JP2017078824A - Heating device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heating device that can suppress flicker and noise terminal voltage.SOLUTION: A control part comprises: setting means that sets a duty ratio that is a ratio of a supply period during which a power from an AC power source is supplied to a heating part to a unit period according to a detected temperature of an object to be heated; and switching means that switches control of a switch part between a first mode of supplying a power in a cycle period of a first number according to the duty ratio from among a plurality of AC voltage cycles included in a predetermined control cycle when the duty ratio is equal to or higher than the set value, and a second mode of supplying a power over a phase period according to the duty ratio in a cycle period of a second number when the duty ratio is lower than the set value. The second number is larger than the first number when the duty ratio is equal to the set value in the first mode. The set value is set larger as the rated power consumption of the heating part becomes larger.SELECTED DRAWING: Figure 13

Description

  The present disclosure relates to a heating device, and more particularly to a heating device used in an image forming apparatus.

  Generally, an electrophotographic image forming apparatus uses a fixing device in which a pressure roller is brought into pressure contact with a fixing roller. Fixing devices often include a halogen heater to heat the fixing roller.

  Although the halogen heater is excellent in temperature rise performance, it has a characteristic of relatively high power consumption. Therefore, there is a problem that a flicker phenomenon occurs such that a peripheral device connected to the same AC power source as the fixing device, for example, a lighting device flickers.

  With regard to the technology for suppressing the flicker, Japanese Patent Application Laid-Open No. 2012-37804 (Patent Document 1) uses a predetermined control cycle as a unit, and turns on or off all the half-waves of the AC voltage within the control cycle for each lighting duty. Discloses a heater control device that controls the lighting of a heater based on the lighting pattern assigned to. More specifically, when the lighting duty is equal to or less than a predetermined value, the heater control device performs lighting control of the heater using a composite pattern incorporating a flicker suppression pattern and a soft start pattern.

  Japanese Patent Laying-Open No. 2008-40072 (Patent Document 2) describes the power supply wiring in an environment in which an electrical device such as an image forming apparatus is installed and the impedance of the power wiring of the same system. Discloses a heater power control device that can suppress inrush current and suppress flickering of a fluorescent lamp. More specifically, this heater power control device monitors the illuminance of a fluorescent lamp placed in the environment where the electrical equipment is installed, the indoor ceiling, etc., and the heater according to the flickering of the fluorescent lamp from time to time. Switch the power control to phase control or half-wave control.

JP 2012-37804 A Japanese Patent Laid-Open No. 2008-40072

  However, the technique disclosed in Patent Document 1 does not consider the power consumption of the heater, and performs lighting control of the heater uniformly using a composite pattern when the lighting duty becomes a predetermined value or less. Therefore, there is a problem that flicker cannot be sufficiently suppressed depending on the power consumption of the heater.

  Moreover, since the technique disclosed in Patent Document 2 performs switching between half-wave control and phase control only in accordance with the flickering of the fluorescent lamp from time to time, there is a problem in that the noise terminal voltage increases in some cases. there were.

  This indication is made in order to solve the above problems, and the objective in a certain situation is to provide the heating device which can control flicker and a noise terminal voltage.

  A heating unit that receives power from an AC power source and heats the object, a detection unit that detects the temperature of the object, a switch unit that intermittently supplies power supplied from the AC power source to the heating unit, and the switch unit And a control unit connected to. The control unit is configured to set a duty ratio, which is a ratio of a supply period during which power from the AC power source is supplied to the heating unit according to the detected temperature, and to control the switch unit. Is supplied in the first number of cycle periods according to the duty ratio among a plurality of AC voltage cycles included in the predetermined control cycle when And switching means for switching between the mode and the second mode in which power is supplied over the phase period corresponding to the duty ratio in the second number of cycle periods when the duty ratio is lower than the set value. The second number is larger than the first number when the duty ratio is a set value in the first mode. The set value is set higher as the rated power consumption of the heating unit is larger.

  Preferably, the switching unit performs switching from the first mode to the second mode and switching from the second mode to the first mode.

  Preferably, the control unit determines switching between the first mode and the second mode by the switching unit for each control cycle.

  Preferably, the setting unit sets the duty ratio according to a temperature difference obtained by subtracting the detected temperature from a predetermined temperature.

  Preferably, it further includes a zero-cross detection unit that detects a timing at which the AC voltage output from the AC power source becomes zero and outputs a signal to the control unit. The control unit controls the switch unit based on the signal.

  Preferably, the switch unit receives an input of a signal instructing conduction between the AC power source and the heating unit at a phase angle different from a predetermined phase angle when the AC voltage output from the AC power source is AC at the phase angle. Conducts electricity to the power source and the heating unit.

  Preferably, the apparatus further includes a second heating unit that receives power from the AC power source and heats the object, and a second switch unit that intermittently supplies power supplied from the AC power source to the second heating unit. The control unit includes a second setting unit configured to set a second duty ratio, which is a ratio of a supply period in which power from the AC power supply with respect to the unit period is supplied to the second heating unit according to the detected temperature. In addition, the second switch unit is controlled to supply power in a third number of cycle periods corresponding to the second duty ratio among a plurality of AC voltage cycles included in the control cycle.

More preferably, the rated power consumption of the second heating unit is not more than a predetermined rated power consumption.
More preferably, the second switch unit receives an input of a signal instructing conduction to the AC power source and the heating unit at a phase angle different from the predetermined phase angle when the AC voltage output from the AC power source is different from the predetermined phase angle. Conduction between the AC power source and the heating unit is performed at a predetermined phase angle.

  According to another aspect, the image forming apparatus includes an image forming unit that forms a toner image on a recording material, and a fixing heating unit that fixes the toner image on the recording material. The fixing heating unit includes a heating unit that receives power from an AC power source and heats the object, a detection unit that detects the temperature of the object, a switch unit that intermittently supplies power supplied from the AC power source to the heating unit, And a control unit electrically connected to the switch unit. The control unit is configured to set a duty ratio, which is a ratio of a supply period during which power from the AC power source is supplied to the heating unit according to the detected temperature, and to control the switch unit. Is supplied in the first number of cycle periods according to the duty ratio among a plurality of AC voltage cycles included in the predetermined control cycle when When the duty ratio is lower than the set value, there is switching means for switching to the second mode in which power is supplied over the phase period corresponding to the duty ratio in the second number of cycle periods. The second number is larger than the first number when the duty ratio is a set value in the first mode. The set value is set higher as the rated power consumption of the heating unit is larger.

  According to the heating device according to the embodiment, flicker and noise terminal voltage can be suppressed.

