JP5440303B2 - Fixing device, image forming apparatus using the same, fixing device control method, and fixing device control program - Google Patents

Description

  The present invention relates to a fixing device, an image forming apparatus using the same, a control method for the fixing device, and a control program for the fixing device, and more particularly to an electromagnetic induction heating type fixing device, an image forming apparatus using the fixing device, and a fixing device. The present invention relates to a control method and a control program for a fixing device.

  In electrophotographic image forming apparatuses (MFP (Multi Function Peripheral), facsimile apparatus, copier, printer, etc.) having a scanner function, a facsimile function, a copying function, a function as a printer, a data communication function, and a server function. A fixing device using various heating methods such as a heat roller method and a belt method is used. As such a fixing device, there is an electromagnetic induction heating type in which a roller or the like is heated by electromagnetic induction and the toner is fixed to the paper by the heat.

  In recent years, an electromagnetic induction heating type fixing device has been used in place of a fixing device that uses a halogen heater or the like that has been conventionally used as a heat source. The electromagnetic induction heating type fixing device is characterized by being capable of heating rapidly and having high energy efficiency, and responds to demands for shortening the warm-up time and energy saving. . As such an electromagnetic induction heating type fixing device, there is an outer coil type fixing device in which an electromagnetic induction coil (excitation coil) is arranged on the outside so that a roller, a belt, or the like can be directly heated.

  In an electromagnetic induction heating type fixing device, for example, an induction heating power supply circuit resonates a current flowing in an exciting coil with a capacitor to generate a magnetic field line based on AC power used for commercial purposes. The rollers are heated. The heat capacity of the roller or the like is kept low in order to ensure its temperature rise characteristics. In particular, the outer coil type fixing device is configured such that the roller directly generates heat, and the temperature raising performance is enhanced. The induction heating power supply circuit supplies electric energy so that the amount of heat necessary for fixing and the amount of heat absorbed by the paper are compensated. The fixing device performs control so that the roller generates heat uniformly so as not to cause a temperature gradient in the longitudinal direction of the roller, and generates heat energy.

  The fixing device fixes toner images formed on various sizes of paper. For this reason, when a sheet having a size less than the size in the longitudinal direction of the roller is used, the balance between supply and consumption of heat energy is lost on the roller. That is, the temperature of the non-sheet passing portion where the sheet does not pass among the rollers rises too much. Therefore, the fixing device may be provided with a degaussing coil disposed at a position corresponding to a part of the roller and a degaussing coil switching circuit for switching whether to operate the degaussing coil. The degaussing coil switching circuit operates the degaussing coil as needed, and the magnetic flux generated in the exciting coil is canceled by the degaussing coil, thereby suppressing the heat generation of that part of the roller and preventing overheating of the non-sheet passing part. it can.

  Patent Document 1 below discloses a fixing device including the demagnetizing coil as described above.

JP 2007-226125 A

  FIG. 16 is a block diagram illustrating an example of an internal circuit configuration of the induction heating power supply circuit 811.

  Referring to the figure, induction heating power supply circuit 811 includes rectifier circuit 831, switching circuit 832, power detection circuit 833, and induction heating power supply control circuit 834.

  The rectifier circuit 831 rectifies AC commercial power and outputs it to the switching circuit 832.

  The switching circuit 832 outputs high frequency power to the exciting coil 803 based on the control of the induction heating power supply control circuit 834.

  The power detection circuit 833 detects the power in the rectifier circuit 831 and outputs a detection signal to the induction heating power supply control circuit 834.

  The induction heating power supply control circuit 834 controls the operation of the switching circuit 832 based on the detection signal output from the power detection circuit 833 and the output power control signal sent from the thermal fixing control circuit 821, thereby controlling the output power. High frequency power corresponding to signal reception is output from the switching circuit 832.

  FIG. 17 is a block diagram showing an internal circuit configuration of the degaussing coil switching circuit 813.

  With reference to the figure, the degaussing coil switching circuit 813 includes a degaussing coil switching switch 841 and a degaussing coil switching control circuit 842.

  The degaussing coil changeover switch 841 is controlled by the degaussing coil switching control circuit 842, and the degaussing coil 808 operates to demagnetize part of the magnetic flux generated by the exciting coil 803, and the degaussing coil 808 does not operate and the exciting coil 803 does not operate. The normal state in which the generated magnetic flux is not canceled is switched.

  The degaussing coil switching control circuit 842 is controlled by the thermal fixing control circuit 821 and controls the operation of the degaussing coil switching switch 841. The heat fixing control circuit 821 can prevent the heating roller 801 from being overheated by operating the degaussing coil 808 when, for example, fixing a narrow sheet.

  Here, in the fixing device as described above, the induction heating power supply circuit 811 receives input AC (50/60 Hz) and outputs high-frequency AC power. The high frequency output of the induction heating power supply circuit 811 has a large power fluctuation of 100/120 Hz because the pulsating flow obtained by rectifying the input power is directly used to suppress harmonics. Further, in the fixing device, high-frequency AC power is output by a resonance circuit formed by an inductor and a capacitor of the exciting coil 803. Therefore, when the demagnetizing coil 808 is operated, the mutual inductance varies due to the coupling between the exciting coil 803 and the demagnetizing coil 808, the resonant frequency of the resonant circuit varies, and the induction heating power supply circuit 811 does not operate as expected. May occur.

  On the other hand, in the fixing device described in Patent Document 1, the induction heating power supply circuit is switched by switching the driving frequency of the high frequency power supply circuit with the opening and closing of the degaussing coil or by stopping the output at the time of switching the frequency. Prevents abnormal operation. Immediately after switching the opening and closing of the degaussing coil, it is possible to prevent the occurrence of temperature ripples in the fixing roller by applying power different from the desired power value.

  By the way, in the fixing device, there is a demand for a low heat capacity of the roller in order to increase the printing speed and shorten the warm-up time. However, in the case where the heat capacity of the roller is reduced in this way, as described in the above-mentioned Patent Document 1, when the frequency is changed at the time of switching the degaussing coil or the output at the time of switching the frequency is stopped, Problems may occur. That is, since the temperature uniformity of the roller is lowered, unevenness is likely to occur in fixing the toner image, which may adversely affect the fixing performance. In addition, when the demagnetizing coil is operated, if the output stop period is provided and heating is stopped, the printing speed cannot be increased.

  The present invention has been made to solve such a problem, and can be appropriately and promptly operated, and a fixing device capable of suppressing abnormal temperature rise even in a portion where a sheet does not pass, and an image using the same. It is an object to provide a forming apparatus, a fixing device control method, and a fixing device control program.

In order to achieve the above object, according to one aspect of the present invention, a fixing device is configured to fix a toner on a sheet by fixing the toner on the sheet by heating and conveying the sheet, and to heat the fixing member. An excitation unit that generates magnetic flux and performs electromagnetic induction heating, a demagnetization unit that can cancel at least a part of the magnetic flux that is generated by generating the magnetic flux, and AC power is input, and excitation is performed based on the AC power. A supply unit that supplies high-frequency current to the unit, a zero-cross detection unit that detects a zero-cross point at which the AC power input to the supply unit becomes zero, and a determination that determines the switchable time based on the detection result of the zero-cross detection unit comprising a part, in the switchable determined by the determination unit time, and a switching unit for switching between a normal state of not performing cancellation is demagnetized and demagnetization unit degaussing unit performs cancellation, determination unit further Determining a switchable time based on the fluctuation amount of the power supplied to the excitation portion.

According to another aspect of the present invention, the fixing device generates a magnetic flux to heat the fixing member by fixing the toner on the paper by heating and conveying the paper under pressure, and generating magnetic flux to heat the fixing member. An excitation unit that performs induction heating, a demagnetization unit that can cancel at least a part of the magnetic flux generated by the excitation unit by generating magnetic flux, and AC power is input, and high frequency current is applied to the excitation unit based on the AC power. A supply unit to be supplied; a zero-cross detection unit that detects a zero-cross point at which AC power input to the supply unit is zero; a determination unit that determines a switchable time based on a detection result of the zero-cross detection unit; and a determination unit within determined switchable time in, and a switching unit for switching between a normal state of not performing cancellation is demagnetized and demagnetization unit that performs cancellation demagnetizing unit, demagnetization unit is provided with a plurality, determining unit Further determines a switchable time based on the number of degaussing unit.

