JP2018087922A - Heater controller, heater control method and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heater controller, heater control method and program capable of suppressing occurrence of flicker and affection of harmonic current surely.SOLUTION: The invention is configured so that, based on surface temperature of a fixation roller detected by a temperature sensor (temperature detection means), a necessary voltage estimation part (necessary voltage estimation means) estimates a voltage pattern required for heating of the fixation roller. A heating control part (heating control means) selects an estimated voltage pattern from plural voltage patterns (first voltage pattern, second voltage pattern, third voltage pattern) in which continuous four half wave areas (first half wave area, second half wave area, third half wave area, fourth half wave area) are one period when a half period of AC voltage is one half wave area stored in a ROM being storage means. The heating control part further supplies the selected voltage pattern to the heater (heating means) for controlling surface temperature of the fixation roller.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a heater control device, a heater control method, and a program.

  In an image forming apparatus that heats and fixes a toner image transferred to a recording member such as paper with a fixing unit, the temperature of the fixing unit is appropriately controlled in consideration of user convenience and energy efficiency. The fixing unit includes a heating roller including a heater such as a halogen heater, a temperature sensor that detects the surface temperature of the heating roller, and the heater control device controls energization of the heater based on the surface temperature and the target temperature of the heater. To control the temperature of the fixing unit to the set temperature. As a control method, the wave number control for turning on / off the switching element every half cycle (every half wave) of the commercial AC voltage waveform and the phase for turning on / off the switching element every half cycle of the commercial AC voltage waveform are controlled. A method of controlling the voltage supplied to the heater by phase control, so-called PWM (Pulse Width Modulation) control is known (see, for example, Patent Document 1).

  By the way, the fixing unit is mounted with a high-power heater of 1000 watts or more in order to shorten the time required for the surface temperature to rise to the set temperature in response to a request for shortening the printing time. It is known that an inrush current is generated in the initial stage of temperature control when such a high-power heater is energized. In particular, since the halogen heater has a low resistance value in a low temperature state, the inrush current is likely to increase at an initial stage of temperature control in which the temperature is lowered. Due to the occurrence of the inrush current, the AC voltage as the power source is reduced, and flicker (appears as flickering of the fluorescent lamp) is generated in the fluorescent lamp or the like that shares the fixing unit and the power supply system.

  In addition, if the heater wattage is increased to reduce the stabilization time when the power is turned on, inrush current may be generated when the heater is turned on when the heater on / off state is controlled in half-wave units of the AC power supply waveform. Since it becomes large, flicker is likely to occur. On the other hand, when performing phase control to control the duty ratio of the voltage supplied to the heater, the inrush current at the start-up of the heater can be reduced to suppress flicker due to voltage fluctuations, but phase control is performed. As a result, the AC waveform is greatly distorted, so that a harmonic current is likely to be generated. The generated harmonic current causes malfunction of peripheral devices and the power supply system.

  To solve this problem, the fixing device described in Patent Document 1 suppresses the generation of harmonic currents by preventing the half-waves of the main heater and the sub-heater from being fully turned on or turned off at the same time. ing. However, this method is premised on a configuration including both a main heater and a sub-heater, and thus cannot be applied to a fixing unit including only one heater. Further, the fixing device described in Patent Document 1 has not been optimized to suppress both the effects of flicker and harmonic current.

  The present invention has been made in view of the above, and it is an object of the present invention to reliably suppress both the occurrence of flicker and the influence of harmonic current even when the number of heaters is one. is there.

  In order to solve the above-described problems and achieve the object, the present invention includes a heating unit that heats the fixing roller by supplying an AC voltage, a temperature detection unit that detects a surface temperature of the fixing roller, and the temperature. Based on the detection result of the detection means and the voltage value of the AC voltage, necessary voltage estimation means for estimating a voltage pattern necessary for heating the surface temperature of the fixing roller to a target temperature, and a half cycle of the AC voltage A storage means storing a plurality of voltage patterns to be supplied to the heating means, wherein the quarter voltage area where the AC voltage is continuous is one cycle, and an estimation result of the necessary voltage estimation means Heating control means for controlling the surface temperature of the fixing roller by selecting the voltage pattern corresponding to the above and supplying the selected voltage pattern to the heating means; Characterized in that it comprises.

  According to the present invention, it is possible to provide a heater control device, a heater control method, and a program capable of suppressing both the occurrence of flicker and the influence of harmonic current.

FIG. 1 is a block diagram illustrating a schematic configuration of an image forming apparatus including a heater control device. FIG. 2 is a block diagram illustrating a main configuration of the heater control device included in the image forming apparatus according to the first embodiment. FIG. 3A is a diagram showing specifications of a voltage pattern supplied by the AC power supply. FIG. 3B is a diagram illustrating an example of a supply voltage pattern table when a specified power supply impedance is assumed. FIG. 3C is a diagram illustrating an example of a supply voltage pattern table in consideration of the power supply impedance calculated based on the AC voltage actually detected by the voltage detection unit. FIG. 4 is a diagram illustrating an example of a voltage pattern stored in the supply voltage table, and FIG. 4A is a diagram illustrating an example of the first voltage pattern. FIG. 4B is a diagram illustrating an example of the second voltage pattern. FIG. 4C shows an example of the third voltage pattern. FIG. 5 is a graph showing an example of the voltage pattern stored in the supply voltage table, and FIG. 5A is a diagram showing an example of the first voltage pattern. FIG. 5B is a diagram illustrating an example of the second voltage pattern. FIG. 5C is a diagram illustrating an example of a third voltage pattern. FIG. 6 is a diagram schematically illustrating an example of the first voltage pattern, the second voltage pattern, and the third voltage pattern. FIG. 7 is a diagram illustrating a method for suppressing the generation of harmonic currents by adjusting the third voltage pattern. FIG. 8 is a flowchart showing a flow of a series of processes performed by the heater control device. FIG. 9 is a flowchart showing a flow of voltage pattern determination processing. FIG. 10 is a flowchart showing the flow of the voltage pattern switching process. FIG. 11 is a diagram showing an outline of the soft start process. FIG. 12 is a diagram showing an outline of the soft stop process. FIG. 13 is a block diagram illustrating a main configuration of a heater control device provided in the image forming apparatus according to the second embodiment. FIG. 14 is a diagram illustrating an example of a supply voltage table when the first voltage pattern is supplied to both the two heaters in the second embodiment, and FIG. It is an example in the case of supplying a voltage with a ratio of 0 to 25%. FIG. 14B shows an example in which a voltage with a lighting duty ratio of 25 to 50% is supplied to one heater. FIG. 14C shows an example in which a voltage with a lighting duty ratio of 50 to 75% is supplied to one heater. FIG. 14D shows an example in which a voltage with a lighting duty ratio of 75 to 100% is supplied to one heater. FIG. 15 is a diagram illustrating an example of a supply voltage table when the first voltage pattern is supplied to one heater and the second voltage pattern is supplied to the other heater in the second embodiment. FIG. 15A shows an example in which a voltage having a lighting duty ratio of 0 to 25% is supplied as the first voltage pattern. FIG. 15B shows an example in which a voltage with a lighting duty ratio of 25 to 50% is supplied as the first voltage pattern. FIG. 15C shows an example in which a voltage with a lighting duty ratio of 50 to 75% is supplied as the first voltage pattern. FIG. 15D shows an example in which a voltage having a lighting duty ratio of 75 to 100% is supplied as the first voltage pattern. FIG. 16 is a diagram illustrating an example of a supply voltage table when the first voltage pattern is supplied to one heater and the third voltage pattern is supplied to the other heater in the second embodiment. FIG. 16A shows an example in which a voltage having a lighting duty ratio of 0 to 25% is supplied as the first voltage pattern. FIG. 16B shows an example in which a voltage with a lighting duty ratio of 25 to 50% is supplied as the first voltage pattern. FIG. 16C shows an example in which a voltage with a lighting duty ratio of 50 to 75% is supplied as the first voltage pattern. FIG. 16D shows an example in which a voltage having a lighting duty ratio of 75 to 100% is supplied as the first voltage pattern.

  Hereinafter, an embodiment of a heater control device will be described in detail with reference to the accompanying drawings.

(First embodiment)
FIG. 1 is a block diagram illustrating a schematic configuration of an image forming apparatus including a heater control device according to the present invention. As shown in FIG. 1, the image forming apparatus 100 according to the embodiment performs a predetermined image processing on an image read by the scanner unit 10 that reads an image, and the image after the processing is performed. From the engine unit 20 that transfers the corresponding toner image to the transfer paper, the paper feed tray 30 for storing the transfer paper, and the fixing device 50 for fixing the toner image transferred to the transfer paper by the engine unit 20 It is configured. The heater control device according to the present invention is provided in the fixing device 50.

  The scanner unit 10 scans and exposes a document to convert document information about the document into an image signal, and outputs the image signal to the engine unit 20.

  When an image signal is output from the scanner unit 10, the engine unit 20 performs image processing such as color conversion and gradation correction on the image signal output from the scanner unit 10. The engine unit 20 forms an electrostatic latent image on an image carrier (not shown) according to the image subjected to image processing, and forms a toner image by attaching toner to the formed electrostatic latent image. To do. The engine unit 20 further transfers the formed toner image onto a transfer sheet conveyed from the paper feed tray 30 via the conveyance path 40, and directs the transfer paper toward the fixing device 50 via the conveyance path 40. Send it out.

  When the transfer paper on which the toner image is transferred is sent from the engine unit 20 to the fixing device 50 via the conveyance path 40, the fixing device 50 transfers the heat by the heat from the cylindrical fixing roller 51a and the pressure from the pressure roller 51b. The toner image transferred to the paper is fixed and discharged toward a paper discharge tray (not shown).

