JP2014044617A - Fixing power supply device, image forming apparatus, and fixing power supply control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To heat a fixing member by induction to an intended temperature by properly performing power output from low power to high power, while preventing the occurrence of hard switching.SOLUTION: A fixing power supply unit 50 includes: a voltage step-down circuit 54 that receives an AC voltage of an AC power supply power ACP or a voltage subjected to full-wave rectification by a full-wave rectifier circuit 35 as an input voltage, and outputs a step-down voltage obtained by stepping down the input voltage or the input voltage as an output voltage to an induction heating inverter 57; and a switching element 58 that switch-drives the induction heating inverter 57 in an on-width of a switching signal S from a CPU 56 to heat a fixing roller by induction. The CPU 56 determines the on-width of the switching signal S output to the switching element 58 and a voltage value of the voltage output from the voltage step-down circuit 54, on the basis of the surface temperature of the fixing roller and the power value of the AC power supply power ACP detected by an AC voltage detection circuit 51 and an AC current detection circuit 52.

Description

  The present invention relates to a fixing power supply device, an image forming apparatus, and a fixing power supply control method, and more particularly, a fixing member that appropriately performs power output from low power to high power while preventing occurrence of hard switching. The present invention relates to a fixing power source apparatus that performs induction heating to a temperature, an image forming apparatus, and a fixing power source control method.

  An image forming apparatus that forms an image by an electrophotographic method forms an electrostatic latent image by irradiating a uniformly charged photosensitive member with writing light modulated by image data, thereby forming a static image formed on the photosensitive member. The electrostatic latent image is developed with toner in the developing unit, and the timing is adjusted by the registration roller from the paper feed unit and conveyed between the photosensitive member and the transfer roller. The toner image is formed on the sheet by transferring the toner image on the photosensitive member by applying the transfer bias (voltage, current). The electrophotographic image forming apparatus transports the toner image-transferred paper with the fixing unit, the fixing roller and the heating roller while heating and pressurizing the paper on which the toner image is transferred. Is fixed on the paper.

  In some cases, the fixing unit uses an IH (Inducing Heating) system as one of the heating methods of the fixing roller. The induction heating system fixing unit is mainly used as a power source unit for induction heating. A voltage resonance inverter or a current resonance inverter is used.

  This inverter is equipped with a resonance capacitor, and an alternating current is passed through the induction heating coil by utilizing the resonance operation between the induction heating coil connected to the inverter and the strong vibration capacitor.

  The induction heating type fixing unit generates a magnetic field by causing an alternating current to flow through a conducting wire such as an induction heating coil, and causes an eddy current to flow through a fixing roller disposed near the induction heating coil to generate heat. . The induction heating type fixing unit using an inverter causes the inverter to perform switching control with a switching element to perform a resonance operation, and the current flowing in the induction heating coil, that is, the input power, is changed depending on the time (ON width) when the switching element is turned on. Adjust and heat the fixing roller to the desired fixing temperature.

  In an induction heating type fixing unit, a switching element is generally controlled by a CPU (Central Processing Unit), and input power is required from several hundred W (watts) to several KW. The power is controlled by controlling the width.

  However, the conventional induction heating type fixing unit uses an inverter as a power supply unit to perform power control by on-width control of the switching element, but when the switching element on-time is short (the input power is small), There has been a problem that element destruction due to switching loss (hard switching) may occur when switching on / off of the switching element.

  For example, when a grounded-emitter power transformer is used as a switching element, if the on-time of the switching element is short, the voltage resonance between the resonant capacitor and the induction heating coil is weak, and the collector-emitter of the switching element There is a tendency for hard switching, which is a resonance in which the switching element is turned on before the voltage (Vce) decreases to 0V. Under this hard switching condition, the switching loss increases, the loss increases the heat generation of the switching element, the temperature of the switching element rises above the junction temperature at which the switching element breaks down, and the element breaks down .

  In other words, in an ideal inverter resonance operation, when the switching element is turned on, the Vce of the switching element needs to drop to almost 0 V (switching loss≈0). However, in power control in which the ON width is controlled to be short, in the hard switching region, the switching element is turned on before Vce drops to 0 V, and the switching element may be destroyed. There is a problem that it is difficult to finely control power from several hundred W to several KW.

  Conventionally, a rectifying means for full-wave rectification of an AC power supply, a resonance circuit composed of an induction heating coil and a resonance capacitor, a switching element for driving the resonance circuit, and an ON width control means for controlling the ON width of the switching element And zero cross detection means for detecting the zero cross of the AC power supply, the on-width control is performed in a predetermined half wave period of the commercial power supply based on the detection output and the set power of the zero cross detection means, and another half wave period Has proposed an induction heating power supply device characterized by having on-width control driving means for turning off the switching element during the on-time control without performing the on-width control (see Patent Document 1).

  That is, this prior art performs on / off control of the switching element in units of half-wave of the AC power source based on the output of the zero cross detection means for detecting the point where the AC of the power source becomes 0V, and thereby the wave number of the inverter output Control is performed to achieve small power output in a step-like manner by on-width control and wave number control.

  However, in the prior art described in the above publication, on / off control of the switching element is performed in half-wave units of the AC power supply based on the output of the zero cross detection means for detecting the point where the AC of the power supply becomes 0V. Therefore, since the control is performed in half-wave units, there is a problem that the output on the low power side cannot be finely controlled.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to perform induction heating of a fixing member to an intended temperature by appropriately and finely outputting power from low power to high power while preventing occurrence of hard switching.