It is a figure explaining a flicker. It is a figure explaining the structural example of the image forming apparatus according to an embodiment. It is a figure explaining the fixing heating part according to an embodiment. It is a figure explaining the heating apparatus containing the heating part according to this embodiment. It is a figure explaining the switch part according to this embodiment. It is a figure explaining the control mode of the electric power supply to the heating part according to this embodiment. It is a figure explaining the half wave control mode according to this embodiment. It is a figure explaining the lighting control of the heating part according to this embodiment. It is a figure explaining the phase control mode according to this embodiment. It is a figure explaining the relationship between the duty ratio at the time of phase control, and a noise terminal voltage. It is a figure explaining the lighting control of the heating part according to this embodiment. It is a figure explaining the lighting control of the heating part according to this embodiment. It is a flowchart explaining the setting method of the duty ratio according to this embodiment. It is a figure explaining step S6 (selection of duty ratio) of Drawing 13. It is a block diagram explaining the function structure of the control part according to this embodiment. It is a figure explaining the lighting control at the time of power activation according to this embodiment, and printing. It is a figure explaining the fixing heating part according to other embodiment. It is a figure explaining the heating apparatus according to other embodiment. It is a figure explaining lighting control of the heating part according to other embodiments. It is a flowchart explaining the setting method of the total value of duty ratio according to other embodiment. It is a figure explaining step S44 (selection of the total value of duty ratio) of Drawing 20. It is a figure explaining lighting control of the heating part according to a modification. It is the figure which decomposed | disassembled the lighting pattern of FIG. 22 for every heating part. It is a flowchart explaining lighting control of each heating part according to a modification. It is a figure explaining switch part 23A according to a modification. It is a figure explaining control of electric power supply to a heating part using a zero cross type switch part.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

<A. Introduction>
FIG. 1 is a diagram for explaining flicker. In FIG. 1, it is assumed that a lighting device is further connected to an AC power source to which the fixing device is connected. This fixing device employs a configuration that periodically supplies power to the heating device. In FIG. 1A, the frequency at which power is supplied to the heating device is plotted on the horizontal axis, and the flickering degree (flicker) of the lighting device is plotted on the vertical axis.

  As shown in FIG. 1A, the human eye feels the flickering of the lighting device most at about 10 Hz and feels uncomfortable. In addition, human eyes tend to feel flickering as the electric power per cycle supplied to the heating device increases. Hereinafter, description will be made with reference to the example of FIG.

  In the state (a) of FIG. 1B, the fixing device supplies power to the heating device at 30 Hz, and the power per cycle is set to “medium”. The state (a) corresponds to the point A in FIG. 1A, and the flickering degree of the lighting device in the state (a) is sufficiently lower than the threshold at which human eyes notice flickering of the lighting device. Therefore, in the state (a), the person around the lighting device does not feel uncomfortable.

  In the state (b), the fixing device supplies power to the heating device at 15 Hz, and the power per cycle is set to “medium”. The state (b) corresponds to the point B in FIG. 1A, and the flickering degree of the lighting device in the state (b) is slightly higher than the threshold at which the human eye notices the flickering of the lighting device. Therefore, in the state (b), people around the lighting device feel uncomfortable.

  In the state (c), the fixing device supplies power to the heating device at 15 Hz, and the power per cycle is set to “large”. The state (c) corresponds to the point C in FIG. 1 (A), and the flickering degree of the lighting device in the state (c) is significantly higher than the threshold at which human eyes notice flickering of the lighting device. Therefore, in the state (c), the person around the lighting device is remarkably uncomfortable.

  In the state (d), the fixing device supplies power to the heating device at 30 Hz, and the power per cycle is set to “small”. The state (d) corresponds to the point D in FIG. 1A, and the flickering degree of the lighting device in the state (d) is significantly lower than the threshold at which human eyes notice flickering of the lighting device. Therefore, in the state (d), the person around the lighting device does not feel uncomfortable.

  The electric power supplied to the heating device for a fixed time is set to be equal between the state (d) and the state (b). Therefore, in the state (d) and the state (b), the ability of the heating device to heat the object is approximately equal. Therefore, when lowering the power supplied to the heating device by lowering the frequency of supplying power, if the flickering of the lighting device increases, the power per cycle can be reduced and the frequency of supplying power to the heating device can be increased. preferable. As a result, it is possible to suppress discomfort of people around the lighting device.

  On the other hand, when controlling the electric power per period, a harmonic may generate | occur | produce and a noise terminal voltage may become high. Therefore, the configuration and control of a heating device capable of suppressing flicker and noise terminal voltage will be described below.

<B. Embodiment 1-Case of One Heating Unit>
(B1. Image forming apparatus 100)
FIG. 2 is a diagram illustrating a configuration example of the image forming apparatus 100 according to the embodiment. The image forming apparatus 100 is an electrophotographic image forming apparatus such as a laser printer or an LED printer. As shown in FIG. 1, the image forming apparatus 100 includes an intermediate transfer belt 1 as a belt member at a substantially central portion inside. Below the lower horizontal portion of the intermediate transfer belt 1, four image forming units 2Y, 2M, 2C, and 2K corresponding to yellow (Y), magenta (M), cyan (C), and black (K) colors, respectively. Are arranged side by side along the intermediate transfer belt 1 and have photosensitive drums 3Y, 3M, 3C, and 3K, respectively.

  Around each of the photosensitive drums 3Y, 3M, 3C, and 3K, the chargers 4Y, 4M, 4C, and 4K, the print head units 5Y, 5M, 5C, and 5K, and the developing unit 6Y are sequentially arranged along the rotation direction. , 6M, 6C, and 6K, and primary transfer rollers 7Y, 7M, 7C, and 7K that face the photosensitive drums 3Y, 3M, 3C, and 3K across the intermediate transfer belt 1, respectively.

  A secondary transfer roller 9 is pressed against a portion of the intermediate transfer belt 1 supported by the intermediate transfer belt driving roller 8, and secondary transfer is performed in this region. A fixing heating unit 20 is disposed at a downstream position of the conveyance path R behind the secondary transfer region.

  A paper feed cassette 30 is detachably disposed below the image forming apparatus 100. The sheets P stacked and accommodated in the sheet feeding cassette 30 are sent out one by one from the uppermost one to the transport path R by the rotation of the sheet feeding roller 31.

  In this embodiment, the image forming apparatus 100 employs an intermediate transfer method having a plurality of image forming units (2Y, 2M, 2C, 2K) as an example. However, the present invention is not limited to this. The image forming apparatus may be an electrophotographic system and may include a fixing heating unit. Specifically, the image forming apparatus may include a single image forming unit or a rotary system.

(B2. Schematic operation of image forming apparatus 100)
Next, a schematic operation of the image forming apparatus 100 having the above configuration will be described. When an image signal is input to the image forming apparatus 100 from an external device (for example, a personal computer or the like), the image forming apparatus 100 creates a digital image signal obtained by color-converting the image signal into yellow, cyan, magenta, and black. Based on the input digital signal, the print head units 5Y, 5M, 5C, and 5K of the image forming units 2Y, 2M, 2C, and 2K emit light to perform exposure.

  As a result, the electrostatic latent images formed on the photosensitive drums 3Y, 3M, 3C, and 3K are developed by the developing devices 6Y, 6M, 6C, and 6K, respectively, and become toner images of the respective colors. The toner images of the respective colors are primarily transferred in a superimposed manner on the intermediate transfer belt 1 that moves in the direction of arrow A in FIG. 1 by the action of the primary transfer rollers 7Y, 7M, 7C, and 7K.