  FIG. 2 is a block diagram illustrating a main configuration of the heater control device 60 included in the image forming apparatus 100. As shown in FIG. 2, the heater control device 60 is provided in the fixing device 50, and includes a fixing roller 51a, a heater 52, an AC power source 53, a triac 54, a temperature sensor 55, a control unit 56, and a zero cross. A detection unit 57 and a voltage detection unit 58 are included.

  The fixing roller 51a rotates while being in pressure contact with the pressure roller 51b (FIG. 1), and fixes the toner image transferred to the transfer paper.

  The heater 52 is an example of a heating unit. The heater 52 is built in the fixing roller 51a, melts the toner image transferred onto the transfer paper with heat, and embeds and fixes the toner image in the fibers of the transfer paper. As the heater 52, for example, a halogen heater that performs heating by radiant heat generated when the halogen lamp is turned on is used.

  The AC power supply 53 supplies an AC voltage to the heater 52. In the present embodiment, it is assumed that an alternating voltage that changes in a sine wave shape with time is supplied (see FIG. 3A).

  The triac 54 is a switching unit, and switches (turns on / off) the AC voltage supplied from the AC power source 53 at a timing instructed by the control unit 56. The triac 54 supplies the switched AC voltage to the heater 52. When the triac 54 is on, the heater 52 is energized to generate heat. When the triac 54 is off, the heater 52 is not energized.

  The temperature sensor 55 is an example of a temperature detection unit, and measures the surface temperature of the fixing roller 51a. The temperature sensor 55 includes, for example, a thermistor whose resistance value changes according to the temperature, and measures the surface temperature of the fixing roller 51a based on the resistance value of the thermistor. The temperature sensor 55 may be built in the fixing roller 51a, or the temperature sensor 55 may be installed at a position facing the surface of the fixing roller 51a to measure the surface temperature of the fixing roller 51a without contact. Good.

  The zero cross detector 57 detects the timing at which the AC voltage supplied from the AC power supply 53 crosses 0 volt from the plus side to the minus side or from the minus side to the plus side (hereinafter referred to as the zero cross timing). The zero-cross detection unit 57 outputs a zero-cross detection signal to the control unit 56 when the zero-cross timing is detected.

  The voltage detector 58 detects the voltage value e of the AC voltage supplied from the AC power supply 53. Then, the voltage detector 58 outputs the detected voltage value e to the controller 56.

  The control unit 56 is based on the surface temperature of the fixing roller 51a measured by the temperature sensor 55, the zero-cross timing of the AC voltage detected by the zero-cross detection unit 57, and the voltage value e of the AC voltage detected by the voltage detection unit 58. The timing for switching the AC voltage is determined. Then, the control unit 56 operates the triac 54 based on the determined timing.

  The control unit 56 is implemented as a computer in which a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and an input / output interface not shown in FIG. 2 are connected via a bus. Is done. The CPU reads and executes the program stored in the ROM. The read program is developed on the CPU in an executable format to constitute a necessary voltage estimation unit 62 and a heating control unit 63. The ROM is an example of a storage unit, and stores the above-described program, a supply voltage table 64 in which voltage patterns supplied to the halogen lamps included in the heater 52 are registered, and the like.

  The supply voltage table 64 stores a voltage pattern to be supplied to the halogen lamp included in the heater 52 as heating means, with two cycles of the AC voltage supplied from the AC power supply 53 to the heater control device 60, that is, one half of the quarter wave. To do. The supply voltage table 64 stores, for example, three different types of tables (first voltage pattern E1, second voltage pattern E2, and third voltage pattern E3) (see FIGS. 3, 4, 5, and 6). ).

  In addition, the control unit 56 of the heater control device 60 performs a process (see FIG. 9) described later, based on the first voltage pattern E1, the second voltage pattern E2, and the third voltage pattern E3. A supply voltage pattern table V1 described in 3 (b) and a supply voltage pattern table V corresponding to the supply voltage pattern table V2 described in FIG. 3 (c) are created. The supply voltage table 64 stores the generated supply voltage pattern table V.

  The supply voltage table 64 stores the relationship between the surface temperature of the fixing roller 51a and the lighting duty ratio Do of the AC voltage to be supplied. The relationship between the surface temperature and the lighting duty ratio Do is used to determine the initial value of the voltage pattern supplied to the heater 52. For example, when the surface temperature of the fixing roller 51a is low, the lighting duty ratio Do is set large and a large amount of power is supplied to increase the surface temperature in a short time. Further, when the printing operation is repeated and the surface temperature of the fixing roller 51a is high, the lighting duty ratio Do is set small to reduce the supplied power.

  Further, the supply voltage table 64 stores a harmonic margin when a predetermined voltage pattern is supplied to the heater control device 60 for each voltage pattern (E1, E2, E3) and each phase duty ratio Dp. The harmonic margin is an amount indicating a margin of how much the maximum value of the harmonic current generated when the voltage pattern is supplied is below the design target. Details will be described later. Further, the phase duty ratio Dp is a value indicating timing for starting supply of voltage to the heater control device 60. Details will be described later.

  The necessary voltage estimation unit 62 is an example of necessary voltage estimation means, and estimates the AC voltage supplied to heat the surface of the fixing roller 51a to the target temperature based on the detection result of the temperature sensor 55, which is a temperature detection means. To do. Then, the necessary voltage estimation unit 62 selects and reads an AC voltage pattern that approximates the estimated AC voltage from the supply voltage table 64. More specifically, an AC voltage pattern corresponding to the lighting duty ratio Do estimated by the necessary voltage estimation unit 62 is selected from the supply voltage pattern table V and read. The required voltage estimation unit 62 may refer to, for example, the power consumption of the heater 52 when selecting the AC voltage pattern to be supplied. That is, when using the heater 52 with high power consumption, it is desirable to select a voltage pattern that is advantageous with respect to the harmonic current.

  Further, the necessary voltage estimation unit 62 adjusts the AC voltage pattern selected from the supply voltage table 64 as necessary so as to be advantageous for the harmonic current. A specific method for adjusting the voltage pattern will be described later in detail (see FIG. 7).

  The heating control unit 63 is an example of a heating control unit, and the necessary voltage estimation unit 62 supplies an AC voltage corresponding to the supply voltage pattern table V read from the supply voltage table 64 to the heater 52 based on the estimation result. The surface temperature of the fixing roller 51a is controlled.

(Description of supply voltage table)
Next, the contents of the supply voltage table 64 stored in the ROM serving as the storage means will be described with reference to FIGS. 3, 4, 5, and 6. FIG.

  FIG. 3 is a diagram showing an example of the supply voltage pattern table V stored in the supply voltage table 64, and FIG. 3A is a diagram showing specifications of the voltage pattern supplied by the AC power supply 53 shown in FIG. It is. FIG. 3B is a diagram illustrating an example of the supply voltage pattern table V1 when a specified power supply impedance is assumed. FIG. 3C is a diagram illustrating an example of the supply voltage pattern table V2 in consideration of the power supply impedance calculated based on the AC voltage actually detected by the voltage detection unit 58 (FIG. 2).

  The supply voltage table 64 is described with a quarter wave of the AC voltage supplied from the AC power supply 53 as one cycle. FIG. 3A shows specifications necessary for explaining the description content of the supply voltage table 64.

  The voltage value e supplied from the AC power supply 53 is described as a sine wave with a period T having a peak value e0. And, as shown in FIG. 3A, the four half-wave regions constituting the four half-waves of the alternating voltage that are continuous in the order of time passage, the first half-wave region a, the second half-wave region b, Let the third half-wave region c and the fourth half-wave region d be. That is, when the time is t, the first half-wave region a represents a time range of 0 ≦ t <T / 2. Similarly, the second half-wave region b represents a time range of T / 2 ≦ t <T, the third half-wave region c represents a time range of T ≦ t <3T / 2, and the fourth half-wave region d is It represents a time range of 3T / 2 ≦ t <2T. The heater control device 60 according to the present embodiment controls the AC voltage supplied to the halogen lamp included in the heater 52 using the four half waves shown in FIG. For example, when a 50-V 100 V commercial AC power supply is used as the AC power supply 53, the control cycle is 2T = 40 msec.

  The supply voltage pattern tables V1 and V2 shown in FIGS. 3B and 3C are tables that define the lighting duty ratio Do and the phase duty ratio Dp (Dpa, Dpb, Dpc, Dpd). The lighting duty ratio Do (0 ≦ Do ≦ 100%) indicates what percentage of the voltage supplied from the AC power supply 53 over the control period 2T is supplied to the halogen lamp included in the heater 52. That is, for example, the lighting duty ratio Do = 50% is a time corresponding to 50% of the area formed by the sine wave of the control cycle 2T and the voltage value e = 0 shown in FIG. This means that AC voltage is supplied (power is supplied).

  Further, the phase duty ratio Dp (0 ≦ Dp ≦ 100%) is defined as the supply duration time of the AC voltage in each half-wave region a, b, c, d, and the time interval of the half-wave region (T in FIG. 3 (a)). / 2) is a value expressed as a ratio. That is, the phase duty ratio Dp is defined for each half-wave region (a, b, c, d). Here, the phase duty ratios Dp in the half-wave regions a, b, c, and d are Dpa, Dpb, Dpc, and Dpd, respectively. For example, the phase duty ratio Dpa = 20% means that the voltage is supplied in the first half-wave region a at a time of 20% of the time interval T / 2 of the first half-wave region a, that is, at time t = 2T / 5. And the supply of the AC voltage is continued for a time of T / 10 until the time t = T / 2. When this is illustrated in FIG. 3A, it indicates that a voltage having a waveform indicated by region R is supplied. The phase duty ratios Dpb, Dpc, and Dpd are defined similarly. Note that the timing for starting the supply of voltage may be specified by the phase angle of the sinusoidal AC voltage supplied from the AC power supply 53 in addition to the time specified as described above.

