JP2006244824A - Temperature control method, fixing device using method, and image forming device provided with fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a safe temperature control method improving heating efficiency, and also to provide a fixing device using the method, and an image forming device provided with the fixing device. <P>SOLUTION: The method includes a means for correcting a difference between input power detected by an input power detection means comprising a voltage detecting circuit 105 and a current detecting circuit 106 and power set by a power control circuit 103, and for arbitrarily initializing to a limited value the compensation amount. The actual input power is safely and efficiently matched with the set power to control the temperature. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a temperature control method, a fixing device to which the temperature control method is applied, and an image forming apparatus including the fixing device, and more particularly, to a heat fixing unit using an induction heating method of an electrophotographic image forming apparatus and the inside of the heat fixing unit. This relates to the temperature control of the heating rotator.

  In an apparatus using an electrophotographic process such as an electrophotographic copying machine, an electrostatic printer, or a facsimile, an image is obtained by applying a developer (hereinafter, toner) to an electrostatic latent image obtained by irradiating light onto a photoconductor. After an image is transferred onto a recording medium such as transfer paper by a predetermined means, an unfixed toner image is fixed on the transfer paper, thereby printing the image on the recording medium.

  Such a fixing device includes a heating roller formed by forming a releasable resin film on the surface of a cylindrical metal core, and a pressure roller having an elastic layer on the surface in pressure contact with the heating roller. With the temperature reaching the predetermined fixing temperature, the transfer paper carrying the unfixed toner image is passed through the nip portion between the heating roller and the pressure roller so that the toner image surface is in contact with the heating roller. A heat roller fixing device that fuses and fixes a toner image to a transfer paper surface by pressure is widely used.

  Conventionally, various heating methods of a heating roller of this type of fixing device have been proposed, such as a method using a halogen lamp and a method using a planar heating element. In recent years, a fixing device using an induction heating method has been proposed from the viewpoint of heat exchange efficiency and start-up time. For example, as in Patent Document 1, magnetic force generating means including a coil that generates magnetic force when a high frequency voltage is applied by a high frequency power source, and a cored bar portion of a heating roller made of iron-based metal having magnetism, An apparatus has been devised in which an eddy current is generated in the heating roller cored bar due to an interlinkage magnetic flux generated when a high frequency voltage is applied to the magnetic force generating means from a high frequency power source, and heat is generated by Joule heat.

  By using this heating device, it has become possible to quickly raise the temperature of the fixing roller to the target fixing temperature, and thereafter control to maintain the fixing temperature. In induction heating, the power consumption can be finely varied from the oscillation frequency of the high-frequency power source and the ON / OFF ratio. The control as the fixing device at this time generally detects the temperature of the fixing roller, calculates the input set power from the temperature difference from the target temperature, and feeds back to obtain an optimum heating state. . Further, as the set power calculation method, a feedback control method such as PID control is used.

  However, induction heating is characterized by the temperature dependence of the magnetic permeability of the heating coil, fixing roller, etc., and the resistivity of the fixing roller. The difference of the electric power input into will arise. Further, for example, in recent years, it is required to shorten the start-up time at the start of heating. For this purpose, it is necessary to aim at a quick start-up by continuously applying the maximum power allowed by the apparatus to the fixing device.

However, due to the temperature dependence of the magnetic permeability and resistivity of the roller as described above, even when the maximum allowable power is set to be applied at the start of heating, the temperature of the fixing roller is fixed at a fixed oscillation frequency and ON / OFF ratio. A phenomenon is observed in which the input power decreases more and more as the value rises. In this case, heating cannot be performed with maximum efficiency until the target temperature is reached, and the rise time is delayed. Therefore, as in Patent Document 2, a method of correcting the oscillation frequency or ON / OFF ratio (that is, input power) of the induction heating device with the fixing roller temperature is considered.
Japanese Patent Publication No. 5-9027 JP-A-11-195477

  However, in the case of Patent Document 2, the heating efficiency due to various error factors such as the distance between the coil as the magnetic flux generation source and the fixing roller as the eddy current generator (heating target), the magnetic flux, and the resistivity of the fixing roller. Since variations can be considered, it is difficult to maximize the heating efficiency by power correction based on a temperature difference. Furthermore, unlike the fixing roller, which is a heating source, the temperature rise of the coil and the core is slow. Therefore, fluctuations in magnetic flux due to self-heating of the coil and fluctuations in the magnetic permeability of the core cannot be measured at the fixing roller temperature. It is clear that the correction cannot be sufficiently corrected in this respect.