  In order to achieve the above object, the fixing power supply apparatus according to claim 1 is configured to input a rectifying unit for full-wave rectification of AC power supply power, and an AC voltage of the AC power supply power or a voltage after full-wave rectification by the rectification unit. A predetermined step-down voltage obtained by stepping down the input voltage, or a voltage step-down means for outputting the input voltage as an output voltage, and a fixing member for fixing the recording agent image on the recording medium onto which the recording agent image is transferred Temperature detecting means for detecting the surface temperature of the voltage, and resonance means that is supplied with the output voltage of the voltage step-down means and is driven to resonate and induces a high frequency magnetic field corresponding to the output voltage to the fixing member to heat it, Based on the switching element that resonates by switching driving the resonance means with a predetermined on-width, and the surface temperature of the fixing member detected by the temperature detection means, A control means for determining a voltage value of the output voltage by the width and the voltage step-down means, driving the switching element with the stepping width, and controlling a voltage step-down operation by the voltage step-down means. It is characterized by.

  According to the present invention, the fixing member can be induction-heated to an intended temperature by appropriately and finely outputting power from low power to high power while preventing occurrence of hard switching.

1 is a schematic configuration diagram of a main part of an image forming apparatus to which an embodiment of the present invention is applied. The circuit block diagram of the fixing power supply part provided with the voltage step-down circuit in the back | latter stage of a full wave rectifier circuit. Operation | movement explanatory drawing of an induction heating inverter. The circuit block diagram of the fixing power supply part provided with the voltage step-down circuit in the front | former stage of a full wave rectifier circuit. The detailed circuit block diagram of the fixing power supply part provided with the voltage step-down circuit of the resistance voltage dividing system in the back | latter stage of a full wave rectifier circuit. The detailed circuit block diagram of the fixing power supply part provided with the voltage step-down circuit of the resistance voltage dividing system in the front | former stage of a full wave rectifier circuit. The detailed circuit block diagram of the fixing power supply part provided with the other voltage step-down circuit of a resistance voltage-dividing system in the back | latter stage of a full wave rectifier circuit. The detailed circuit block diagram of the fixing power supply part provided with the voltage step-down circuit of a transformer system in the back | latter stage of a full wave rectifier circuit. The detailed circuit block diagram of the fixing power supply part provided with the voltage step-down circuit of a transformer system in the front | former stage of a full wave rectifier circuit. The detailed circuit block diagram of the fixing power supply part provided with the other voltage step-down circuit of a transformer system in the back | latter stage of a full wave rectifier circuit. The detailed circuit block diagram of the fixing power supply part provided with the voltage step-down circuit of the insulation type forward converter system in the back | latter stage of a full wave rectifier circuit. The circuit block diagram of the voltage step-down circuit of an insulation type half bridge converter system. The circuit block diagram of the voltage step-down circuit of an insulation type full bridge converter system. The figure which shows the relationship between the ON width of the switching signal in normal voltage, and output electric power. The figure which shows the collector-emitter voltage and coil current when the ON width | variety of a switching signal is wide. The figure which shows the collector-emitter voltage and coil current in a hard switching state. The figure which shows the relationship between the ON width of the switching signal in a step-down voltage, and output electric power. The figure which shows the state which the ON width controllable area has expanded by adjustment of the input voltage to an induction heating inverter.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, since the Example described below is a suitable Example of this invention, various technically preferable restrictions are attached | subjected, However, The range of this invention is unduly limited by the following description. However, not all the configurations described in the present embodiment are essential constituent elements of the present invention.

  1 to 18 are diagrams showing an embodiment of a fixing power source apparatus, an image forming apparatus, and a fixing power source control method according to the present invention. FIG. 1 is a schematic configuration diagram of a main part of an image forming apparatus 1 to which an embodiment of a method is applied.

    In FIG. 1, an image forming apparatus 1 includes a paper feeding unit 10, a conveyance belt mechanism unit 20, yellow (Y), magenta (M), and the like disposed along a conveyance belt mechanism unit 20 in a main body housing (not shown). The image forming units 30Y, 30M, 30C, and 30K for each color of cyan (C) and black (K), the fixing unit 40, and the like are provided. A drive mechanism unit that transmits a drive source, an operation display unit, and the like are provided.

  The paper supply unit 10 includes a paper supply cassette 11, a paper supply roller 12, a separation roller 13, and a registration roller (not shown). The paper feed unit 10 separates the paper (recording medium) P in the paper feed cassette 11 one by one by the paper feed roller 12 and the separation roller 13 and sends the paper to the registration roller. The timing adjustment of the paper P sent from is performed, and the paper P is sent to the transport belt mechanism unit 20 at a predetermined timing.

  The transport belt mechanism unit 20 includes a transport belt 21, a driving roller 22, a driven roller 23, a guide plate 24, and the like. The transport belt 21 is an endless ring-shaped belt, and includes a driving roller 22 and a driven roller 23. It is stretched out. The transport belt mechanism unit 20 is rotated in the counterclockwise direction indicated by an arrow in FIG. 1 by the drive roller 22 being rotated by a drive mechanism such as a motor (not shown) under the control of a control unit (not shown). Then, the conveyance belt 21 is sequentially conveyed to the image forming units 30Y, 30M, 30C, and 30K for each color by conveying the paper P that is fed from the paper feeding unit 10 and guided to the conveyance belt 21 by the guide plate 24. The toner images (developer images) of the respective colors of yellow toner image, magenta toner image, cyan toner image, and black toner image are sequentially applied to the paper P by the image forming units 30Y, 30M, 30C, and 30K for each color. Overlaid and transferred, a color toner image is formed.

  In each color image forming section (image forming means) 30Y, 30M, 30C, 30K, the photosensitive bodies 31Y, 31M, 31C, 31K are arranged at predetermined intervals along the transport direction of the transport belt 21, and the respective photoreceptors. Around the periphery of 31Y, 31M, 31C, 31K, charging units 32Y, 32M, 32C, 32K, exposure units 33Y, 33M, 33C, 33K, developing units 34Y, 34M, 34C, 34K, transfer units 35Y, 35M, 35C, 35K In addition, cleaning units 36Y, 36M, 36C, and 36K, a neutralizing unit (not shown), and the like are provided.

