JP2012088533A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an induction heating type fixing device capable of reducing temperature unevenness of a heating belt for heating a paper on which a toner image is formed.SOLUTION: In the fixing device, a power control section 503 controls for adding a second voltage (second physical quantity) to a first voltage (first physical quantity), and controlling for supplying power to a coil 11, in a fixing process of fixing a toner image on a paper. The first voltage is set based on a power indication value for indicating the power supplied to the coil 11. The second voltage is set so as to obtain power opposite phase to the actual power which has been supplied to the coil 11 by supplying the first voltage to the coil 11 while rotating a heating belt 15.

Description

  The present invention relates to an induction heating type fixing device and an image forming apparatus including the same.

  The fixing device is provided in an electrophotographic image forming apparatus, and heats and pressurizes the paper on which the toner image is formed, thereby fixing the toner image on the paper. There is an induction heating method as one of the heating methods of the fixing device. According to this method, it is possible to perform heating more rapidly and efficiently than the halogen lamp method.

  As an induction heating type fixing device, a fixing belt including a nickel film layer, an upper induction heating member disposed above the fixing belt, and a lower induction heating member disposed below the fixing belt are provided. Have been proposed (see, for example, Patent Document 1). An induction coil is disposed in each of the upper induction heating member and the lower induction heating member. The fixing belt is induction-heated by passing a high-frequency current through the induction coil. The fixing belt is an example of a heating member, and heats the paper on which the toner image is formed. According to this fixing device, even when the gap between the fixing belt and the induction coil fluctuates due to the vibration of the fixing belt during traveling, the temperature unevenness of the fixing belt can be reduced. The reason is as follows.

  In this fixing device, the upper induction heating member is positioned above the fixing belt, and the lower induction heating member is positioned below the fixing belt. Therefore, if the gap between the fixing belt and the induction coil of the upper induction heating member becomes large when the fixing belt vibrates during traveling, the gap between the fixing belt and the induction coil of the lower induction heating member becomes small. Conversely, if the gap between the fixing belt and the induction coil of the upper induction heating member is reduced, the gap between the fixing belt and the induction coil of the lower induction heating member is increased. Therefore, even if the fixing belt vibrates, the change in the magnetic field strength acting on the fixing belt can be reduced, so that the temperature unevenness of the fixing belt can be reduced.

JP 2007-108417 A

  In the fixing device, the induction heating member is divided into an upper induction heating member and a lower induction heating member, the upper induction heating member is disposed above the fixing belt, and the lower induction heating member is disposed below the fixing belt. For this reason, the freedom degree of the installation place of an induction heating member falls. In addition, an inverter circuit that supplies electric power to the induction coil of the upper induction heating member and the induction coil of the lower induction heating member is required, which may increase the cost.

  An object of the present invention is to provide an induction heating type fixing device capable of reducing temperature unevenness of a heating member that heats a sheet on which a toner image is formed, and an image forming apparatus including the same.

  The fixing device according to one aspect of the present invention that achieves the above object forms a toner image while rotating with an induction heating coil and an eddy current flowing by induction magnetic flux generated by the magnetic flux generated by the coil. In a fixing process for fixing the toner image to the paper, a heating member for heating the paper, a pressure member for pressing the paper while rotating the paper while the paper is heated by the heating member, Or a power control unit that performs control for adding the second physical quantity to the first physical quantity that is a voltage and supplying the second physical quantity to the coil, wherein the first physical quantity is power for instructing power to be supplied to the coil. The second physical quantity is an actual value supplied to the coil by supplying the first physical quantity to the coil while rotating the heating member. In which the power of the opposite phase is obtained for the power.

  When the first physical quantity based on the power instruction value that instructs the power supplied to the coil is supplied to the coil in a state where the heating member is rotated, the gap between the heating member and the coil fluctuates. The actual power supplied to is different from the power command value. In the present invention, the second physical quantity that can obtain the power in the opposite phase to the actual power is used. The reverse phase means that the phase of one power is shifted by 180 degrees with respect to the phase of one power, and includes both cases where the amplitudes are equal and amplitudes are not equal. According to the present invention, in the fixing process, since the second physical quantity is added to the first physical quantity and supplied to the coil, the power supplied to the coil can be brought close to the power instruction value. Therefore, even if the gap fluctuates, the fluctuation amount of the eddy current flowing through the heating member can be reduced, so that the change in the strength of the magnetic flux generated by the coil can be reduced, and as a result, the temperature unevenness of the heating member can be reduced. Can do.