The power supply impedance Z which is the internal resistance of the AC power supply 53 is not 0 but has a predetermined value. Therefore, when the circuit of FIG. 2 is energized, a voltage drop corresponding to the power source impedance Z of the AC power source 53 occurs. Therefore, even if the AC power supply 53 has a peak value e0, the peak value of the AC voltage waveform actually supplied to the heater 52 is smaller than e0. That is, when it is going to supply predetermined electric power to the heater 52, it is necessary to supply electric power higher than the predetermined electric power. Therefore, it is necessary to supply a voltage having a phase duty ratio Dp higher than the phase duty ratio Dp calculated when the power supply impedance Z is assumed to be zero.

  FIG. 3B is an example of a supply voltage pattern table V1 supplied to the heater 52 when the AC power supply 53 has a specified power supply impedance Z. FIG. 3C is an example of the supply voltage pattern table V2 set based on the power source impedance Z calculated based on the voltage detected by the voltage detector 58 (FIG. 2). The power source impedance Z is calculated by Z = ΔV / I based on the voltage ΔV detected by the voltage detector 58 and the current I flowing through the heater 52. As described above, in the present embodiment, an AC voltage is supplied to the heater 52 in advance to measure the power supply impedance Z, and a voltage pattern corresponding to the power supply impedance Z is created and stored as the supply voltage table 64. The image forming apparatus 100 may store a plurality of supply voltage pattern tables V in advance in the supply voltage table 64 according to the power supply impedance Z. In this case, the image forming apparatus 100 selects and reads the supply voltage pattern table V corresponding to the measured power supply impedance Z.

  Next, FIG. 4A to FIG. 4C respectively show two periods of the AC voltage supplied from the AC power supply 53 to the heater control device 60 stored in the supply voltage table 64, that is, four half waves. It is the figure which tabulated the voltage pattern used as the reference | standard as a period with the same format as FIG.3 (b) mentioned above and FIG.3 (c). FIG. 4A shows a first voltage pattern E1. FIG. 4B shows a second voltage pattern E2. FIG. 4C shows a third voltage pattern E3. The first voltage pattern E1, the second voltage pattern E2, and the third voltage pattern E3 are each described in the same format as the supply voltage pattern table V, that is, the relationship between the lighting duty ratio Do and the phase duty ratio Dp. The The contents of the first voltage pattern E1, the second voltage pattern E2, and the third voltage pattern E3 will be described later.

  FIGS. 5A to 5C are graphs of the first voltage pattern E1, the second voltage pattern E2, and the third voltage pattern E3, respectively.

  For example, FIG. 5A shows the first voltage pattern E1 with the horizontal axis representing the lighting duty ratio Do and the vertical axis representing the phase duty ratio Dp. Hereinafter, the first voltage pattern E1, the second voltage pattern E2, and the third voltage pattern E3 will be described with reference to FIGS.

  In the first voltage pattern E1, the phase duty ratio Dp is set in order from any one half-wave region in the four-half wave region in accordance with an increase in power supplied to the heater 52, which is a heating means, in the control cycle 2T. This is a voltage pattern that is increased (the time to start supplying the voltage in each half-wave region is advanced).

  The first voltage pattern E1 is defined as follows in each of the first half-wave region a, the second half-wave region b, the third half-wave region c, and the fourth half-wave region d that are continuous in the order of time. The That is, when the lighting duty ratio Do is 25% or less, the phase duty ratio Dpa of the first half-wave region a is set from 0% to 100% according to the lighting duty ratio Do (FIG. 5A). Section Q1). Then, the phase duty ratios Dpb, Dpc, Dpd of the second half-wave region b, the third half-wave region c, and the fourth half-wave region d are all set to 0% (section Q2 in FIG. 5A). Since the voltage value e supplied from the AC power supply 53 changes in a sine wave shape, the phase duty ratio Dpa monotonously increases nonlinearly with respect to the lighting duty ratio Do in the section Q1. The same applies to sections Q4, Q7, and Q10 described later.

  Further, in the first voltage pattern E1, when the lighting duty ratio Do is greater than 25% and equal to or less than 50%, the phase duty ratio Dpa of the first half-wave region a is set to 100% (FIG. 5 ( Section Q3) of a). Then, the phase duty ratio Dpc of the third half-wave area c not adjacent to the first half-wave area a is set from 0% to 100% according to the lighting duty ratio Do (section Q4 in FIG. 4A). Furthermore, the phase duty ratios Dpb and Dpd of the second half-wave region b and the fourth half-wave region d are both set to 0% (section Q5 in FIG. 5A).

  Further, when the lighting duty ratio Do is greater than 50% and equal to or less than 75%, the first voltage pattern E1 sets the phase duty ratios Dpa and Dpc of the first half-wave region a and the third half-wave region c. Both are set to 100% (section Q6 in FIG. 5A). Then, the phase duty ratio Dpb of the second half-wave region b is set from 0% to 100% according to the lighting duty ratio Do (section Q7 in FIG. 5A). Further, the phase duty ratio Dpd of the fourth half-wave region d is set to 0% (section Q8 in FIG. 5A).

  When the lighting duty ratio Do is larger than 75%, the first voltage pattern E1 has the phase duty ratios Dpa, Dpc, Dpa, Dpc of the first half-wave region a, the third half-wave region c, and the second half-wave region b. Both Dpb are set to 100% (section Q9 in FIG. 5A). Then, the phase duty ratio Dpd of the fourth half-wave area d not adjacent to the second half-wave area b is set from 0% to 100% according to the lighting duty ratio Do (section Q10 in FIG. 5A).

  Next, the second voltage pattern E2 shown in FIG. 5B shows a lighting duty ratio Do and a phase duty ratio Dp (Dpa, Dpb, Dpc, Dpd) different from those in FIG. 5A. It is a table defined in.

  The second voltage pattern E2 is equally applied to two non-adjacent two half-wave regions in the four half-wave regions in accordance with an increase in power supplied to the heater 52 that is the heating means in the control period 2T. It is a voltage pattern that increases both the phase duty ratio Dp (energization time).

  That is, as shown in FIG. 5 (b), the second voltage pattern E2 has a first half-wave region when the lighting duty ratio Do is 50% or less in each half-wave region continuous in the order of passage of time. The phase duty ratios Dpa and Dpc of the third half-wave area c not adjacent to the first half-wave area a are set from 0% to 100% according to the lighting duty ratio Do (section Q11 in FIG. 5B). ). Then, the phase duty ratios Dpb and Dpd of the second half-wave region b and the fourth half-wave region d not adjacent to the second half-wave region b are both set to 0% (section Q12 in FIG. 5B). Since the voltage value e supplied from the AC power supply 53 changes in a sine wave shape, the phase duty ratios Dpa and Dpc monotonously increase nonlinearly with respect to the lighting duty ratio Do in the section Q11. The same applies to the section Q14 described later.

  Further, in the second voltage pattern E2, when the lighting duty ratio Do is larger than 50%, the phase duty ratio of the first half-wave area a and the third half-wave area c not adjacent to the first half-wave area a Both Dpa and Dpc are set to 100% (section Q13 in FIG. 5B). Then, the phase duty ratios Dpb and Dpd of the second half-wave area b and the fourth half-wave area d not adjacent to the second half-wave area b are set from 0% to 100% according to the lighting duty ratio Do (FIG. Section (B14) of 5 (b)).

  Further, in the third voltage pattern E3 shown in FIG. 5C, the lighting duty ratio Do and the phase duty ratio Dp (Dpa, Dpb, Dpc, Dpd) are different from those in FIGS. 5A and 5B. It is a table defined by the relationship.

  The third voltage pattern E3 is a phase duty ratio Dp that is equally applied to all the half-wave regions of the four half-wave regions in accordance with an increase in power supplied to the heater 52 that is the heating means in the control cycle 2T. It is a voltage pattern which increases both (energization time).

  That is, as shown in FIG. 5 (c), the third voltage pattern E3 has a phase duty ratio Dp (Dpa, Dpb, Dpc, Dpd) and a lighting duty ratio Do in each half-wave region continuous in the order of time. Accordingly, the value is set from 0% to 100% (section Q15 in FIG. 5C). Each phase duty ratio (Dpa, Dpb, Dpc, Dpd) is set to an equal value. Since the voltage value e supplied from the AC power supply 53 changes in a sine wave shape, the phase duty ratios Dpa, Dpb, Dpc, and Dpd monotonously increase nonlinearly with respect to the lighting duty ratio Do in the interval Q15.

  Next, FIG. 6 is a diagram schematically illustrating an example of the first voltage pattern E1, the second voltage pattern E2, and the third voltage pattern E3.

  As shown in FIG. 6, when the lighting duty ratio Do is 25% or less (voltage waveform W11), the first voltage pattern E1 is within one half wave of the AC power supply waveform in the first half wave region a. The phase control is performed to switch the voltage supply ON / OFF at any phase. Note that the phase control in the first half-wave region a is an example, and the phase control may be performed in one of the other arbitrary half-wave regions.

  When the lighting duty ratio Do is 25 to 50% (voltage waveform W12), a voltage (AC voltage) is supplied over the entire first half-wave region a and adjacent to the first half-wave region a. In the third half-wave region c that is not, the supplied voltage is controlled by phase control. Note that the half-wave region where the voltage is supplied over the entire region is the half-wave region where phase control is performed in the voltage waveform W11 of FIG. For example, when phase control is performed in the second half-wave region b in the voltage waveform W11, the voltage is supplied over the entire second half-wave region b in the voltage waveform W12, and the second half-wave region b is supplied. Phase control is performed in the fourth half-wave region d that is not adjacent to.

  Further, when the lighting duty ratio Do is 50 to 75% (voltage waveform W13), the voltage is supplied over the entire first half wave region a and third half wave region c, and the second half wave region. In b, the supplied voltage is controlled by phase control.

  When the lighting duty ratio Do is 75 to 100% (voltage waveform W14), a voltage is supplied over the entire first half-wave region a, second half-wave region b, and third half-wave region c. At the same time, the voltage to be supplied is controlled by phase control in the fourth half-wave region d that is not adjacent to the second half-wave region b.