  Each of the image forming units 30Y, 30M, 30C, and 30K includes photosensitive members 31Y, 31M, 31C, and 31K that are driven to rotate clockwise in FIG. 1 by a driving mechanism (not shown), and charging units 32Y, 32M, 32C, and 32K. The photosensitive members 31Y, 31M, 31C, and 31K are irradiated with writing light that is uniformly charged and modulated by the image data of each color from the exposure units 33Y, 33M, 33C, and 33K, thereby forming an electrostatic latent image. The YMCK toners are attached to the photoreceptors 31Y, 31M, 31C, and 31K on which the electrostatic latent images are formed by the developing units 34Y, 34M, 34C, and 34K, thereby forming the toner images of the respective colors. To do. The image forming units 30Y, 30M, 30C, and 30K are disposed on the back surface of the conveyance belt 21 when the sheet P is conveyed between the conveyance belt 21 and the photoreceptors 31Y, 31M, 31C, and 31K. The transfer units 35Y, 35M, 35C, and 35K apply transfer potentials, and transfer the YMCK toner images of the respective colors on the photoreceptors 31Y, 31M, 31C, and 31K to the paper P in order. The photoreceptors 31Y, 31M, 31C, and 31K, to which the toner image has been transferred, are cleaned by the cleaning units 36Y, 36M, 36C, and 36K, and after being neutralized by the neutralization unit, the charging units 32Y, 32M, Charged by 32C and 32K and used for the next image forming operation.

  The sheet P on which the color image is formed by sequentially superimposing and transferring the toner images of each color of YMCK as described above is further conveyed by the conveying belt 21 while being electrostatically attracted to the conveying belt 21. Thus, it is separated from the conveyor belt 21 at the drive roller 22 and is conveyed to the fixing unit 40.

  The fixing unit 40 includes a fixing roller (fixing member) 41, a pressure roller 42, a thermistor 43, a thermostat 44, an induction heating coil 57L (see FIG. 2), a relay circuit, a discharge roller pair, and the like. The fixing roller 41 and the pressure roller 42 are pressed with a predetermined pressing force, and one of them is rotationally driven, and the other is rotated. The fixing roller 41 is energized to correspond to the energization amount. An induction heating coil 57L (heat generating means) that heats the fixing roller 41 to a temperature is disposed in close proximity, and the ON width of the induction alternating current to the induction heating coil 57L is controlled, so that the induction heating is performed to a predetermined fixing temperature. Be controlled.

  The fixing unit 40 transfers the color toner image in which each color of YMCK is superimposed, and heats and presses the paper P conveyed by the conveyance belt 21 by the fixing roller 41 and the pressure roller 42, thereby the color toner image. Is fixed on the paper P and discharged onto a paper discharge tray (not shown) by a pair of paper discharge rollers.

  The thermistor (temperature detection means) 43 is disposed in the vicinity of the fixing roller 41, detects the surface temperature of the fixing roller 41, and outputs an analog voltage value detection temperature signal.

  The thermostat 44 is connected to the power line to the induction heating coil 57L in the vicinity of the fixing roller 41. When the temperature rises above a predetermined cutoff temperature, the thermostat 44 is turned off to cut off the energization to the induction heating coil. .

  Each of the exposure units 33Y, 33M, 33C, and 33K includes, for example, an LED (Light Emitting Diode) array head for each color of YMCK, and the LEDs are controlled to be turned on according to the image data of each color of YMCK. The photoconductors 31Y, 31M, 31C, and 31K are irradiated with writing light.

  As shown in FIG. 2, the image forming apparatus 1 includes a fixing power source unit (fixing power source device) 50 that performs power control of the fixing unit 40. The fixing power supply unit 50 includes an AC voltage detection circuit 51, an AC current detection circuit 52, a full-wave rectification circuit 53, a voltage step-down circuit 54A, an LC filter 55, a CPU (Central Processing Unit) 56, an induction heating inverter 57, a switching element 58, and the like. The commercial AC power supply ACP is supplied to the full-wave rectifier circuit 53.

  The full-wave rectifier circuit (rectifier means) 53 is a normal full-wave rectifier circuit using a diode bridge or the like, and full-wave rectifies the commercial AC power supply ACP and applies it via the voltage step-down circuit 54A and the LC filter 55. The voltage Vi is supplied to the induction heating inverter 57.

  The AC voltage detection circuit 51 detects the voltage value of the commercial AC power supply ACP supplied to the full-wave rectification circuit 53 and outputs the detected voltage value to the CPU 56. The AC current detection circuit 52 is the full-wave rectification circuit 53. Is detected and the detected current value is output to the CPU 56. The AC voltage detection circuit 51 and the AC current detection circuit 52 function as power value detection means for detecting the power value of the commercial AC power supply power ACP as a whole.

  A voltage step-down circuit (voltage step-down means) 54A is a step-down DC voltage obtained by stepping down the DC power supply voltage (input voltage) that has been full-wave rectified by the full-wave rectifier circuit 53 based on a step-down instruction signal from the CPU 56, or an input voltage. Is supplied to the induction heating inverter 57 as an applied voltage (output voltage) Vi through the LC filter 55 as an output voltage. The voltage step-down circuit 54A will be described in detail later.

  The LC filter 55 includes a resonance coil 55L and a resonance capacitor 55C, and selectively removes noise having a frequency corresponding to the reactance of the resonance coil 55L and the resonance capacitor 55C and supplies the noise to the induction heating inverter 57.

  The induction heating inverter (resonance means) 57 is a voltage resonance type inverter and includes a resonance capacitor 57C, an induction heating coil 57L, and the like, and is resonated by a switching element 58 such as a switching transistor having a common emitter.