  In the above configuration, the second physical quantity is a physical quantity that can obtain power equal to the difference between the power instruction value and the actual power supplied to the coil as the power of the opposite phase.

  According to this configuration, in the fixing process, by adding the second physical quantity to the first physical quantity and supplying the same to the coil, the power supplied to the coil can be made the same as the power instruction value. The second physical quantity in this configuration is a physical quantity from which power having an amplitude equal to the amplitude of the actual power supplied to the coil is obtained out of the antiphase power.

  In the above configuration, if the first physical quantity is a voltage, the current is a current, and if the current is a current, a third physical quantity that is a voltage is measured. While rotating the heating member, the first physical quantity is applied to the coil. Using the physical quantity measuring unit that measures the third physical quantity supplied to the coil by supplying the physical quantity, and using the first physical quantity and the third physical quantity measured by the physical quantity measuring unit. A physical quantity computing unit that computes the actual power supplied to the coil and computes the second physical quantity that provides power in the opposite phase to the actual power.

  According to this configuration, since the second physical quantity can be calculated, the actual power supplied to the coil when the first physical quantity is supplied to the coil while rotating the heating member is the factory shipment of the fixing device. Even if it changes from time to time, it is possible to cope with the change.

  In the above-described configuration, the physical quantity calculation unit can calculate the actual power supplied to the coil, with the cycle of the actual power supplied to the coil as a cycle of one rotation of the heating member.

  In this configuration, when the first physical quantity is supplied to the coil while rotating the heating member, the period of the actual power supplied to the coil is considered to be the same as the period of one rotation of the heating member. According to this configuration, the calculation of the period can be omitted in the calculation of the actual power supplied to the coil.

  In the above-described configuration, the sensor includes a sensor capable of detecting one rotation of the heating member, and the physical quantity calculation unit determines a cycle of the rotation of the heating member detected by the sensor as a cycle of an actual power supplied to the coil. As a result, the actual power supplied to the coil can be calculated.

  According to this configuration, since one rotation of the heating member is detected by the sensor, it is possible to cope with a change in the period of one rotation of the heating member over time from the factory shipment of the fixing device.

  In the above configuration, the physical quantity calculation unit calculates the actual power supplied to the coil, with a cycle of the rotation of the heating member stored in advance as a cycle of the actual power supplied to the coil. Can do.

  According to this configuration, it is not necessary to provide a sensor that can detect one rotation of the heating member.

  An image forming apparatus according to another aspect of the present invention that achieves the above object includes an image forming unit that forms the toner image on the sheet, and the fixing device.

  In the present invention, the fixing device according to one aspect of the present invention is applied to an image forming apparatus, and the effects of the above-described fixing device can be obtained.

  According to the present invention, temperature unevenness of a heating member that heats a sheet on which a toner image is formed can be reduced.

1 is a diagram illustrating an outline of an internal structure of an image forming apparatus according to an embodiment of the present invention. It is a longitudinal cross-sectional view which shows the structure of an example of a fixing part. It is a top view of a center core. FIG. 2 is a block diagram illustrating a configuration of the image forming apparatus illustrated in FIG. 1. It is a graph which shows the data of the electric power of the electric power instruction value which wants to supply to a coil, the data of the electric power actually supplied to the coil under the electric power of an electric power instruction value, and the data of the electric power of an antiphase. It is a flowchart explaining acquiring the data of the electric power of an antiphase. 6 is a flowchart for describing a fixing process by the fixing device according to the embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing an outline of the internal structure of an image forming apparatus 1 according to an embodiment of the present invention. The image forming apparatus 1 can be applied to, for example, a digital multifunction machine having functions of a copy, a printer, a scanner, and a facsimile. The image forming apparatus 1 includes an apparatus main body 100, a document reading unit 200 disposed on the apparatus main body 100, a document feeding unit 300 disposed on the document reading unit 200, and an operation disposed on the upper front surface of the apparatus main body 100. Part 400 is provided.

  The document feeder 300 functions as an automatic document feeder, and can continuously send a plurality of documents placed on the document placement unit 301 to the document reading unit 200.

