JP2016180913A - Power supply device, image forming apparatus, and control method of power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a flicker value and perform stable, accurate fixing control.SOLUTION: A power supply device performs power control to heaters by using a combination arrangement pattern taking two heaters of a plurality of heaters heating a heating roller of a fixing device as one combination of control target, the combination arrangement pattern including a combination arrangement pattern including sections where the two heaters are turned on, only one heater is turned on, and the two heaters are turned off.SELECTED DRAWING: Figure 12

Description

  The present invention relates to a power supply device, an image forming apparatus, and a control method for the power supply device.

  In an electrophotographic image forming apparatus, in order to fix a toner image formed on a sheet to the sheet, the sheet is conveyed to a fixing nip formed by a fixing member such as a pair of heated rollers, and heated and heated. Perform pressure treatment. This fixes the toner image on the paper.

  Generally, a heater such as a halogen lamp is used as a heat source for the fixing member. In an image forming apparatus using such a heater, a drop in power supply voltage is caused by an inrush current to the heater that is generated when power supply to an unheated heater is started, and flicker due to this causes a problem.

  Half-wave duty control (HDC control: Half Cycle Duty control) is used. Duty control in half-wave units uses a predetermined period that includes multiple half-waves of the AC waveform of the AC power supply as a control period, and controls the number of waves that are turned on within that control period, so that the power supplied to the heater is highly accurate. To control.

  In addition, since the heater is turned on or off in accordance with the timing when the AC power supply voltage becomes zero (zero cross timing), the heater is turned on at the timing when the power supply voltage is 0 V, so that the AC power supply voltage reaches the peak. Since the heater is heated and the resistance rises to some extent, the inrush current can be reduced.

  In Patent Document 1, when performing such half-wave duty control, flicker is further reduced by using a specific arrangement pattern. Specifically, in Patent Document 1, an arrangement pattern is used that is configured so that all of the sections with the smaller half-wave total number are discontinuous among the sections in which the heater is turned on or off within the control cycle. By using such an arrangement pattern, the heaters are turned on and off at a cycle shorter than the cycle (8.8 Hz) that is most unpleasant to humans.

JP 2009-237070 A

  However, the number of heaters used as a heat source for the fixing member is not limited to one, and in many cases, a plurality of heaters are used. As a result, fine temperature control can be performed, and papers having different widths can be handled.

  In the technique disclosed in Patent Document 1, even when there is an effect of reducing flicker when power control is performed on one heater, the timing of turning on / off is performed when power control is simultaneously performed on a plurality of heaters. Depending on the case, the effect is not necessarily obtained.

  The present invention has been made in view of the above circumstances, and provides a power supply apparatus, an image forming apparatus, and a control method for the power supply apparatus that can reduce flicker even when a plurality of heaters are used simultaneously. Intended to provide

  The above object of the present invention is achieved by the following means.

(1) A power supply device that performs power control of a fixing member that includes a fixing member that heat-fixes a sheet on which a toner image is formed, and a plurality of heaters that heat the fixing member,
A control unit that determines a duty ratio, which is a ratio of an on-section supplying power to the heater within a predetermined control cycle, based on a detected temperature of the fixing member, with a half-wave cycle of the AC power supply as a unit section;
A storage unit that stores a plurality of array patterns indicating on / off sections of the half wave within the control period corresponding to the duty ratio;
A switching unit that switches on / off of the heater according to the arrangement pattern,
The array pattern includes a plurality of set array patterns corresponding to a total duty ratio within a range of a duty ratio of 0 to 200% in which two heaters of the plurality of heaters are controlled as a set.
The control unit determines the total duty ratio of a set of heaters to be controlled, controls the switching unit based on a set arrangement pattern selected according to the determined total duty ratio,
Furthermore, the plurality of group arrangement patterns include at least two group arrangement patterns including a group arrangement pattern configured to turn on two heaters, turn on only one heater, and turn off two heaters.

(2) Within the range of 0 to 200% of the total duty ratio, it is composed of sections in which the two heaters are turned on, only one heater is turned on, and two heaters are turned off, in a range before and after 100%. Group arrangement pattern,
The group arrangement pattern having a total duty ratio of 100% is a group arrangement pattern in which one of the two heaters has a duty ratio of 100% and the other of the two heaters has a duty ratio of 0% in all sections in the control cycle. The power supply device according to 1).

  (3) The power supply device according to (1) or (2), wherein the arrangement pattern is set based on a flicker measurement value.

  (4) The power supply device according to any one of (1) to (3), wherein different set arrangement patterns are stored in the storage unit depending on a combination of rated powers of the two heaters. .

  (5) The two heaters to be controlled are a heater having the same calorific value distribution in the width direction perpendicular to the sheet conveying direction of the fixing member. The power supply device according to any one of the above.

  (6) Additional information indicating which one of the two heaters to turn on is given to the group arrangement pattern for a section in which only one heater is turned on. The power supply device according to any one of (5) to (5).

(7) A power supply device that performs power control of a fixing member that includes a fixing member that heat-fixes a sheet on which a toner image is formed, and a plurality of heaters that heat the fixing member,
A control unit that determines a duty ratio, which is a ratio of an on-section supplying power to the heater within a predetermined control cycle, based on a detected temperature of the fixing member, with a half-wave cycle of the AC power supply as a unit section;
A storage unit that stores a plurality of array patterns indicating on / off sections of the half wave within the control period corresponding to the duty ratio;
A switching unit that switches on / off of the heater according to the arrangement pattern,
The array pattern includes a plurality of set array patterns corresponding to a total duty ratio within a range of a duty ratio of 0 to 200% in which two heaters of the plurality of heaters are controlled as a set.
The set arrangement pattern is an arrangement pattern in which the ON intervals of the two heaters in each unit interval and the total ON number are described, and the plurality of the set arrangement patterns include at least two pieces. A set arrangement pattern composed of sections in which the heater is turned on, only one heater is turned on, and two heaters are turned off is included.
The control unit determines the total duty ratio of a set of heaters to be controlled and the duty ratio of each heater, the set arrangement pattern selected according to the determined total duty ratio, and the determined each of the set The power supply apparatus which calculates | requires the arrangement | sequence pattern with respect to each of said two heaters based on a duty ratio by calculation, and controls the said switching part based on the calculated | required arrangement | sequence pattern.