  Although not shown in FIG. 2, the CPU (control means) 56 receives a detected temperature signal from the thermistor 43, compares the fixing temperature stored in advance in a ROM (Read Only Memory) or the like (not shown), etc. The induction power induced by the heating coil 57L with respect to the fixing roller 41 is determined, the determined induction power and the power value that is the step-down DC voltage output from the voltage step-down circuit 54A, the AC voltage detection circuit 51, and the AC The on-width of the switching element 58 corresponding to the detected voltage value detected by the current detection circuit 52 and the detected current value is determined with reference to a table stored in advance in a ROM or the like, and the switching signal S having the on-width is switched. Output to the base of the element 58.

  In the induction heating inverter 57, as shown in FIG. 3, when the switching element 58 receives the switching signal S from the CPU 56, the coil current in the direction indicated by the arrow in the induction heating coil 57L while the switching signal S is on. As Il flows, charge is accumulated in the resonance capacitor 57C, and while the switching signal S is OFF, the charge accumulated in the resonance capacitor 57C is discharged through the induction heating coil 57, whereby a current flows in the direction opposite to the arrow. Voltage resonance occurs.

  In the induction heating inverter 57, when the switching element 58 is repeatedly turned on / off, an alternating current flows through the induction heating coil 57L and charges are accumulated in the resonance capacitor 57C. The charges in the resonance capacitor 57C are discharged through the induction heating coil 57L. Repeatedly, voltage resonance occurs between the induction heating coil 57L and the resonance capacitor 57C, a magnetic field is generated in the induction heating coil 57L, and an eddy current is generated in the fixing roller 41 disposed near the induction heating coil 57l. To generate heat.

  Note that the voltage step-down circuit 54A does not have to be arranged at the subsequent stage of the full-wave rectifier circuit 53, and may be arranged as the voltage step-down circuit 54B at the front stage of the full-wave rectifier circuit 53 as shown in FIG. Good. In this case, voltage step-down circuit 54B steps down the voltage of commercial power supply power ACP and outputs it to full-wave rectifier circuit 53.

  The voltage step-down circuit 54A and the voltage step-down circuit 54B include, for example, resistors RaA and RbA and switching elements TraA and TrbA as shown in FIG. 5 for the voltage step-down circuit 54A and in FIG. 6 for the voltage step-down circuit 56B, respectively. The voltage of the commercial power supply ACP can be reduced by bypassing or connecting the resistors RaB and RbB by turning the switching elements TraB and TrbB on and off. The voltage rectified by the full-wave rectifier circuit 53 is used as an input voltage, and the input voltage is directly subjected to induction heating via the LC filter 55 as the output voltage, or the step-down voltage obtained by dividing the voltage by the voltage step-down circuits 54A and 54B. The applied voltage Vi is supplied to the inverter 57.

  Then, the CPU 56 controls the on / off of the switching elements TraA and TrbA and the switching elements TraB and TrbB. The switching ON width of the switching element 58 described later decreases to the collector-emitter voltage Vce of the switching element 58 of 0 V. When the hard switching width is narrowed to a width that does not increase, the hard voltage switching circuit 54A, 54B steps down the input voltage and outputs it to the induction heating inverter 57 via the LC filter 55 so as to prevent the hard switching. That is, in the voltage step-down circuits 54A and 54B, when the input voltage is used as it is as the output voltage, the switching elements TraA and TrbB are turned on and the switching elements TrbA and TrbB are turned off by the CPU 56, so that the resistors RaA and RaB do not flow. That is, an input voltage that does not drop is defined as an output voltage. On the other hand, when the voltage drops in the voltage step-down circuits 54A and 54B, the switching elements TraA and TrbB are turned off and the switching elements TrbA and TrbB are turned on by the CPU 56, thereby flowing through the resistors RaA and RaB and the resistors RbA and RbB. The divided step-down voltage (divided voltage) is used as the output voltage.

  The voltage dividing circuits 54A and 54B of the resistance voltage dividing system shown in FIGS. 5 and 6 divide the input voltage by using the two resistors RaA and RbA and the two resistors RaB and RbB to obtain an output voltage. However, the present invention is not limited to one using two resistors. For example, in the case of the voltage step-down circuit 54A, as shown in FIG. 7, three resistors RaA, RbA, RcA are used, and the resistors RaA, RbA, The switching element TraA, TrbA, TrcA is connected in parallel with or in series with RcA, and the on / off control of each switching element TraA, TrbA, TrcA is performed by the CPU 56, so that the output voltage is more finely divided. Thus, hard switching of the switching element 58 that switches the induction heating inverter 57 may be prevented.

  Further, the voltage step-down circuit 54A and the voltage step-down circuit 54B include, for example, a transformer TA and a transformer TB and transformers TA and TB as shown in FIG. 8 for the voltage step-down circuit 54A and in FIG. 9 for the voltage step-down circuit 54B, respectively. A transformer system including a switching element TrdA and a switching element TrdB that switch the outlet of the secondary winding may be used. The transformer type voltage step-down circuit 54A and voltage step-down circuit 54B are controlled by the CPU 56 so that the switching element TrdA and the switching element TrdB are prevented from being hard-switched by the switching element 58 that switches the induction heating inverter 57. Then, the output voltage is adjusted by switching the outlet of the secondary winding of the transformers TA and TB.

  Note that the transformer voltage step-down circuits 54A and 54B shown in FIGS. 8 and 9 are not limited to those in which the secondary side extraction port of the transformers TA and TB is switched to two stages by one switching element TrdA and TrdB. For example, in the case of the voltage step-down circuit 54A, as shown in FIG. 10, two switching elements TrdA and a switching element TreA are provided on the secondary side, and on / off control of these switching elements TrdA and TreA is performed by the CPU 56. And the winding outlet may be switched to three. In this case, as the switching element TrdA and the switching element TreA that are turned on increase, the number of windings of the secondary side winding decreases, and when the secondary side output voltage is output without being stepped down, Turn off TrdA and TreA.