  The toner images formed on the intermediate transfer belt 1 in this way are secondarily transferred onto the paper P collectively by the action of the secondary transfer roller 9.

  The toner image secondarily transferred to the paper P reaches the fixing heating unit 20. The toner image is fixed on the paper P by the fixing heating unit 20. The paper P on which the toner image is fixed is discharged to the paper discharge tray 60 via the paper discharge roller 50. Hereinafter, the configuration and control of the fixing heating unit will be described more specifically.

(B3. Fixing and heating unit 20)
FIG. 3 is a diagram illustrating the fixing heating unit 20 according to the embodiment. FIG. 3A is a diagram of the fixing heating unit 20 as viewed from the front of the image forming apparatus 100. The fixing heating unit 20 includes a fixing roller 10, a pressure roller 11, and a heating unit 21. The toner image is fixed on the paper P by the pressure contact portion between the fixing roller 10 and the pressure roller 11.

  In the present embodiment, a halogen heater (infrared heating device) is used as an example of the heating means of the heating unit, but is not limited to this. For example, a resistor heating device such as a thermal heater or a ceramic heater may be used instead of the halogen heater. Alternatively, the fixing roller 10 may be induction-heated using a magnetic flux generator (not shown).

  3B is a diagram when the fixing heating unit 20 is viewed from the side of the image forming apparatus 100. FIG. The heating unit 21 (halogen heater) is provided over the longitudinal direction of the fixing roller 10 and heats the entire fixing roller 10. The temperature detector 22 measures the temperature of the heated fixing roller 10. For example, a thermistor may be used as the temperature measuring means of the temperature detector 22.

  FIG. 4 is a diagram illustrating a heating device 200 including the heating unit 21 according to the present embodiment. The heating device 200 includes an AC power supply 40, a heating unit 21, a temperature detection unit 22, a switch unit 23, a zero cross detection unit 42, and a control unit 44.

  The control unit 44 is electrically connected to the temperature detection unit 22, the switch unit 23, and the zero cross detection unit 42. The temperature detection unit 22 measures the temperature of the fixing roller 10 that is an object to be heated by the heating unit 21, and outputs the measurement result to the control unit 44. The zero cross detection unit 42 monitors the AC voltage output from the AC power supply 40 and outputs a detection signal to the control unit 44 when the AC voltage becomes zero or near zero. The control unit 44 outputs a control signal to the switch unit 23 and adjusts the power supplied to the heating unit 21 by intermittently supplying the power supplied from the AC power supply 40 to the heating unit 21.

(B4. Switch unit 23)
FIG. 5 is a diagram illustrating the switch unit 23 according to the present embodiment. As shown in FIG. 5, the switch unit 23 includes a phototriac coupler 70, a triac Tr, resistors R1 to R3, and a capacitor C.

  The phototriac coupler 70 includes an LED (Light Emitting Diode) 71 and an optical triac 72. The control unit 44 outputs a control signal having a predetermined voltage to the LED 71 to cause the LED 71 to emit light. When the LED 71 emits light, light is input to the gate of the optical triac 72 and the optical triac 72 becomes conductive.

  When the optical triac 72 is turned on, a current is input to the gate of the triac Tr, the triac Tr is turned on, and power is supplied to the heating unit 21 via the snubber circuit including the capacitor C and the resistor R3. The snubber circuit is a protection circuit that absorbs a transient high voltage generated when the switch is shut off.

  The phototriac coupler 70 is a non-zero-cross type that does not include a zero-cross circuit that detects that the AC voltage output from the AC power supply 40 is zero or near zero. Therefore, when the switch unit 23 receives the control signal from the control unit 44 at an arbitrary phase angle where the AC voltage is not zero, the switch unit 23 conducts the AC power supply 40 and the heating unit 21 at the arbitrary phase angle. .

  The control unit 44 can switch the power supply mode to the heating unit 21 by controlling the timing of inputting the control signal to the phototriac coupler 70.

(B5. Power supply mode)
FIG. 6 is a diagram illustrating a control mode for supplying power to the heating unit according to the present embodiment. The control unit 44 has a half-wave control mode and a phase control mode as control modes for supplying power to the heating unit 21.

  FIG. 6A is a diagram for explaining the half-wave control mode. The control unit 44 receives an input of a detection signal from the zero cross detection unit 42 at a zero cross point where the AC voltage becomes zero. In the half-wave control mode, the control unit 44 outputs a control signal to the switch unit 23 at the timing of receiving the detection signal. Once the optical triac 72 is turned on by the self-holding function, the light triac 72 maintains the conduction until the next zero cross point. Therefore, in the half-wave control mode, the control unit 44 turns on the heating unit 21 for each AC half-wave of the AC power supply 40 (supplies power to the heating unit 21).

  FIG. 6B is a diagram illustrating the phase control mode. The control unit 44 receives an input of a detection signal from the zero cross detection unit 42 and grasps the timing when the AC voltage becomes zero. In the phase control mode, the control unit 44 outputs a control signal to the switch unit 23 based on the timing at which the detection signal is received. That is, the control unit 44 adjusts the amount of power supplied to the heating unit 21 by controlling the firing angle (θ) of the optical triac 72.

  Note that the control unit 44 does not necessarily have to perform control based on the detection signal from the zero cross detection unit when performing the lighting control in the phase control mode. In another aspect, heating device 200 further includes an ammeter (not shown), which measures the output current of AC power supply 40 and outputs the measurement result to control unit 44. The control unit 44 may perform phase control based on the timing when the current value becomes zero or the timing when the current value reaches a peak. In addition, when using the timing which becomes a peak, the control part 44 needs to grasp | ascertain the power supply frequency of AC power supply previously.

  In the half-wave control mode, the control unit 44 adjusts the amount of power supplied to the heating unit 21 by controlling the number of cycles that are turned on among a plurality of AC voltage cycles included in a predetermined control cycle.

  FIG. 7 is a diagram for explaining the half-wave control mode. As an example, it is assumed that the control cycle includes 15 AC half-wave cycles. In the situation shown in FIG. 7, the control unit 44 turns on the first, sixth, and eleventh AC half-waves in the control cycle, and turns off the other AC half-waves. At this time, the duty ratio, which is the ratio of the supply period (3 cycles) in which power from the AC power supply is supplied to the heating unit 21 with respect to the control period (15 cycles) that is a unit period, is 20%.

(B6. Lighting control)
FIG. 8 is a diagram illustrating lighting control of the heating unit 21 according to the present embodiment. Referring to FIG. 8, when the duty ratio is 20%, control unit 44 sets the number of lighting cycles to 3/15, and lights the first, sixth, and eleventh AC half waves in the control cycle. When the duty ratio is 60%, the control unit 44 sets the number of lighting cycles to 9/15 cycles, and the second, third, fifth, seventh, eighth, tenth, twelfth, thirteenth, and fifteenth AC half-waves in the control cycle. Light. As described above, the control unit 44 controls the number of lighting cycles of the AC half wave within the control period and the lighting timing according to the duty ratio.