  The document reading unit 200 includes a carriage 201 on which an exposure lamp or the like is mounted, a document table 203 made of a transparent member such as glass, a CCD (Charge Coupled Device) sensor (not shown), and a document reading slit 205. When reading a document placed on the document table 203, the document is read by the CCD sensor while moving the carriage 201 in the longitudinal direction of the document table 203. On the other hand, when reading a document fed from the document feeding unit 300, the carriage 201 is moved to a position facing the document reading slit 205, and the document fed from the document feeding unit 300 is scanned. Reading is performed by the CCD sensor through the reading slit 205. The CCD sensor outputs the read original as image data.

  The apparatus main body 100 includes a sheet storage unit 101, an image forming unit 103, and a fixing unit 105. The sheet storage unit 101 is disposed at the lowermost part of the apparatus main body 100 and includes a sheet tray 107 that can store a bundle of sheets. In the bundle of sheets stored in the sheet tray 107, the uppermost sheet is fed out toward the sheet conveyance path 111 by driving the pickup roller 109. The sheet is conveyed to the image forming unit 103 through the sheet conveyance path 111.

  The image forming unit 103 forms a toner image on the conveyed paper. The image forming unit 103 includes a photosensitive drum 113, an exposure unit 115, a developing unit 117, and a transfer unit 119. The exposure unit 115 generates light corresponding to image data (image data output from the document reading unit 200, image data transmitted from a personal computer, image data received by facsimile, etc.), and is uniformly charged photosensitive drum. The peripheral surface 113 is irradiated. As a result, an electrostatic latent image corresponding to the image data is formed on the peripheral surface of the photosensitive drum 113. In this state, a toner image corresponding to image data is formed on the peripheral surface by supplying toner from the developing unit 117 to the peripheral surface of the photosensitive drum 113. This toner image is transferred by the transfer unit 119 to the sheet conveyed from the sheet storage unit 101 described above.

  The sheet on which the toner image is transferred is sent to the fixing unit 105. In the fixing unit 105, heat and pressure are applied to the toner image and the paper to fix the toner image on the paper. The paper is discharged to the stack tray 121 or the paper discharge tray 123.

  The operation unit 400 includes an operation key unit 401 and a display unit 403. The display unit 403 has a touch panel function, and displays a screen including soft keys. The user operates the soft keys while viewing the screen to make settings necessary for executing functions such as copying.

  The operation key unit 401 is provided with operation keys including hard keys. Specifically, a start key 405, a numeric key 407, a stop key 409, a reset key 411, a function switching key 413 for switching between copy, printer, scanner, and facsimile are provided.

  A start key 405 is a key for starting operations such as copying and facsimile transmission. A numeric keypad 407 is a key for inputting numbers such as the number of copies and a facsimile number. A stop key 409 is a key for stopping a copying operation or the like halfway. A reset key 411 is a key for canceling the set contents.

  The function switching key 413 includes a copy key, a transmission key, and the like, and is a key for switching between a copy function and a transmission function. When the copy key is operated, an initial copy screen is displayed on the display unit 403. When the transmission key is operated, an initial screen for facsimile transmission and mail transmission is displayed on the display unit 403.

  Next, the fixing unit 105 will be described in detail. FIG. 2 is a longitudinal sectional view showing an example of the structure of the fixing unit 105. The fixing unit 105 includes a heating roller 13, a heating belt (an example of a heating member) 15, a fixing roller 17, a pressure roller (an example of a pressure member) 19, a sensor 21, and an induction heating unit 23. These extend in the direction perpendicular to the paper surface of FIG.

  An endless heating belt 15 is hung on the fixing roller 17 and the heating roller 13. The surface layer of the fixing roller 17 is a silicone sponge elastic layer. Following the rotation of the fixing roller 17, the heating belt 15, the heating roller 13, and the pressure roller 19 are rotated. A thermistor 25 is disposed in the vicinity of the fixing roller 17. The temperature of the fixing roller 17 is measured by the thermistor 25.

  The heating belt 15 includes a base material, a surface layer, and a release layer. The substrate includes a ferromagnetic material (eg, nickel). The surface layer is formed on the substrate and includes a thin elastic layer (eg, silicone rubber). The release layer coats the surface layer and includes, for example, PFA (polytetrafluoroethylene).