  Further, the voltage step-down circuit 54A and the voltage step-down circuit 54B are connected in series to the primary winding of the transformer TA and the transformer TA and controlled to be turned on / off by the CPU 56, for example, as shown for the voltage step-down circuit 54A in FIG. Switching element TrfA, the capacitor Ca connected between the primary windings of the transformer TA, the secondary winding of the transformer TA and the resonance coil 55L connected to the resonance coil 55L of the LC filter 55 respectively. An insulating forward converter system including diodes Da and Db in the forward direction may be used. In this insulated forward converter type voltage step-down circuit 54A, when the input voltage is smoothed by the capacitor Ca and the switching element TrfA is turned on, the primary side current of the transformer TA increases and the primary side current increases. The secondary side current of the transformer TA increases. Insulated forward converter type voltage step-down circuit 54A includes an induction heating inverter in which a secondary current induced by a primary current of transformer TA when switching element TrfA is turned on passes through a resonant coil 55L of diode DA and LC filter 55. When the resonant capacitor 57C is charged and the switching element TrfA is turned off and the secondary current of the transformer TA is stopped, the charge of the resonant capacitor 57C of the LC filter 55 flows back through the diode Db and the resonant coil 55L. To do.

  This isolated forward converter type voltage step-down circuit 54A is configured such that the number of turns of the primary winding of the transformer TA is Np, the number of turns of the secondary winding is Ns, the primary voltage is V1, and the secondary voltage is When the duty ratio by the CPU 56 of V2 and the switching element TrfA is D (= ton / T), the secondary voltage V2 is given by the following equation (1).

V2 = D × Ns / Np × V1 (1)
That is, in the voltage step-down circuit 54A of the insulation type forward converter system, the output voltage changes as the CPU 56 adjusts the duty ratio D of the switching element TrfA.

  Further, the voltage step-down circuit 54A and the voltage step-down circuit 54B are not limited to the voltage step-down circuits of the above-described methods, and various types of voltage step-down circuits can be used. For example, an insulation type half circuit as shown in FIG. A bridge converter system or an insulation type full bridge converter system shown in FIG. 13 may be used.

  Insulated half-bridge converter type voltage step-down circuits 54A and 54B shown in FIG. 12 include a transformer T1, switching elements Tr1 and Tr2, input-side diodes Di1 and Di2, input-side capacitors C1 and C2, and a divided secondary-side winding. The output side diodes Do1, Do2 and the like connected to the lines are provided, and the switching element Tr1 and the switching element Tr2 are alternately turned on by the CPU 56 in the on time (ton). The voltage drop circuits 54A and 54B of the insulated half bridge converter system are configured such that the switching element Tr1 and the switching element Tr2 are divided into ½, and the transformer T1 is turned on when one of the switching elements Tr1 and the switching element Tr2 is on. Is given a value of ½ of the input voltage. The voltage drop circuits 54A and 54B of the insulated half bridge converter system are configured such that the number of turns of the primary side winding of the transformer T1 is Np, the number of turns of the secondary side winding is Ns, and the primary side voltage is V1 and secondary. When the side voltage is V2 and the duty ratio of the switching elements Tr1 and Tr2 is D (= ton / T), the secondary voltage V2 is given by the following equation (2).

V2 = D × Ns / Np × V1 (2)
Therefore, the output voltage of the voltage drop circuits 54A and 54B of the insulated half bridge converter system changes as the duty ratio of the switching elements Tr1 and Tr2 is adjusted by the CPU 56.

  Insulated full bridge converter type voltage step-down circuits 54A and 54B shown in FIG. 13 include a transformer T1, primary four switching elements Tr1, Tr2, Tr3, Tr4, input side diodes Di1, Di2, Di3, Di4, 2 The output side diodes Do1, Do2 and the like connected to the divided secondary windings are provided, and the switching element Tr1, the switching element Tr4, the switching element Tr2, and the switching element Tr3 are turned on by the CPU 56. Each time it is turned on alternately. The isolated full-bridge converter type voltage step-down circuits 54A and 54B operate on the same principle of operation as the isolated half-bridge converter type voltage step-down circuits 54A and 54B, and output the same output voltage.

  In the case of the voltage step-down circuits 54A and 54B using the transformer shown in FIG. 8 to FIG. 13, noise and surge voltage (abnormal voltage) from the commercial AC power supply power ACP are transmitted to the induction heating inverter 57 and the CPU 56. Can be prevented.

The image forming apparatus 1, ROM, EEPROM (Electrically Erasable and Programmable Read Only Memory), EPROM, flash memory, flexible disk, CD-ROM (Compact Disc Read Only Memory), CD-RW (Compact Disc Rewritable), DVD ( A fixing power supply control program for executing the fixing power supply control method of the present invention recorded on a computer-readable recording medium such as a digital versatile disk (SD), a secure digital (SD) card, or an MO (Magneto-Optical Disc) is read. Fixing power supply control that inductively heats the fixing member to an intended temperature by appropriately performing power output from low power to high power while preventing the occurrence of hard switching, which will be described later, by introducing it into a nonvolatile memory such as a ROM It is constructed as an image forming apparatus equipped with a fixing power supply unit 50 for executing the method. The fixing power supply control program is a computer-executable program written in a legacy programming language such as assembler, C, C ++, C #, Java (registered trademark), an object-oriented programming language, or the like, and is stored in the recording medium. And can be distributed.

  Next, the operation of this embodiment will be described. The image forming apparatus 1 according to this embodiment performs induction heating of the fixing roller 41 to an intended temperature by appropriately and finely outputting power from small power to large power while preventing occurrence of hard switching.

  That is, the image forming apparatus 1 separates the sheets P from the sheet feeding unit 10 one by one and sends them to the conveyance belt mechanism unit 20, and the conveyance belt mechanism unit 20 adsorbs the sheet P on the conveyance belt 21. The images are sequentially conveyed to the image forming units 30Y, 30M, 30C, and 30K arranged along the conveyance belt 21.