  On the other hand, desired power may not be input even at a predetermined drive frequency and ON / OFF ratio due to breakage / short circuit of the oscillation coil, damage to the core and the fixing roller, and the like. In such a case, correcting the drive frequency and ON / OFF ratio until the actual power detected by the power detection circuit reaches the desired power will result in an excessive load applied to the drive circuit and eventually destruction. It is dangerous. In addition, the power required for startup, the maximum power required for standby, and the power required for printing are usually different, and the target temperature is usually different. Come different.

  In other words, for example, using the power correction amount calculated when the fixing unit is started up as it is as the power correction amount during the printing operation may cause an overpower phenomenon, which also increases the possibility of failure of the drive circuit. It is.

  The present invention provides a temperature control method that solves the above problems, increases heating efficiency, and is safe, a fixing device to which the temperature control method is applied, and an image forming apparatus including the fixing device.

  In order to solve this problem, the temperature control method of the present invention is a temperature control method in which the heating member is heated and adjusted to a predetermined target temperature, and is adjusted by the power value supplied to the heating means for heating the heating member. The power supply target value is corrected based on a comparison between the power supply target value and the actual power supply value, and control is performed so that the power supply value does not exceed at least a predetermined upper limit value.

  Here, the correction of the power supply target value is performed by adding or subtracting the difference between the power supply target value and the actual power supply value. The correction of the power supply target value is performed by increasing or decreasing the added value corresponding to the difference between the previous power supply target value and the actual power supply value. The heating adjustment is a heating adjustment in an induction heating type fixing device comprising a heating member made of a ferromagnetic material and an exciting coil, which fixes the developer transferred on the recording medium by pressure heating. The power supply target value is determined based on the temperature detected from the heating member and the target temperature, and the correction is initialized in response to switching of the state of the fixing device.

  According to another aspect of the present invention, there is provided a fixing device for fixing a developer transferred onto a recording medium by press-contact heating, a temperature detecting means for detecting a temperature of a heating member, and a temperature detected by the temperature detecting means. Power setting means for setting a power supply target value to the heating means for heating the heating member, and power measurement means for measuring the power supply value actually supplied to the heating means, The power setting means includes target power correction means for setting a new power supply target value so that the measured power supply value matches the power supply target value.

  Here, the target power correction means adds or subtracts the unit correction power according to the difference between the measured power supply value and the set power supply target value power. The target power correcting means has a correction limit value. The target power correction unit is initialized at the timing when the operation mode of the fixing device is changed. The operation modes of the fixing device include initial startup, standby, and printing operation, respectively. The target power correction unit is initialized at the timing when the end shielding unit of the fixing device moves.

  The image forming apparatus of the present invention is an image forming apparatus having a fixing device for fixing the developer transferred onto the recording medium by press-contact heating, wherein the fixing device detects the temperature of the heating member. A power setting means for setting a power supply target value to the heating means for heating the heating member based on a detection temperature of the detection means, and a power supply value actually supplied to the heating means. Power measuring means for measuring the power supply means, and the power setting means includes target power correction means for setting a new power supply target value so that the measured power supply value matches the power supply target value. It is characterized by including.

  According to the above configuration, it is possible to provide a temperature control method that improves heating efficiency and is safe, a fixing device to which the temperature control method is applied, and an image forming apparatus including the fixing device.

  In particular, in an electromagnetic induction heating type fixing device, it is possible to eliminate an error between the set power and the actual input power, and to realize an image forming apparatus that operates efficiently within a predetermined power by minimizing the lack of overheating power and excessive power. be able to.