  The heating roller 13 includes a core material and a release layer (for example, PFA) formed around the core material. The core material includes a magnetic metal (for example, iron).

  The sensor 21 is disposed between the fixing roller 17 and the heating roller 13 and in the vicinity of the heating belt 15. The sensor 21 is a sensor that detects one rotation of the heating belt 15. The sensor 21 is, for example, an optical sensor that includes a light projecting unit and a light receiving unit. The light emitted from the light projecting unit is reflected by the heating belt 15, and the reflected light is received by the light receiving unit. A mark 27 having a different light reflectivity from other portions is provided at a predetermined portion of the heating belt 15. The position of the heating belt 15 when the heating belt 15 rotates and the mark 27 is detected by the sensor 21 indicates the home position of the heating belt 15.

  The pressure roller 19 is disposed in contact with the fixing roller 17 via the heating belt 15. The sheet 39 on which the toner image is formed is nipped by the rotating heating belt 15 and the pressure roller 19 and sent to the downstream side of the sheet conveyance path. At the time of the nip, the paper 39 on which the toner image is formed is heated by the heating belt 15 and is pressed by the pressure roller 19, and the toner image is fixed on the paper 39. A thermistor 29 is disposed in the vicinity of the pressure roller 19. The thermistor 29 measures the temperature of the pressure roller 19.

  The induction heating unit 23 is disposed so as to cover the upper half of the heating roller 13. The induction heating unit 23 includes an induction heating coil 11, an arch core 31, a side core 33, and a center core 35.

  An upstream portion and a downstream portion of the coil 11 in the sheet conveyance direction, a pair of arch cores 31 and a pair of side cores 33 are disposed with the center core 35 interposed therebetween.

  The coil 11 is disposed with a predetermined gap from the portion of the heating belt 15 that is hung on the heating roller 13 and the heating roller 13.

  One of the arch cores 31 is disposed so as to cover one of the coils 11, and the other of the arch cores 31 is disposed so as to cover the other of the coils 11. The material of the arch core 31 is ferrite.

  A center core 35 is disposed on one side of the end of the arch core 31, and a side core 33 is disposed on the other side of the end. The material of the side core 33 is ferrite. One of the coils 11 is disposed in a space formed by one of the arch cores 31, one of the side cores 33, and the center core 35. In the space formed by the other of the arch core 31, the other of the side cores 33, and the center core 35, the other of the coils 11 is disposed.

  The center core 35 has a cylindrical shape. The material of the center core 35 is ferrite. The center core 35 is rotatable by a rotation mechanism (not shown). FIG. 3 is a plan view of the center core 35. The center core 35 is provided with shielding layers 37 at both ends thereof. 3A shows a state where the shielding layer 37 is located outside the induction heating unit 23, and FIG. 3B shows a state where the shielding layer 37 faces both ends of the heating roller 13. FIG.

  The material of the shielding layer 37 is preferably a non-magnetic and highly conductive member, for example, oxygen-free copper. The shielding layer 37 is shielded by generating a reverse magnetic field by an induced current caused by the penetration of a magnetic field perpendicular to the surface of the shielding layer 37 and canceling the complex magnetic flux. Further, by using a highly conductive member, Joule heat generation due to eddy current can be suppressed, and the magnetic field can be efficiently shielded.

  The induction heating in the fixing unit 105 will be briefly described. By applying a high-frequency current to the coil 11, a magnetic field (alternating magnetic flux) is generated by the coil 11. Due to this magnetic field, an eddy current flows through the heating roller 13 and the heating belt 15 to generate Joule heat, and the heating roller 13 and the heating belt 15 are induction-heated.

  Here, the heating belt 15 is an example of a heating member. The heating member heats the paper 39 on which the toner image is formed while rotating in a state where the eddy current flows by the magnetic flux generated by the coil 11 and induction heating. The pressure roller 19 is an example of a pressure member. The pressure member pressurizes the sheet 39 while rotating in a state where the sheet 39 is heated by the heating member.

  If the size of the sheet 39 is large, the center core 35 is in the state of FIG. 3A, and if small, the center core 35 is in the state of FIG. Thereby, when the size of the paper 39 is small, both end portions of the heating roller 13 and the heating belt 15 are prevented from being excessively heated by induction.