  The “flicker value” refers to the degree of flicker of a lighting device (not shown) connected to the same power system as the AC power supply 40 when the power supply to the heating unit 21 is controlled with each lighting pattern shown in FIG. In FIG. 8, it is assumed that the rated power consumption of the heating unit 21 is 1000 W and the power supply frequency of the AC power supply 40 is 50 Hz.

  As an example, if the flicker value exceeds 0.9, a person around the lighting device feels uncomfortable. Referring to FIG. 8, when the duty ratio for supplying power to heating unit 21 is 7% to 20%, the flicker value becomes 0.9 or more, and people around the lighting device feel uncomfortable.

  Therefore, when the flicker value becomes higher (for example, 0.9 or more) in the half-wave control mode and becomes less than a predetermined duty ratio, the control unit 44 changes the control mode for supplying power to the heating unit 21 to the half-wave control mode. To phase control mode. For example, when the duty ratio is 20%, the switch unit is configured so that 20% of the power (area) when the AC half-wave is fully lit is supplied in each cycle within the control period as shown in FIG. 23 is controlled. In the example shown in FIG. 9, the light is lit in all the cycles within the control period, but is not limited thereto. Specifically, the number of lighting cycles in the phase control mode may be larger than the number of lighting cycles in the half-wave control mode at a predetermined duty ratio immediately before switching to the phase control mode. As described above, the control unit 44 lights the heating unit over the phase period corresponding to the duty ratio during the phase control.

  The heating device 200 can suppress flicker by increasing the number of lighting cycles in the phase control mode. On the other hand, in the phase control mode, conduction by the switch unit 23 is performed at a point other than the zero cross point, so that there is a problem that the noise terminal voltage due to harmonics becomes high.

  Generally, measures such as providing a noise filter are taken to satisfy the noise terminal voltage standard value defined in VCCI or the like. There are various types of noise filters, but when mounted on industrial products, it is preferable that the noise filter be as inexpensive as possible.

  FIG. 10 is a diagram illustrating the relationship between the duty ratio and the noise terminal voltage during phase control. In FIG. 10, the control unit 44 performs lighting control of each cycle within the control period in the phase control mode. In addition, the rated power consumption of the heating unit 21 is 1000 W, the power supply frequency of the AC power supply 40 is 50 Hz, and the heating device 200 further includes an inexpensive noise filter (not shown).

  As the duty ratio at the time of phase control is increased, the noise terminal voltage of the heating device 200 is increased. Therefore, as shown in FIG. 10, as the duty ratio at the time of phase control is increased, the margin for a predetermined regulation value (for example, 66 dBμV) of the noise terminal voltage is reduced.

  As an example, if the target margin for a predetermined regulation value is set to 6 dBμV or more, the target level of the noise terminal voltage cannot be achieved at least when the duty ratio exceeds 40%.

  When the duty ratio is less than the predetermined duty ratio, the control unit 44 switches the control mode for supplying power to the heating unit 21 from the half-wave control mode to the phase control mode. This predetermined duty ratio is set so that the flicker value does not increase (for example, does not exceed 0.9) and the target level of the noise terminal voltage can be achieved. In the present embodiment, as an example, when the rated power consumption of the heating unit 21 is 1000 W and the power supply frequency of the AC power supply 40 is 50 Hz, the predetermined duty ratio is set to 27%.

  As described with reference to FIG. 1, when the power per cycle supplied to the heating unit 21 increases, in other words, the rated power consumption of the heating unit 21 increases, the flicker value increases. FIG. 11 shows the flicker value in the half-wave control mode when the heating unit 21A having a rated power consumption of 1300 W is used instead of the heating unit 21.

  8 and 11, the lighting patterns for supplying power to the heating unit are the same. However, when the rated power consumption of the heating unit is changed from 1000 W to 1300 W, the flicker value in the half-wave control mode with a duty ratio of 27% becomes 0.9 or more. Therefore, when the rated power consumption of the heating unit is 1300 W and the power supply frequency of the AC power supply 40 is 50 Hz, the predetermined duty ratio is set to 33%.

  On the other hand, FIG. 12 shows the flicker value in the half-wave control mode when the heating unit 21B having a rated power consumption of 700 W is used instead of the heating unit 21. 8 and 12, the lighting patterns for supplying power to the heating unit are the same. However, when the rated power consumption of the heating unit is changed from 1000 W to 700 W, the flicker value in the half-wave control mode with a duty ratio of 20% becomes less than 0.9. Therefore, when the rated power consumption of the heating unit is 700 W and the power supply frequency of the AC power supply 40 is 50 Hz, the predetermined duty ratio is set to 20%.

  As described above, the predetermined duty ratio for switching from the half-wave control mode to the phase control mode is set higher as the rated power consumption of the heating unit is larger.

  According to the above, the heating device according to the present embodiment can set a predetermined duty ratio that switches between the half-wave control mode and the phase control mode according to the rated power consumption of the heating unit. Therefore, this heating device can suppress flicker and noise terminal voltage regardless of the rated power consumption of the heating unit.

(B7. Duty ratio setting)
Next, a method for setting the duty ratio will be described. FIG. 13 is a flowchart for explaining a duty setting method. The process shown in FIG. 13 is realized by a processor (not shown) of the control unit 44 executing a control program stored in a storage unit (not shown). In other aspects, some or all of the processing may be performed by circuit elements or other hardware. These assumptions (conditions) are the same in the flowcharts from FIG.

  Referring to FIG. 13, in step S <b> 2, control unit 44 acquires the temperature of the object (fixing roller 10) heated by heating unit 21 from temperature detection unit 22. In step S4, the control unit 44 calculates a temperature obtained by subtracting the acquired temperature from the target temperature (hereinafter also referred to as “differential temperature”). As an example, the target temperature is 180 ° C.

  In step S6, the control unit 44 selects a duty ratio based on the differential temperature. A method for selecting the duty ratio will be described later.

  In step S8, the control unit 44 compares the selected duty ratio with the duty ratio table shown in FIG. 8, and sets the duty ratio closest to the selected duty ratio.

  This is because, in the present embodiment, the AC half-wave 15 cycles are set as the control period, and the duty ratio can be set only in increments of about 7% in the half-wave control mode.

  In step S10, the control unit 44 determines whether or not the set duty ratio is equal to or greater than a predetermined duty ratio corresponding to the rated power consumption of the heating unit. Since the rated power consumption of the heating unit 21 is 1000 W, the predetermined duty ratio is set to 27%.

  When it is determined that the set duty ratio is equal to or higher than the predetermined duty ratio (YES in step S10), control unit 44 advances the control to step S12. On the other hand, when it is determined that the set duty ratio is less than the predetermined duty ratio (NO in step S10), control unit 44 advances the control to step S14.

  In step S12, the control unit 44 performs lighting control in the half-wave control mode according to the lighting pattern shown in FIG. 8 according to the set duty ratio. In step S14, the control unit 44 performs lighting control in the phase control mode according to the set duty ratio.