  Specifically, by providing a correction amount limit value and a means that can be arbitrarily initialized, the temperature is controlled by matching the actual input power to the set power safely and efficiently.

    Hereinafter, embodiments of an image forming apparatus according to the present invention will be described in detail with reference to the accompanying drawings. In the present embodiment, temperature control in a fixing device having an induction heating system having an end portion temperature rise prevention mechanism will be described. However, the present invention is not limited to this, and the present invention is a general temperature adjustment of a heating member. Are also effective, and these are also included in the present invention.

<Example of Configuration of Image Forming Apparatus of Present Embodiment>
FIG. 2 is a schematic cross-sectional view showing a schematic configuration of an electrophotographic laser beam printer 201 (hereinafter abbreviated as a printer 201), which is an example of an image forming apparatus according to the present embodiment.

  The printer 201 forms and records an image corresponding to image information provided from an image information providing device (not shown) such as a host computer provided outside the main body of the printer 201 on a sheet-like recording material P. The image forming apparatus is configured to perform a series of image forming processes in accordance with a known electrophotographic system.

  As shown in FIG. 2, the printer 201 includes a drum-shaped rotatable photosensitive member 202 as a latent image carrier and a process cartridge 204 holding a developing device 203, and an exposure process corresponding to image information from an image information providing device. A laser scanner unit 205 (hereinafter abbreviated as “scanner 205”) for forming an electrostatic latent image corresponding to the image information on the outer peripheral surface of the photosensitive member 202 and a recording material P are subjected to a transfer processing step. A roll-shaped rotatable transfer member 206 and a fixing device 207 as a heating device adapted to perform fixing processing on the recording material P that has been subjected to transfer processing by heating and pressing.

  In addition to the photosensitive member 202 and the developing device 203, the process cartridge 204 provided in the printer 201 holds a charging roller 208 that charges the outer peripheral surface of the photosensitive member 202 to a specified potential distribution before the exposure processing by the scanner 205. In addition, a cover that is detachably supported by the main body of the printer 201 and that is openably and closably supported by the main body when maintenance such as repair of the photosensitive member 202 and supply of developer to the developing device 203 is necessary. After opening 209, the entire process cartridge 204 is replaced to speed up and simplify the maintenance.

  Next, a series of image forming processes in the printer 201 will be described.

  First, when a start button or the like (not shown) provided on the main body of the printer 201 is pressed to instruct the printer 201 to start a series of image forming processes, the photosensitive member 202 is moved to a specified peripheral speed in the arrow K1 direction. And the charging roller 208 to which the specified bias is applied and the photoconductor 202 are in sliding contact with each other, so that the outer peripheral surface of the photoconductor 202 is charged to the specified potential distribution.

  Next, a charged portion on the outer peripheral surface of the photosensitive member 202 is scanned and exposed by the scanner 205 in accordance with image information from the image information providing apparatus, so that the electrostatic latent image corresponding to the image information becomes the portion. After that, the electrostatic latent image is visualized as a visible image by the developer of the developing device 203, and a predetermined number of recording materials P can be accommodated and detachably supported by the main body of the printer 201. The recording material P is conveyed from the cassette 211 to the space formed between the photoconductor 202 and the transfer body 206 by a rotatable paper feed roller 212 or the like at a predetermined timing. The visible image is transferred.

  The recording material P that has been subjected to the transfer process is subjected to a fixing process by the fixing device 207, and is then discharged out of the apparatus by a discharge roller 213 that is rotatably supported by the main body of the printer 201. By stacking on the tray 214 attached to the side, a series of image forming processes is completed.

(Fixing device configuration example)
The fixing device 207, which is a heating device of the present embodiment, will be described in detail with reference to a schematic perspective view showing a schematic configuration of the fixing device 207 in FIG.