  (8) In the array pattern, there is no information specifying whether one of the two heaters is to be turned on in the section where only one heater is turned on. The power supply device according to (7), wherein a heater to be turned on is specified in a section in which only the heater is turned on.

  (9) In the above (7) or (8), the two heaters to be controlled are heaters having different calorific value distributions in the width direction perpendicular to the sheet conveying direction of the fixing member. The power supply described.

(10) an image forming unit that forms a toner image on a sheet;
A fixing member that heat-fixes the paper on which the toner image is formed, and a fixing unit that includes a plurality of heaters that heat the fixing member;
The power supply device according to any one of (1) to (9) above,
An image forming apparatus comprising:

(11) A control method for a power supply apparatus that supplies power to a fixing member that heat-fixes a sheet on which a toner image is formed and a plurality of heaters that heat the fixing member.
A step of determining a duty ratio, which is a ratio of an ON section for supplying power to the heater within a predetermined control period, based on a detected temperature of the fixing member, with a half wave period of the AC power supply as a unit section,
Selecting the arrangement pattern corresponding to the duty ratio from among the arrangement patterns indicating the on / off sections of the half-waves in the plurality of control cycles stored in the storage unit;
Switching on / off the heater at the half-wave period based on the selected array pattern,
The array pattern includes a plurality of set array patterns corresponding to a total duty ratio within a range of a duty ratio of 0 to 200% in which two heaters of the plurality of heaters are set as a control target.
In the determining step, the total duty ratio of a set of heaters to be controlled is determined;
In the switching step, on / off of the heater is switched based on the set arrangement pattern selected in the selecting step according to the determined total duty ratio,
The control method, wherein the plurality of group arrangement patterns include at least two group arrangement patterns configured by turning on two heaters, turning on only one heater, and turning off two heaters.

(12) A control method for a power supply apparatus that supplies power to a fixing member that heat-fixes a sheet on which a toner image is formed, and a plurality of heaters that heat the fixing member.
A step of determining a duty ratio, which is a ratio of an ON section for supplying power to the heater within a predetermined control period, based on a detected temperature of the fixing member, with a half wave period of the AC power supply as a unit section,
Selecting the arrangement pattern corresponding to the duty ratio from among the arrangement patterns indicating the on / off sections of the half-waves in the plurality of control cycles stored in the storage unit;
Switching the heater on / off in the half-wave period according to the arrangement pattern,
The array pattern includes a plurality of set array patterns corresponding to a total duty ratio within a range of a duty ratio of 0 to 200% with two heaters as a set of control targets.
The set arrangement pattern is an arrangement pattern in which the ON intervals of the two heaters in each unit interval and the total ON number are described, and the plurality of the set arrangement patterns include at least two pieces. A set arrangement pattern composed of sections in which the heater is turned on, only one heater is turned on, and two heaters are turned off is included.
In the determining step, a total duty ratio of a set of heaters to be controlled and a duty ratio of each heater are determined,
In the selecting step, an array pattern for each of the two heaters is obtained by calculation based on the set array pattern selected according to the determined total duty ratio and each determined duty ratio.
In the switching step, the heater is switched on / off based on the obtained arrangement pattern.

  According to the present invention, a set arrangement pattern in which two heaters are set as a control target, and includes two sections on, only one heater on, and two heaters off. By controlling the power for one set of heaters using the set arrangement pattern including the set set arrangement pattern, it is possible to reduce the flicker value and perform stable and highly accurate fixing control.

1 is a diagram illustrating a schematic configuration of an image forming apparatus 10 according to an embodiment. 2 is a block diagram illustrating a hardware configuration of the image forming apparatus 10. FIG. It is a figure which shows the emitted-heat amount distribution of the heaters L31-L33 in the width direction. 3 is a diagram illustrating a circuit configuration of a power supply device 200. FIG. It is a timing chart explaining duty control of a half wave period. It is an example of the arrangement pattern at the time of making one heater control object. It is an example of the arrangement pattern in consideration of simultaneous ON of two heaters as a reference example. The combination of the duty ratios of the two heaters in the reference example and the measured value of the flicker value are shown. It is a figure which shows the table 2A of the group arrangement pattern based on a comparative example. It is a figure which shows the table 2B of the arrangement | sequence pattern based on a comparative example. It is a figure which shows the table 2C of the arrangement pattern based on a comparative example. It is a figure which shows the table 3A of the group arrangement pattern based on an Example. It is a figure which shows the table 3B of the arrangement | sequence pattern based on an Example. It is a figure which shows the table 3C of the arrangement | sequence pattern based on an Example. A part of the array arrangement patterns and the arrangement patterns are extracted from the tables 3A to 3C. It is a graph corresponding to the tables 3A to 3C. FIG. 17A is a flowchart illustrating a method for controlling the power supply apparatus according to the first embodiment, and FIG. 17B is a table illustrating the determination method in step S102. It is a figure which shows the table 4 of the group arrangement pattern based on a modification. It is a flowchart which shows the control method which concerns on 2nd Embodiment. It is a corresponding | compatible table which shows the duty ratio of a center heater and an edge part heater, and the number of total ON area. It is a figure which shows the table 5 of the group arrangement pattern which concerns on 2nd Embodiment. It is a figure explaining the procedure of the calculation of step S204. It is a figure explaining the procedure of the calculation of step S204.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may be different from the actual ratios.