According to still another aspect of the present invention, the fixing device generates a magnetic flux to heat the fixing member, and a fixing member that fixes the toner on the paper to the paper by heating and conveying the paper under pressure. An excitation unit that performs electromagnetic induction heating, a demagnetization unit that can cancel at least a part of the magnetic flux generated by the excitation unit by generating magnetic flux, and AC power is input, and high frequency current is supplied to the excitation unit based on the AC power A supply unit that supplies zero, a zero-cross detection unit that detects a zero-cross point at which AC power input to the supply unit becomes zero, a determination unit that determines a switchable time based on a detection result of the zero-cross detection unit, and a determination within determined switchable time in parts, and a switching unit for switching between a normal state of not performing cancellation is demagnetized and demagnetization unit degaussing unit performs cancellation, demagnetization unit is a coil, determination unit Further determines a switchable time based on at least one of the cross-sectional area of the turns and the coil of the coil.

According to still another aspect of the present invention, the fixing device generates a magnetic flux to heat the fixing member, and a fixing member that fixes the toner on the paper to the paper by heating and conveying the paper under pressure. An excitation unit that performs electromagnetic induction heating, a demagnetization unit that can cancel at least a part of the magnetic flux generated by the excitation unit by generating magnetic flux, and AC power is input, and high frequency current is supplied to the excitation unit based on the AC power A supply unit that supplies zero, a zero-cross detection unit that detects a zero-cross point at which AC power input to the supply unit becomes zero, a determination unit that determines a switchable time based on a detection result of the zero-cross detection unit, and a determination within determined switchable time in parts, and a switching unit for switching between a normal state of not performing cancellation is demagnetized and demagnetization unit degaussing unit performs cancellation, determination unit further switching unit degaussing unit Determining a switchable time based on the switching characteristics when performing switching of demagnetized state / normal state.

According to still another aspect of the present invention, an image forming apparatus includes a toner image forming unit that forms a toner image on a sheet and the fixing device described in any of the above, and the sheet is formed by the toner image forming unit in the fixing device. The toner image formed on the sheet is fixed on the sheet.

According to still another aspect of the present invention, a fixing member that fixes and conveys toner on a sheet to the sheet by pressurizing and conveying the sheet while heating the sheet, and a magnetic flux is generated to heat the fixing member and electromagnetic induction heating is performed. An excitation unit to be performed, a demagnetization unit capable of canceling at least a part of the magnetic flux generated by the excitation unit by generating a magnetic flux, and a supply for supplying high-frequency current to the excitation unit based on the AC power input And a determination method for determining a switchable time based on a detection result of the zero cross detection step and a detection result of the zero cross detection step in which the AC power input to the supply unit becomes zero. Switching step for switching between a degaussing state in which the degaussing part cancels and a normal state in which the degaussing part does not cancel within the switchable time determined in the determination step. Tsu and a flop, the determining step further determines a switchable time based on the fluctuation amount of the power supplied to the excitation portion.
According to still another aspect of the present invention, a fixing member that fixes and conveys toner on a sheet to the sheet by pressurizing and conveying the sheet while heating the sheet, and a magnetic flux is generated to heat the fixing member and electromagnetic induction heating is performed. An excitation unit to be performed, a demagnetization unit capable of canceling at least a part of the magnetic flux generated by the excitation unit by generating a magnetic flux, and a supply for supplying high-frequency current to the excitation unit based on the AC power input And a determination method for determining a switchable time based on a detection result of the zero cross detection step and a detection result of the zero cross detection step in which the AC power input to the supply unit becomes zero. Switching step for switching between a degaussing state in which the degaussing part cancels and a normal state in which the degaussing part does not cancel within the switchable time determined in the determination step. Tsu and a flop, demagnetization unit is provided with a plurality, determining step further determines a switchable time based on the number of degaussing unit.
According to still another aspect of the present invention, a fixing member that fixes and conveys toner on a sheet to the sheet by pressurizing and conveying the sheet while heating the sheet, and a magnetic flux is generated to heat the fixing member and electromagnetic induction heating is performed. An excitation unit to be performed, a demagnetization unit capable of canceling at least a part of the magnetic flux generated by the excitation unit by generating a magnetic flux, and a supply for supplying high-frequency current to the excitation unit based on the AC power input And a determination method for determining a switchable time based on a detection result of the zero cross detection step and a detection result of the zero cross detection step in which the AC power input to the supply unit becomes zero. Switching step for switching between a degaussing state in which the degaussing part cancels and a normal state in which the degaussing part does not cancel within the switchable time determined in the determination step. A-up, demagnetization unit is a coil, the determining step further determines a switchable time based on at least one of the cross-sectional area of the turns and the coil of the coil.
According to still another aspect of the present invention, a fixing member that fixes and conveys toner on a sheet to the sheet by pressurizing and conveying the sheet while heating the sheet, and a magnetic flux is generated to heat the fixing member and electromagnetic induction heating is performed. An excitation unit to be performed, a demagnetization unit capable of canceling at least a part of the magnetic flux generated by the excitation unit by generating a magnetic flux, and a supply for supplying high-frequency current to the excitation unit based on the AC power input And a determination method for determining a switchable time based on a detection result of the zero cross detection step and a detection result of the zero cross detection step in which the AC power input to the supply unit becomes zero. Switching step for switching between a degaussing state in which the degaussing part cancels and a normal state in which the degaussing part does not cancel within the switchable time determined in the determination step. Tsu and a flop, the determining step further switching step determines a switchable time based on the switching characteristics when performing switching of demagnetized state / normal state of the degaussing unit.

According to still another aspect of the present invention, a fixing member that fixes and conveys toner on a sheet to the sheet by pressurizing and conveying the sheet while heating the sheet, and a magnetic flux is generated to heat the fixing member and electromagnetic induction heating is performed. An excitation unit to be performed, a demagnetization unit capable of canceling at least a part of the magnetic flux generated by the excitation unit by generating a magnetic flux, and a supply for supplying high-frequency current to the excitation unit based on the AC power input And a determination program for determining a switchable time based on a zero-cross detection step for detecting a zero-cross point at which the AC power input to the supply unit becomes zero and a detection result of the zero-cross detection step. Switching between the step and the degaussing state in which the degaussing part cancels and the normal state in which the degaussing part does not cancel within the switchable time determined in the determination step To execute the exchange steps in a computer, determination step further determines a switchable time based on the fluctuation amount of the power supplied to the excitation portion.
According to still another aspect of the present invention, a fixing member that fixes and conveys toner on a sheet to the sheet by pressurizing and conveying the sheet while heating the sheet, and a magnetic flux is generated to heat the fixing member and electromagnetic induction heating is performed. An excitation unit to be performed, a demagnetization unit capable of canceling at least a part of the magnetic flux generated by the excitation unit by generating a magnetic flux, and a supply for supplying high-frequency current to the excitation unit based on the AC power input And a determination program for determining a switchable time based on a zero-cross detection step for detecting a zero-cross point at which the AC power input to the supply unit becomes zero and a detection result of the zero-cross detection step. Switching between the step and the degaussing state in which the degaussing part cancels and the normal state in which the degaussing part does not cancel within the switchable time determined in the determination step To execute the exchange step in the computer, demagnetization unit is provided with a plurality, determining step further determines a switchable time based on the number of degaussing unit.
According to still another aspect of the present invention, a fixing member that fixes and conveys toner on a sheet to the sheet by pressurizing and conveying the sheet while heating the sheet, and a magnetic flux is generated to heat the fixing member and electromagnetic induction heating is performed. An excitation unit to be performed, a demagnetization unit capable of canceling at least a part of the magnetic flux generated by the excitation unit by generating a magnetic flux, and a supply for supplying high-frequency current to the excitation unit based on the AC power input And a determination program for determining a switchable time based on a zero-cross detection step for detecting a zero-cross point at which the AC power input to the supply unit becomes zero and a detection result of the zero-cross detection step. Switching between the step and the degaussing state in which the degaussing part cancels and the normal state in which the degaussing part does not cancel within the switchable time determined in the determination step To execute the exchange step in the computer, demagnetization unit is a coil, the determining step further determines a switchable time based on at least one of the cross-sectional area of the turns and the coil of the coil.
According to still another aspect of the present invention, a fixing member that fixes and conveys toner on a sheet to the sheet by pressurizing and conveying the sheet while heating the sheet, and a magnetic flux is generated to heat the fixing member and electromagnetic induction heating is performed. An excitation unit to be performed, a demagnetization unit capable of canceling at least a part of the magnetic flux generated by the excitation unit by generating a magnetic flux, and a supply for supplying high-frequency current to the excitation unit based on the AC power input And a determination program for determining a switchable time based on a zero-cross detection step for detecting a zero-cross point at which the AC power input to the supply unit becomes zero and a detection result of the zero-cross detection step. Switching between the step and the degaussing state in which the degaussing part cancels and the normal state in which the degaussing part does not cancel within the switchable time determined in the determination step To execute the exchange step in the computer, the determining step further switching step determines a switchable time based on the switching characteristics when performing switching of demagnetized state / normal state of the degaussing unit.