  As shown in FIG. 3, the fixing device 207 includes a hollow fixing roller 100 as a heat generating member that is a magnetic metal member for melting and fixing the toner on the recording material to the recording material, and the fixing device 207 is provided in the fixing roller. An induction heating coil L1, which is a magnetic flux generating means, cores 1, 2, and 3, and a magnetic shielding member 150 are provided. Further, the fixing roller 100 constitutes a surface (hereinafter referred to as a nip) that is disposed to face the driven pressure roller 102 and is in contact with the longitudinal direction.

  A high-frequency magnetic field is generated by applying a high-frequency current to the induction heating coil L1, and the core 1, the core 2 and the core 3 are formed of ferrite or the like having high permeability, and the high-frequency by the induction heating coil L1. A magnetic circuit that organically couples a magnetic field to the inner surface of the fixing roller 100 is configured.

  The magnetic shielding member 150 is made of a material such as pure copper or aluminum having a smaller resistance value than that of the fixing roller 100, and is provided so as to be able to enter and leave a space that forms a magnetic circuit between the inner surface of the fixing roller and the core. Therefore, when the shielding member 150 is retracted from the coupling space, the magnetic flux generated by the induction heating coil L1 is coupled to the inner surface of the fixing roller 100, so that an induced current is generated in the nip portion and the roller surface is heated. When the shielding material 150 exists in the space, the magnetic flux is blocked by the shielding material 150, so that the surface of the roller 100 is hardly heated.

(Configuration and operation example of magnetic shielding member)
FIG. 4 shows an example of the shape of the magnetic field shielding member 150. In this example, three steps of retraction, shielding 1 and shielding 2 are possible with respect to the magnetic flux coupling portion.

  FIG. 5 shows a heating region when the magnetic field shielding member 150 is moved to three positions.

  In FIG. 5A, since the shielding member 150 is in the retracted position, the entire nip portion in the fixing roller longitudinal direction is uniformly heated. However, when the shielding material 150 is positioned as shown in FIGS. 5B and 5C, the regions where the shielding material 150 is contained in the space between the fixing roller 100 and the core 3 are hardly heated.

<Example of Control Circuit of Fixing Device of this Embodiment>
FIG. 1 is a block diagram illustrating a configuration including a drive power supply circuit, a temperature, voltage and current detection circuit, and a power control circuit of the induction heating coil L1 of the fixing device according to the present embodiment.

(Example of drive power control)
The drive power supply circuit 101 includes a power switching element TR1 that is a MOS-FET, an induction heating coil L1 that is a power load of the circuit, and a flywheel diode D5 that regenerates the power accumulated in the induction heating coil L1. It is configured. The temperature detecting element TH1 as temperature detecting means is disposed at a position for detecting the surface temperature of the fixing roller 100 serving as a heating element, and an output Vth1 corresponding to the detected temperature is a temperature via an analog / digital conversion circuit (A / D). It is input to the detection circuit 104. The temperature detection circuit 104 converts the data into temperature data (THERMO_DATA) according to the thermistor voltage data (TH_DATA) and inputs the data to the power control circuit 103.

  On the other hand, the voltage detection circuit 105 measures the input voltage applied to the induction heating power supply 101 via the transformer T1, and inputs it to the power control circuit 103 as voltage data Vs. Similarly, the current detection circuit 106 detects an input current to 101 and inputs it to the power control circuit 103 as current data Is.

  The power control circuit 103 calculates the required input power Pout determined from the difference between the temperature target value and the current temperature (THERMO_DATA), the measured voltage value Vs, the current value Is, and the operation mode, and the drive power supply circuit 101 supplies the input The control signal Vrefdata is determined so as to consume the power Pout, and is controlled to be input to the digital / analog conversion circuit (D / A). Further, the control signal Vrefdata is input as an analog voltage Vref to a pulse modulation oscillation circuit (hereinafter referred to as a PFM resonance control circuit) 102 via a D / A. The PFM resonance control circuit 102 generates a PFM pulse corresponding to the control signal value Vref and outputs it to the gate of the power switching element TR1 to drive the power switching element TR1.

  Next, the operation of the drive power supply circuit will be described.