  Returning to the description of the image forming apparatus 1. FIG. 4 is a block diagram showing the configuration of the image forming apparatus 1 shown in FIG. The image forming apparatus 1 has a configuration in which an apparatus main body 100, a document reading unit 200, a document feeding unit 300, an operation unit 400, a control unit 500, a communication unit 600, and a resonance power source 701 are connected to each other via a bus. Since the apparatus main body 100, the document reading unit 200, the document feeding unit 300, and the operation unit 400 have already been described, description thereof will be omitted.

  The control unit 500 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an image memory, and the like. The CPU executes control necessary for operating the image forming apparatus 1 on the above-described components of the image forming apparatus 1 such as the apparatus main body 100. The ROM stores software necessary for controlling the operation of the image forming apparatus 1. The RAM is used for temporary storage of data generated during execution of software, storage of application software, and the like. The image memory temporarily stores image data (image data output from the document reading unit 200, image data transmitted from a personal computer, image data received by facsimile, etc.).

  The control unit 500 includes a rotation control unit 501, a power control unit 503, and a voltage calculation unit 505. The rotation control unit 501 controls the rotation of the fixing roller 17 by controlling a motor, a clutch, and the like provided in the image forming apparatus 1. Following the rotation of the fixing roller 17, the heating belt 15, the heating roller 13, and the pressure roller 19 are rotated. Accordingly, the rotation control unit 501 controls the rotation of the heating roller 13, the heating belt 15, the fixing roller 17, and the pressure roller 19.

  In the fixing process, the power control unit 503 controls the resonance power supply 701 to add the second voltage to the first voltage and supply it to the coil 11. The first voltage means a first physical quantity, and the second voltage means a second physical quantity. The first voltage is based on a power instruction value that instructs power supplied to the coil 11. The first voltage is a constant voltage, and if the first voltage is supplied to the coil 11, the power of the power instruction value is supplied to the coil 11 in an ideal state.

  The second voltage is a voltage that generates electric power in an antiphase with respect to the actual electric power supplied to the coil 11 by supplying the first voltage to the coil 11 while rotating the heating belt 15. Furthermore, the second voltage is a voltage at which the power of the opposite phase having the amplitude equal to the amplitude of the actual power supplied to the coil 11 is obtained, in other words, the power instruction value and the actual power supplied to the coil 11. Is a voltage that produces power equal to the difference between

  FIG. 5 is a graph showing an example of a power instruction value D1 for instructing power supplied to the coil 11, an actual power D2 supplied to the coil 11, and a power D3 having an opposite phase to the power D2. The power instruction value D1 is a constant power of 1000W. The first voltage is a constant voltage based on the power instruction value D1. However, when the first voltage is supplied to the coil 11 while rotating the heating belt 15, the actual power D2 supplied to the coil 11 is different from the power command value D1. The reason for this will be explained.

  The resonant power supply 701 is feedback controlled to output a first voltage that is a constant voltage. As the heating roller 13, the heating belt 15, and the fixing roller 17 rotate, the gap between the heating belt 15 and the coil 11 inevitably changes. Therefore, since the eddy current flowing through the heating roller 13 and the heating belt 15 changes, the current (third physical quantity) supplied from the resonance power source 701 to the coil 11 changes accordingly. As a result, even if the first voltage is supplied to the coil 11, the actual power D <b> 2 supplied to the coil 11 does not coincide with the power command value D <b> 1 that is constant power, and becomes pulsating power.

  The power indicated by reference sign D3 is power having an amplitude equal to the amplitude of the actual power D2 supplied to the coil 11 (amplitude based on the power command value D1) as power of opposite phase, in other words, the power command value D1. Is equal to the difference between the actual power D2 supplied to the coil 11 and the actual power D2. Therefore, if the electric power D2 and the electric power D3 are added, it coincides with the electric power instruction value D1.

  The fluctuation of the gap between the heating roller 13 and the coil 11 is caused by the eccentricity of the heating roller 13. The fluctuation of the gap also occurs due to the eccentricity of the fixing roller 17 and the pressure roller 19 such that the fixing belt 15 pulls the heating roller 13 and the rotating shaft of the heating roller 13 is bent. Therefore, instead of the period of one rotation of the heating roller 13, the period of one rotation of the heating belt 15 is regarded as one period of the electric power D2 and the electric power D3.