  FIG. 1 is a diagram illustrating a schematic configuration of an image forming apparatus 10 according to the embodiment. FIG. 2 is a block diagram illustrating a hardware configuration of the image forming apparatus 10.

  As shown in FIGS. 1 and 2, the image forming apparatus 10 includes a control unit 110, an image forming unit 120, a fixing unit 130, a storage unit 140, an operation display unit 150, a power supply unit 160, a scanner 170, a paper feed conveyance unit 180, and the like. A signal line 190 for electrically connecting them is provided.

  The control unit 110 includes a CPU, a RAM, and a ROM, reads various programs stored in the ROM, the storage unit 140, and the like as appropriate, develops them on the RAM, and implements various functions by executing the programs. .

  The image forming unit 120 includes developing units 121Y to 121K corresponding to toners of Y, M, C, and K colors. The toner images formed through the charging, exposure, and development processes by the developing units 121 </ b> Y to 121 </ b> K are sequentially stacked on the intermediate transfer belt 122 and transferred onto the paper S by the secondary transfer roller 123.

  The fixing unit 130 includes a heating roller 135 and a pressure roller 136 serving as a fixing member, and heats and pressurizes the paper S conveyed to the fixing nip of both rollers, so that a toner image on the paper S is obtained. It melts and fixes to the surface. The heating roller 135 includes, in order from the inside, a cored bar made of a cylindrical metal, an elastic layer made of a material such as silicone rubber or foamed silicone rubber formed on the surface thereof, and a release layer such as a fluororesin. A plurality of halogen lamp heaters L3 (heaters L31 to L34) are arranged inside the metal core. The length of the heating roller 135 in the rotation axis direction (hereinafter, simply referred to as “width direction”) orthogonal to the conveyance direction of the sheet S is long enough to fix the sheet S having the maximum sheet width that can be conveyed. The plurality of heaters L3 may be composed of heaters having different heat distributions (light distribution characteristics) corresponding to a plurality of stages of paper widths that can be fed by the apparatus (see FIG. 3 and the like described later).

  The pressure roller 136 includes, in order from the inside, a cored bar made of a cylindrical metal, an elastic layer made of a material such as silicone rubber or foamed silicone rubber formed on the surface thereof, and a release layer such as a fluororesin. The outer diameter and axial length of the pressure roller 136 are about the same as those of the heating roller 135. Note that the heater L3 may also be disposed inside the core of the pressure roller 136.

  The temperature sensors 131 to 133 detect the temperature of the surface of the heating roller 135. The temperature sensors 131 to 133 are arranged at different positions in the width direction such as the back side, the center portion, and the near side, and measure the temperature distribution of the heating roller 135 in the width direction. As the temperature sensors 131 to 135, for example, a thermistor arranged in a non-contact manner with respect to the heating roller 135 is used.

  The storage unit 140 is an auxiliary storage device configured by a semiconductor memory such as an HDD (Hard Disk Drive) or an SSD (Solid State Drive). The storage unit 140 stores a plurality of arrangement patterns that indicate on / off sections to be described later.

  The operation display unit 150 is, for example, a touch sensor superimposed on a display surface of an LCD (liquid crystal display), displays an operation screen, and accepts various operations by a user.

  The power supply unit 160 includes a zero-cross detection unit 610 and a plurality of switching elements 620 (switching elements 621 to 624). The power supply unit 160 is connected to a commercial AC power supply 90 (see FIG. 4) having a voltage of 100 V and a frequency of 50/60 Hz, for example, and supplies power to the heater L3 (heaters L31 to L34) and the components of the image forming apparatus 10. The zero cross detection unit 610 outputs a zero cross signal at the timing when the voltage output of the commercial AC power supply 90 crosses 0V. The control unit 110 performs on / off control of the switching element 620 configured by a triac or the like based on the zero cross signal.

  The scanner 170 includes an optical system composed of a mirror and a lens and a reading sensor such as a CCD, and reads an original placed on a platen glass or an original conveyed from an ADF (not shown) and outputs an image signal. Image data obtained by reading is stored in the storage unit 140 or the like.

  The paper feeding / conveying unit 180 includes a plurality of paper feeding trays 181 and 182 and a plurality of conveyance roller pairs driven by a conveyance motor (not shown). A large number of sheets S are stored in the sheet feeding trays 181 and 182. The stored sheets S are fed one by one to the downstream conveyance path.

  FIG. 3 is a diagram showing a heat generation amount distribution of the heaters L31 to L34 in the width direction. The back and front correspond to both ends of the maximum paper width. As shown in FIG. 3, among the four heaters, L31 and L32 are central heaters having a calorific value distribution in which the calorific value at the center is larger than the calorific values at both ends. The heaters L33 and L34 are end heaters having a calorific value distribution in which the calorific value at both ends is greater than the calorific value at the center. Both edges in the width direction of the heaters L33 and L34 correspond to the maximum sheet width (for example, 300 mm). The heaters L31 and L32 are heaters having the same rated power of 1000 W, and the heat amount distribution in the width direction is equal. The heaters L33 and L34 are heaters having the same rated power of 625 W, and the heat generation amount distribution in the width direction is equal. As will be described later, the heaters L31 and L32 and the heaters L33 and L34 are controlled as a set of control objects. The temperature sensors 131 and 133 detect the surface temperature on the end side of the heating roller 135, and the temperature sensor 132 detects the surface temperature of the center portion.