  When the AC input voltage AC_IN is applied, the AC input voltage becomes a pulsating current rectified by the rectifying elements D1 to D4, and the voltage is applied to both ends of the capacitor C1 through the transformer NF1. At this time, the voltage across the capacitor C1 has a waveform obtained by rectifying the AC input voltage. Further, the transformer NF1 and the capacitor C1 form a noise filter, and are set to constants that ensure a sufficient attenuation with respect to the switching frequency of the power switching element TR1 and pass through the power supply frequency without attenuation. It is supposed to be.

The PFM resonance control circuit 102 generates a rectangular wave PFM signal by comparing the control voltage Vref output from the power control circuit 103 via D / A with the sawtooth wave signal Vsaw. Here, when Vref changes as shown in FIG. 6, the ON / OFF ratio of the PFM signal changes. The PFM signal is applied between the gate and source of the power switching element TR1 via SW1, and the drain current ID flows through the power switching element TR1 to energize the induction heating coil L1. In addition, since the induction heating coil L1 stores the current that flows when the power switching element TR1 is turned on, a reverse electromotive voltage is generated when the power switching element TR1 is turned off, and a forward current is caused to flow through the flywheel diode D5 for storage. The current is charged into the high frequency resonant capacitor C2. After that, when the power switching element TR1 is turned on again, a current flows through the induction heating coil L1, and the current is repeatedly accumulated in the induction heating coil L1, so that the induction heating coil L1 of the load is placed between the high frequency resonant capacitor C2. Resonant current flows.
The current flowing in the power switching element TR1 and the induction heating coil L1 is smoothed by charging and discharging the high frequency component by the high frequency resonant capacitor C2. Therefore, the high frequency current does not flow through the transformer NF1, and only the AC input current rectified waveform flows. Since the current flowing through the rectifier diodes D1 to D4 is a current waveform obtained by filtering the current waveform flowing through the power switching element TR1 and the induction heating coil L1 by a noise filter using the capacitor C1 and the transformer NF1, the AC input current waveform before rectification Becomes an input current waveform having a shape close to an AC input voltage waveform, and the harmonic component contained in the input current is greatly reduced. Further, the transformer NF1 and the capacitor C1 which are noise filters used in the drive power supply circuit may be any filter that exhibits a filter effect with respect to the high frequency oscillation frequency by the PFM resonance control circuit IC1, and the capacitance of the capacitor C1. Since the inductance value of the transformer NF1 can be reduced, the size and weight can be reduced.

  When a temperature adjustment signal is input to the drive power supply circuit for the induction heating coil L1, high frequency AC power having a frequency of about 20 KHz to 100 KHz is generated at the output terminal of the power supply for induction heating. With the above operation, the induction heating coil L1 generates an alternating magnetic field. The AC magnetic field generated in the induction heating coil L 1 passes through the core 1, the core 2, and the core 3, which are ferrite cores, and the high-frequency magnetic flux penetrates the fixing roller 100 through the space between the core 2 and the core 3. By generating an electric current and generating Joule heat on the inner surface of the fixing roller 100, the fixing roller 100 itself generates heat.

  Accordingly, the ON / OFF ratio of the PFM signal generated by the PFM oscillation circuit 102 is determined based on the Vref value set by the power control circuit 103 described above, and the energization time for the coil L1 is determined. The amount of heat generated is also determined. The power consumed in the heating operation is usually about 200 W to several KW in the case of the fixing unit. When the detected temperature at TH1 reaches the target temperature, the power control circuit 103 adjusts the power while keeping the temperature constant, and the printer control unit (not shown) shifts to a printable state.

<Configuration Example of Control Unit for Realizing Temperature Control of this Embodiment>
FIG. 7 shows a configuration example of a control unit that realizes the power control circuit 103.

  The control unit in FIG. 7 includes a CPU 71 for arithmetic control, a RAM 72 that is used as a temporary storage during the processing of the CPU 71, and ROM (or a disk or the like) that stores fixed parameters and programs used by the CPU 71. In this example, the temperature Vth1 of the fixing roller 100 detected by TH1, the power supply voltage Vs detected by the voltage detection circuit 105, and the power consumption current detected by the current detection circuit 106 are input. It has an input interface 74 for inputting Is, and an output interface 75 for outputting control data determined by the processing of the CPU 71, in this example, control data Vref to the resonance control circuit 102.