  In the second voltage pattern E2, when the lighting duty ratio Do is 0 to 50% (voltage waveforms W21 and W22), the first half-wave region a and the third half-wave not adjacent to the first half-wave region a In the region c, the supplied voltage is controlled by phase control. When the lighting duty ratio Do is 50 to 100% (voltage waveforms W23 and W24), the voltage is supplied over the entire first half-wave region a and third half-wave region c, and the second half-wave region c is supplied. In the wave region b and the fourth half-wave region d not adjacent to the second half-wave region b, the supplied voltage is controlled by phase control.

  The third voltage pattern E3 controls the voltage to be supplied by phase control regardless of the lighting duty ratio Do in all of the first half-wave region a to the fourth half-wave region d (voltage waveforms W31, W32, W33, W34).

  Note that the voltage supply start timing in each half-wave region is the zero-cross timing of the AC voltage detected by the zero-cross detection unit 57 (FIG. 2) and the value of the phase duty ratio Dp in each half-wave region. The heating control unit 63 determines using the energization time to converted to the time at. Specifically, the supply of voltage is started at the time when 10 msec-to has elapsed from the zero cross timing of the AC voltage as a reference. Here, 10 msec is the time of one half-wave region corresponding to the phase duty ratio Dp = 100% when a commercial AC power supply of 50 Hz is used.

  Comparing the three voltage patterns shown in FIG. 6 (first voltage pattern E1, second voltage pattern E2, and third voltage pattern E3), the inrush current is the smallest in terms of suppressing the occurrence of flicker. The third voltage pattern E3 is most suitable. Since the inrush current increases in the order of the second voltage pattern E2 and the first voltage pattern E1, the effect of suppressing the occurrence of flicker is reduced.

  From the viewpoint of suppressing the generation of harmonic current, the first voltage pattern E1 having the smallest harmonic component among the three voltage patterns is most suitable. And since a harmonic component increases in order of the 2nd voltage pattern E2 and the 3rd voltage pattern E3, the effect which suppresses generation | occurrence | production of a harmonic current becomes small. Thus, by selecting the voltage pattern supplied to the heater 52, it is possible to selectively suppress the occurrence of flicker and the generation of harmonic current.

  Furthermore, the necessary voltage estimation unit 62 (FIG. 2) can suppress the generation of the harmonic current by adjusting the third voltage pattern E3. FIG. 7 is a diagram for explaining the method.

  As shown in FIG. 7, the required voltage estimation unit 62 keeps the output power of the third voltage pattern E3 constant, that is, does not change the total area of hatching within the control cycle 2T (lighting duty ratio). While maintaining Do), the generation of harmonic current can be suppressed by adjusting the phase duty ratio Dp of each half-wave region. In this operation, for example, the phase duty ratios Dpb and Dpd of the second half-wave region b and the fourth half-wave region d are adjusted to be small (for example, −1%), respectively, and the first half-wave region a and the third half-wave are adjusted. This is realized by largely adjusting (for example, + 1%) the phase duty ratios Dpa and Dpc of the region c. Note that adjusting the phase duty ratio Dp to be small can be realized by delaying the time at which the voltage supply is started or increasing the phase angle at which the voltage supply is started. On the contrary, the phase duty ratio Dp can be largely adjusted by increasing the time at which the voltage supply is started or by reducing the phase angle at which the voltage supply is started. In FIG. 7, the phase duty ratios Dpa and Dpc of the first half-wave area a and the third half-wave area c are adjusted to be small, respectively, and the phase duty ratios of the second half-wave area b and the fourth half-wave area d are adjusted. The same effect can be obtained by adjusting Dpb and Dpd to a large extent.

  As described above, in each half-wave region in the control cycle 2T, the generation of the harmonic current can be suppressed by reducing the number of half-wave regions having a large number of harmonic components and having a small phase duty ratio Dp. . Therefore, the generation of higher harmonic current can be further suppressed by using the third voltage pattern E3 that has a high effect of suppressing the generation of flicker.

(Description of the flow of a series of processes performed by the heater control device)
Next, a flow of a series of processes performed by the control unit 56 (FIG. 2) of the heater control device 60 will be described with reference to FIG. FIG. 8 is a flowchart showing a flow of a series of processes performed by the heater control device 60.

  The necessary voltage estimation unit 62 performs a voltage pattern determination process for determining an initial value of the voltage pattern supplied to the heater 52 (step S10). Details of the voltage pattern determination process will be described later (see FIG. 9). Here, the voltage pattern determination process performed in step S <b> 10 may be executed by an external device connected to the image forming apparatus 100 instead of the image forming apparatus 100. In this case, the external device acquires and stores a plurality of supply voltage pattern tables V in advance. The external apparatus may select and read the supply voltage pattern table V corresponding to the power supply impedance Z based on the power supply impedance Z measured by the image forming apparatus 100.

  Subsequently, the heating control unit 63 detects a predetermined operation state of the image forming apparatus 100 such as at the start of printing, at a steady state, at the end of printing, and the like, and performs a voltage pattern switching process for switching a voltage pattern supplied to the heater 52. It performs (step S12). The details of the voltage pattern switching process will be described later (see FIG. 10).

  Subsequently, in step S <b> 14, the control unit 56 confirms whether the power of the image forming apparatus 100 is turned off. When the image forming apparatus 100 is powered off (step S14: Yes), the heater control device 60 ends the process of FIG. On the other hand, when the power of the image forming apparatus 100 is not off (step S14: No), the process returns to step S10.

(Description of the flow of voltage pattern determination processing)
Next, the flow of voltage pattern determination processing in which the required voltage estimation unit 62 (FIG. 2) determines the voltage patterns (E1, E2, E3) to be supplied to the heater 52 will be described with reference to FIG. FIG. 9 is a flowchart showing a flow of voltage pattern determination processing performed by the necessary voltage estimation unit 62 (FIG. 2). Hereinafter, the contents of processing performed in each step will be described in order.

  The necessary voltage estimation unit 62 determines a voltage pattern to be supplied to the heater 52 while increasing the lighting duty ratio Do from 0% to 100% by a predetermined value. In FIG. 9, it is assumed that the lighting duty ratio Do is increased by 1%. First, the necessary voltage estimation unit 62 sets the lighting duty ratio Do to 0% (step S28).

  Next, the necessary voltage estimation unit 62 sets a voltage pattern E3 having the highest flicker reduction effect in FIG. 6 (step S30). The voltage pattern set in step S30 is hereinafter referred to as an initial waveform.

  Next, the necessary voltage estimation unit 62 does not adjust the phase duty ratio Dp, that is, when the initial waveform set in step S30 is supplied to the heater 52 in a state of Dpa = Dpb = Dpc = Dpd. It is determined whether the wave margin exceeds the design target (step S32). When it is determined that the harmonic margin exceeds the design target (step S32: Yes), the process proceeds to step S34, and otherwise (step S32: No), the process proceeds to step S36.

  When the harmonic margin exceeds the design target, the maximum value of the current of each order of the harmonic has a predetermined margin with respect to the standard value (for example, 85% or less of the standard value), and other orders. This means that a preset design target is achieved such that the maximum current value has a predetermined margin with respect to the standard value (for example, 50% or less of the standard value). Specifically, the determination process performed in step S32 is performed when a voltage having a predetermined voltage pattern (E1, E2, E3) and a predetermined phase duty ratio Dp is supplied to the heater control device 60 as described above. The harmonic margin is obtained by an experiment or the like in advance and stored in the supply voltage table 64, and the table is referred to.

  In step S32, when it is determined that the harmonic margin exceeds the design target, the heating control unit 63 is set to supply the initial waveform set in step S30 to the heater 52 without adjusting the phase duty ratio Dp. (Step S34). Thereafter, the process proceeds to step S46.

  On the other hand, when it is determined in step S32 that the harmonic margin does not exceed the design target (step S32: No), the required voltage estimation unit 62 performs the lighting duty on the initial waveform set in step S30. When the phase duty ratio Dp is adjusted while maintaining the ratio Do (see FIG. 7) and supplied to the heater 52, it is determined whether the harmonic margin exceeds the design target (step S36). When it is determined that the harmonic margin exceeds the design target (step S36: Yes), the process proceeds to step S38, and otherwise (step S36: No), the process proceeds to step S40.

  The adjustment of the phase duty ratio Dp performed in step S36 includes, for example, the phase duty ratio Dpa of the first half-wave area a and the phase duty ratio Dpc of the third half-wave area c that is not adjacent to the first half-wave area a. , And the phase duty ratio Dpb of the second half-wave region b and the phase duty ratio Dpd of the fourth half-wave region d not adjacent to the second half-wave region b, respectively, by 1%. Decrease and repeat the evaluation of the size of the harmonic margin.

  In step S36, when it is determined that the harmonic margin exceeds the design target (step S36: Yes), the heating control unit 63 adjusts the phase duty ratio Dp with respect to the initial waveform set in step S30. The voltage is set to be supplied to the heater 52 (step S38). Thereafter, the process proceeds to step S46.

  On the other hand, if it is determined in step S36 that the harmonic margin does not exceed the design target (step S36: No), the required voltage estimation unit 62 has the same lighting duty ratio Do as the initial waveform set in step S30. When the second voltage pattern E2 having is supplied to the heater 52, it is determined whether the harmonic margin exceeds the design target (step S40). When it is determined that the harmonic margin exceeds the design target (step S40: Yes), the process proceeds to step S42, and otherwise (step S40: No), the process proceeds to step S44. The determination process performed in step S40 is performed in the same manner as steps S32 and S36 described above.

  In step S40, when it is determined that the harmonic margin exceeds the design target (step S40: Yes), the heating control unit 63 is set to supply the second voltage pattern E2 to the heater 52 (step S40). S42). Thereafter, the process proceeds to step S46.