(Power supply)
FIG. 4 is a diagram illustrating a circuit configuration of the power supply device 200. The power supply device 200 individually controls power supply to each functional component of the entire image forming apparatus 10, but only the power supply circuit related to power supply to the heater L <b> 3 of the fixing unit 160 is shown in FIG. The power supply circuit relating to the functional component is omitted. The power supply apparatus 200 includes a control unit 110, a power supply unit 160, a heater L3, and temperature sensors 131 to 133. As shown in FIG. 4, the power supply circuit of the power supply apparatus 200 includes a switching element 620, a heater L <b> 3, and a zero cross detection unit 610, which are connected to a common commercial AC power supply 90. Although not shown in the figure, each of the heaters L31 to L34 is connected in parallel with the AC power supply 90, and each power line corresponds to the heaters L31 to L34 and the switching elements 621 to 624. Are provided.

    FIG. 5 is a timing chart illustrating half-wave period duty control (hereinafter simply referred to as “duty control”) in the embodiment. The figure shows the input voltage to the switching element 620 and the output voltage to the heater L3, the zero-cross signal from the zero-cross detector 610, and the control signal from the controller 110.

  The control unit 110 determines a heater L3 to be controlled from a plurality of heaters based on paper information such as paper size and the detected temperatures of the temperature sensors 131 to 133. Further, a switching element and a duty ratio (control signal) for controlling the duty to the heater L3 to be the target are determined.

  The control unit 110 performs duty control using a predetermined period that is an integral multiple of a half wave of the commercial AC power supply 90 as a control period. The example shown in FIG. 5 shows an example of a duty ratio of 66.7% in which 15 half wavelengths are set as a control period and a 10 half wave period of the control period is turned on. A combination of on / off intervals indicating which half-wave period is selected (on) among the 15 half-waves is described in the array pattern. A plurality of arrangement patterns corresponding to the duty ratio are stored in the storage unit 140.

  The zero cross detection unit 160 outputs a zero cross signal to the control unit 110 at a timing when the AC voltage becomes zero. The control unit 110 switches the control signal to the switching element from off to on, or from on to off in synchronization with the on timing of the zero cross signal. In the example shown in FIG. 5, the control unit 110 switches the control signal from off to on at time t1, maintains the on state at time t2, and switches from on to off at time t3.

  In the period from time t1 to time t3, the switching element is turned on in accordance with the control signal, and thereby electric power is supplied to the heater L3 connected to the switching element (hereinafter referred to as “on section”). During the period from time t3 to t4, the turn-off is performed according to the control signal, and thereby the power supply to the heater L3 is cut off (hereinafter referred to as “off section”).

(Sequence pattern of reference example)
Hereinafter, with reference to FIGS. 6 to 8, the arrangement pattern as a reference and the measurement result of the flicker value will be described.

  Table 1 shown in FIG. 6 is an example of an arrangement pattern when one heater is a control target. Each row shows an array pattern corresponding to each duty ratio. The numbers 1 to 15 in the column indicate the 1st to 15th sections corresponding to the 15 half waves of the control period. In each arrangement pattern, a section indicated by “ON” is an on section. For example, when an array pattern with a duty ratio of 67% shown in FIG. 6 is selected, power is supplied to the heater L3 with a duty ratio as shown in FIG.

  Further, in the same figure, flicker values when electric power is supplied to the heater L3 in each arrangement pattern are shown. The flicker value in the figure is measured by a measurement method conforming to the flicker standard (for example, IEC61000-3-11). The standard cannot use a flicker value of 1.0 or more.

  FIG. 7 is an example of an arrangement pattern in consideration of simultaneous ON of two heaters as a reference example. 7A to 7D show arrangement patterns corresponding to the total duties 33%, 47%, 66%, and 100%, respectively. For example, in the arrangement with a total duty of 33% shown in FIG. 7A, among the 15 sections corresponding to one control period (15 half wavelengths), the first, 10th, and 13th sections are the on-sections of the end heaters. The fourth and seventh sections are on sections of the central heater. In the on section, power is supplied to each heater.

  The table shown in FIG. 8 shows the measurement results of the combinations of the duty ratios of the two heaters and the flicker value. In the figure, a dark shaded area where no numerical value is entered is unusable, that is, a combination in which the measured flicker value is 1.0 or more. Thin shaded areas with numerical values are used carefully, that is, the flicker value is less than 1.0, but it is 0.8 or more and close to 1.0, so it is designed in consideration of manufacturing variations such as heater rated power. Is a combination that should be avoided. In the example shown in the figure, the flicker value cannot be used or is used with care when at least one duty ratio is 0 to 27%. For example, the combination of the end heater duty ratio 7% and the central heater duty ratio 0-13, 73-87, or 100% cannot be used. The end heater duty ratio 7% and the central heater duty ratio 20 The combination of% has a flicker value of 0.873.

(Example of assembly arrangement pattern, comparative example)
9 to 11 are diagrams showing a set arrangement pattern and an arrangement pattern according to a comparative example. 9 to 11 show a table 2A and a plurality of arrangement patterns in which a plurality of group arrangement patterns corresponding to a total duty ratio within a range of a duty ratio of 0 to 200% are arranged with two heaters as one set of control targets. Tables 2B and 2C in which are arranged are shown respectively. As a combination of heaters, there are a combination of a central heater L31 and a central heater L32 having the same calorific value distribution as shown in FIG. 3, or a combination of an end heater L33 and an end heater L34. Table 2A shows a set arrangement pattern of two heaters. In the table, the “blank frame” section is a section in which both of the heaters are turned off, and the section indicated by “on1” in a thin shaded area is a heater. This is a section in which one of the two is turned on, and a section indicated by “on2” in dark shading is a section in which both the two heaters are turned on (the same applies to other tables described later).

  Tables 2B and 2C are array patterns corresponding to the set array pattern shown in Table 2A, and each show an array pattern of one heater 1 and the other heater 2 of the two heaters. As shown in Tables 2B and 2C, between the total duty ratios of 0 to 100%, the duty ratio of the heater 2 is fixed at 0% and is not turned on at all. In this range, only the duty ratio of the heater 1 increases as the total duty ratio increases. In addition, between the total duty ratios of 107 to 200%, the heater 1 is fixed at a duty ratio of 100%, and only the duty ratio of the heater 2 increases as the total duty ratio increases. The arrangement pattern of the heater 1 having a total duty ratio of 0 to 100% is the same as the arrangement pattern of the heater 2 having a total duty ratio of 100 to 200%.