  Here, the RAM 72 has, as data storage areas, an area 72a for storing the temperature data Vth1 from the temperature sensor TH1, an area 72b for storing the power supply voltage Vs, an area 72c for storing the power consumption current Is, and an area for storing the Vref value. 72d, a region 72e for storing the temperature difference ΔT between the target temperature and the measured temperature, a region 72f for storing the set power Pset directly calculated from ΔT, and a power consumption pout calculated from the power supply voltage Vs and the power consumption current Is. A region 72g for storing the error power perr, which is the difference between the set power Pset and the power consumption pout, a region 72i for storing the corrected power Padj obtained by correcting the set power Pset with the error power perr, and switching the mode of the fixing device ( For example, an area 72j for storing the change of the shielding plate position), an area 72k for storing the current mode, and information SH indicating the current shielding plate position憶 region 72m, a has. The RAM 72 has a program load area when it is configured to load a program from a ROM (external storage device) 73 and execute it by the CPU 71.

  In the ROM 73, in a data storage area, a target temperature (T0, T1,..., Tn) 73a corresponding to each mode, and a correction coefficient Kf73b that is fixedly determined by the efficiency of the drive power supply circuit and the voltage / current detection circuit are stored. , Error power perr (upper limit value PerrMAX, lower limit value PerrMIN) 73c, unit power values Pplus and Pminus 73d for increasing / decreasing error power perr, and table 73e for obtaining set power Pset from temperature difference ΔT (this table value is device specific) Therefore, an experimental value, an empirical value, etc. may be obtained and stored in advance, or an arithmetic expression may be used without using a table.), And a power control value Vref is obtained from the corrected power Padj. Table 73f (Because this table value is unique to the device and D / A characteristics, experimental values, experience values, etc. may be obtained and stored in advance. Even if processing There.) And a. The ROM 73 has an area for storing a fixing roller temperature control program 73g and a power determination module 73h constituting the program as a program storage area.

  Note that only the information used in the present embodiment is shown in the RAM / ROM of FIG. 7, and information used in other processing is omitted. In general, such a control unit is provided independently as a fixing temperature control chip. However, even if this control unit is configured integrally with a control unit that controls the entire fixing device, this control unit further includes image formation. The configuration may be integrated with the control unit of the apparatus.

<Procedure Example 1 for Fixing Roller Temperature Control According to this Embodiment>
Next, an example of the procedure by which the power control circuit 103 determines Vrefdata will be described with reference to the flowchart of FIG.

  At a certain time n, in step S701, the current fixing roller surface temperature Tc calculated from the output Vth1 of the temperature detection element TH1 is compared with the set value To of the heating target temperature to obtain a difference ΔT. In step S702, the set power Pset (n) to be updated is calculated from the difference ΔT. For power calculation at this time, generally known feedback control such as temperature difference → power table conversion or PID control is used.

  Further, in step S703, the currently consumed power Pout (n−1) is obtained from the measured voltage Vs and the current Is by Pout (n−1) = Vs × Is × Kf. Here, Kf is a correction coefficient that is fixedly determined by the efficiency of the drive circuit and the voltage / current detection circuit. Since Pout (n−1) calculated at this time is obtained as a result of driving the drive power supply circuit with the previous set power Pset (n−1), ideally Pout (n−1) = Pset ( There should be n-1). However, as described in the above-mentioned conventional problems, a difference usually occurs due to temperature or the like.

  Therefore, in step S704, the error Perr is calculated from Pset (n-1) and Pout (n-1), and in step S709, Perr is added to the previously calculated set power Pset (n) that is updated this time. Thus, the correction power Padj (n) for conversion to Vrefdata is calculated. However, if Perr exceeds the maximum limit value PerrMAX or the minimum limit value PerrMIN in steps S705 to S708, Perr is set to the maximum (minimum) limit value.