  The image forming apparatus 1 forms a color toner image by sequentially superimposing and transferring the toner images of each color on the paper P transported on the transport belt 21 by the image forming units 30Y, 30M, 30C, and 30K. The paper P on which the toner image is transferred is sent to the fixing unit 40.

  The fixing unit 40 heats and presses the sheet P onto which the toner image is transferred and is transported by the transport belt 21 with a fixing roller 41 and a pressure roller 42 that are heated to a fixing temperature by a fixing heater. The color toner image is fixed on the paper P and discharged onto a paper discharge tray (not shown) by a pair of paper discharge rollers.

  In the image forming apparatus 1, during image formation, the fixing control unit 50 appropriately outputs power from small power to large power while preventing the occurrence of hard switching, and induces the fixing roller 41 to an intended temperature. Heat.

  That is, the fixing temperature control unit 50 determines the on time ton of the switching signal S output from the CPU 56 to the switching element 58 of the induction heating inverter 57 based on the detected temperature signal from the thermistor 43 that detects the surface temperature of the fixing roller 41. And the induction heating coil 57L heats the fixing roller 41 to the intended fixing temperature by the induced electromotive force induced in the fixing roller 41.

  That is, the CPU 56 receives the detected temperature signal from the thermistor 43 and compares the fixing temperature stored in advance in a ROM or the like (not shown) to determine the induced power induced by the induction heating coil 57L to the fixing roller 41. Then, the determined induced power and the step-down DC voltage output from the voltage step-down circuit 54, and the detected voltage value and the detected current value detected by the AC voltage detection circuit 51 and the AC current detection circuit 52, that is, the commercial AC power supply The ON width of the switching element 58 corresponding to the power value of the power ACP is determined with reference to a table stored in advance in a ROM or the like, and the switching signal S having the ON width is output to the base of the switching element 58.

  In the induction heating inverter 57, as shown in FIG. 3, when the switching element 58 receives the switching signal S from the CPU 56, the direction indicated by the arrow on the induction heating coil 57L while the switching signal S is on. When the coil current Il flows, the electric charge is accumulated in the resonance capacitor 57C, and the electric charge accumulated in the resonance capacitor 57C is discharged through the induction heating coil 57L while the switching signal S is OFF. A voltage resonance occurs in which a current flows.

  When the switching element 58 is repeatedly turned on and off, an alternating current flows through the induction heating coil 57L and voltage resonance occurs, thereby generating a magnetic field and causing a vortex in the fixing roller 41 disposed near the induction heating coil 57l. Apply current to generate heat.

  That is, as shown in FIG. 14, the CPU 56 generates a control signal that does not cause the voltage step-down circuits 54A and 54B to step down the voltage when the induction heating inverter 57 generates a large amount of power and heats the fixing roller 41. A normal voltage, that is, a DC voltage that is full-wave rectified by the full-wave rectifier circuit 53 and filtered by the LC filter 55, for example, 100 V, is input to the induction heating inverter 57 as the applied voltage Vi, and the switching element 58 A switching signal S having a predetermined ON width required for induction heating of the fixing roller 41 is output. In the ON width with this high power heating, as shown in FIG. The emitter-to-emitter voltage Vce is 0V, and the coil current Il normally flows through the induction heating coil 57L. The fixing roller 41 is induction heating.

  However, as shown in FIG. 16, when the required induction heating power is reduced and the CPU 56 reduces the ON width (ton) of the switching signal S output to the switching element 58, the collector-emitter of the switching element 58. Before the tube voltage Vce drops to 0V, the switching signal S is turned on, and the hard switching state indicated by the broken line in FIG. That is, when the applied voltage Vi inputted is a normal voltage (for example, 100 V), the induction heating inverter 57 reaches the hard switch state as the output power from about 1500 W to about 600 W as shown in FIG. However, when the output power is smaller than 600 W, the on-width of the switching signal S to the switching element 58 enters the hard switching region where hard switching occurs.

  Therefore, as shown in FIG. 17, the CPU 56 outputs power (600 W in FIG. 14) in which the ON width of the switching signal S to the switching element 58 is a hard switching region when the applied voltage Vi to the induction heating inverter 57 is a normal voltage. ) Is output from the output power larger than the output voltage to the voltage step-down circuits 54A and 54B, that is, the step-down voltage (for example, 80V) is reduced to the induction heating inverter 57 so as to reduce the switching loss. Is supplied as an applied voltage Vi.

  When the applied voltage Vi of the induction heating inverter 57 is lowered to the step-down voltage, the switching element 58 has a timing at which the switching signal S is turned on, even if the switching signal S is turned on at a normal voltage. The collector-emitter voltage is reduced to 0V, and hard switching is not performed.

  For example, when the input voltage is 80 V, the switching element 58 can perform the switching process without generating hard switching up to the signal width of the switching signal S whose output power is about 100 W. In this case, the maximum value of the output power is the maximum output power at the normal voltage (for example, 1500 W in the case of FIG. 14), but decreases to, for example, 800 W as shown in FIG. However, if there is a region where the maximum power at the lower limit of the hard switching occurrence region at the normal voltage and the maximum power at the step-down voltage overlap, by appropriately setting the timing to step down the voltage, as shown in FIG. By performing the step-down operation, the switching element 58 can be appropriately switched even in the switching signal ON width which has been a hard switching region at a normal voltage, and necessary output power can be ensured.