  In such a comparative example, as shown in Table 2A, the total duty ratio is 87%, and the group arrangement pattern (within the broken line frame) in the range of 107% to 120% is flicker value 0.8 or more and NG, Use caution or use disabled. In order to satisfy the flicker value standards, if the temperature of the fixing unit (fixing device) is controlled with a set arrangement pattern other than the use arrangement pattern that cannot be used or cannot be used, the duty ratio is skipped. Must be used. In this case, the temperature ripple of the fixing member increases and high-precision fixing control cannot be performed.

(Example of assembly arrangement pattern, example)
12-15 is a figure which shows the group arrangement | sequence pattern and arrangement | sequence pattern based on an Example. 12 to 14, a table 3A in which a plurality of set arrangement patterns corresponding to a total duty ratio within a range of a duty ratio of 0 to 200% are arranged for two heaters as a set of control targets, and each heater is supported. Tables 3B and 3C in which a plurality of arrangement patterns are arranged are shown. As a combination of the heaters, there are a combination of the central heater L31 and the central heater L32 having the same calorific value distribution as described above, or a combination of the end heater L33 and the end heater L34. Tables 3A to 3C are tables corresponding to combinations of the central heater L31 and the central heater L32 in which two heaters having a rated power of 1000 W are combined. A table corresponding to the combination of the end heater L33 and the end heater L34 with the rated power of 625W is also stored in the storage unit 140.

  The table 3A shows a set arrangement pattern of two heaters, and the tables 3B and 3C are arrangement patterns as additional information of the set arrangement pattern shown in the table 3A. is there. These set array patterns and array patterns are array patterns determined based on flicker actual measurement values, and are stored in the storage unit 140 in advance.

  In the table 3A according to the embodiment, the front and rear ranges other than the total duty ratio of 100%, that is, the group arrangement pattern (within the broken line frame) with the total duty ratio of 80 to 93% and 107 to 120% are turned on ( on2) A set arrangement pattern composed of sections in which only one heater is turned on (on1) and two heaters are turned off (blank frame). Further, when the total duty ratio is 100%, the set arrangement pattern is configured by only a section in which only one heater is turned on.

  As shown in Table 3A, in the group arrangement pattern constituted by such a combination of sections, the flicker values in the case of the group arrangement pattern having a total duty ratio of 87% and 107% to 120% are all 0. It can be seen that the flicker value is reduced as compared with the group arrangement pattern of the comparative example of Table 2A.

  FIG. 15 shows a group arrangement pattern and a part of the arrangement pattern included in the tables 3A to 3C. FIG. 15A and FIG. 15B correspond to the total duty ratios of 87% and 113%, respectively. For example, in the example shown in FIG. 15A, both heaters are turned on in the fifth, tenth and twelfth sections of the control period, and the heaters are used in the first to third, seventh, eighth, fourteenth and fifteenth sections. Only 1 is turned on, and the two heaters are turned off in the fourth, sixth, ninth, eleventh and thirteenth sections.

  FIG. 16 is a graph corresponding to the tables 3A to 3C, in which the horizontal axis indicates the total duty ratio, the vertical axis indicates the number of ON sections of the heater 1 and the heater 2, and the total number of ON sections. As shown in FIG. 15, when the total duty ratio is 0 to 73%, the number of ON sections of the heater 1 increases at a constant rate. Further, when the total duty ratio is 127% to 200%, the number of ON sections of the heater 2 increases at a constant rate. On the other hand, when the total duty ratio is between 80% and 120%, the number of ON sections of the heaters 1 and 2 is discontinuous. For example, in the heater 1, the number of ON sections is smaller in the latter when the total duty is 73% and 80%.

(Control flow)
FIG. 17A is a flowchart illustrating a method for controlling the power supply device according to the first embodiment. First, the control unit 110 acquires the detected temperature of the heating roller from the temperature sensors 131 to 133 (S101).

  Next, based on the difference between the target temperature and the detected temperature, the total duty ratio of each of the pair of central heaters L31 and L32 and the pair of end heaters L32 and L34 to be controlled is determined (S102).

  FIG. 17B is a table showing the determination method in step S102. As shown in the figure, the total duty when the power control is performed with the central heaters L31 and L32 as a set of control objects based on the temperature difference of the target temperature (for example, 170 ° C.) with respect to the detected temperature of the temperature sensor 132 corresponding to the central portion Determine the ratio. For example, if the detected temperature of the temperature sensor 132 is 169 ° C. and the differential temperature is + 1 ° C., the total duty ratio is determined to be 120%. The same applies to the end heaters L33 and L34. The total duty ratio is determined based on the detected temperatures of the temperature sensors 131 and 133 corresponding to the end positions, and power control as shown below is performed with reference to a table corresponding to the rated power 625W.

  Subsequently, in step S103 of FIG. 17A, the control unit 110 refers to a table (for example, table 3A) corresponding to a control target (for example, a set of two central heaters) stored in the memory 140, and in step S102. A set arrangement pattern is selected according to the determined total duty ratio. For example, if the central duty L31, L32 is controlled and the total duty ratio is determined to be 120%, two heaters corresponding to 120% of the table 3A are turned on, only one heater is turned on, and two heaters are turned on. A group arrangement pattern composed of sections in which the heater is turned off is selected. Then, the control unit 110 controls the switching elements 621 and 622 based on the selected set arrangement pattern, thereby executing duty control with the half wave period as a unit section.