  In step S710, the power value Padj (n) thus obtained is converted into PFM width control data Vrefdata and output. For such conversion, table conversion of corrected power value → control data is desirable.

  By repeatedly performing this power control at regular intervals, it is possible to control the heating and temperature by applying the target power while correcting the error as needed. The time interval at this time is generally about 10 ms to 1 s, although it depends on the temperature rise at the maximum power and the reaction speed of the voltage / electric pole detection circuits 105 and 106. Also, the power error limit values PerrMAX and PerrMin should be set in a range that is considered to be normal due to the temperature coefficient and error variation of the components that make up the magnetic circuit, and it is appropriate to set it to approximately the maximum power × 0.4 to 0.7. is there.

<Procedure Example 2 for Fixing Roller Temperature Control According to this Embodiment>
FIG. 9 is a flowchart of the procedure example 2 of the fixing roller temperature control according to this embodiment. Components similar to those in FIG. 8 are denoted by the same reference numerals.

In step S703, the current power consumption is calculated in the same manner as in FIG. 8. Next, in steps S801 and S803, the actual power consumption is compared with the previous set power Pset (n-1), and the actual power consumption is compared. Is smaller, in step S802, the positive unit correction power amount Pplus is added to the correction power amount Perr (n-1) used last time. On the contrary, if the power consumption is larger, the negative unit correction power amount Pminus is added to the correction power amount Perr (n-1) in the same manner in step S804.

However, if the addition result Perr (n) exceeds the maximum limit value PerrMAX or the minimum limit value PerrMIN as in Procedure Example 1, Perr (n) is set to the maximum (minimum) limit value. When there is an error between the power consumption and the set power in this way, the final power value Padj (n) is obtained in the same manner as in the first embodiment by integrating and correcting the correction power amount, and Vrefdata is calculated as Padj (n). According to the output.

<Procedure Example 3 for Fixing Roller Temperature Control According to this Embodiment>
FIG. 10 is a flowchart of the procedure example 3 of the fixing roller temperature control according to this embodiment. Components similar to those in FIG. 8 or 9 are denoted by the same reference numerals.

After calculating Perr (n) as in Procedure Example 2, it is checked in step S901 whether mode switching has occurred between the previous power calculation and this time. If mode switching has occurred as a result, Perr (n) is initialized (= 0) in step S902. Here, mode switching is as follows. Start-up heating → Print standby
2. Print operation → Print end (standby),
3. Standby target temperature switching,
Such as when the maximum allowable power switches greatly,
4). This is the case when the load characteristics of the coil fluctuate greatly when the shutter position is switched during the printing operation.

  In such a case, it is expected that Perr (n) that has been accumulated and corrected so far cannot follow the fluctuation of the power error, so it is necessary to initialize and recalculate it once.

  The mode switching includes changing the position of the shielding plate of the end portion heating adjustment means. In this example, the end heating adjustment is realized by using a shielding plate, but a method using a plurality of other heating coils and an independent drive power source or a method of changing the position of the core in the coil. However, the end heating adjustment of this embodiment is possible, and such switching is also included in mode switching.

  Further, the present invention can be applied to a system (copier, printer, facsimile machine, etc.) consisting of a single device even if it is applied to a system consisting of a plurality of devices (eg, computer, interface device, reader, printer, etc.). May be.

  Another object of the present invention is to store a storage medium storing a program code for realizing the procedure of the flowchart shown in the above-described embodiment, and a program code stored in the storage medium by a computer (or CPU or MPU) of the system or apparatus. It is also achieved by reading and executing.

  In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention.

  As a storage medium for supplying the program code, for example, a floppy (registered trademark) disk, hard disk, optical disk, magneto-optical disk, CD-ROM, CD-R, magnetic tape, nonvolatile memory card, ROM, or the like is used. be able to.

  Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an OS (operating system) operating on the computer based on the instruction of the program code. A case where part or all of the actual processing is performed and the functions of the above-described embodiments are realized by the processing is also included.