  According to these inventions, whether or not to cancel is switched within the switchable time determined based on the detection result of the zero cross point where the AC power becomes zero. Accordingly, it is possible to provide a fixing device that can operate properly and promptly and can suppress abnormal temperature rise even in a portion where paper does not pass, an image forming apparatus using the fixing device, a fixing device control method, and a fixing device control program. can do.

1 is a side view illustrating a hardware configuration of an image forming apparatus according to one embodiment of the present invention. 1 is a block diagram illustrating a configuration of an image forming apparatus. FIG. 3 is a diagram illustrating a configuration of a fixing unit. 3 is a block diagram illustrating a configuration of a control circuit of a fixing unit. FIG. It is a block diagram which shows the circuit structure inside an induction heating power supply circuit. It is a block diagram which shows the circuit structure inside a degaussing coil switching circuit. It is a graph which shows the relationship between the electric power detection pulsating flow signal after the rectification in a rectifier circuit, and the zero cross signal which a zero cross generation circuit outputs. It is a figure which shows an example of the waveform of the high frequency electric power which the induction heating power circuit outputs in the vicinity of the zero crossing of an electric power detection pulsating flow signal. It is a 1st figure for demonstrating the influence of the magnetic flux by the kind of coil. It is a 2nd figure for demonstrating the influence of the magnetic flux by the kind of coil. It is a 3rd figure for demonstrating the influence of the magnetic flux by the kind of coil. It is a 4th figure for demonstrating the influence of the magnetic flux by the kind of coil. It is a timing chart which shows operation | movement of an induction heating power supply circuit and a degaussing coil switching circuit. It is a flowchart which shows switching control of a degaussing coil. It is a flowchart which shows the detection process of a zero cross. It is a block diagram which shows an example of the circuit structure inside an induction heating power supply circuit. It is a block diagram which shows an example of the circuit structure inside a degaussing coil switching circuit.

  Hereinafter, an image forming apparatus according to one embodiment of the present invention will be described.

  The image forming apparatus has a print function for transporting a sheet or the like by a roller and performing printing (printing) on the sheet or the like by an electrophotographic method. The image forming apparatus uses a toner image forming unit that forms a toner image on a sheet, and heats a heating roller by an electromagnetic induction heating method, and pressurizes and conveys the sheet while heating the sheet using the heating roller. And a fixing device that fixes the toner on the sheet formed by the forming unit to the sheet.

  The fixing device includes an exciting coil for heating the heating roller and a degaussing coil for canceling the magnetic flux of the exciting coil. The fixing device switches whether to cancel the magnetic flux by switching open / close of the circuit that drives the demagnetizing coil, and suppresses an increase in the end temperature of the heating roller.

  Opening / closing of the degaussing coil circuit (switching of the degaussing coil) is performed at the timing of zero crossing of the input AC power input to the fixing device. That is, the fixing device detects a zero cross point of the input AC power, sets a predetermined time before and after the zero cross point as a switchable time of the demagnetizing coil, and switches the demagnetizing coil within the switchable time. Since the degaussing coil is switched at a timing close to the zero cross point, the output reduction of the power output to the exciting coil is minimized, and stable temperature control of the fixing device is performed.

  [Embodiment]

  First, the overall configuration of the image forming apparatus according to the present embodiment will be described.

  [Entire configuration of image forming apparatus]

  FIG. 1 is a side view showing a hardware configuration of an image forming apparatus according to one embodiment of the present invention.

  Referring to the figure, the image forming apparatus 1 includes a paper feed cassette 3, a paper discharge tray 5, and a printing unit 30.

  The paper feed cassette 3 is disposed in the lower part of the image forming apparatus 1 so as to be detachable from the housing of the image forming apparatus 1. The paper loaded in each paper feed cassette 3 is fed one by one from the paper feed cassette 3 and sent to the printing unit 30 at the time of printing. The number of paper feed cassettes 3 is not limited to one and may be larger.

  The paper discharge tray 5 is disposed above the housing of the image forming apparatus 1. A sheet on which an image is formed by the printing unit 30 is discharged from the inside of the housing to the discharge tray 5.

  The print unit 30 is disposed inside the housing of the image forming apparatus 1. The printing unit 30 roughly includes a paper transport unit 200, a toner image forming unit 300, a fixing unit 400, and a driving unit (shown in FIG. 2) 500. The print unit 30 is configured to be able to form a color image on a sheet by synthesizing four color images of CMYK by a so-called tandem method.

  The paper transport unit 200 includes a paper feed roller 210, a transport roller 220, a paper discharge roller 230, and the like. The paper feed roller 210, the transport roller 220, and the paper discharge roller 230 each transport the paper by rotating the rollers while sandwiching the paper between two opposing rollers, for example. The paper feed roller 210 feeds paper one by one from the paper feed cassette 3. The transport roller 220 transports the paper fed by the paper feed roller 210 to the toner image forming unit 300. Further, the conveyance roller 220 conveys the sheet that has passed through the fixing unit 400 to the paper discharge roller 230. The paper discharge roller 230 discharges the paper transported by the transport roller 220 to the outside of the casing of the image forming apparatus 1. In addition to these, the paper transport unit 200 may include rollers that are used to transport paper.

  The toner image forming unit 300 includes four color toner bottles 301Y, 301M, 301C, and 301K (hereinafter, these may be collectively referred to as a toner bottle 301), an intermediate transfer belt 305, a transfer roller 307, 4 A pair of developing units 310Y, 310M, 310C, and 310K (hereinafter, these may be collectively referred to as a developing unit 310), a laser scan unit 320, and the like.

  The yellow toner bottle 301Y, the magenta toner bottle 301M, the cyan toner bottle 301C, and the black toner bottle 301K store CMYK toners of yellow (Y), magenta (M), cyan (C), and black (K), respectively. To do.

  The intermediate transfer belt 305 has an annular shape and is stretched between two rollers. The intermediate transfer belt 305 rotates in conjunction with the paper transport unit 200. The transfer roller 307 is disposed so as to face a portion of the intermediate transfer belt 305 that is in contact with one roller. The sheet is conveyed while being sandwiched between the intermediate transfer belt 305 and the transfer roller 307.

  The developing unit 310 includes a photosensitive member 311 (photosensitive members 311Y, 311M, 311C, and 311K are provided for each developing unit), a developing device, a cleaner, a charger, and the like. The yellow developing unit 310Y, the magenta developing unit 310M, the cyan developing unit 310C, and the black developing unit 310K are arranged to form Y, M, C, and K images, respectively. The developing unit 310 is juxtaposed directly below the intermediate transfer belt 305. The laser scan unit 320 is disposed on each photoconductor 311 so as to be able to scan with laser light.