  Returning to the description of FIG. The image forming apparatus 1 includes an ammeter 703 that is an example of a physical quantity measuring unit. The ammeter 703 measures the current (third physical quantity) supplied to the coil 11 by supplying the first voltage (first physical quantity) to the coil 11 while rotating the heating belt 15. If the first physical quantity is voltage, the third physical quantity is current, and if the first physical quantity is current, the third physical quantity is voltage. In the present embodiment, the first physical quantity is a voltage, and the third physical quantity is a current.

  The voltage calculation unit 505 is an example of a physical quantity calculation unit, and the actual voltage supplied to the coil 11 using the first voltage (first physical quantity) and the current (third physical quantity) measured by the ammeter 703. Power D2 is calculated, and a second voltage (second physical quantity) for obtaining power D3 having an opposite phase to the actual power D2 is calculated.

  The communication unit 600 includes a facsimile communication unit 601 and a network I / F unit 603. The facsimile communication unit 601 includes an NCU (Network Control Unit) for controlling connection of a telephone line with a destination facsimile and a modulation / demodulation circuit for modulating / demodulating a signal for facsimile communication. The facsimile communication unit 601 is connected to the telephone line 605.

  A network I / F unit 603 is connected to a LAN (Local Area Network) 607. A network I / F unit 603 is a communication interface circuit for executing communication with a terminal device such as a personal computer connected to the LAN 607.

  Next, the operation of the fixing device according to the present embodiment will be described mainly with reference to FIGS. The fixing device includes a fixing unit 105, a rotation control unit 501, a power control unit 503, a voltage calculation unit 505, and an ammeter 703 shown in FIG. As a premise of the fixing process, the fixing device acquires second voltage data from which the power D3 having the opposite phase can be obtained in the following steps. FIG. 6 is a flowchart for explaining the acquisition of the second voltage data.

  The second voltage data is acquired, for example, during automatic maintenance of the image forming apparatus 1. The automatic maintenance means that when the number of sheets on which images are formed in the image forming apparatus 1 reaches a predetermined number, the image forming apparatus 1 performs a maintenance operation and automatically performs maintenance.

  The rotation controller 501 controls the fixing roller 17 to rotate, and the fixing roller 17 rotates. Thereby, the heating belt 15 rotates. As the heating belt 15 rotates, the heating roller 13 rotates. Further, when the fixing roller 17 rotates, the pressure roller 19 is driven and rotated (step S1).

  The power control unit 503 performs control to supply the first voltage from the resonance power source 701 to the coil 11 based on the power instruction value D1 that instructs the power supplied to the coil 11. Thereby, a high frequency current flows from the resonance power source 701 to the coil 11, and the heating roller 13 and the heating belt 15 are induction-heated (step S3).

  When the heating belt 15 rotates and the mark 27 passes the detection range of the sensor 21, the sensor 21 detects the mark 27 (step S5).

  When the sensor 21 detects the mark 27, that is, when the heating belt 15 is located at the home position, the control unit 500 starts measuring the current supplied to the coil 11 using the ammeter 703 (step S7).

  A first voltage, which is a constant voltage, is supplied from the resonance power source 701 to the coil 11. As described above, the gap between the heating roller 13 and the coil 11 inevitably changes according to the rotation of the heating roller 13, the heating belt 15, and the fixing roller 17. Therefore, since the eddy current flowing through the heating roller 13 and the heating belt 15 changes, the current supplied to the coil 11 varies accordingly.

  Data of the current supplied to the coil 11 measured by the ammeter 703 is sent to the voltage calculation unit 505 and stored in the memory 507 of the voltage calculation unit 505. As a result, data on the current supplied to the coil 11 is stored in the memory 507.

  When the heating belt 15 rotates once after the sensor 21 detects the mark 27, the mark 27 comes within the detection range of the sensor 21, so the sensor 21 detects the mark 27 again (step S9).

  When the sensor 21 detects the mark 27 again, that is, when the heating belt 15 is again positioned at the home position, the control unit 500 ends the measurement of the current supplied to the coil 11 using the ammeter 703 (step S11). .