  As described above, according to the present embodiment, the group arrangement pattern composed of the sections in which the two heaters illustrated in the table 3A are turned on, only one heater is turned on, and the two heaters are turned off. By using it, the flicker value can be reduced. In addition, the group arrangement pattern (the range enclosed by the broken line in the table 2A) that could not be used in the comparative example can be used by reducing the flicker value (the range enclosed by the broken line in the table 3A). Thus, by performing duty control using a larger number of set arrangement patterns, it is possible to perform high-precision fixing control with a reduced temperature ripple of the fixing member.

(Modification)
FIG. 18 is a diagram illustrating a set arrangement pattern according to a modification. The set arrangement pattern shown in the table 4 of the figure is an example of a table used when the rated power of the heater 1 is 1000 W and the rated power of the heater 2 is 500 W, which are different from each other. In FIG. 3, the rated powers of the heaters L31 to L34 are 1000 W, 1000 W, 625 W, and 6125 W, respectively. In the example of FIG. 18, the rated powers of these heaters are 1000 W, 500 W, 1000 W, and 500 W, respectively. The table 4 is used for the combination of the central heaters L31 and L32 or the combination of the end heaters L33 and L34.

  As another example, for example, two central heaters are combined with the same rated power such as 1000 W and 1000 W, and two end heaters are combined with different rated powers such as 1000 W and 500 W. Think. In this case, the set arrangement pattern of the table 3A is used for the two heaters of the central heater, and the set arrangement pattern of the table 4 is used for the two heaters of the end heaters. As another example, when three heaters of 1000 W, 1000 W, and 500 W are used, when a combination of 1000 W and 1000 W is to be controlled, table 3A is to be controlled, and a combination of 1000 W and 500 W is to be controlled. Uses Table 4.

  The table 4 according to the modification shown in FIG. 18 uses a set arrangement pattern different from the table 3A in correspondence with a combination of two heaters having different rated powers. In Table 4, two heaters are turned on, only one heater is turned on, and two heaters are turned off in a combined arrangement pattern having a total duty ratio of 67% to 93% and 107% to 133% within a broken line frame. It is a set arrangement pattern composed of sections. In the table 4, in the section where only one heater is turned on, the heater 1 (rated power 1000 W) is turned on. In Table 4, the second heater 2 (rated power 500 W) is turned on from a total duty ratio of 67%.

(Control method according to the second embodiment)
Next, a control method according to the second embodiment will be described with reference to FIGS. In the first embodiment, the arrangement patterns of the heaters 1 and 2 are determined based on the set arrangement pattern, additional information, and the total duty ratio. On the other hand, in the second embodiment, the arrangement patterns of the heaters 1 and 2 are calculated and determined based on the set arrangement pattern, the total duty ratio, and the respective duty ratios. Further, in the first embodiment, the two heaters to be controlled are a heater having the same calorific value distribution such as end heaters or central heaters. On the other hand, in the second embodiment, not only heaters having the same calorific value distribution but also two heaters having different calorific value distributions such as a central heater L31 and an end heater L33 as shown in FIG. Power control may be performed as a set of control targets. Hereinafter, an example in which power control is performed using a central heater with a rated power of 1000 W and an end heater with a rated power of 1000 W as a set of control objects will be described.

  First, the control unit 110 acquires the detected temperature of the heating roller from the temperature sensors 131 to 133 (S201).

  Next, the duty ratio of each heater and the total duty ratio of one set of heaters are determined from the difference between the target temperature and the detected temperature (S202). For example, the duty ratio of the central heater is determined from the difference between the detected temperature of the temperature sensor 132 and the target temperature, and the duty ratio of the end heater is determined from the difference between the detected temperature of the temperature sensors 131 and 133 and the target temperature.

  FIG. 20 is a correspondence table showing the duty ratios of the central heater and the end heater and the total number of ON sections. For example, if the duty ratio of the central heater is 80% and the duty ratio of the end heater is 47%, the total number of ON sections is 19.

  Subsequently, the control unit 110 refers to the table 5 (FIG. 21) stored in the storage unit 140, and selects a set arrangement pattern from the total number of ON sections (total duty ratio) (S203). The table 5 is a table showing a set arrangement pattern in which two heaters with a rated power of 1000 W (for example, an end heater and a central heater) are controlled.

  In this group arrangement pattern, the table 5 has the same ON / OFF pattern as the table 3A, but unlike the table 3A, the ON section indicated by “on” indicates which heater is turned on. Additional information such as 3C is not given. That is, which heater is turned on cannot be specified from the set arrangement pattern (indefinite). In the second embodiment, the heater is specified by the calculation shown in step S204.

  22 and 23 are diagrams for explaining the calculation procedure of step S204. (A) to (j) shown in these figures are performed in this order.

  In procedure 1 shown in FIG. 22A, corresponding to step S203, a set arrangement pattern is selected from the total duty ratio of the central heater and the end heater. At this time, the number of remaining sections of the arrangement pattern of the central heater and the end heater is defined by the number of ON sections corresponding to the respective duty ratios determined in step S202.

  In the procedure 2 shown in FIG. 22B, the section of the group arrangement pattern is “on 2”, that is, the section of the arrangement pattern of the central heater and the end heater corresponding to the section in which the two heaters are both turned on is the on section. To decide. Along with this determination, the number of remaining sections is reduced by the number determined for each ON section. In the example of FIG. 22B, the number of remaining sections is decreased by 4. At this time, STEP_COUNT, STEP_H1, and STEP_H2 are defined and set to values of 0, 1, and 2, respectively, as follows. STEP_COUNT is a counter. STEP_H1 and STEP_H2 are variables respectively corresponding to the heater 1 (central heater) and the heater 2 (end heater), and the ratio of the number of remaining sections at this time is calculated in an INT type and substituted. The INT type is a function that cuts off the decimal part. For example, since the number of remaining sections of the heaters 1 and 2 at this time is 8 and 3, respectively, STEP_H1 = INT (8/3) = 2 is substituted. Substitute 1 for the smaller STEP_H2. Further, at the time of (b) in FIG. 22, the one with the larger number of remaining sections is substituted into H_INDEX. In this case, it is the heater 1.