  In the toner image forming unit 300, the laser scanning unit 320 forms a latent image on the photoreceptor 311 that is uniformly charged by the charger based on the image data for each color of YMCK. The developing device forms a toner image for each color on each photoconductor 311. Each photoconductor 311 transfers the toner image to the intermediate transfer belt 305, and forms a mirror image of the toner image formed on the paper on the intermediate transfer belt 305 (primary transfer). Thereafter, the transfer roller 307 to which a high voltage is applied transfers the toner image formed on the intermediate transfer belt 305 to the sheet, and a toner image is formed on the sheet (secondary transfer).

  When the toner in the developing unit 310 decreases due to image formation, the toner stored in the toner bottle 301 of each color is supplied to the developing unit.

  The fixing unit 400 includes a heating roller 401 and a pressure roller 402. The fixing unit 400 melts the toner adhering to the paper and fixes it on the paper to form an image on the paper.

  The drive unit 500 includes, for example, a main motor 501, a fixing motor 502, a black developing motor 503, a color developing motor 504, and a color photoreceptor motor 505 (hereinafter, these motors are simply referred to as motors 501 to 505, etc.). Sometimes called). The drive unit 500 is driven under the control of a CPU 21 (shown in FIG. 2) described later. The main motor 501 carries the paper from the paper feeding process to the transfer process and drives the intermediate transfer belt 305 and the black photoconductor 311K. The fixing motor 502 drives the heating roller 401 and the pressure roller 402 of the fixing unit 400. The black developing motor 503 drives the black developing unit 310K. A color developing motor 504 drives yellow, magenta, and cyan developing units 310Y, 310M, and 310C. The color photoconductor motor 505 drives the yellow, magenta, and cyan photoconductors 311Y, 311M, and 311C.

  When printing is instructed to the image forming apparatus 1, the sheets stored in the sheet feeding cassette 3 are taken out one by one by the sheet feeding roller 210. The paper is transported by the paper feed roller 210 and the transport roller 220. In parallel with the paper feeding, the charged photoreceptors 311Y, 311M, 311C, 311K are exposed by the laser scan unit 320 based on the image data. A toner image is formed on the photoreceptor 311 by developing with toner in the developing units 310Y, 310M, 310C, and 310K of the respective colors. The toner images formed on the photoreceptors 311 of the respective colors are transferred onto the intermediate transfer belt 305, and toner images for four colors are formed on the intermediate transfer belt 305. Next, a voltage is applied to the transfer roller 307 so that the toner image formed on the intermediate transfer belt 305 is transferred to the conveyed paper. The toner image formed on the sheet is fixed on the sheet by passing the sheet through the fixing unit 400 and applying heat and pressure. The paper on which the toner image is fixed is discharged to the paper discharge tray 3 by the paper discharge roller 230.

  FIG. 2 is a block diagram illustrating a configuration of the image forming apparatus 1.

  Referring to the figure, image forming apparatus 1 further includes an operation unit 11, a control unit (CPU unit) 20, a nonvolatile memory 27, an interface unit 29, and a power supply device 600.

  The operation unit 11 is disposed in the casing of the image forming apparatus 1 so that it can be operated by a user. A display panel 13 is disposed on the operation unit 11. The display panel 13 is, for example, an LCD (Liquid Crystal Display) provided with a touch panel. The display panel 13 displays a guidance screen for the user or displays an operation button to accept a touch operation from the user. The display panel 13 performs display under the control of the CPU 21 of the control unit 20. When the user operates the display panel 13, operation buttons (not shown), or the like, the operation unit 11 transmits an operation signal or a predetermined command corresponding to the operation to the CPU 21. That is, the user can cause the image forming apparatus 1 to execute various operations by operating the operation unit 11.

  The control unit 20 includes a CPU 21, a ROM (Read Only Memory) 23, a RAM (Random Access Memory) 25, and the like. The control unit 20 is connected to the system bus together with the operation unit 11, the nonvolatile memory 27, the interface unit 29, the power supply device 600, and the like. Thereby, the control part 20 and each part of the image forming apparatus 1 are connected so that signals can be transmitted and received.

  The CPU 21 controls various operations of the image forming apparatus 1 by executing a control program 23 a or the like stored in the ROM 23, RAM 25, or nonvolatile memory 27. When an operation signal is sent from the operation unit 11 or an operation command is sent from a client PC or the like, the CPU 21 executes a control program 23a according to them. Thereby, the operation of the image forming apparatus 1 is performed according to the operation of the operation unit 11 by the user.

  The ROM 23 is, for example, a flash ROM (Flash Memory). The ROM 23 stores data used for operating the image forming apparatus 1. The ROM 23 stores a control program (program) 23 a for performing various operations of the image forming apparatus 1 including the fixing unit 400. In addition, the ROM 23 may store function setting data of the image forming apparatus 1. The CPU 21 reads data from the ROM 23 and writes data to the ROM 23 by performing predetermined processing. The ROM 23 may be non-rewritable.

  The RAM 25 is a main memory of the CPU 21. The RAM 25 is used for storing data necessary when the CPU 21 executes the control program 23a.

  The nonvolatile memory 27 stores, for example, job data sent from the outside via the interface unit 29. The nonvolatile memory 27 may be configured to store setting information of the image forming apparatus 1 and a control program for performing various operations of the image forming apparatus 1. The nonvolatile memory 27 is composed of, for example, an HDD (Hard Disk Drive), a flash ROM, or the like.

  The interface unit 29 is configured, for example, by combining a hardware unit such as a NIC (Network Interface Card) and a software unit that performs communication using a predetermined communication protocol. The interface unit 29 connects the image forming apparatus 1 to an external network such as a LAN. As a result, the image forming apparatus 1 can communicate with an external apparatus such as a client PC connected to the external network. The image forming apparatus 1 can receive a job from a client PC. Further, the image forming apparatus 1 can transmit the image data to the client PC or by E-mail via a mail server or the like.

  The interface unit 29 may be configured to be connectable to an external network by wireless communication. The interface unit 29 may be, for example, a USB (Universal Serial Bus) interface. In this case, the interface unit 29 enables communication between the external device connected via the communication cable and the image forming apparatus 1.

  The power supply device 600 is provided inside the housing of the image forming apparatus 1. The power supply device 600 is connected to a commercial power supply and supplies power to each unit of the image forming apparatus 1 based on the commercial power supply. The power supply device 600 includes an induction heating power supply circuit 411 and a demagnetizing coil control circuit 413 that supply power to the fixing unit 400 as will be described later.

  The developing units 310Y, 310M, 310C, and 310K are provided with nonvolatile memories 319Y, 319M, 319C, and 319K, respectively. The toner bottles 301Y, 301M, 301C, and 301K are provided with nonvolatile memories 309Y, 309M, 309C, and 309K, respectively. The CPU 21 stores information such as the life status of the developing unit 310 and the toner bottle 301 that are consumables in these nonvolatile memories 319Y to 319K and 309Y to 309K. Thereby, even when each consumable is removed and mounted on another image forming apparatus, the life state of the consumable can be reflected in the image forming apparatus of the transfer destination. Therefore, it is possible to reliably manage the life of each consumable and appropriately print an image.

  [Configuration of Fixing Unit 400]

  Next, the configuration of the fixing unit 400 will be described.

  FIG. 3 is a side view showing the configuration of the fixing unit 400.

  Referring to the figure, a fixing unit 400 includes a heating roller (an example of a fixing member) 401, a pressure roller 402, an excitation coil (sometimes referred to as an electromagnetic induction coil; an example of an excitation unit) 403, and a temperature detection device 404. have.

  The pressure roller 402 is urged toward the heating roller 401 and is arranged so that its axis is substantially parallel to the axis of the heating roller 401. The paper is nipped and conveyed between the heating roller 401 and the pressure roller 402.

  The exciting coil 403 is disposed so as to cover a part of the surface of the heating roller 401 along the longitudinal direction of the heating roller 401. The excitation coil 403 generates magnetic flux that passes through the heating roller 401 when high-frequency power is supplied as will be described later.

  The temperature detection device 404 detects the temperature of the surface of the heating roller 401 and outputs the detection result.