  The voltage calculation unit 505 uses the first voltage and the current supplied to the coil 11 stored in the memory 507 to calculate the actual power D2 supplied to the coil 11 in the period of one rotation of the heating belt 15. Calculation is performed (step S13). That is, the power (in other words, amplitude) at each phase is calculated in the period of one rotation of the heating belt 15. The voltage calculation unit 505 calculates a power D3 having an opposite phase with respect to the calculated power D2. Then, the second voltage at which the anti-phase power D3 is obtained is calculated (step S15). The voltage calculation unit 505 stores it in the memory 509 of the power control unit 503 as the latest data of the second voltage.

  Note that the actual power D2 data and the second voltage data acquired at the time of factory shipment of the image forming apparatus 1 and after that are stored in the memory 507, and when the latest second voltage data is calculated, these data are stored. Data may be used.

  The above is the step of acquiring the second voltage data. Next, fixing processing by the fixing device according to the present embodiment will be described. FIG. 7 is a flowchart for explaining the processing. When an image forming job is generated in the image forming apparatus 1, the heating roller 13, the heating belt 15, the fixing roller 17, and the pressure roller 19 are rotated under the control of the rotation control unit 501 (step S21).

  When the sensor 21 detects the mark 27 (step S23), the power control unit 503 reads the latest data of the second voltage stored in the memory 509, and adds the second voltage to the first voltage. Is supplied from the resonance power source 701 to the coil 11 (step S25). As a result, when the first voltage is supplied to the coil 11, the electric power D <b> 3 having the opposite phase can be added to the actual electric power D <b> 2 supplied to the coil 11 and supplied to the coil 11. That is, it is possible to supply the coil 11 with the power of the power instruction value D1.

  Then, the image forming unit 103 shown in FIG. 4 forms an electrostatic latent image based on the image data, develops the electrostatic latent image to form a toner image, and forms a toner image on the paper 39. (Step S27).

  The paper 39 on which the toner image is formed is sent to the fixing unit 105, nipped by the heating belt 15 and the pressure roller 19, and sent downstream of the paper conveyance path. At the time of this nip, the toner image is fixed on the paper 39 (step S29).

  The main effects of this embodiment will be described.

  When the first voltage based on the power instruction value D1 for instructing the power supplied to the coil 11 is supplied to the coil 11 while the heating belt 15 is rotated, the gap between the heating belt 15 and the coil 11 varies. For this reason, the actual power D2 supplied to the coil 11 is different from the power command value D1. In the present embodiment, a second voltage that generates a power D3 having an antiphase equal to the difference between the power command value D1 and the actual power D2 supplied to the coil 11 is used. According to the present embodiment, as described in step S25, since the second voltage is added to the first voltage and supplied to the coil 11 in the fixing process, the power supplied to the coil 11 is supplied. It can be the same as the power instruction value D1. Therefore, even if the gap fluctuates, the fluctuation amount of the eddy current flowing through the heating belt 15 can be reduced, so that the change in the strength of the magnetic flux generated by the coil 11 can be reduced. As a result, the circumferential direction of the heating belt 15 can be reduced. Temperature unevenness can be reduced.

  In the present embodiment, the case of the antiphase power D3 having the same amplitude as that of the actual power D2 supplied to the coil 11 has been described. However, the antiphase power D3 has the same amplitude as the actual power D2. There may be no aspect. In this aspect, in the fixing process, by adding the second voltage to the first voltage and supplying it to the coil 11, the power supplied to the coil 11 can be brought close to the power instruction value D1.

  Further, according to this embodiment, the second voltage is added to the first voltage and supplied to the coil 11 to reduce the temperature unevenness in the circumferential direction of the heating roller 13 and the heating belt 15. Therefore, since it is not necessary to provide induction heating members above and below the heating belt 15, the degree of freedom of the installation location of the induction heating member (induction heating unit 23) can be improved. In addition, since there is no need to provide induction heating members above and below the heating belt 15, there is no need to provide inverter circuits for supplying power to the upper induction heating member coil and the lower induction heating member coil, respectively. There is a possibility to reduce the cost accordingly.

  Further, according to the present embodiment, as described in step S15, the fixing device has a function of calculating the second voltage. Therefore, even if the actual power D2 supplied to the coil 11 when the first voltage is supplied to the coil 11 while rotating the heating belt 15 changes over time from the factory shipment of the image forming apparatus 1, It can respond to the change.