  On the other hand, when it is determined in step S40 that the harmonic margin does not exceed the design target (step S40: No), the heating control unit 63 sets the same lighting duty ratio Do as the initial waveform set in step S30. The first voltage pattern E1 is set to be supplied to the heater 52 (step S44). Thereafter, the process proceeds to step S46.

  The necessary voltage estimation unit 62 determines whether the setting of the voltage pattern corresponding to all the lighting duty ratios Do has been completed (step S46). When the setting of voltage patterns corresponding to all lighting duty ratios Do is completed (step S46: Yes), that is, when the setting of voltage patterns corresponding to lighting duty ratios Do = 0 to 100% is completed, FIG. The process is terminated and the process returns to the main routine (FIG. 8). On the other hand, when the setting of the voltage pattern corresponding to all the lighting duty ratios Do has not been completed (step S46: No), the process proceeds to step S48.

  The lighting duty ratio Do is added by 1% (step S48). Then, it returns to step S30 and repeats the process mentioned above. The addition amount of the lighting duty ratio Do is not limited to 1%, and may be set as a design parameter as appropriate.

(Explanation of voltage pattern switching process)
The heating control unit 63 (FIG. 2) performs a voltage pattern switching process for appropriately switching the voltage pattern determined by the voltage pattern determination process described above based on the operation state of the fixing device 50. The flow of this voltage pattern switching process will be described with reference to FIG. FIG. 10 is a flowchart showing the flow of the voltage pattern switching process. Hereinafter, the contents of processing performed in each step will be described in order.

  The heating control unit 63 determines whether to start supplying voltage to the heater 52 (step S50). When supply of voltage to the heater 52 is started (step S50: Yes), the process proceeds to step S52, and otherwise (step S50: No), step S50 is repeated. For example, the heating control unit 63 determines to start supplying voltage based on the instruction to start printing to the image forming apparatus 100 and the completion of the voltage pattern determination process (FIG. 9).

  The heating control unit 63 starts a soft start process for gradually increasing the voltage supplied to the heater 52 until the initial waveform is reached (step S52). Details of the soft start process will be described later (see FIG. 11).

  The heating control unit 63 supplies a voltage waveform for performing a soft start process to the heater 52 (step S54).

  The heating control unit 63 determines whether to end the soft start process (step S56). When the soft start process is finished (step S56: Yes), the process proceeds to step S58, and otherwise (step S56: No), the process returns to step S54. In addition, when performing the soft start process, the heating control unit 63 determines whether to end the soft start process based on the number of changes in the phase duty ratio Dp. Details will be described later (see FIG. 11).

  The heating controller 63 supplies the heater 52 with the voltage pattern determined in the voltage pattern determination process (FIG. 9) (step S58).

  The heating control unit 63 determines whether or not the variation amount of the lighting duty ratio Do of the voltage pattern to be supplied is within a predetermined value and the voltage supply time has exceeded the allowable control period Ta (step S60). When the fluctuation amount of the lighting duty ratio Do is within a predetermined value and the voltage supply time exceeds the allowable control cycle Ta (step S60: Yes), the process proceeds to step S62, and otherwise (step S60: No). Returns to step S58. Here, the allowable control cycle Ta is the time required for the print medium to pass through the fixing roller 51a when the print medium is passed through the fixing device 50, that is, the time during which the print medium is in contact with the fixing roller 51a. It is.

  In step S60, it is determined whether or not the voltage supply time exceeds the allowable control period Ta when the initial waveform is continuously supplied to the heater 52 by increasing the time average value of the harmonic current. This is because the influence of current may occur. That is, when continuing the supply of the initial waveform beyond the allowable control cycle Ta, it is desirable to supply a voltage waveform with fewer harmonic components, so that in step S60, the voltage supply time exceeds the allowable control cycle Ta. When the determination is made, the voltage pattern is switched.

  When the heater 52 is continuously turned on, the lighting duty ratio Do of the voltage waveform is kept substantially constant, but varies somewhat depending on the case. An allowable amount of this variation is defined as an allowable variation duty. In step S60 described above, it is also determined whether the lighting duty ratio Do of the voltage waveform is within the allowable variation duty.

  In step S60, when it is determined that the fluctuation amount of the lighting duty ratio Do of the voltage waveform is within a predetermined value and the voltage supply time has exceeded the allowable control period Ta (step S60: Yes), the heating control unit 63 supplies The first voltage pattern E1 stored in the voltage table 64 is selected (step S62). The reason why the first voltage pattern E1 is selected in step S62 is to switch to a voltage pattern that is less affected by the harmonic current.

  On the other hand, in step S60, when it is not determined that the variation amount of the lighting duty ratio Do of the voltage waveform is within a predetermined value and the voltage supply time has exceeded the allowable control period Ta (step S60: No), the process returns to step S58.

  The heating control unit 63 supplies the heater 52 with the first voltage pattern E1 selected in step S62 based on the lighting duty ratio Do estimated by the necessary voltage estimation unit 62 (step S64).

  Subsequent to step S64, the heating control unit 63 determines whether printing is completed (step S66). If it is determined that printing has been completed (step S66: Yes), the process proceeds to step S68, and otherwise (step S66: No), the process returns to step S64. Note that whether or not printing has ended may be determined by detecting that the number of prints has reached the set number set at the start of printing, for example. Alternatively, in the case of a print job without setting the number of sheets, it may be performed by detecting that a predetermined time has elapsed after the print medium passes through the fixing roller 51a.

  If it is determined in step S66 that printing has ended (step S66: Yes), the heating control unit 63 starts a soft stop process for gradually decreasing the voltage supplied to the heater 52 (step S68). Details of the soft stop process will be described later (see FIG. 12).

  The heating control unit 63 supplies a voltage waveform for performing a soft stop process to the heater 52 (step S70).

  Subsequently, the heating control unit 63 determines whether to end the soft stop process (step S72). When the soft stop process is finished (step S72: Yes), the process of FIG. 10 is finished and the process returns to the main routine (FIG. 8). On the other hand, when the soft stop process is not terminated (step S72: No), the process returns to step S70. In addition, when performing the soft stop process, the heating control unit 63 determines whether to end the soft stop process based on the number of changes in the phase duty ratio Dp. Details will be described later (see FIG. 12).

(Description of soft start processing)
Next, the outline of the soft start process will be described with reference to FIG. FIG. 11 is a diagram showing an outline of the soft start process. When the control unit 56 performs the soft start process, the heating control unit 63 supplies the second voltage pattern E2 or the third voltage pattern E3 to the heater 52.

  In FIG. 11, during time t0 to time t8, a state in which the soft start process is performed using the third voltage pattern E3 is shown. When the soft start process is started, the heating control unit 63 supplies a third voltage pattern E3 determined based on the lighting duty ratio Do = 20% in the first period (first quarter wave period) ( t = t0 to t4). Then, the third voltage pattern E3 determined based on the lighting duty ratio Do = 40% is supplied for the second period (second quarter wave period) (t = t4 to t8). Note that the change width (+ 20% in the example of FIG. 11) of the lighting duty ratio Do in the first cycle and the second cycle may be set as appropriate within a preset fluctuation amount upper limit value. In addition, how many cycles the soft start process is performed may be set as appropriate.

  In this way, by performing a soft start process and gradually increasing the voltage supplied to the heater 52, it is possible to prevent a large inrush current from being generated at the start of energization of the heater 52. Can be suppressed.

  When the soft start process is completed, the heater 52 shifts to a steady supply period (after time t = t8) in which a voltage pattern based on the supply voltage pattern table V is supplied. During this steady supply period, the voltage pattern switching process described in step S62 in FIG. 10 is performed as necessary.

(Explanation of soft stop processing)
Next, the outline of the soft stop process will be described with reference to FIG. FIG. 12 is a diagram showing an outline of the soft stop process. In FIG. 12, when the steady supply period ends, the control unit 56 performs a soft stop process for gradually decreasing the voltage waveform.

  In FIG. 12, during the period from time t25 to time t33, a state in which the soft stop process is performed using the third voltage pattern E3 is shown. When the soft stop process is started, the heating control unit 63 supplies the third voltage pattern E3 determined based on the lighting duty ratio Do = 40% in the first cycle (first quarter wave period) ( t = t25-t29). Then, the third voltage pattern E3 determined based on the lighting duty ratio Do = 20% is supplied for the second periphery (second quarter wave period) (t = t29 to t33). Note that the change width of the lighting duty ratio Do in the first cycle and the second cycle (−20% in the example of FIG. 12) may be set as appropriate within a preset variation amount upper limit value. Moreover, what is necessary is just to set suitably how many times a soft stop process is performed.

  When the soft stop process ends, the CPU ends the supply of the voltage value e to the heater 52.

  As described above, since the voltage value e supplied to the heater 52 is gradually reduced by performing the soft stop process, it is possible to prevent the current value from suddenly becoming zero when the energization of the heater 52 is stopped. The occurrence of flicker can be suppressed.

(Second Embodiment)
Next, a schematic configuration of an image forming apparatus including a heater control device according to the second embodiment of the present invention will be described.

  FIG. 13 is a block diagram illustrating a main configuration of the heater control device 60a included in the image forming apparatus 100a. The heater control device 60a differs from the heater control device 60 described above in that it includes two heaters (heaters 152a and 152b) for heating the fixing roller 51a. That is, as shown in FIG. 13, the heater control device 60a is provided in the fixing device 50a, and includes a fixing roller 51a, heaters 152a and 152b, an AC power source 153, triacs 154a and 154b, and temperature sensors 155a and 155b. A controller 156a, a zero-cross detector 157a, and a voltage detector 158a.

  As described above, the fixing roller 51a rotates while being in pressure contact with the pressure roller 51b (FIG. 1) to fix the toner image transferred to the transfer paper.