  In step 3 shown in FIG. 22C, it is determined in order from the first section whether each section of the set array pattern is a section in which only one is turned on. If so, the heater of H_INDEX is determined. The corresponding section of the array pattern is determined as the ON section. At this time, if each section of the set array pattern is a section in which both two sections other than the section in which only one is turned on or a section in which both are turned off, the section is skipped and the determination is made in order from the next section. . In FIG. 22C, the second section of the arrangement pattern of the heaters 1 (center heater) is determined as the ON section.

  Accordingly, the number of remaining sections of the heater 1 is decremented (change from 8 to 7), STEP_COUNT is incremented (change from 0 to 1), and the variable of the heater (STEP_H1) to which STEP_COUNT and H_INDEX after the increment are added ) Or not. At this time, STEP_COUNT and STEP_H1 are not equal, so H_INDEX is not changed. The heater 1 remains.

  Similarly, in step 4 shown in FIG. 22D, it is determined whether or not the section (third section) of the next group arrangement pattern is a section in which only one is turned on. The corresponding section of the heater arrangement pattern is determined as the ON section. In FIG. 22D, the third section of the arrangement pattern of the heaters 1 (center heater) is determined as the ON section.

  Accordingly, the number of remaining sections of the heater 1 is decremented (changed from 7 to 6), STEP_COUNT is incremented (changed from 1 to 2), and the incremented STEP_COUNT and H_INDEX variable of the heater (STEP_H1) ) Or not. STEP_COUNT = STEP_H1. Further, it is determined whether the number of remaining sections of the other heater to which H_INDEX is not assigned at present is 1 or more. If so, H_INDEX is switched to the other heater. That is, it switches to the heater 2. Also, STEP_COUNT is reset to the initial value 0.

  Similarly, in step 5 shown in (e) of FIG. 22, it is determined whether or not the section (fourth section) of the next set array pattern is a section in which only one is turned on. The corresponding section of the heater arrangement pattern is determined as the ON section. In FIG. 22E, the fourth section of the arrangement pattern of the heaters 2 (end heaters) is determined as the ON section.

  Accordingly, the number of remaining sections of the heater 2 is decremented (changed from 3 to 2), STEP_COUNT is incremented (changed from 0 to 1), and the incremented STEP_COUNT and H_INDEX variable of the heater (STEP_H2) ) Or not. Here, STEP_COUNT = STEP_H1. Further, at this time, it is determined whether the number of remaining sections of the other heater to which H_INDEX is not assigned is 1 or more. If so, H_INDEX is switched to the other heater. Also, STEP_COUNT is reset to the initial value 0.

  By performing the calculation of the procedure of (f) of FIG. 22 and the procedures of (g) to (j) of FIG. 23 in such a procedure, all sections of the arrangement pattern of each of the two heaters can be determined.

  Returning to the description of FIG. In step S205 in the figure, the control unit 110 controls the switching elements corresponding to each set of heaters based on the arrangement pattern obtained by calculation according to the procedure shown in FIGS. Execute duty control with a half-wave period as a unit interval.

  As described above, also in the second embodiment, a set arrangement pattern constituted by sections in which two heaters are exemplified as shown in Table 4 is turned on, only one heater is turned on, and two heaters are turned off is used. As a result, as the same effect as that of the first embodiment, it is possible to perform high-precision fixing control in which the flicker value is reduced and the temperature ripple of the fixing member is reduced. In addition to this, in the second embodiment, it is sufficient to determine only the set arrangement pattern in advance, and the arrangement pattern can be determined by calculation without setting the arrangement pattern of each heater.

(Other variations)
The embodiments described so far may be applied to three heaters having the same rated power. In this case, duty control is performed on the first and second heaters using the set arrangement pattern of the table 3A, and the third heater is turned off (duty fixed at 0%). Alternatively, the first one is fixed at a duty of 100%, and the other two are duty controlled using the set arrangement pattern of the table 3A.

  The additional information may be information that “the section where only one is turned on is the heater 1”. For example, if “on1” in the table 3A is replaced with the information “heater 1 is turned on”, the additional information is The arrangement pattern such as the tables 3B and 3C in FIG.

  In the example shown in Table 3A, the AC power supply has 15 half-wavelengths as a predetermined period. However, the length of the predetermined period is not limited to 15 half-wavelengths. Also good.

  In addition, the present invention is defined by the contents described in the claims, and various modifications are possible.

10 image forming apparatus,
110 control unit,
120 image forming unit,
130 fixing unit,
L3, L31, L32, L33, L34 heater,
131, 132, 133 temperature sensors,
135 heating roller,
136 pressure roller,
140 storage unit,
150 operation display section,
160 power supply,
610 Zero cross detector,
620, 621, 622, 623, 624 switching element (switching unit),
170 scanner,
180 paper feeding and conveying section,
181 and 182 paper feed trays,
190 signal line,
200 power supply,
90 Commercial AC power supply.