  Further, according to the present embodiment, when the first voltage is supplied to the coil 11 while rotating the heating belt 15, the actual period of the electric power D <b> 2 supplied to the coil 11 is the period of one rotation of the heating belt 15. Is considered the same. Therefore, the calculation of the cycle can be omitted in the calculation of the actual power D2 supplied to the coil 11.

  According to the present embodiment, one rotation of the heating belt 15 is detected by the sensor 21 as described in steps S5 and S9. Therefore, even if the period of one rotation of the heating belt 15 changes with time from the time of shipment of the image forming apparatus 1, it is possible to cope with it.

  A modification of this embodiment will be described.

  As described in step S <b> 13, in the present embodiment, the actual power D <b> 2 supplied to the coil 11 is measured using a cycle in which the heating belt 15 detected by the sensor 21 rotates once. In the first modification, data of a cycle in which the heating belt 15 rotates once is stored in advance in the memory 507 of the voltage calculation unit 505. The voltage calculation unit 505 measures the actual power D <b> 2 supplied to the coil 11 using the period of one rotation of the heating belt 15 stored in advance in the memory 507. According to the first modification, the sensor 21 that can detect one rotation of the heating belt 15 may not be provided.

  In the present embodiment, the voltage calculation unit 505 calculates the second voltage that generates the power D3 having the opposite phase. In the second modification, the data of the second voltage is stored in the memory 509 in advance when the image forming apparatus 1 is shipped from the factory. According to the modified example 2, since the calculation of the second voltage is unnecessary, it is not necessary to provide the voltage calculation unit 505.

  In this embodiment, a heating belt type fixing device is described. In the third modification, the heating belt 15 is not provided, but a roller that serves as both the heating roller 13 and the fixing roller 17 is provided. The sheet 39 on which the toner image is formed is heated and pressed by the roller that also serves as the pressure roller 19.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 11 Coil 15 for induction heating Heating belt (an example of a heating member)
19 Pressure roller (an example of a pressure member)
21 Sensor 505 Voltage calculator (an example of a physical quantity calculator)
703 Ammeter (Example of physical quantity measurement unit)

Claims (7)

A coil for induction heating;
A heating member that heats a sheet on which a toner image is formed while rotating in a state in which an eddy current flows and is induction-heated by magnetic flux generated by the coil;
A pressure member that pressurizes the paper while rotating in a state where the paper is heated by the heating member;
A power control unit that performs control for adding the second physical quantity to the first physical quantity that is current or voltage and supplying the second physical quantity to the coil in a fixing process for fixing the toner image on the paper;
The first physical quantity is based on a power command value that instructs power supplied to the coil,
The second physical quantity is obtained by supplying the first physical quantity to the coil while rotating the heating member, thereby obtaining an electric power having an opposite phase to the actual power supplied to the coil. A fixing device.   2. The fixing device according to claim 1, wherein the second physical quantity is a physical quantity that can obtain power equal to a difference between the power instruction value and the actual power supplied to the coil as the power of the opposite phase. If the first physical quantity is a voltage, the current is a current, and if the current is a current, the third physical quantity is a voltage, and the first physical quantity is supplied to the coil while rotating the heating member. A physical quantity measuring unit for measuring the third physical quantity supplied to the coil,
Using the first physical quantity and the third physical quantity measured by the physical quantity measuring unit, the actual power supplied to the coil is calculated, and the power in the opposite phase to the actual power is obtained. The fixing device according to claim 1, further comprising: a physical quantity computing unit that computes the second physical quantity.   4. The fixing device according to claim 3, wherein the physical quantity calculation unit calculates the actual power supplied to the coil by setting the cycle of the actual power supplied to the coil as a cycle in which the heating member rotates once. A sensor capable of detecting one rotation of the heating member;
The physical quantity calculation unit calculates the actual power supplied to the coil, with a period of one rotation of the heating member detected by the sensor as a period of the actual power supplied to the coil. The fixing device according to 1.   The said physical quantity calculating part calculates the actual electric power supplied to the said coil by making into a period of the actual electric power supplied to the said coil the period when the said heating member memorize | stored previously is made into one rotation. Fixing device. An image forming unit that forms the toner image on the paper;
An image forming apparatus comprising: the fixing device according to claim 1.

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