  The control unit 44 performs the lighting control according to the duty ratio set in step S12 or step S14, and then returns the control to step S2 again. The control unit 44 determines lighting control based on the differential temperature for each predetermined control cycle.

  Based on the above, the control unit 44 can set the duty ratio for supplying power to the heating unit 21 based on the temperature of the heating object.

  FIG. 14 is a diagram for explaining step S6 (selection of duty ratio) in FIG. Referring to FIG. 14, in step S20, control unit 44 determines whether or not the differential temperature is 7 ° C. or higher.

  When controller 44 determines that the difference temperature is 7 ° C. or higher (YES in step S20), controller 44 selects 100% as the duty ratio in step S22.

  In step S24, the control unit 44 determines whether or not the difference temperature is less than 7 ° C. and 2 ° C. or more. When controller 44 determines that the difference temperature is less than 7 ° C. and 2 ° C. or more (YES in step S24), it selects 95% as the duty ratio in step S26.

  In step S28, the control unit 44 determines whether or not the differential temperature is less than 2 ° C. and 0 ° C. or more. If controller 44 determines that the difference temperature is less than 2 ° C. and 0 ° C. or more (YES in step S28), it selects 55% as the duty ratio in step S26.

  In step S32, the control unit 44 determines whether or not the differential temperature is less than 0 ° C. and −2 ° C., that is, whether or not the temperature obtained by subtracting the target temperature from the detected temperature is higher than 0 ° C. and lower than 2 ° C. . When it is determined that the temperature obtained by subtracting the target temperature from the detected temperature is higher than 0 ° C. and equal to or lower than 2 ° C. (YES in step S32), control unit 44 selects 15% as the duty ratio in step S34.

  When it is determined that the difference temperature is less than −2 ° C., that is, the temperature obtained by subtracting the target temperature from the detected temperature is higher than 2 ° C. (NO in step S32), the control unit 44 sets the duty ratio to 0 in step S36. %, And the power supply to the heating unit 21 is stopped.

  For example, when the differential temperature is 1 ° C., the control unit 44 selects 55% as the duty ratio (step S6). Thereafter, the control unit 44 refers to the duty ratio table shown in FIG. 8 and sets 53% of the value closest to 55% as the duty ratio (step S8). Subsequently, the control unit 44 determines that 53% is equal to or greater than a predetermined duty ratio (27%) (step S10), and 2, 4, 6, 7 in the control period (15 cycles) in the half-wave control mode. , 9, 11, 13, and 15th AC half-waves are turned on (step S12).

  If the temperature obtained by subtracting the target temperature from the detected temperature is 1 ° C., the control unit 44 selects 15% as the duty ratio (step S6). Thereafter, the control unit 44 refers to the duty ratio table shown in FIG. 8 and sets 13% of the value closest to 15% as the duty ratio (step S8). Subsequently, the control unit 44 determines that 13% is less than a predetermined duty ratio (27%) (step S10). And the control part 44 is the point of the optical triac 72 so that the electric power of 13% of the electric power (area) when all the AC half-waves are turned on in each cycle in the control period is supplied in the phase control mode. Control the arc angle θ.

  Based on the above, the control unit 44 can select and set the duty ratio for supplying power to the heating unit 21 based on the temperature of the heating object.

  In the above example, the control unit 44 sets the duty ratio from the differential temperature and switches the phase control mode / half-wave control mode based on the set duty ratio, but is not limited thereto. In another aspect, the control unit 44 may switch the phase control mode / half-wave control mode based on the calculated difference temperature. For example, lighting control in the phase control mode may be performed when the differential temperature is less than 0 ° C., and lighting control in the half-wave control mode may be performed in other temperature ranges.

  FIG. 15 is a block diagram illustrating a functional configuration of the control unit 44 according to the present embodiment. How the control unit 44 performs the processing shown in FIGS. 13 and 14 will be described with reference to FIG.

  Referring to FIG. 15, control unit 44 includes a difference calculation unit 81, a storage unit 82, a duty ratio setting unit 83, and a comparison unit 84. First, the difference calculation unit 81 acquires the temperature of the object of the heating unit 21 from the temperature detection unit 22 and also acquires the target temperature (180 ° C.) stored in the storage unit 82. Further, the difference calculation unit 81 calculates the difference temperature by subtracting the temperature of the heating object from the target temperature, and outputs the difference temperature to the duty ratio setting unit 83.

  The duty ratio setting unit 83 determines in which temperature range shown in FIG. 14 the differential temperature exists, and selects a duty ratio according to the temperature range. Subsequently, the duty ratio setting unit 83 compares the selected duty ratio with the duty ratio table shown in FIG. 8 stored in the storage unit 82. Then, the duty ratio setting unit 83 sets a value closest to the selected duty ratio as the duty ratio, and outputs the set duty ratio to the comparison unit 84.

  The comparison unit 84 compares whether or not the set duty ratio is greater than or equal to a predetermined duty ratio stored in the storage unit 82. When determining that the set duty ratio is equal to or greater than the predetermined duty ratio, the control unit 44 controls the on / off of the switch unit 23 in the half-wave control mode. On the other hand, when determining that the set duty ratio is less than the predetermined duty ratio, the control unit 44 controls on / off of the switch unit 23 in the phase control mode. The predetermined duty ratio may be stored in the storage unit 82 separately from the rated power consumption of the heating unit.

(B8. Scene for switching control modes)
Typical scenes in which flicker is suppressed by phase control include when the image forming apparatus 100 including the heating apparatus 200 is turned on and when printing using the image forming apparatus 100 is performed.

FIG. 16 is a diagram illustrating lighting control at power-on and printing.
When the image forming apparatus 100 is turned on, an inrush current larger than the rated current flows through a load such as the heating unit 21. When an inrush current occurs, a lighting device connected to the same AC power source as the image forming apparatus 100 flickers due to a rapid voltage fluctuation. In order to suppress the flickering of the lighting device due to the inrush current, the power supplied to the heating device is lowered by phase control when the power is turned on to suppress the inrush current. More specifically, when power supply to the heating unit 21 is started by starting power supply to the image forming apparatus 100, the control unit 44 gradually decreases the firing angle θ of the optical triac 72. Perform slow start control. As a result, it is possible to achieve both suppression of flicker and rapid temperature rise of the fixing roller 10 that is a heating target.

  On the other hand, when the image forming apparatus 100 is printing, the control unit 44 sets the heating unit 21 to the target temperature (180 ° C.). When the temperature of the fixing roller 10 is away from the target temperature (for example, at 50 ° C.), the duty ratio is set to 100%, and the temperature of the fixing roller 10 as the heating target is rapidly increased. As the temperature of the fixing roller 10 approaches the target temperature, the duty ratio is set lower, and when the temperature exceeds the target temperature, the duty ratio is set lower. At this time, since the duty ratio is equal to or less than the predetermined duty ratio, the control unit 44 switches from the half-wave control mode to the phase control mode.

