [8] The controller updates the amount of additional correction for the type of medium used in the printing process based on the correlation between the types of media used in the printing process, using an additional correction value determined from the average value of the detected temperature of the non-contact temperature sensor detected during the first period. [7] Fixing device as described above. [9] The memory stores a correlation formula that shows an additional correction value corresponding to the average value of the temperature detected by 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, corresponding to the average value of the temperature detected by the non-contact temperature sensor during the first period, using the correlation formula for the type of medium used in the printing process. [8] Fixing device as described above.

[10] The heat source comprises 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 comprises a first non-contact temperature sensor that detects the temperature of the first region in the fixing member in a non-contact manner, and a second non-contact temperature sensor that detects the temperature of the second region in the fixing member in a non-contact manner. The memory stores the additional correction amount for the first non-contact temperature sensor and the additional correction amount for the second non-contact temperature sensor. The controller controls the first heat source during the first period using 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 using 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. [1] Fixing device as described above. [Explanation of Symbols]

[0117] 1…Image forming apparatus, 12…Communication interface, 13… Controller, 14… Heater control circuit, 21... Fuser (fusing device), 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 (edge ​​temperature sensor), 81…Processor, 82...ROM, 83...RAM, 84...Data memory (memory).

Claims

1. A fixing member in contact with the medium on 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 the region through which the medium passes in the fixing member without contact, A contact temperature sensor that detects temperature at a detection unit that contacts a non-passing region in 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 the actual temperature of the fixing member, and an additional correction value set according to the average value of the temperature detected by the non-contact temperature sensor during a first period from the start of the printing process, including the fixing process, to a predetermined time, The system includes a controller that controls the heat source based on a value obtained by correcting the temperature detected by 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 temperature detected by the non-contact temperature sensor using the steady-state correction value during the second period after the first period has elapsed. 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. Fixing device.

2. The memory stores additional correction values ​​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 the type of medium used for printing in addition to the steady-state correction value during the first period. The fixing device according to claim 1.

3. A fixing member in contact with a medium on which a 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 the region through which the medium passes in the fixing member without contact, A contact temperature sensor that detects temperature at a detection unit that contacts a non-passing region in 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 the actual temperature of the fixing member, and an additional correction value set according to the average value of the temperature detected by the non-contact temperature sensor during a first period from the start of the printing process, including the fixing process, to a predetermined time, The system includes a controller that controls the heat source based on a value obtained by correcting the temperature detected by 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 temperature detected by the non-contact temperature sensor using the steady-state correction value during the second period after the first period has elapsed. The controller updates the additional correction value stored in the memory based on a correlation that indicates an additional correction value corresponding to the average value of the temperature detected by the non-contact temperature sensor during the first period, using an additional correction value identified from the average value of the temperature detected by the non-contact temperature sensor during the first period. Fixing device.

4. The memory stores a correlation formula that indicates an additional correction value corresponding to the average value of the temperature detected by the non-contact temperature sensor. The controller calculates an additional correction value corresponding to the average value of the detected temperature of the non-contact temperature sensor detected during the first period using the correlation formula. The fixing device according to claim 3.

Images