  As described above, in the image forming apparatus 1 according to the present exemplary embodiment, the fixing power supply unit (fixing power supply device) 50 has a full-wave rectifier circuit (rectifier unit) 53 that performs full-wave rectification of the AC power supply power, and an alternating current of the AC power supply power. A voltage or a voltage step-down circuit (voltage step-down means) 54 that outputs the voltage or the voltage after full-wave rectification by the full-wave rectification circuit 35 as an input voltage and outputs a predetermined step-down voltage obtained by stepping down the input voltage or the input voltage as an output voltage; A thermistor (temperature detecting means) 43 for detecting the surface temperature of a fixing roller (fixing member) 41 for fixing the toner image on a sheet (recording medium) P on which a toner image (recording agent image) is transferred; The output voltage of the step-down circuit 54 is supplied and resonantly driven, and an induction heating inverter (resonance means) 57 that induces and heats the fixing roller 41 with a high frequency magnetic field corresponding to the output voltage, and induction heating in The switching element 58 that resonates by switching the data 57 with a predetermined ON width, and the output of the ON width of the switching element 58 and the voltage step-down circuit 54 based on the surface temperature of the fixing roller 41 detected by the thermistor 43. A CPU (control means) 56 that determines the voltage value of the voltage, drives the switching element 58 with the ON width, and controls the voltage step-down operation by the voltage step-down circuit 54 is provided.

  Therefore, the ON width of the switching element 58 and the voltage value of the output voltage by the voltage step-down circuit 54 can be determined based on the surface temperature of the fixing roller 41, and full-wave rectification and a step-down voltage are used as necessary. Thus, the fixing roller 41 can be induction-heated to an intended temperature by appropriately performing power output from low power to high power while preventing occurrence of hard switching of the switching element 58. Further, the CPU 56 controls the ON width when the voltage is stepped down, so that the output can be finely controlled in the low power range.

  Further, in the image forming apparatus 1 of the present embodiment, the fixing power supply unit 50 has a rectification processing step for full-wave rectification of AC power supply power and an AC voltage of the AC power supply power or after full-wave rectification by the rectification processing step. A predetermined step-down voltage obtained by stepping down the input voltage using the voltage as an input voltage, or a voltage step-down processing step for outputting the input voltage as an output voltage, and fixing for fixing the toner image on the paper P on which the toner image is transferred The temperature detection processing step for detecting the surface temperature of the roller 41 and the output voltage of the voltage step-down processing step are supplied and driven to resonate, and the fixing roller 41 is heated by inducing a high-frequency magnetic field corresponding to the output voltage. A resonance processing step, a switching processing step in which the resonance processing step is driven to switch at a predetermined ON width to resonate, and the temperature detection Determining the ON width of the switching processing step and the voltage value of the output voltage in the voltage step-down processing step based on the surface temperature of the fixing roller 41 detected in the control step, and performing the switching processing step with the ON width. And a control processing step for controlling the voltage step-down operation by the voltage step-down processing step.

  Therefore, the ON width of the switching element 58 and the voltage value of the output voltage by the voltage step-down circuit 54 can be determined based on the surface temperature of the fixing roller 41, and full-wave rectification and a step-down voltage are used as necessary. Thus, the fixing roller 41 can be induction-heated to an intended temperature by appropriately performing power output from low power to high power while preventing occurrence of hard switching of the switching element 58.

  Further, in the image forming apparatus 1 of this embodiment, the fixing power supply unit 50 includes an AC voltage detection circuit 51 and an AC current detection circuit 52 which are power value detection means for detecting the power value of the AC power supply, and the CPU 56. However, the ON width and the voltage value of the output voltage are determined based on the surface temperature of the fixing roller 41 and the power values detected by the AC voltage detection circuit 51 and the AC current detection circuit 52.

  Therefore, it is possible to accurately determine the voltage input to the induction heating inverter 57 and determine the ON width of the switching signal S to the switching element 58 and the output voltage of the voltage step-down circuit 54. By using the voltage stepped down in this manner, hard switching of the switching element 58 is more appropriately prevented, and power output from low power to high power is more appropriately performed to bring the fixing roller 41 to the intended temperature. Induction heating is possible.

  Further, in the fixing power supply unit 50 of this embodiment, the voltage step-down circuit 54 has a plurality of resistors RaA, RbA, RcA, RaB, RbB, and a plurality of resistors RaA, RbA, RcA, RaB, RbB. Switching elements TraA, TrbA, TrcA, TraB, TrbB that output the output voltage by switching the connection state.

  Therefore, the voltage can be stepped down with a simple and inexpensive configuration of only a resistor and a switching element, and the power output from a small power to a large power is inexpensive and appropriate while preventing the occurrence of hard switching of the switching element 58 at a low cost. In this way, the fixing roller 41 can be induction heated to an intended temperature.

  Further, in the fixing power supply unit 50 of this embodiment, the voltage step-down circuit 54 includes transformers TA and TB each having a primary winding and a secondary winding to which the input voltage is input, and the secondary winding. Switching elements TrdA and TrdB which are switching means for switching the output take-up winding position and outputting the output voltage are provided.

  Therefore, noise and surge voltage (abnormal voltage) from AC power supply ACP can be prevented from being transmitted, and the voltage can be lowered appropriately, and occurrence of hard switching of switching element 58 can be prevented appropriately. On the other hand, the fixing roller 41 can be induction-heated to an intended temperature by appropriately outputting power from low power to high power.

  The fixing power supply unit 50 of this embodiment is an insulating forward converter whose voltage step-down circuit 54 converts the input voltage into the output voltage according to the duty ratio of the switching element (switching means) TrfA and outputs the converted output voltage. is there.

  Therefore, the output voltage can be controlled only by changing the duty ratio of the switching element TrfA, and the hard switching of the switching element 58 can be easily and easily generated using the full-wave rectification and the voltage stepped down as necessary. The fixing roller 41 can be inductively heated to the intended temperature by appropriately performing power output from low power to high power while preventing appropriately.