  A heated belt 407 is provided on the surface of the heating roller 401. When the exciting coil 403 is driven to generate magnetic flux, the heated belt 407 is heated by an electromagnetic induction heating method.

  A pressure roller 402 is pressed against the heating roller 401. As a result, a fixing nip 405 is formed between the heating roller 401 and the pressure roller 402 to hold the sheet and pressurize and heat the sandwiched portion of the sheet. The toner image is fixed on the paper 406 by rotating the heating roller 401 and the pressure roller 402 while the paper 406 on which the toner image is formed in the toner image forming unit 300 is sandwiched between the fixing nips 405.

  FIG. 4 is a block diagram illustrating a configuration of a control circuit of the fixing unit 400.

  Referring to the figure, fixing unit 400 further includes a demagnetizing coil (an example of a demagnetizing unit) 408 and a thermal fixing control circuit 421 in addition to the above-described units. The fixing unit 400 is driven by an induction heating power circuit (an example of a supply unit) 411 and a degaussing coil switching circuit (an example of a switching unit) 413.

  In the present embodiment, the thermal fixing control circuit 421 is a circuit for controlling only the fixing unit 400 and is provided in the fixing unit 400. The thermal fixing control circuit 421 controls the fixing unit 400 under the control of the control unit 20. The induction heating power supply circuit 411 and the degaussing coil switching circuit 413 are included in the power supply device 600. That is, the fixing device that fixes the sheet in the image forming apparatus 1 includes, for example, the fixing unit 400 and the power supply device 600.

  The thermal fixing control circuit 421 may be a part of the control circuit of the entire image forming apparatus 1, that is, the control unit 20. In this case, the fixing device includes, for example, the control unit 20 in addition to the fixing unit 400 and the power supply device 600. Further, the induction heating power supply circuit 411 and the demagnetizing coil switching circuit 413 may be provided in the fixing unit 400 independently of the power supply device 600 of the image forming apparatus 1. In this case, the fixing device includes, for example, a fixing unit 400.

  The degaussing coil 408 is disposed so as to overlap a part of the exciting coil 403. In the present embodiment, one demagnetizing coil 408 is disposed at a position corresponding to both ends of the exciting coil 403, that is, both ends of the heating roller 401. Note that the degaussing coil 408 may be arranged close to one side, that is, at a position corresponding to one end of the heating roller 401. Further, the degaussing coil 408 may be configured by overlapping a plurality of windings. The demagnetizing coil 408 is controlled and driven as described below to generate magnetic flux, so that a part of the magnetic flux generated by the exciting coil 403 can be canceled (can be canceled).

  The degaussing coil 408 operates according to the size of the paper, for example. That is, the demagnetizing coil 408 provided at a position corresponding to the non-sheet passing portion of the heating roller 401 is driven, so that the non-sheet passing portion of the heating roller 401 is not heated, and the temperature of the heating roller 401 is increased. Is prevented from rising partly.

  The induction heating power supply circuit 411 converts commercial power (an example of AC power) supplied from the commercial power supply 412 into high-frequency alternating power. The converted high frequency power is supplied to the exciting coil 403. That is, the induction heating power supply circuit 411 supplies a high frequency current to the exciting coil 403 based on commercial power. When the high frequency power output from the induction heating power supply circuit 411 is applied to the exciting coil 403, an electric field is generated by the exciting coil 403, and the heating roller 401 generates heat. That is, when the magnetic flux is generated by the exciting coil 403, the heating roller 401 is heated.

  The degaussing coil 408 is connected to the degaussing coil control circuit 413 in series or in parallel.

  The heat fixing control circuit 421 has a function of setting the power of the high frequency power output from the induction heating power supply circuit 411 by outputting an output power control signal to the induction heating power supply circuit 411. The temperature detection signal output from the temperature detection device 404 is input to the heat fixing control circuit 421.

  The thermal fixing control circuit 421 receives the temperature detection signal output from the temperature detection device 404 and outputs an output power control signal in accordance with the temperature detection signal. The induction heating power supply circuit 411 generates high-frequency power according to the output power control signal sent from the heat fixing control circuit 421 and supplies it to the exciting coil 403. That is, high frequency power having a power value determined by the thermal fixing control circuit 421 is supplied from the induction heating power supply circuit 411 to the exciting coil 403. As described above, the temperature of the heating roller 401 is controlled to an appropriate temperature by the control loop including the temperature detection device 404, the thermal fixing control circuit 421, and the induction heating power supply circuit 411.

  FIG. 5 is a block diagram showing an internal circuit configuration of the induction heating power supply circuit 411.

  Referring to the drawing, an induction heating power supply circuit 411 includes a rectifier circuit 431, a switching circuit 432, a power detection circuit 433, an induction heating power supply control circuit 434, and a zero cross generation circuit (an example of a zero cross detection unit) 435. I have.

  The rectifier circuit 431 rectifies AC commercial power 412 and outputs it to the switching circuit 432.

  The switching circuit 432 outputs high frequency power to the exciting coil 403 based on the control of the induction heating power supply control circuit 434.

  The power detection circuit 433 detects the power in the rectifier circuit 431 and outputs a detection signal to the induction heating power supply control circuit 434.

  The zero cross generation circuit 435 outputs a zero cross signal (pulse signal) corresponding to the current after rectification in the rectification circuit 431 to the induction heating power supply control circuit 434, as will be described later.

  The induction heating power supply control circuit 434 is based on the detection signal output from the power detection circuit 433, the zero cross signal output from the zero cross generation circuit 435, and the output power control signal sent from the thermal fixing control circuit 421. The operation of the switching circuit 432 is controlled. That is, the induction heating power supply control circuit 434 confirms the operation of the switching circuit 432 with the power detection circuit 433, and considers the zero cross signal, and generates high frequency power corresponding to the output power control signal received from the thermal fixing control circuit 421. Output from the switching circuit 432. The zero cross signal is sent to the thermal fixing control circuit 421.

  FIG. 6 is a block diagram showing an internal circuit configuration of the degaussing coil switching circuit 413.

  Referring to the drawing, the degaussing coil switching circuit 413 includes a degaussing coil switching switch 441 and a degaussing coil switching control circuit 442.

  The degaussing coil changeover switch 441 is controlled by the degaussing coil switching control circuit 442. The degaussing coil 408 operates to demagnetize part of the magnetic flux generated by the excitation coil 403, and the degaussing coil 408 does not operate and the excitation coil 403 The normal state in which the generated magnetic flux is not canceled is switched. In the present embodiment, the degaussing coil selector switch 441 is configured using a switch element using a semiconductor, and can perform a switching operation at high speed.

  The degaussing coil switching control circuit 442 is controlled by the thermal fixing control circuit 421 and controls the operation of the degaussing coil switching switch 441. That is, the degaussing coil switching circuit 413 switches the degaussing state / normal state of the degaussing coil 408 based on the control of the thermal fixing control circuit 421. The heat fixing control circuit 421 can prevent the heating roller 401 from being overheated by setting the degaussing coil 408 to a degaussing state when, for example, fixing a narrow sheet.

  [Explanation regarding control of operation of degaussing coil 408]

  In this embodiment, when the zero cross signal output from the zero cross generation circuit 435 is sent to the heat fixing control circuit 421 via the induction heating power control circuit 434, the heat fixing control circuit 421 responds to the zero cross signal. Take control. That is, the thermal fixing control circuit 421 controls the operation of the degaussing coil 408 by outputting a switching signal for switching the state of the degaussing coil 408 at a timing corresponding to the zero cross signal. As a result, the operation of the degaussing coil 408 is synchronized with the change in power input to the induction heating power supply circuit 411.

  The degaussing coil switching circuit 413 is controlled by the thermal fixing control circuit 421 and switches the degaussing state / normal state of the degaussing coil 408 within the switchable time corresponding to the zero cross signal. The thermal fixing control circuit 421 determines the switchable time based on the zero cross signal output from the zero cross generation circuit 435, that is, the detection result of the zero cross.

  FIG. 7 is a graph showing the relationship between the power detection pulsating signal after rectification in the rectifier circuit 431 and the zero cross signal output from the zero cross generation circuit 435.