  As described above, the control unit 44 suppresses flicker and noise terminal voltages and switches the fixing roller 10 by switching from the phase control mode to the half-wave control mode and from the half-wave control mode to the phase control mode. Rapid heating can be compatible.

<C. Embodiment 2-In the case where there are a plurality of heating means>
In FIG. 8, when the duty ratio for supplying power to the heating unit 21 exceeds 80%, the flicker value is high although it is less than 0.9. Since the flicker value is an index determined based on human subjectivity, some people feel uncomfortable even if the flicker value is less than 0.9. Therefore, it is preferable that the flicker value is as low as possible.

  Thus, in the present embodiment, control for suppressing flicker by heating an object by a plurality of heating units instead of a single unit in an area where the duty ratio is high will be described.

(C1. Fixing and heating unit 20A)
FIG. 17 is a diagram illustrating a fixing heating unit 20A according to another embodiment. Since the same reference numerals as those in FIG. 3 are the same, the description thereof will not be repeated.

  FIG. 17A is a diagram when the fixing heating unit 20A is viewed from the front of the image forming apparatus 100. FIG. The fixing heating unit 20 </ b> A includes a heating unit 24 in addition to the heating unit 21. FIG. 17B is a diagram of the fixing heating unit 20 </ b> A viewed from the side surface of the image forming apparatus 100. The heating unit 24 (halogen heater) is provided on the side surface of the fixing roller 10. This is because the side surface of the fixing roller has an increased surface area, and therefore, when heated only by the heating unit 21, temperature unevenness (temperature of the side surface decreases) is avoided. The temperature detection unit 25 measures the temperature near the side surface of the fixing roller 10. For example, a thermistor may be used as the temperature measuring means of the temperature detector 25.

  In the present embodiment, the heating unit 24 is provided on the side surface of the fixing roller 10, but is not limited thereto. For example, like the heating unit 21, the fixing roller 10 may be provided over the longitudinal direction.

  FIG. 18 is a diagram illustrating a heating device 200A according to another embodiment. Since the same reference numerals as those in FIG. 4 are the same, the description thereof will not be repeated.

  200 A of heating apparatuses contain the heating part 24, the temperature detection part 25, the switch part 26, and the control part 46. FIG. The control unit 46 is electrically connected to the temperature detection unit 25 and the switch unit 26 in addition to the temperature detection unit 22, the switch unit 23, and the zero cross detection unit 42. The temperature detector 25 measures the temperature near the side surface of the fixing roller 10 and outputs the measurement result to the controller 46. The control unit 46 outputs control signals to the switch units 23 and 26 and adjusts the power supplied to the heating units 21 and 24 by intermittently supplying the power supplied from the AC power supply 40 to the heating units 21 and 24.

(C2. Lighting control)
FIG. 19 is a diagram illustrating lighting control of heating units 21 and 24 according to another embodiment. In the present embodiment, the heating units 21 and 24 have 15 cycles of 50 Hz AC half-wave as a control period. In FIG. 19, it is assumed that the rated power consumption of the heating units 21 and 24 is 1000 W, and the power supply frequency of the AC power supply 40 is 50 Hz.

  Referring to FIG. 19, “total value of duty ratio” refers to the sum of duty ratios in heating units 21 and 24. Although detailed control will be described later, when the temperature of the fixing roller 10 is far from the target temperature (for example, 180 ° C.), the control unit 46 increases the duty ratio of each heating unit (for example, the total value of the duty ratio). Is set to 175%).

  The control unit 46 sets the total value of the duty ratio to be lower as the temperature of the fixing roller 10 approaches the target temperature. At this time, first, the duty ratio of the heating unit 24 is gradually lowered, and then the duty ratio of the heating unit 21 is lowered.

  Further, the control unit 46 does not gradually decrease the duty ratio of the heating unit 21 after the duty ratio of the heating unit 24 is set to 0%, but even if the total value of the duty ratio is less than 100%, The lighting unit 24 is turned on. In FIG. 8, when the duty ratio for supplying power to the heating unit 21 is 80% to 93%, the flicker value is about 0.8 and some people may feel uncomfortable. In order to avoid this, the heating device 200A in the present embodiment uses not only the heating unit 21 but also the heating unit 24 when the total value of the duty ratio is 80% to 93%. As a result, the flicker value can be suppressed to about 0.6.

  However, when the total value of the duty ratio is 7% to 20%, the heating device 200A performs heating using only the heating unit 21, so that the flicker value becomes 0.9 or more as in the case of FIG. Therefore, when the total value of the duty ratio is less than the predetermined duty ratio (27%), the control unit 46 switches the heating unit 21 from the half-wave control mode to the phase control mode as in the first embodiment, and Lighting control is performed.

  According to the above, the heating device 200 </ b> A can further suppress flicker than the heating device 200. In addition, the heating device 200 </ b> A can realize a rapid temperature increase of the fixing roller 10 that is a heating target by including a plurality of heating units.

(C3. Duty ratio setting)
Next, a method for setting the duty ratio will be described with reference to FIG. Referring to FIG. 20, in step S <b> 40, control unit 46 acquires the temperature of fixing roller 10 from each of temperature detection units 22 and 25. In step S42, the control unit 46 calculates a temperature obtained by subtracting the average temperature from the target temperature (hereinafter also referred to as “gap temperature”). “Average temperature” refers to the average temperature of the fixing roller 10 acquired from each of the temperature detection units 22 and 25.

  In step S44, the control unit 46 selects the total duty value according to the gap temperature. A method for selecting the total value of the duty ratio will be described later.

  In step S46, the control unit 46 compares the selected duty ratio total value with the duty ratio total value table shown in FIG. 19, and determines the duty ratio total value closest to the selected duty ratio total value. Set.

  In step S <b> 48, the control unit 46 determines whether or not the total value of the set duty ratio is greater than or equal to a predetermined value of the predetermined duty ratio according to the rated power consumption of the heating unit 21. As an example, since the rated power consumption of the heating unit 21 is 1000 W, the total value of the predetermined duty ratio is set to 27%.

  If control unit 46 determines that the total value of the set duty ratios is equal to or greater than the total value of the predetermined duty ratios (YES in step S48), control proceeds to step S50. On the other hand, when determining that the total value of the set duty ratios is less than the total value of the predetermined duty ratios (NO in step S10), control unit 44 advances the control to step S52.

  In step S50, the control unit 46 performs lighting control of the heating units 21 and 24 in the half-wave control mode according to the lighting pattern shown in FIG. 19 according to the total value of the set duty ratio. In step S52, the control unit 44 performs lighting control of the heating unit 24 in the phase control mode according to the set total value of the duty ratio.

  The control unit 46 performs the lighting control according to the total value of the duty ratio set in step S50 or step S52, and then returns the control to step S40 again. The control unit 46 determines lighting control based on the gap temperature for each predetermined control cycle.

  Based on the above, the control unit 46 can set the total value of the duty ratio based on the temperature of the heating object.

  FIG. 21 is a diagram for explaining step S44 (selection of total duty ratio) in FIG. Referring to FIG. 21, in step S60, control unit 46 determines whether or not the gap temperature is 20 ° C. or higher.