Claims (12)

A power supply device that performs power control of a fixing unit that includes a fixing member that heat-fixes a sheet on which a toner image is formed, and a plurality of heaters that heat the fixing member,
A control unit that determines a duty ratio, which is a ratio of an on-section supplying power to the heater within a predetermined control cycle, based on a detected temperature of the fixing member, with a half-wave cycle of the AC power supply as a unit section;
A storage unit that stores a plurality of array patterns indicating on / off sections of the half wave within the control period corresponding to the duty ratio;
A switching unit that switches on / off of the heater according to the arrangement pattern,
The array pattern includes a plurality of set array patterns corresponding to a total duty ratio within a range of a duty ratio of 0 to 200% in which two heaters of the plurality of heaters are controlled as a set.
The control unit determines the total duty ratio of a set of heaters to be controlled, controls the switching unit based on a set arrangement pattern selected according to the determined total duty ratio,
Furthermore, the plurality of group arrangement patterns include at least two group arrangement patterns including a group arrangement pattern configured to turn on two heaters, turn on only one heater, and turn off two heaters. A set arrangement composed of sections in which the two heaters are turned on, only one heater is turned on, and two heaters are turned off in a range other than 100% within the range of the total duty ratio of 0 to 200%. Pattern included,
The group arrangement pattern having a total duty ratio of 100% is a group arrangement pattern in which one of the two heaters has a duty ratio of 100% and the other has a duty ratio of 0% in all sections in the control cycle. The power supply device according to 1.   The power supply apparatus according to claim 1, wherein the arrangement pattern is set based on a flicker measurement value.   4. The power supply device according to claim 1, wherein different storage arrangement patterns are stored in the storage unit depending on a combination of rated powers of the two heaters. 5.   5. The heater according to claim 1, wherein the two heaters to be controlled are a heater having the same calorific value distribution in the width direction perpendicular to the sheet conveyance direction of the fixing member. The power supply device described in 1.   The additional information which shows which heater is turned on among the two heaters is given to the group arrangement pattern for a section in which only one heater is turned on. The power supply device according to any one of 5. A power supply device that performs power control of a fixing unit that includes a fixing member that heat-fixes a sheet on which a toner image is formed, and a plurality of heaters that heat the fixing member,
A control unit that determines a duty ratio, which is a ratio of an on-section supplying power to the heater within a predetermined control cycle, based on a detected temperature of the fixing member, with a half-wave cycle of the AC power supply as a unit section;
A storage unit that stores a plurality of array patterns indicating on / off sections of the half wave within the control period corresponding to the duty ratio;
A switching unit that switches on / off of the heater according to the arrangement pattern,
The array pattern includes a plurality of set array patterns corresponding to a total duty ratio within a range of a duty ratio of 0 to 200% in which two heaters of the plurality of heaters are controlled as a set.
The set arrangement pattern is an arrangement pattern in which the ON intervals of the two heaters in each unit interval and the total ON number are described, and the plurality of the set arrangement patterns include at least two pieces. A set arrangement pattern composed of sections in which the heater is turned on, only one heater is turned on, and two heaters are turned off is included.
The control unit determines the total duty ratio of a set of heaters to be controlled and the duty ratio of each heater, the set arrangement pattern selected according to the determined total duty ratio, and the determined each of the set The power supply apparatus which calculates | requires the arrangement | sequence pattern with respect to each of said two heaters based on a duty ratio by calculation, and controls the said switching part based on the calculated | required arrangement | sequence pattern.   In the arrangement pattern, there is no information for specifying which of the two heaters to turn on in the section in which only one heater is turned on. The power supply device according to claim 7, wherein a heater to be turned on is specified in a section to be turned on.   9. The power supply device according to claim 7, wherein the two heaters to be controlled are a heater having different calorific value distributions in a width direction perpendicular to a sheet conveyance direction of the fixing member. An image forming unit that forms a toner image on paper;
A fixing member that heat-fixes the paper on which the toner image is formed, and a fixing unit that includes a plurality of heaters that heat the fixing member;
The power supply device according to any one of claims 1 to 9,
An image forming apparatus comprising: A control method for a power supply apparatus that supplies power to a fixing member that heat-fixes a sheet on which a toner image is formed and a plurality of heaters that heat the fixing member.
A step of determining a duty ratio, which is a ratio of an ON section for supplying power to the heater within a predetermined control period, based on a detected temperature of the fixing member, with a half wave period of the AC power supply as a unit section,
Selecting the arrangement pattern corresponding to the duty ratio from among the arrangement patterns indicating the on / off sections of the half-waves in the plurality of control cycles stored in the storage unit;
Switching on / off the heater at the half-wave period based on the selected array pattern,
The array pattern includes a plurality of set array patterns corresponding to a total duty ratio within a range of a duty ratio of 0 to 200% in which two heaters of the plurality of heaters are set as a control target.
In the determining step, the total duty ratio of a set of heaters to be controlled is determined;
In the switching step, on / off of the heater is switched based on the set arrangement pattern selected in the selecting step according to the determined total duty ratio,
The control method, wherein the plurality of group arrangement patterns include at least two group arrangement patterns configured by turning on two heaters, turning on only one heater, and turning off two heaters. A control method for a power supply apparatus that supplies power to a fixing member that heat-fixes a sheet on which a toner image is formed and a plurality of heaters that heat the fixing member.
A step of determining a duty ratio, which is a ratio of an ON section for supplying power to the heater within a predetermined control period, based on a detected temperature of the fixing member, with a half wave period of the AC power supply as a unit section,
Selecting the arrangement pattern corresponding to the duty ratio from among the arrangement patterns indicating the on / off sections of the half-waves in the plurality of control cycles stored in the storage unit;
Switching the heater on / off in the half-wave period according to the arrangement pattern,
The array pattern includes a plurality of set array patterns corresponding to a total duty ratio within a range of a duty ratio of 0 to 200% with two heaters as a set of control targets.
The set arrangement pattern is an arrangement pattern in which the ON intervals of the two heaters in each unit interval and the total ON number are described, and the plurality of the set arrangement patterns include at least two pieces. A set arrangement pattern composed of sections in which the heater is turned on, only one heater is turned on, and two heaters are turned off is included.
In the determining step, a total duty ratio of a set of heaters to be controlled and a duty ratio of each heater are determined,
In the selecting step, an array pattern for each of the two heaters is obtained by calculation based on the set array pattern selected according to the determined total duty ratio and each determined duty ratio.
In the switching step, the heater is switched on / off based on the obtained arrangement pattern.