  Referring to the figure, zero-cross generation circuit 435 detects a zero-cross point at which AC power input to induction heating power supply circuit 411, that is, commercial power, becomes zero, and outputs a zero-cross signal accordingly. More specifically, the zero cross signal is a pulse waveform indicating a 0 V point in the voltage waveform after full wave rectification by a rectifier circuit 431 as shown in the upper part of the figure. Since the commercial power is 50 Hz or 60 Hz, the zero cross signal is output approximately every 10 ms.

  FIG. 8 is a diagram illustrating an example of a waveform of the high-frequency power output from the induction heating power supply circuit 411 near the zero cross of the power detection pulsating signal.

  Referring to the figure, when induction heating power supply circuit 411 receives AC power input from commercial power supply 412 and performs rectification by rectifier circuit 431, the voltage drop in the semiconductors inside rectifier circuit 431 and switching circuit 432, and others Due to the influence of the voltage drop in the power supply unit, a non-output time during which the high-frequency power cannot be output even when the switching circuit 432 performs the switching operation is generated. That is, this non-output time is a time during which high frequency power is not supplied to the exciting coil 403. The thermal fixing control circuit 421 controls the non-output time as the minimum switchable time.

  Here, the degree of influence of the degaussing coil 408 on the exciting coil 403 varies depending on the amount of magnetic flux passing through the loop of the degaussing coil 408.

  FIG. 9 is a first diagram for explaining the influence of magnetic flux depending on the type of coil.

  When a current is passed through a coil such as the exciting coil 403 or the degaussing coil 408, a magnetic flux is generated. As shown in the figure, when the electric power supplied to the coil changes, the generated magnetic flux is also affected.

  FIG. 10 is a second diagram for explaining the influence of the magnetic flux depending on the type of coil.

  As shown in the figure, when the cross-sectional areas of the coils are different, the magnetic flux generated is affected by the influence.

  FIG. 11 is a third diagram for explaining the influence of magnetic flux depending on the type of coil.

  As shown in the figure, when the number of turns of the coil is different, the generated magnetic flux is different due to the influence.

  FIG. 12 is a fourth diagram for explaining the influence of magnetic flux depending on the type of coil.

  As shown in the figure, when the number of coils is different, the magnetic flux generated as a whole is also affected by the influence.

  Thus, the magnetic flux generated in the coil varies depending on the power supplied, the size of the coil diameter (coil cross-sectional area), the number of turns of the coil, and the number of coils (number of circuits). The magnetic flux generated by the excitation coil 403 varies depending on the amount of fluctuation of the power supplied to the excitation coil 403. Further, the magnetic flux generated by the degaussing coil 408 varies depending on the number of turns of the degaussing coil 408, the cross-sectional area of the degaussing coil 408, the number of circuits of the degaussing coil 408, and the like.

  In this way, the magnetic flux is affected by the type and method of the exciting coil 403 and the demagnetizing coil 408. Therefore, the amount of magnetic flux passing through the demagnetizing coil 408, that is, the short circuit is shorted according to the power to be applied and the circuit method of the demagnetizing coil 408. The amount of current flowing through the degaussing coil 408 at this time changes. The effect of switching the degaussing coil 408 on the exciting coil 403 and the induction heating power supply circuit 411 increases as the amount of current flowing through the degaussing coil 408 increases.

  FIG. 13 is a timing chart showing the operations of the induction heating power supply circuit 411 and the degaussing coil switching circuit 413.

  Referring to the figure, the demagnetizing coil 408 is switched in the non-output time (illustrated in FIG. 8), that is, in the period before and after the zero cross signal, so that the switching of the degaussing coil 408 is performed. The influence on the power output to the coil 403 is reduced.

  Here, in the switching control of the degaussing coil 408 using the zero cross signal as described above, for example, when there is an AC input of 50 Hz, a delay of about 5 ms at maximum may occur. On the other hand, for example, if the fluctuation amount of the power supplied to the exciting coil 403 is small and the configuration of the demagnetizing coil 408 has little influence on the exciting coil 403, the degaussing coil 408 is not necessarily within the switchable time corresponding to the zero cross signal. Even if the switching is not performed, the influence of the switching on the induction heating power supply circuit 411 may not be a relatively large problem.

  The heat fixing control circuit 421 determines that the problem is unlikely to occur as described above based on, for example, the amount of fluctuation in the power supplied to the exciting coil 403, the number of turns of the degaussing coil 408, the cross-sectional area, and the number of circuits. When possible, the decision is made to shift the switchable period. In particular, when it is necessary to finely adjust the temperature of the heating roller 401, the amount of power fluctuation is reduced. In such a case, the thermal fixing control circuit 421 determines that the switchable time is a better time for temperature control by shifting from the non-output time while not affecting the induction heating power supply circuit 411. I do. Thereby, in a state where the influence on the induction heating power supply circuit 411 and the exciting coil 403 is suppressed, better temperature control, for example, proper and fine temperature control is executed.

  [Description of control according to switching characteristics of degaussing coil switching circuit]

  The heat fixing control circuit 421 can determine, that is, adjust the switchable time based on the switching characteristics (switching method) of the degaussing coil switching circuit 413. Here, the switching characteristics of the degaussing coil switching circuit 413 refer to, for example, the time required for the degaussing coil switching switch 441 to switch the state of the degaussing coil 408 and the state at the time of switching.

  In the present embodiment, a demagnetizing coil changeover switch 441 is a switch that can perform a switching operation at high speed using a semiconductor. The contact SW) can also be used as the degaussing coil selector switch 441. Since the contact switch is relatively inexpensive, the manufacturing cost of the fixing unit 400 can be reduced.

  A contact switch requires a longer operation time than a semiconductor switch. Therefore, when such a contact switch is used as the degaussing coil changeover switch 441, there occurs a time during which the state of the degaussing coil 408 cannot be fixed to the degaussing state or the normal state. Therefore, as shown in the figure, the thermal fixing control circuit 421 provides an output prohibition section in which output is prohibited, and performs control to shift the switchable time. As described above, the thermal fixing control circuit 421 performs control according to the switching characteristics of the degaussing coil switching circuit 413, so that the operation of the fixing unit 400 can be stabilized. Further, since the output is not performed when the operation of the contact switch is performed, the life of the contact switch can be improved.

  [Description of demagnetizing coil switching control]

  FIG. 14 is a flowchart showing switching control of the degaussing coil 408.

  The zero cross position and the non-output time are determined from the result of independent zero cross detection as described later. The switchable time is determined based on this result and the detection result regarding each confirmation item. A switching signal is output during the switchable time, and the degaussing coil 408 is switched based on the switching signal, whereby a switching operation that minimizes the influence on the induction heating power supply circuit 411 is performed.

  Referring to the figure, when the switching process of degaussing coil 408 is started, the configuration and state of fixing unit 400 are confirmed in steps S101 to S105.

  That is, in step S <b> 101, the thermal fixing control circuit 421 confirms the fluctuation amount of the power supplied to the exciting coil 403.

  In step S <b> 103, the thermal fixing control circuit 421 confirms the configuration of the degaussing coil 408. The cross-sectional area, number of turns, number of circuits, etc. of the degaussing coil 408 are confirmed.

  In step S105, the thermal fixing control circuit 421 confirms the configuration of the degaussing coil changeover switch 441. Thereby, for example, it is confirmed whether the demagnetizing coil changeover switch 441 has a fast switching operation using a semiconductor or a relatively slow switching operation using a contact switch. Note that the thermal fixing control circuit 421 may check the switching characteristics of other demagnetizing coil changeover switches 441 and the like.

  Next, when the confirmation of the configuration and state of the fixing unit 400 is completed, in step S107, the thermal fixing control circuit 421 acquires a zero-cross detection result as described below. Further, the thermal fixing control circuit 421 determines the switchable time based on the acquired zero-cross detection result and the confirmation results in steps S101 to S105.