  When controller 46 determines that the gap temperature is 20 ° C. or higher (YES in step S60), it selects 175% as the total value of the duty ratio in step S62.

  In step S64, the control unit 46 determines whether or not the gap temperature is less than 20 ° C and 7 ° C or more. If controller 46 determines that the gap temperature is less than 20 ° C. and 7 ° C. or more (YES in step S64), it selects 135% as the total value of the duty ratio in step S66.

  In step S68, the control unit 46 determines whether or not the gap temperature is less than 7 ° C. and 2 ° C. or more. When controller 46 determines that the gap temperature is less than 7 ° C. and 2 ° C. or more (YES in step S68), it selects 95% as the total value of the duty ratio in step S70.

  In step S72, the control unit 46 determines whether or not the gap temperature is less than 2 ° C. and 0 ° C. or more. When controller 46 determines that the gap temperature is less than 2 ° C. and 0 ° C. or more (YES in step S72), it selects 55% as the total value of the duty ratio in step S74.

  In step S76, the control unit 46 determines whether or not the gap temperature is less than 0 ° C. and −2 ° C., that is, whether or not the temperature obtained by subtracting the target temperature from the average temperature is higher than 0 ° C. and lower than or equal to 2 ° C. Judging. When it is determined that the temperature obtained by subtracting the target temperature from the average temperature is higher than 0 ° C. and equal to or lower than 2 ° C. (YES in step S76), control unit 46 selects 15% as the total value of the duty ratio in step S78.

  When the controller 46 determines that the gap temperature is less than −2 ° C., that is, the temperature obtained by subtracting the target temperature from the average temperature is higher than 2 ° C. (NO in step S76), the total value of the duty ratio in step S80. Is set to 0%, and power supply to the heating units 21 and 24 is stopped.

  For example, when the gap temperature is 10 ° C., the control unit 46 selects 135% as the total value of the duty ratio (step S44). After that, the control unit 46 refers to the duty ratio total value table shown in FIG. 19, and sets 133% of the value closest to 135% as the total value of the duty ratio (step S46). Subsequently, the control unit 46 determines that the total value (133%) of the set duty ratio is equal to or greater than the total value (27%) of the predetermined duty ratio (step S48). The control unit 46 controls the lighting of the heating units 21 and 24 in the half wave control mode according to the lighting pattern shown in FIG. 19 according to the set total value of the duty ratio. Specifically, in the control period (15 cycles), the control unit 46 turns on the AC half-waves of all the cycles in the heating unit 21, and the 1, 4, 7, 10, 13th in the heating unit 24. Are turned on (step S50).

  Based on the above, the control unit 46 can select and set the total value of the duty ratio based on the temperature of the heating object.

  In the present embodiment, the selection and setting of the total value of the duty ratio is based on the difference between the gap temperature and the target temperature, but is not limited thereto. In another aspect, control unit 46 calculates a difference in target temperature for each of the temperatures detected from temperature detection units 22 and 25, and calculates a duty ratio set according to the control according to FIG. A value obtained by adding the calculated duty ratios may be used as the total value of the duty ratios.

<D. Modification>
As shown in FIG. 19, when the control in the half-wave control mode is performed when the total value of the duty ratio is less than 20%, the flicker value becomes 0.9 or more, and people around the lighting device feel uncomfortable. Remember. This is because the heating unit 21 having a relatively large rated power consumption of 1000 W is used as the heating unit used when the total value of the duty ratio is less than 20%.

  As described with reference to FIG. 1, flicker is suppressed when a load having a small rated power consumption is used. Therefore, in this modification, the heating unit 21C having a small rated power consumption is used in place of the heating unit 21, and flicker is reduced even when the control is performed in the half-wave control mode when the total value of the duty ratio is low. A configuration that can be suppressed will be described. Since other apparatus configurations are the same as those in FIG. 18, the description thereof will not be repeated.

(D1. Lighting control)
FIG. 22 is a diagram illustrating lighting control of heating units 21C and 24 according to the modification. In this modification, the heating units 21C and 24 have 15 cycles of 50 Hz AC half-wave as the control period. Further, it is assumed that the rated power consumption of the heating unit 21C is 500 W, the rated power consumption of the heating unit 24 is 1000 W, and the power supply frequency of the AC power supply 40 is 50 Hz.

  Referring to FIG. 22, even when the total value of the duty ratio is less than 20%, the flicker value is less than 0.9. This is because the rated power consumption of the heating unit 21C is 500 W, which is smaller than the rated power consumption of the heating unit 21.

  On the other hand, since the rated power consumption of the heating unit 24 is 500 W greater than the rated power consumption of the heating unit 21C, the effect on the flicker value is greater in the heating unit 24 than in the heating unit 21C. Therefore, when the duty ratio of the heating unit 24 is low, it can be read that the flicker value is higher than that in the case of FIG.

  FIG. 23 is an exploded view of the lighting pattern of FIG. 22 into a heating unit 21C and a heating unit 24. The total value of the duty ratio is set by the control shown in FIG. When the total value of the duty ratio is determined, the lighting pattern and the duty ratio of each heating unit are determined as shown in FIG.

  In this modification, when the duty ratio of the heating unit 24 having a large rated power consumption is less than a predetermined duty ratio, the control unit 46 controls the power supply to the heating unit 24 in the phase control mode. As an example, the predetermined duty ratio is 27%. The predetermined duty ratio is preferably defined separately from the rated power consumption of the heating unit.

  Next, the lighting control according to this modification will be described with reference to FIG. Since the same reference numerals as those in FIG. 20 are the same, the description thereof will not be repeated.

  In step S48A, the control unit 46 determines whether or not the duty ratio of the heating unit 24 based on the set total value of the duty ratio is equal to or greater than a predetermined duty ratio.

  When the control unit 46 determines that the duty ratio of the heating unit 24 is equal to or higher than the predetermined duty ratio (YES in step S48A), the lighting pattern shown in FIG. 24 is displayed according to the total value of the set duty ratios. Accordingly, lighting control of the heating parts 21C and 24 is performed in the half-wave control mode.

  On the other hand, when control unit 46 determines that the duty ratio of heating unit 24 is less than the predetermined duty ratio (NO in step S48A), it is shown in FIG. 24 according to the total value of the set duty ratios. According to the lighting pattern, lighting control is performed on the heating unit 21C in the half-wave control mode. Furthermore, the control unit 46 performs lighting control of the heating unit 24 in the phase control mode according to the set total value of the duty ratio.

  The control unit 46 performs the lighting control according to the total value of the duty ratio set in step S50A or step S52A, and then returns the control to step S40 again.