  Further, in the fixing power supply unit 50 of this embodiment, the voltage step-down circuit 54 converts the input voltage into the output voltage according to the duty ratio of the switching elements Tr1 and Tr2 as switching means, and outputs it. It is an insulated full bridge converter that converts the input voltage into the output voltage according to the duty ratio of the switching elements Tr1 to Tr4 that are bridge converters or switching means and outputs the converted output voltage.

  Therefore, the output voltage can be controlled only by changing the duty ratio of the switching elements Tr1 and Tr2 or the switching elements Tr1 to Tr4, and the switching element 58 can be controlled by using full-wave rectification and a voltage stepped down as necessary. It is possible to perform induction heating of the fixing roller 41 to an intended temperature by more appropriately performing power output from low power to high power while easily and appropriately preventing the occurrence of hard switching.

  The invention made by the present inventor has been specifically described based on the preferred embodiments. However, the present invention is not limited to that described in the above embodiments, and various modifications can be made without departing from the scope of the invention. It goes without saying that it is possible.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Paper feed part 11 Paper feed cassette 12 Paper feed roller 13 Separation roller 20 Conveyance belt mechanism part 21 Conveyance belt 22 Drive roller 23 Driven roller 24 Guide plate 35 Secondary transfer roller 30Y, 30M, 30C, 30K Image formation Part 31Y, 31M, 31C, 31K Photoconductor 32Y, 32M, 32C, 32K Charging part 33Y, 33M, 33C, 33K Exposure part 34Y, 34M, 34C, 34K Development part 35Y, 35M, 35C, 35K Transfer part 36Y, 36M, 36C, 36K Cleaning unit 40 Fixing unit 41 Fixing roller 42 Pressure roller 43 Thermistor 44 Thermostat 50 Fixing power supply unit 51 AC voltage detection circuit 52 AC current detection circuit 53 Full wave rectification circuit 54A, 54B Voltage step-down circuit 55 LC filter 55l Resonant coil 55 Resonant capacitor 56 CPU
57 Induction heating inverter 57c Resonance capacitor 57l Induction heating coil 58 Switching element ACP Commercial power supply power Il Coil current RaA, RbA, RaB, RbB, RcA Resistance TraA, TrbA, TraB, TrbB Switching element TA, TB transformer TrdA, TrdB, TreA switching Element Ca Capacitor Da, Db Diode T1 Transformer Tr1, Tr2, Tr3, Tr4 Switching element Di1, Di2, Di3, Di4 Input side diode C1, C2 Input side capacitor Do1, Do2 Output side diode

JP 2005-176485 A

Claims (8)

Rectification means for full-wave rectification of AC power supply power;
An AC voltage of the AC power supply power or a voltage after full-wave rectification by the rectifying means as an input voltage, a predetermined step-down voltage obtained by stepping down the input voltage or a voltage step-down means for outputting the input voltage as an output voltage;
Temperature detecting means for detecting a surface temperature of a fixing member for fixing the recording agent image on a recording medium on which the recording agent image is transferred;
Resonance means that is supplied with the output voltage of the voltage step-down means and is resonantly driven to induce a high frequency magnetic field corresponding to the output voltage to the fixing member to heat it.
A switching element that resonates by switching driving the resonance means with a predetermined ON width;
Based on the surface temperature of the fixing member detected by the temperature detecting means, the ON width of the switching element and the voltage value of the output voltage by the voltage step-down means are determined, and the switching element is driven with the ON width. And control means for controlling the voltage step-down operation by the voltage step-down means;
A fixing power supply device comprising: The fixing power supply device
Power value detection means for detecting the power value of the AC power supply power,
The control means includes
The fixing power supply apparatus according to claim 1, wherein the ON width and the voltage value of the output voltage are determined based on a surface temperature of the fixing member and the power value detected by the power value detection unit. The voltage step-down means is
A plurality of resistors for dividing the input voltage;
A switching element that switches the connection state of the plurality of resistors and outputs the output voltage;
The fixing power supply apparatus according to claim 1, further comprising: The voltage drop means is
A transformer having a primary winding and a secondary winding to which the input voltage is input;
Switching means for switching the output winding position of the secondary winding to output the output voltage;
The fixing power supply apparatus according to claim 1, further comprising: The voltage drop means is
3. The fixing power supply apparatus according to claim 1, wherein the fixing power supply apparatus is an isolated forward converter that converts the input voltage into the output voltage according to a duty ratio of a switching unit and outputs the converted output voltage. The voltage drop means is
3. The fixing power source according to claim 1, wherein the fixing power source is an isolated half-bridge converter or an isolated full-bridge converter that converts the input voltage into the output voltage according to a duty ratio of a switching unit and outputs the converted output voltage. apparatus. An image forming apparatus that heats a recording medium onto which a recording agent image has been transferred by an image forming means, and fixes the recording agent image on the recording medium by a fixing unit that is supplied with power from a fixing power source unit,
7. An image forming apparatus comprising the fixing power supply unit according to claim 1 as the fixing power supply unit. Rectification processing step for full-wave rectification of AC power supply power;
An AC voltage of the AC power supply or a voltage after full-wave rectification in the rectification processing step as an input voltage, a predetermined step-down voltage obtained by stepping down the input voltage, or a voltage step-down processing step for outputting the input voltage as an output voltage; ,
A temperature detection processing step for detecting a surface temperature of a fixing member for fixing the recording agent image on a recording medium on which the recording agent image is transferred;
A resonance processing step in which the output voltage of the voltage step-down processing step is supplied and resonantly driven to induce and heat a high frequency magnetic field corresponding to the output voltage to the fixing member;
A switching processing step for causing the resonance processing step to perform switching driving with a predetermined ON width to resonate;
Based on the surface temperature of the fixing member detected in the temperature detection processing step, the ON width of the switching processing step and the voltage value of the output voltage in the voltage step-down processing step are determined, and the switching is performed with the ON width. A control processing step for driving the processing step and controlling a voltage step-down operation by the voltage step-down processing step;
A fixing power supply control method characterized by comprising:

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