  In step S109, the thermal fixing control circuit 421 determines whether it is necessary to output a switching signal. Whether or not it is necessary to acquire the switching signal is determined based on, for example, an instruction given by the CPU 21 of the image forming apparatus 1 in accordance with the size of the sheet on which image formation is to be performed. When there is no need to output a switching signal, the degaussing coil 408 is not switched.

  When it is necessary to output a switching signal in step S109, in step S111, the thermal fixing control circuit 421 causes the degaussing coil switching control circuit 442 to output a switching signal for the determined switchable time. Thereby, the switching of the state of the degaussing coil 408 by the degaussing coil changeover switch 441 is executed during the switchable time.

  FIG. 15 is a flowchart showing a zero cross detection process.

  In step S201, the thermal fixing control circuit 421 stands by until a zero cross is detected. When the zero cross signal is output from the zero cross generation circuit 435, the thermal fixing control circuit 421 determines that the zero cross is detected.

  When a zero cross is detected in step S201, in step S203, the thermal fixing control circuit 421 performs a timer operation and stores the final value. That is, a time counting operation is performed.

  In step S205, the thermal fixing control circuit 421 detects the next zero cross of the zero cross detected in step S201 (hereinafter referred to as the next zero cross). The thermal fixing control circuit 421 executes the process of step S203 until the next zero cross is detected. That is, the timer operation is continued until the next zero cross is detected.

  When the next zero cross is detected in step S205, in step S207, the thermal fixing control circuit 421 digitizes the zero cross interval. The thermal fixing control circuit 421 converts the information regarding the interval between the zero cross and the next zero cross into a numerical value and uses it as the zero cross detection result. This zero cross detection result is acquired in step S107 of the process in FIG.

  [Effects of the embodiment]

  In the image forming apparatus configured as described above, switching of the degaussing state / normal state of the degaussing coil is performed at the timing of zero crossing of the commercial power input to the induction heating power supply circuit. That is, when the zero cross point is detected, the thermal fixing control circuit determines a predetermined time before and after the zero cross point as a switchable time of the degaussing coil. The degaussing coil is switched by the degaussing coil switching circuit within the switchable time. Since the degaussing coil is switched at a timing close to the zero cross point, the output reduction of the power output to the exciting coil is minimized, and stable temperature control of the fixing unit is performed.

  The stop time of the induction heating power supply circuit is shortened, and fine power control can be performed. Therefore, even when the heating roller or the like has a low heat capacity in order to increase the printing speed or shorten the warm-up time, the fixing operation is properly performed.

  [Others]

  Note that the various processes described above, such as the process shown in FIG. 14 and the process shown in FIG. 15, are not limited to the thermal fixing control circuit, and are executed by other parts constituting the fixing device, the control unit of the image forming apparatus, and the like. May be.

  The induction heating power supply circuit and the degaussing coil switching circuit may have the same configuration. In this case, the high frequency power output from the induction heating power supply control circuit to the demagnetizing coil may be controlled based on the zero cross signal output from the zero cross generation circuit.

  The fixing device is not limited to a heat roller type, and may be a type using another heating method such as a belt method. Further, the fixing device is not limited to the one that performs electromagnetic induction heating by the so-called outer coil method as described above, and may be one that uses a roller configured by arranging an exciting coil, a demagnetizing coil, or the like inside the roller. .

  The image forming apparatus may be any of a monochrome / color copying machine, a printer, a facsimile machine, and the like. The image forming apparatus may be an MFP (Multi Function Peripheral) having a scanner function, a copying function, a printer function, a facsimile function, a data communication function, and a server function. In the scanner function, an image of a set original is read and stored in an HDD or the like. In the copying function, it is further printed (printed) on paper or the like. In the function as a printer, when a print instruction is received from an external terminal such as a PC, printing is performed on a sheet based on the instruction. In the facsimile function, facsimile data is received from an external facsimile machine or the like and stored in an HDD or the like. In the data communication function, data is transmitted / received to / from a connected external device. In the server function, a plurality of users can share data stored in the HDD or the like.

  The processing in the above embodiment may be performed by software or by using a hardware circuit.

  A program for executing the processing in the above-described embodiment can be provided, or the program can be recorded on a recording medium such as a CD-ROM, a flexible disk, a hard disk, a ROM, a RAM, or a memory card and provided to the user. It may be. The program may be downloaded to the apparatus via a communication line such as the Internet. The processing described in the text in the above flowchart is executed by the CPU according to the program.

  The above embodiment should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 20 Control part 23a Program (control program)
400 fixing unit (an example of a fixing device)
401 Heating roller (an example of a fixing member)
403 Excitation coil (example of excitation unit)
408 Degaussing coil (an example of a degaussing part)
411 Induction heating power supply circuit (an example of a supply unit)
412 Commercial power supply 413 Degaussing coil control circuit (an example of a switching unit)
421 Thermal fixing control circuit 435 Zero cross generation circuit (an example of zero cross detection unit)
600 Power supply

Claims (13)