  For example, when the gap temperature is 5 ° C., the control unit 46 selects 95% as the total value of the duty ratio (step S44). Thereafter, the control unit 46 refers to the duty ratio total value table shown in FIG. 24 and sets 93% of the value closest to 95% as the total value of the duty ratio (step S46). Subsequently, the control unit 46 refers to the table shown in FIG. 23B, and the duty ratio (20%) of the heating unit 24 corresponding to the set total value (93%) of the duty ratio is a predetermined duty ratio. It is determined that it is less than (27%) (step S48A). Control unit 46 controls lighting of heating unit 21 </ b> C in the half-wave control mode according to the lighting pattern shown in FIG. 24 according to the set total value of the duty ratio. Moreover, the control part 46 carries out lighting control of the heating part 24 by a phase control mode according to the total value of the set duty ratio.

  According to the above, when the rated power consumption of the heating unit used for lighting control when the total value of the duty ratio is low is equal to or lower than the predetermined rated power consumption, the control unit 46 has a low total value of the duty ratio. Even so, the power supply to the heating unit can be controlled by the half-wave control mode. In this modification, as an example, the predetermined rated power consumption is 500 W.

  In this modification, the selection and setting of the total value of the duty ratio is based on the difference between the gap temperature and the target temperature, but is not limited thereto. In another aspect, control unit 46 calculates a difference in target temperature for each of the temperatures detected from temperature detection units 22 and 25, and calculates a duty ratio set according to the control according to FIG. A value obtained by adding the calculated duty ratios may be used as the total value of the duty ratios.

(D2. Switch part)
In this modification, the control unit 46 performs only lighting control in the half-wave control mode on the heating unit 21C. Therefore, a zero cross type switch unit 23A having a built-in zero cross circuit can be used instead of the non-zero cross type switch unit 23.

  FIG. 25 is a diagram illustrating a switch unit 23A according to the present modification. Since the same reference numerals as those in FIG. 5 are the same, description thereof will not be repeated.

  Referring to FIG. 25, switch unit 23A further includes a zero-cross circuit 73. The zero cross circuit 73 monitors the AC voltage output from the AC power supply 40, and outputs a trigger signal that causes the triac Tr to conduct at a timing at which the AC voltage is detected to be zero or near zero.

  FIG. 26 is a diagram illustrating control of power supply to the heating unit using the zero-cross type switch unit. The control unit 46 outputs a control signal to the switch unit 23A at an arbitrary phase angle of the AC voltage. Even if the switch unit 23A receives a control signal input from the control unit 46 at a phase angle where the AC voltage is non-zero, the switch unit 23A uses the zero cross circuit 73 to triac at a phase angle at which the AC voltage is zero or near zero. A trigger current is output to the gate of Tr. As a result, the triac Tr is turned on at a phase angle where the AC voltage is zero or near zero.

  According to the above, the control unit 46 may output a control signal to the switch unit 23A at an arbitrary phase angle of the AC voltage when performing the lighting control in the half-wave control mode of the heating unit 21C. Therefore, the control unit 46 does not need to output a control signal at a timing when the AC voltage becomes zero based on the detection signal output from the zero cross detection unit 42, and the processing load is reduced.

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

  DESCRIPTION OF SYMBOLS 10 Fixing roller, 11 Pressure roller, 20, 20A Fixing heating part, 21, 21A, 21B, 21C, 24 Heating part, 22, 25 Temperature detection part, 23, 23A, 26 Switch part, 40 AC power supply, 42 Zero cross detection Section, 44, 46 control section, 70 phototriac coupler, 72 optical triac, 73 zero cross circuit, 100 image forming apparatus, Tr triac.

Claims (10)

A heating unit that heats an object by receiving power from an AC power source;
A detection unit for detecting the temperature of the object;
A switch unit for intermittently supplying power supplied from the AC power source to the heating unit;
A control unit electrically connected to the switch unit,
The controller is
Setting means for setting a duty ratio, which is a ratio of a supply period in which power from the AC power supply to a unit period is supplied to the heating unit, according to the detected temperature;
When the duty ratio is greater than or equal to a predetermined set value, the first number corresponding to the duty ratio among a plurality of AC voltage cycles included in the predetermined control period is controlled for the switch unit. A second mode for supplying power over a phase period corresponding to the duty ratio in a second number of cycle periods when the duty ratio is lower than the set value. Switching means for switching to the mode of
The second number is larger than the first number when the duty ratio is the set value in the first mode,
The heating apparatus, wherein the set value is set higher as the rated power consumption of the heating unit is larger.   The heating device according to claim 1, wherein the switching unit performs switching from the first mode to the second mode and switching from the second mode to the first mode.   The heating device according to claim 1 or 2, wherein the control unit determines switching between the first mode and the second mode by the switching unit for each control cycle.   The heating device according to claim 1, wherein the setting unit sets the duty ratio according to a temperature difference obtained by subtracting the detected temperature from a predetermined temperature. A zero-cross detection unit that detects a timing at which the AC voltage output from the AC power source becomes zero and outputs a signal to the control unit;
The said control part is a heating apparatus of any one of Claims 1-4 which controls the said switch part based on the said signal.   The switch unit receives the input of a signal instructing conduction between the AC power source and the heating unit at a phase angle different from a predetermined phase angle when the AC voltage output from the AC power source is the phase angle. The heating apparatus according to any one of claims 1 to 5, wherein conduction to the AC power source and the heating unit is performed. A second heating unit that receives power from the AC power source and heats the object;
A second switch unit for intermittently supplying power supplied from the AC power source to the second heating unit;
The controller is
A second setting unit configured to set a second duty ratio, which is a ratio of a supply period in which power from the AC power supply to the second heating unit is supplied to the second heating unit according to the detected temperature; Including
The second switch unit is controlled to supply electric power in a third number of cycle periods according to the second duty ratio among a plurality of AC voltage cycles included in the control cycle. The heating apparatus according to any one of 1 to 6.   The heating apparatus according to claim 7, wherein the rated power consumption of the second heating unit is equal to or lower than a predetermined rated power consumption.   When the second switch unit receives an input of a signal instructing conduction to the AC power source and the heating unit at a phase angle different from a predetermined phase angle of the AC voltage output from the AC power source, The heating apparatus according to claim 7 or 8, wherein conduction to the AC power source and the heating unit is performed at the predetermined phase angle. An image forming unit for forming a toner image on a recording material;
A fixing heating unit for fixing the toner image to the recording material,
The fixing heating unit includes:
A heating unit that heats an object by receiving power from an AC power source;
A detection unit for detecting the temperature of the object;
A switch unit for intermittently supplying power supplied from the AC power source to the heating unit;
A control unit electrically connected to the switch unit,
The controller is
Setting means for setting a duty ratio, which is a ratio of a supply period in which power from the AC power supply to a unit period is supplied to the heating unit, according to the detected temperature;
When the duty ratio is greater than or equal to a predetermined set value, the first number corresponding to the duty ratio among a plurality of AC voltage cycles included in the predetermined control period is controlled for the switch unit. A second mode for supplying power over a phase period corresponding to the duty ratio in a second number of cycle periods when the duty ratio is lower than the set value. Switching means to switch between the modes,
The second number is larger than the first number when the duty ratio is the set value in the first mode,
The image forming apparatus, wherein the set value is set higher as the rated power consumption of the heating unit is larger.

Images