  The heaters 152a and 152b are an example of a heating unit, and are built in the fixing roller 51a to melt the toner image transferred to the transfer paper with heat, and embed and fix it in the fibers of the transfer paper.

  The AC power source 153 supplies an AC voltage to the heaters 152a and 152b. In the present embodiment, it is assumed that an alternating voltage that changes in a sine wave shape with time is supplied.

  The triacs 154a and 154b are switching means, and switch (ON / OFF) the AC voltage supplied from the AC power source 153 at a timing instructed by the control unit 156a. The triacs 154a and 154b supply the switched AC voltage to the heaters 152a and 152b. When the triacs 154a and 154b are turned on, the heaters 152a and 152b are energized to generate heat. When the triacs 154a and 154b are off, the heaters 152a and 152b are not energized.

  The temperature sensors 155a and 155b are an example of temperature detection means, and measure the surface temperature of the fixing roller 51a. The temperature sensors 155a and 155b incorporate, for example, a thermistor whose resistance value changes according to the temperature, and measures the surface temperature of the fixing roller 51a based on the resistance value of the thermistor. The temperature sensor 155a measures the temperature of the area heated by the heater 152a on the surface of the fixing roller 51a. The temperature sensor 155b measures the temperature of the area heated by the heater 152b on the surface of the fixing roller 51a.

  The zero-cross detector 157a detects the timing at which the AC voltage supplied from the AC power source 153 crosses 0 volt from the plus side to the minus side or from the minus side to the plus side (hereinafter referred to as zero-cross timing). And the zero cross detection part 157a outputs a zero cross detection signal with respect to the control part 156a, when the timing of zero cross is detected.

  The voltage detection unit 158a detects the voltage value e of the AC voltage supplied from the AC power source 153. Then, the voltage detection unit 158a outputs the detected voltage value e to the control unit 156a.

  The controller 156a includes the surface temperature of the fixing roller 51a measured by the temperature sensors 155a and 155b, the zero-cross timing of the AC voltage detected by the zero-cross detector 157a, and the voltage value e of the AC voltage detected by the voltage detector 158a. Based on the above, the timing for switching the AC voltage is determined. Then, the control unit 156a operates the triacs 154a and 154b based on the determined timing.

  The control unit 156a is implemented as a computer in which a CPU, a RAM, a ROM, and an input / output interface (not shown in FIG. 13) are connected via a bus. The CPU reads and executes the program stored in the ROM. The read program is developed on the CPU in an executable form, and constitutes a necessary voltage estimation unit 162a and a heating control unit 163a. The ROM is an example of a storage unit, and stores the above-described program and a supply voltage table 164a in which voltage patterns supplied to the halogen lamps included in the heaters 152a and 152b are registered.

  The supply voltage table 164a stores voltage patterns supplied to the halogen lamps included in the heaters 152a and 152b serving as heating means, with two periods of the AC voltage supplied from the AC power supply 153, that is, four half waves as one period. The supply voltage table 164a includes the supply voltage pattern table V described in the first embodiment, and three different voltage patterns (first voltage pattern E1, second voltage pattern E2, and third voltage pattern, respectively). E3) is stored. A specific example of the supply voltage table 164a will be described later (see FIGS. 14, 15, and 16).

  The supply voltage table 164a stores the relationship between the surface temperature of the fixing roller 51a and the lighting duty ratio Do of the supplied AC voltage, as described in the first embodiment.

  Further, as described in the first embodiment, the supply voltage table 164a indicates the harmonic margin when a predetermined voltage pattern is supplied to the heater control device 60a, as voltage patterns (E1, E2, E3). The data is stored every time and every phase duty ratio Dp.

  The necessary voltage estimation unit 162a is an example of necessary voltage estimation means, and an AC voltage necessary for heating the surface of the fixing roller 51a to a target temperature based on the measurement results of the temperature sensors 155a and 155b as temperature detection means. Is estimated. Then, the necessary voltage estimation unit 162a reads an AC voltage pattern that approximates the estimated AC voltage from the supply voltage table 164a.

  The heating control unit 163a is an example of a heating control unit, and supplies the supply voltage pattern table V read from the supply voltage table 164a by the necessary voltage estimation unit 162a or the voltages of the voltage patterns E1, E2, and E3 to the heaters 152a and 152b. By doing so, the surface temperature of the fixing roller 51a is controlled.

(Description of supply voltage table)
Next, the contents of the supply voltage table 164a will be described with reference to FIG. 14, FIG. 15, and FIG.

  FIG. 14 is a diagram illustrating an example of the supply voltage table 164a. A supply voltage table 164a shown in FIG. 14 shows an example in which the first voltage pattern E1 is supplied to the two heaters 152a and 152b.

  First, FIG. 14A will be described. FIG. 14A is an example of a supply voltage table 164a when a voltage with a lighting duty ratio Do = 0 to 25% is supplied to the heater 152a. In FIG. 14 to FIG. 16, “phase” indicates that phase control is performed. Further, a portion described as “half wave” represents performing wave number control. For example, phase control for supplying a voltage with a phase duty ratio Dp to the first half-wave region a of the heater 152a is performed. At this time, when a voltage with a lighting duty ratio Do = 0 to 25% is supplied to the heater 152b, a phase in which a voltage with a phase duty ratio Dp is supplied to the third half-wave area c not adjacent to the first half-wave area a. Take control. As described above, the voltage supplied to the heater 152a and the voltage supplied to the heater 152b are set so that the half-wave regions for supplying the voltage are not adjacent to each other. In the description of FIGS. 14 to 16, the phase duty ratio Dp when performing the phase control can be set to an arbitrary value of 0 to 100%.

  In FIG. 14A, when a voltage with a lighting duty ratio Do = 25 to 50% is supplied to the heater 152b, a half wave with a phase duty ratio Dp = 100% is applied to the third half wave region c. Control the wave number to be supplied. Then, phase control for supplying a voltage of the phase duty ratio Dp to either the second half-wave region b or the fourth half-wave region d is performed. In addition, the symbol () described in FIGS. 14 to 16 indicates that the information described in () can be interchanged.

  In FIG. 14A, when a voltage with a lighting duty ratio Do = 50 to 75% is supplied to the heater 152b, wave number control for supplying a half wave to the third half wave region c is performed. Then, wave number control for supplying a half wave to the second half wave region b is performed, and phase control for supplying a voltage of the phase duty ratio Dp to the fourth half wave region d is performed. Note that the voltage supplied to the second half-wave region b and the voltage supplied to the fourth half-wave region d can be interchanged.

  Further, in FIG. 14A, when a voltage with a lighting duty ratio Do = 75 to 100% is supplied to the heater 152b, the second half-wave region b, the third half-wave region c, and the fourth half-wave region. Wave number control for supplying a half wave to d is performed. And the phase control which supplies the voltage of the phase duty ratio Dp to the 1st half-wave area | region a is performed.

  In FIG. 14A, the phase of the voltage supplied to the first half-wave region a is controlled as the voltage waveform supplied to the heater 152a. However, as described in the description of FIG. Phase control may be performed on the half-wave region. When the phase control is performed on the other half-wave region, the voltage waveform pattern supplied to the heater 152b may be changed according to the position of the half-wave region. The same applies to FIGS. 15 and 16 described below.

  Next, FIG. 14B will be described. FIG. 14B is an example of a supply voltage table 164a when a voltage with a lighting duty ratio Do = 25 to 50% is supplied to the heater 152a. For example, the wave number control for supplying the half wave to the first half wave region a of the heater 152a is performed, and the phase control for supplying the voltage of the phase duty ratio Dp to the third half wave region c is performed. At this time, when a voltage with a lighting duty ratio Do = 0 to 25% is supplied to the heater 152b, a voltage with a phase duty ratio Dp is applied to either the second half-wave region b or the fourth half-wave region d. Control the phase to be supplied.

  In FIG. 14B, when a voltage with a lighting duty ratio Do = 25 to 50% is supplied to the heater 152b, wave number control for supplying a half wave to the second half wave region b is performed. And the phase control which supplies the voltage of the phase duty ratio Dp to the 4th half-wave area | region d is performed. Note that the voltage supplied to the second half-wave region b and the voltage supplied to the fourth half-wave region d can be interchanged.

  In FIG. 14B, when supplying a voltage with a lighting duty ratio Do = 50 to 75% to the heater 152b, the wave number for supplying a half wave to the second half wave region b and the fourth half wave region d. Take control. And the phase control which supplies the voltage of the phase duty ratio Dp to the 3rd half-wave area | region c is performed.

  Further, in FIG. 14B, when a voltage with a lighting duty ratio Do = 75 to 100% is supplied to the heater 152b, the second half-wave region b, the third half-wave region c, and the fourth half-wave region. Wave number control for supplying a half wave to d is performed. And the phase control which supplies the voltage of the phase duty ratio Dp to the 1st half-wave area | region a is performed.

  Next, FIG. 14C will be described. FIG. 14C is an example of a supply voltage table 164a when a voltage with a lighting duty ratio Do = 50 to 75% is supplied to the heater 152a. For example, the wave number control for supplying the half wave to the first half wave region a and the third half wave region c of the heater 152a is performed, and the phase is set to either the second half wave region b or the fourth half wave region d. Phase control for supplying a voltage having a duty ratio Dp is performed. At this time, when supplying a voltage with a lighting duty ratio Do = 0 to 25% to the heater 152b, phase control is performed to supply a voltage with a phase duty ratio Dp to the fourth half-wave region d.

  In FIG. 14C, when a voltage with a lighting duty ratio Do = 25 to 50% is supplied to the heater 152b, wave number control for supplying a half wave to the fourth half wave region d is performed. And the phase control which supplies the voltage of the phase duty ratio Dp to the 2nd half-wave area | region b is performed.