A fixing member that fixes the toner on the paper to the paper by conveying the paper under pressure while heating;
An exciting unit that generates magnetic flux to heat the fixing member and performs electromagnetic induction heating;
A demagnetizing part capable of canceling at least a part of the magnetic flux generated by the exciting part by generating a magnetic flux;
AC power is input, a supply unit that supplies a high-frequency current to the excitation unit based on the AC power;
A zero-cross detection unit that detects a zero-cross point at which the AC power input to the supply unit becomes zero; and
A determination unit that determines a switchable time based on the detection result of the zero-cross detection unit,
A switching unit that switches between a degaussing state in which the degaussing unit performs the cancellation and a normal state in which the degaussing unit does not perform the cancellation within the switchable time determined by the determination unit;
The determination unit further determines the switchable time based on the fluctuation amount of the power supplied to the exciting unit, a fixing device. A fixing member that fixes the toner on the paper to the paper by conveying the paper under pressure while heating;
An exciting unit that generates magnetic flux to heat the fixing member and performs electromagnetic induction heating;
A demagnetizing part capable of canceling at least a part of the magnetic flux generated by the exciting part by generating a magnetic flux;
AC power is input, a supply unit that supplies a high-frequency current to the excitation unit based on the AC power;
A zero-cross detection unit that detects a zero-cross point at which the AC power input to the supply unit becomes zero; and
A determination unit that determines a switchable time based on the detection result of the zero-cross detection unit,
A switching unit that switches between a degaussing state in which the degaussing unit performs the cancellation and a normal state in which the degaussing unit does not perform the cancellation within the switchable time determined by the determination unit;
A plurality of the demagnetizing parts are provided,
The determination unit further determines the switchable time based on the number of the demagnetization unit, a fixing device. A fixing member that fixes the toner on the paper to the paper by conveying the paper under pressure while heating;
An exciting unit that generates magnetic flux to heat the fixing member and performs electromagnetic induction heating;
A demagnetizing part capable of canceling at least a part of the magnetic flux generated by the exciting part by generating a magnetic flux;
AC power is input, a supply unit that supplies a high-frequency current to the excitation unit based on the AC power;
A zero-cross detection unit that detects a zero-cross point at which the AC power input to the supply unit becomes zero; and
A determination unit that determines a switchable time based on the detection result of the zero-cross detection unit,
A switching unit that switches between a degaussing state in which the degaussing unit performs the cancellation and a normal state in which the degaussing unit does not perform the cancellation within the switchable time determined by the determination unit;
The demagnetizing part is a coil,
The determination unit further determines the switchable time based on at least one of the cross-sectional area of the winding number and the coil of the coil, the fixing device. A fixing member that fixes the toner on the paper to the paper by conveying the paper under pressure while heating;
An exciting unit that generates magnetic flux to heat the fixing member and performs electromagnetic induction heating;
A demagnetizing part capable of canceling at least a part of the magnetic flux generated by the exciting part by generating a magnetic flux;
AC power is input, a supply unit that supplies a high-frequency current to the excitation unit based on the AC power;
A zero-cross detection unit that detects a zero-cross point at which the AC power input to the supply unit becomes zero; and
A determination unit that determines a switchable time based on the detection result of the zero-cross detection unit,
A switching unit that switches between a degaussing state in which the degaussing unit performs the cancellation and a normal state in which the degaussing unit does not perform the cancellation within the switchable time determined by the determination unit;
The determination unit further determines the switchable time based on the switching characteristics when the switching unit performs switching of the demagnetized state / normal state of the demagnetization unit, a fixing device. A toner image forming unit that forms a toner image on paper;
A fixing device according to any one of claims 1 to 4 ,
An image forming apparatus for fixing a toner image formed on a sheet by the toner image forming unit to the sheet by the fixing apparatus. A fixing member that fixes the toner on the paper to the paper by conveying the paper under pressure while heating;
An exciting unit that generates magnetic flux to heat the fixing member and performs electromagnetic induction heating;
A demagnetizing part capable of canceling at least a part of the magnetic flux generated by the exciting part by generating a magnetic flux;
A control method for a fixing device comprising: an AC power input; and a supply unit that supplies a high frequency current to the excitation unit based on the AC power,
A zero-crossing detecting step for detecting a zero-crossing point at which AC power input to the supply unit becomes zero;
A determination step of determining a switchable time based on the detection result of the zero-cross detection step;
Within the switchable time determined in the determining step, the demagnetizing unit comprises a switching step for switching between a degaussing state in which the demagnetization is performed and a normal state in which the demagnetizing unit does not perform the cancellation ,
The fixing step further includes determining the switchable time based on a fluctuation amount of electric power supplied to the excitation unit .   A fixing member that fixes the toner on the paper to the paper by conveying the paper under pressure while heating;
  An exciting unit that generates magnetic flux to heat the fixing member and performs electromagnetic induction heating;
  A demagnetizing part capable of canceling at least a part of the magnetic flux generated by the exciting part by generating a magnetic flux;
  A control method for a fixing device comprising: an AC power input; and a supply unit that supplies a high-frequency current to the excitation unit based on the AC power,
  A zero-crossing detecting step for detecting a zero-crossing point at which AC power input to the supply unit becomes zero;
  A determination step of determining a switchable time based on the detection result of the zero-cross detection step;
  Within the switchable time determined in the determining step, the demagnetizing unit comprises a switching step for switching between a degaussing state in which the demagnetization is performed and a normal state in which the demagnetizing unit does not perform the cancellation,
  A plurality of the demagnetizing parts are provided,
  The determination step further includes a fixing device control method in which the switchable time is determined based on the number of demagnetization units.   A fixing member that fixes the toner on the paper to the paper by conveying the paper under pressure while heating;
  An exciting unit that generates magnetic flux to heat the fixing member and performs electromagnetic induction heating;
  A demagnetizing part capable of canceling at least a part of the magnetic flux generated by the exciting part by generating a magnetic flux;
  A control method for a fixing device comprising: an AC power input; and a supply unit that supplies a high-frequency current to the excitation unit based on the AC power,
  A zero-crossing detecting step for detecting a zero-crossing point at which AC power input to the supply unit becomes zero;
  A determination step of determining a switchable time based on the detection result of the zero-cross detection step;
  Within the switchable time determined in the determining step, the demagnetizing unit comprises a switching step for switching between a degaussing state in which the demagnetization is performed and a normal state in which the demagnetizing unit does not perform the cancellation,
  The demagnetizing part is a coil,
  The determination step further includes a fixing device control method in which the switchable time is determined based on at least one of the number of turns of the coil and the cross-sectional area of the coil.   A fixing member that fixes the toner on the paper to the paper by conveying the paper under pressure while heating;
  An exciting unit that generates magnetic flux to heat the fixing member and performs electromagnetic induction heating;
  A demagnetizing part capable of canceling at least a part of the magnetic flux generated by the exciting part by generating a magnetic flux;
  A control method for a fixing device comprising: an AC power input; and a supply unit that supplies a high-frequency current to the excitation unit based on the AC power,
  A zero-crossing detecting step for detecting a zero-crossing point at which AC power input to the supply unit becomes zero;
  A determination step of determining a switchable time based on the detection result of the zero-cross detection step;
  Within the switchable time determined in the determining step, the demagnetizing unit comprises a switching step for switching between a degaussing state in which the demagnetization is performed and a normal state in which the demagnetizing unit does not perform the cancellation,
  The fixing device control method, wherein the determining step further determines the switchable time based on switching characteristics when the switching step switches between the demagnetization state / normal state of the demagnetization unit. A fixing member that fixes the toner on the paper to the paper by conveying the paper under pressure while heating;
An exciting unit that generates magnetic flux to heat the fixing member and performs electromagnetic induction heating;
A demagnetizing part capable of canceling at least a part of the magnetic flux generated by the exciting part by generating a magnetic flux;
A control program for a fixing device including an AC power input and a supply unit that supplies a high-frequency current to the excitation unit based on the AC power,
A zero-crossing detecting step for detecting a zero-crossing point at which AC power input to the supply unit becomes zero;
A determination step of determining a switchable time based on the detection result of the zero-cross detection step;
Within a switchable time determined in the determination step, the computer executes a switching step of switching between a degaussing state in which the degaussing unit performs the cancellation and a normal state in which the degaussing unit does not perform the cancellation ,
The determination step further includes a fixing device control program for determining the switchable time based on a fluctuation amount of electric power supplied to the excitation unit .   A fixing member that fixes the toner on the paper to the paper by conveying the paper under pressure while heating;
  An exciting unit that generates magnetic flux to heat the fixing member and performs electromagnetic induction heating;
  A demagnetizing part capable of canceling at least a part of the magnetic flux generated by the exciting part by generating a magnetic flux;
  A control program for a fixing device including an AC power input and a supply unit that supplies a high-frequency current to the excitation unit based on the AC power,
  A zero-crossing detecting step for detecting a zero-crossing point at which AC power input to the supply unit becomes zero;
  A determination step of determining a switchable time based on the detection result of the zero-cross detection step;
  Within a switchable time determined in the determination step, the computer executes a switching step of switching between a degaussing state in which the degaussing unit performs the cancellation and a normal state in which the degaussing unit does not perform the cancellation,
  A plurality of the demagnetizing parts are provided,
  The determination step further includes a fixing device control program for determining the switchable time based on the number of the demagnetization units.   A fixing member that fixes the toner on the paper to the paper by conveying the paper under pressure while heating;
  An exciting unit that generates magnetic flux to heat the fixing member and performs electromagnetic induction heating;
  A demagnetizing part capable of canceling at least a part of the magnetic flux generated by the exciting part by generating a magnetic flux;
  A control program for a fixing device including an AC power input and a supply unit that supplies a high-frequency current to the excitation unit based on the AC power,
  A zero-crossing detecting step for detecting a zero-crossing point at which AC power input to the supply unit becomes zero;
  A determination step of determining a switchable time based on the detection result of the zero-cross detection step;
  Within a switchable time determined in the determination step, the computer executes a switching step of switching between a degaussing state in which the degaussing unit performs the cancellation and a normal state in which the degaussing unit does not perform the cancellation,
  The demagnetizing part is a coil,
  The determining step further includes a fixing device control program for determining the switchable time based on at least one of the number of turns of the coil and a cross-sectional area of the coil.   A fixing member that fixes the toner on the paper to the paper by conveying the paper under pressure while heating;
  An exciting unit that generates magnetic flux to heat the fixing member and performs electromagnetic induction heating;
  A demagnetizing part capable of canceling at least a part of the magnetic flux generated by the exciting part by generating a magnetic flux;
  A control program for a fixing device including an AC power input and a supply unit that supplies a high-frequency current to the excitation unit based on the AC power,
  A zero-crossing detecting step for detecting a zero-crossing point at which AC power input to the supply unit becomes zero;
  A determination step of determining a switchable time based on the detection result of the zero-cross detection step;
  Within a switchable time determined in the determination step, the computer executes a switching step of switching between a degaussing state in which the degaussing unit performs the cancellation and a normal state in which the degaussing unit does not perform the cancellation,
  The determination program further includes a fixing device control program for determining the switchable time based on switching characteristics when the switching step switches between the demagnetization state / normal state of the demagnetization unit.

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