  Further, after the program code read from the storage medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion board is based on the instruction of the program code. Also included is a case where the CPU or the like provided in the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.

It is a figure which shows the structural example of the heating apparatus and power control circuit of an induction heating system of this embodiment. It is a figure which shows the structural example of the laser printer with which this embodiment is applied. 1 is a schematic perspective view of a fixing device in the present embodiment. It is a shape figure of the edge part shielding board in this embodiment. It is a related figure of the edge part shielding board position and roller axial direction heating area | region in this embodiment. It is a figure which shows the example of the drive (PFM) signal generation in this embodiment. It is a block diagram which shows the structural example of the control part which implement | achieves temperature control of this embodiment. It is a flowchart which shows the procedure example 1 of the electric power correction sequence in this embodiment. It is a flowchart which shows the procedure example 2 of the electric power correction sequence in this embodiment. It is a flowchart which shows the procedure example 3 of the electric power correction sequence in this embodiment.

Explanation of symbols

1 Core 2 Core 3 Core 100 Fixing roller (heating member, magnetic metal member)
150 Magnetic shielding member 201 Electrophotographic laser beam printer (image forming apparatus)
207 Fixing device L1 Induction heating coil (magnetic field generating means, coil)
C2 resonant capacitor
D1 ~ D4 Rectifier diode
TR1 Switching element P Recording material
TH1-3 Temperature detection element (temperature detection means)
T1 voltage detection transformer
T2 current detection transformer

Claims (11)

A temperature control method for heating and adjusting a heating member to a predetermined target temperature,
Perform heating adjustment by the power value supplied to the heating means for heating the heating member,
A temperature control method comprising: correcting a power supply target value from a comparison between a power supply target value and an actual power supply value, and controlling the power supply value so as not to exceed at least a predetermined upper limit value.   The temperature control method according to claim 1, wherein the correction of the power supply target value is performed by adding or subtracting a difference between the power supply target value and an actual power supply value.   3. The temperature control method according to claim 2, wherein the correction of the power supply target value is performed by increasing or decreasing an added value corresponding to a difference between a previous power supply target value and an actual power supply value. .   The heating adjustment is a heating adjustment in an induction heating type fixing device including a heating member made of a ferromagnetic material and an exciting coil, which fixes the developer transferred onto the recording medium by pressure heating. 4. The power supply target value is determined based on a temperature detected from a heating member and a target temperature, and the correction is initialized in response to switching of the state of the fixing device. The temperature control method according to any one of the above. A fixing device that fixes a developer transferred onto a recording medium by pressure-contact heating,
Temperature detecting means for detecting the temperature of the heating member;
Power setting means for setting a power supply target value to the heating means for heating the heating member based on the detected temperature of the temperature detecting means;
Power measuring means for measuring the power supply value actually supplied to the heating means,
The fixing device includes: a target power correcting unit that sets a new power supply target value so that the measured power supply value matches the power supply target value.   The fixing device according to claim 5, wherein the target power correction unit adds or subtracts unit correction power according to a difference between the measured power supply value and a set power supply target value power.   The fixing device according to claim 5, wherein the target power correction unit has a correction limit value.   The fixing device according to claim 5, wherein the target power correcting unit is initialized at a timing when an operation mode of the fixing device is changed.   9. The fixing device according to claim 8, wherein the operation modes of the fixing device include an initial startup time, a standby time, and a printing operation time, respectively.   The fixing device according to claim 5, wherein the target power correcting unit is initialized at a timing when an end shielding unit of the fixing device moves. An image forming apparatus having a fixing device that fixes a developer transferred onto a recording medium by pressure heating.
The fixing device;
Temperature detecting means for detecting the temperature of the heating member;
Power setting means for setting a power supply target value to the heating means for heating the heating member based on the detected temperature of the temperature detecting means;
Power measuring means for measuring the power supply value actually supplied to the heating means,
The image forming apparatus, wherein the power setting unit includes a target power correction unit that sets a new power supply target value so that the measured power supply value matches the power supply target value.

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