  In FIG. 14C, when a voltage with a lighting duty ratio Do = 50 to 75% is supplied to the heater 152b, a half wave is supplied to the second half wave region b and the fourth half wave region d. Perform wave number control. Then, phase control for supplying a voltage of the phase duty ratio Dp to either the first half-wave region a or the third half-wave region c is performed.

  Further, in FIG. 14C, when a voltage with a lighting duty ratio Do = 75 to 100% is supplied to the heater 152b, a half wave is supplied to the second half wave region b and the fourth half wave region d. Perform wave number control. Then, wave number control for supplying a half wave to the first half wave region a is performed, and phase control for supplying a voltage of the phase duty ratio Dp to the third half wave region c is performed. Note that the voltage supplied to the first half-wave region a and the voltage supplied to the third half-wave region c can be interchanged.

  Further, FIG. 14D is an example of a supply voltage table 164a when a voltage with a lighting duty ratio Do = 75 to 100% is supplied to the heater 152a. For example, the wave number control for supplying the half wave to the first half wave region a and the third half wave region c of the heater 152a is performed, and the wave number control for supplying the half wave to the second half wave region b is performed to perform the fourth half wave. Phase control for supplying a voltage having a phase duty ratio Dp to the wave region d is performed. Note that the voltage supplied to the second half-wave region b and the voltage supplied to the fourth half-wave region d can be interchanged. At this time, when a voltage with a lighting duty ratio Do = 0 to 25% is supplied to the heater 152b, phase control for supplying a voltage with a phase duty ratio Dp to the fourth half-wave region d is performed.

  Further, in FIG. 14D, when a voltage with a lighting duty ratio Do = 25 to 50% is supplied to the heater 152b, wave number control for supplying a half wave to the fourth half wave region d is performed, and Phase control for supplying a voltage having a phase duty ratio Dp to the two half-wave region b is performed.

  In FIG. 14D, when a voltage with a lighting duty ratio Do = 50 to 75% is supplied to the heater 152b, a half wave is supplied to the second half wave region b and the fourth half wave region d. Perform wave number control. Then, phase control for supplying a voltage of the phase duty ratio Dp to either the first half-wave region a or the third half-wave region c is performed.

  Further, in FIG. 14D, when a voltage with a lighting duty ratio Do = 75 to 100% is supplied to the heater 152b, a half wave is supplied to the second half wave region b and the fourth half wave region d. Perform wave number control. Then, wave number control for supplying a half wave to the first half wave region a is performed, and phase control for supplying a voltage of the phase duty ratio Dp to the third half wave region c is performed. Note that the voltage supplied to the first half-wave region a and the voltage supplied to the third half-wave region c can be interchanged.

  Next, FIG. 15 will be described. A supply voltage table 164a illustrated in FIG. 15 illustrates an example in which the first voltage pattern E1 is supplied to the heater 152a and the second voltage pattern E2 is supplied to the heater 152b. Note that the symbol () described in FIG. 15 indicates that the information described in () can be interchanged.

  First, FIG. 15A will be described. FIG. 15A is an example of a supply voltage table 164a when a voltage with a lighting duty ratio Do = 0 to 25% is supplied to the heater 152a. For example, phase control for supplying a voltage with a phase duty ratio Dp to the first half-wave region a of the heater 152a is performed. At this time, when supplying a voltage with a lighting duty ratio Do = 0 to 50% to the heater 152b, phase control is performed to supply a voltage with a phase duty ratio Dp to the second half-wave region b and the fourth half-wave region d. Do.

  In FIG. 15A, when a voltage with a lighting duty ratio Do = 50 to 100% is supplied to the heater 152b, a half wave is supplied to the second half wave region b and the fourth half wave region d. Perform wave number control. Then, phase control for supplying a voltage with a phase duty ratio Dp to the first half-wave region a and the third half-wave region c is performed.

  Next, FIG. 15B will be described. FIG. 15B is an example of a supply voltage table 164a when a voltage with a lighting duty ratio Do = 25 to 50% is supplied to the heater 152a. For example, the wave number control for supplying the half wave to the first half wave region a of the heater 152a is performed, and the phase control for supplying the voltage of the phase duty ratio Dp to the third half wave region c is performed. At this time, when supplying a voltage with a lighting duty ratio Do = 0 to 50% to the heater 152b, phase control is performed to supply a voltage with a phase duty ratio Dp to the second half-wave region b and the fourth half-wave region d. Do.

  In FIG. 15B, when a voltage with a lighting duty ratio Do = 50 to 100% is supplied to the heater 152b, the wave number for supplying a half wave to the second half wave region b and the fourth half wave region d. Take control. Then, phase control for supplying a voltage with a phase duty ratio Dp to the first half-wave region a and the third half-wave region c is performed.

  Next, FIG. 15C will be described. FIG. 15C is an example of a supply voltage table 164a when a voltage with a lighting duty ratio Do = 50 to 75% is supplied to the heater 152a. For example, the wave number control for supplying the half wave to the first half wave region a and the third half wave region c of the heater 152a is performed, and the phase is set to either the second half wave region b or the fourth half wave region d. Phase control for supplying a voltage having a duty ratio Dp is performed. At this time, when supplying a voltage with a lighting duty ratio Do = 0 to 50% to the heater 152b, phase control is performed to supply a voltage with a phase duty ratio Dp to the second half-wave region b and the fourth half-wave region d. Do.

  In FIG. 15C, when a voltage with a lighting duty ratio Do = 50 to 100% is supplied to the heater 152b, a half wave is supplied to the second half wave region b and the fourth half wave region d. In addition to performing wave number control, phase control for supplying a voltage with a phase duty ratio Dp to the first half-wave region a and the third half-wave region c is performed.

  Further, FIG. 15D is an example of a supply voltage table 164a when a voltage with a lighting duty ratio Do = 75 to 100% is supplied to the heater 152a. For example, the wave number control for supplying the half wave to the first half wave region a and the third half wave region c of the heater 152a is performed, and the wave number control for supplying the half wave to the second half wave region b is performed to perform the fourth half wave. Phase control for supplying a voltage having a phase duty ratio Dp to the wave region d is performed. Note that the voltage supplied to the second half-wave region b and the voltage supplied to the fourth half-wave region d can be interchanged. At this time, when supplying a voltage with a lighting duty ratio Do = 0 to 50% to the heater 152b, phase control is performed to supply a voltage with a phase duty ratio Dp to the second half-wave region b and the fourth half-wave region d. Do.

  In FIG. 15D, when a voltage with a lighting duty ratio Do = 50 to 100% is supplied to the heater 152b, a half wave is supplied to the second half wave region b and the fourth half wave region d. In addition to performing wave number control, phase control for supplying a voltage with a phase duty ratio Dp to the first half-wave region a and the third half-wave region c is performed.

  Next, FIG. 16 will be described. A supply voltage table 164a shown in FIG. 16 shows an example in which the first voltage pattern E1 is supplied to the heater 152a and the third voltage pattern E3 is supplied to the heater 152b.

  First, FIG. 16A will be described. FIG. 16A is an example of a supply voltage table 164a when a voltage with a lighting duty ratio Do = 0 to 25% is supplied to the heater 152a. For example, phase control for supplying a voltage with a phase duty ratio Dp to the first half-wave region a of the heater 152a is performed. At this time, the phase control for supplying the voltage of the phase duty ratio Dp to all of the first half-wave region a, the second half-wave region b, the third half-wave region c, and the fourth half-wave region d to the heater 152b. I do. At this time, in order to reduce the influence of the harmonic current, the phase duty ratio Dp of each half-wave region may be further adjusted.

  That is, while maintaining the lighting duty ratio Do constant, the phase duty ratio Dpa of the first half-wave region a, the phase duty ratio Dpb of the second half-wave region b, and the phase duty ratio Dpc of the third half-wave region c And the phase duty ratio Dp of the fourth half-wave region d may be individually adjusted. More specifically, in accordance with the concept described in FIG. 7, the phase duty ratio Dpa of the first half-wave region a and the phase duty ratio Dpc of the third half-wave region c are reduced, that is, the supply of voltage is started. By adjusting the time later (increasing the phase angle at which voltage supply is started), the phase duty ratio Dpb of the second half-wave region b and the phase duty ratio Dpd of the fourth half-wave region d are increased, that is, voltage supply Is adjusted early (decreasing the phase angle at which voltage supply is started). That is, the phase duty ratio Dp is adjusted so that the period during which the voltage is applied to both the two heaters 152a and 152b becomes as small as possible. The method for adjusting the phase duty ratio Dp can be similarly applied to FIGS. 16B to 6D described below.

  Next, FIG. 16B will be described. FIG. 16B is an example of a supply voltage table 164a when a voltage with a lighting duty ratio Do = 25 to 50% is supplied to the heater 152a. For example, the wave number control for supplying the half wave to the first half wave region a of the heater 152a is performed, and the phase control for supplying the voltage of the phase duty ratio Dp to the third half wave region c is performed. At this time, the phase control for supplying the voltage of the phase duty ratio Dp to all of the first half-wave region a, the second half-wave region b, the third half-wave region c, and the fourth half-wave region d to the heater 152b. I do.

  Next, FIG. 16C will be described. FIG. 16C is an example of a supply voltage table 164a when a voltage with a lighting duty ratio Do = 50 to 75% is supplied to the heater 152a. For example, the wave number control for supplying the half wave to the first half wave region a and the third half wave region c of the heater 152a is performed, and the phase duty is applied to either the second half wave region b or the fourth half wave region d. Phase control for supplying a voltage of the ratio Dp is performed. At this time, the phase control for supplying the voltage of the phase duty ratio Dp to all of the first half-wave region a, the second half-wave region b, the third half-wave region c, and the fourth half-wave region d to the heater 152b. I do.

  FIG. 16D is an example of a supply voltage table 164a when a voltage with a lighting duty ratio Do = 75 to 100% is supplied to the heater 152a. For example, the wave number control for supplying the half wave to the first half wave region a and the third half wave region c of the heater 152a is performed, and the wave number control for supplying the half wave to the second half wave region b is performed to perform the fourth half wave. Phase control for supplying a voltage having a phase duty ratio Dp to the wave region d is performed. Note that the voltage supplied to the second half-wave region b and the voltage supplied to the fourth half-wave region d can be interchanged. At this time, the phase control for supplying the voltage of the phase duty ratio Dp to all of the first half-wave region a, the second half-wave region b, the third half-wave region c, and the fourth half-wave region d to the heater 152b. I do.

  The heater control device 60a operates in the same manner as the heater control device 60 described in the first embodiment. At this time, since the heater control device 60a includes two heaters 152a and 152b, the required voltage estimation unit 162a estimates the AC voltage necessary for heating for each of the heaters 152a and 152b, and heats the heaters. The control unit 163a selects and supplies a voltage pattern to be supplied. Since the detailed contents and procedure of the operation are the same as those described in the first embodiment, the description thereof is omitted.

  As described above, even when a plurality of heaters 152a and 152b are provided, as in the case where only one heater 52 is provided, the occurrence of flicker and the generation of harmonic current when an AC voltage is supplied to the heaters 152a and 152b. Both generation can be suppressed.

  As described above, according to the heater control device 60 according to the first embodiment, the necessary voltage estimation unit 62 (necessary) is based on the surface temperature of the fixing roller 51a detected by the temperature sensor 55 (temperature detecting means). Voltage estimation means) estimates a voltage pattern necessary for heating the fixing roller 51a. Then, when the heating control unit 63 (heating control means) uses the estimated voltage pattern as a half-wave region in which the half cycle of the AC voltage stored in the ROM as the storage means is one half-wave region, A plurality of voltage patterns (first voltage pattern E1, second half-wave region a, second half-wave region b, third half-wave region c, fourth half-wave region d) having one cycle as a region. The voltage pattern E2 or the third voltage pattern E3) is selected. The heating control unit 63 further controls the surface temperature of the fixing roller 51a by supplying the selected voltage pattern to the heater 52 (heating means). Therefore, it is possible to suppress both the occurrence of flicker and the influence of the harmonic current.

  Further, according to the heater control device 60 according to the first embodiment, the voltage pattern is set to any one half wave in the four half wave region in accordance with an increase in power supplied to the heater 52 (heating means). A first voltage pattern E1 that increases the phase duty ratio Dp (energization time) in order from the region is included. Therefore, since the harmonic component contained in the voltage waveform is reduced, it is possible to provide a voltage pattern that is further less affected by the harmonic current.

  In addition, according to the heater control device 60 according to the first embodiment, the voltage pattern is changed to two non-adjacent half-wave regions in the four-half wave region in accordance with an increase in power supplied to the heater 52 (heating means). A second voltage pattern E2 that increases both the phase duty ratio Dp (energization time) equally applied to the wave region is included. Therefore, although the harmonic component is increased as compared with the first voltage pattern E1, the inrush current is reduced, so that it is possible to provide a voltage pattern that can further suppress the occurrence of flicker.

  Further, according to the heater control device 60 according to the first embodiment, the voltage pattern is applied to all half-wave regions of the four half-wave regions in accordance with an increase in power supplied to the heater 52 (heating means). And a third voltage pattern E3 that increases the phase duty ratio Dp (energization time) equally applied to each other. Therefore, it is possible to provide a voltage pattern that can further suppress the occurrence of flicker.

  Further, according to the heater control device 60 according to the first embodiment, the heating control unit 63 (heating control means) includes the first voltage pattern E1, the second voltage pattern E2, and the third voltage pattern E3 ( Among the plurality of voltage patterns), the power consumption of the heater 52 (heating means) and the margin of how much the maximum value of the harmonic current generated when each voltage pattern is supplied falls below the design target A voltage pattern to be supplied to the heater 52 is selected based on the harmonic margin. Therefore, the occurrence of flicker and the influence of harmonic current can be reliably suppressed.

  Further, according to the heater control device 60 according to the first embodiment, the heating control unit 63 (heating control means) has a variation in the sum of energization times in the four-half wave region within a predetermined value, and On the condition that the same voltage pattern is supplied for a predetermined time or longer, the voltage pattern is switched to a voltage pattern with less influence of the harmonic current and supplied to the heater 52 (heating means). Therefore, before the influence of the harmonic current appears, the voltage pattern supplied to the heater 52 (heating means) can be switched to a voltage pattern with less influence of the harmonic current.

  Further, according to the heater control device 60 according to the first embodiment, the heating control unit 63 (heating control unit) suppresses the occurrence of flicker during the period in which the amount of change in the energization time ratio is controlled. The voltage pattern can be switched to be supplied to the heater 52 (heating means). Therefore, the occurrence of flicker can be reliably suppressed.

  In addition, according to the heater control device 60 according to the first embodiment, the necessary voltage estimation unit 62 (necessary voltage estimation means) further maintains each energization time in the four half wave region while maintaining each half wave. It has a function of changing the energization time of each region. Therefore, it is possible to supply a voltage pattern that further reduces the influence of the harmonic current while keeping the power supplied to the heater 52 constant.

  Although the embodiment has been described above, the specific configuration of each part, the content of processing, and the like are not limited to those described in the embodiment.

  For example, the program described in the first embodiment is provided in a form that can be installed or executed in addition to a program stored in a ROM that is a storage unit in advance, and a CD-ROM, a flexible disk ( FD), CD-R, DVD (Digital Versatile Disc), etc. may be provided by being recorded on a computer-readable recording medium. Furthermore, the program may be provided by being stored on a computer connected to a network such as the Internet and downloaded via the network. The program may be provided or distributed via a network such as the Internet.

50 Fixing device 51a Fixing roller 52 Heater (heating means)
53 AC power supply 54 Triac 55 Temperature sensor (temperature detection means)
56 Control Unit 57 Zero Cross Detection Unit 58 Voltage Detection Unit 60 Heater Control Device 62 Required Voltage Estimation Unit (Required Voltage Estimation Unit)
63 Heating control unit (heating control means)
64 supply voltage table 100 image forming apparatus Do lighting duty ratio Dp phase duty ratio E1 first voltage pattern E2 second voltage pattern E3 third voltage pattern 2T control period Ta allowable control period

JP 2008-191333 A

Claims (10)

Heating means for heating the fixing roller by supplying an AC voltage;
Temperature detecting means for detecting the surface temperature of the fixing roller;
Necessary voltage estimation means for estimating a voltage pattern necessary for heating the surface temperature of the fixing roller to a target temperature based on the detection result of the temperature detection means and the voltage value of the AC voltage;
A storage means for storing a plurality of voltage patterns supplied to the heating means, wherein the half cycle of the AC voltage is one half wave region, and the four half wave region of the AC voltage is one cycle;
Heating control means for controlling the surface temperature of the fixing roller by selecting the voltage pattern corresponding to the estimation result of the necessary voltage estimation means and supplying the selected voltage pattern to the heating means;
A heater control device comprising: The voltage pattern includes a first voltage pattern that increases energization time sequentially from any one half-wave region in the four-half wave region in accordance with an increase in power supplied to the heating unit. The heater control device according to claim 1. The voltage pattern is a second voltage pattern that increases both energization time equally applied to two non-adjacent half-wave regions in the four-half wave region according to an increase in power supplied to the heating means. The heater control apparatus according to claim 1 or 2, characterized by comprising: The voltage pattern includes a third voltage pattern that increases both energization times equally applied to all the half-wave regions of the four-half wave region in accordance with an increase in power supplied to the heating unit. The heater control device according to any one of claims 1 to 3, wherein the heater control device is characterized in that: The heating control means determines, from among the plurality of voltage patterns, how much power consumption of the heating means and the maximum value of the harmonic current generated when the voltage pattern is supplied are below a design target. The heater control device according to claim 4, wherein the voltage pattern is selected based on a harmonic margin indicating a margin. The heating control means has the effect of harmonic current on the condition that the fluctuation of the sum of the energization times in the four-half wave region is within a predetermined value and the same voltage pattern is supplied for a predetermined time or more. The heater control device according to claim 4 or 5, wherein a voltage pattern with less is selected and supplied to the heating means. The heating control means selects a voltage pattern capable of suppressing the occurrence of flicker and supplies it to the heating means during a period in which the amount of fluctuation of the energization time ratio is controlled. The heater control device according to any one of claims 4 to 6. The said required voltage estimation means has further the function to each change the energization time of each half-wave area | region, keeping the energization time in the said 4 half-wave area | region constant. The heater control apparatus of any one of these. A temperature detection step for detecting the surface temperature of the fixing roller;
A necessary voltage estimating step for estimating a voltage pattern necessary for heating the surface temperature of the fixing roller to a target temperature based on the surface temperature and a voltage value of an AC voltage supplied to a heating unit for heating the fixing roller. When,
When the half cycle of the AC voltage is set to one half wave region, the necessary voltage estimation is performed from among a plurality of voltage patterns supplied to the heating means, wherein the four quarter wave region where the AC voltage is continuous is set to one cycle. A voltage pattern selection step for selecting the voltage pattern estimated by the step;
A voltage supply step of supplying the selected voltage pattern to the heating means;
A heater control method characterized by comprising: Computer
Based on the detection result of the temperature detecting means for detecting the surface temperature of the fixing roller heated by the AC voltage and the voltage value of the AC voltage, a voltage pattern necessary for heating the surface temperature of the fixing roller to the target temperature is obtained. A necessary voltage estimating means for estimating;
A storage means for storing a plurality of voltage patterns supplied to the heating means, wherein the half cycle of the AC voltage is one half wave region, and the four half wave region of the AC voltage is one cycle;
Heating control means for controlling the surface temperature of the fixing roller by selecting the voltage pattern corresponding to the estimation result of the necessary voltage estimation means and supplying the selected voltage pattern to the heating means;
Program to make it work.

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