Patent Publication Number: US-11022919-B2

Title: Power control for heating device, fixing device, and image forming apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2019-165287 filed Sep. 11, 2019. 
     BACKGROUND 
     (i) Technical Field 
     The present disclosure relates to a heating device, a fixing device, and an image forming apparatus. 
     (ii) Related Art 
     Japanese Unexamined Patent Application Publication No. 2015-219461 discloses a fixing device that includes a plurality of heaters that fix an image onto a sheet, a switching unit that switches between an ON state in which the plurality of heaters are connected to an alternating-current (AC) power source and an OFF state in which the plurality of heaters are disconnected from the AC power source, and a controller that controls turning on and off of the plurality of heaters by causing the switching unit to perform its switching operation in accordance with a turn on/off pattern in units of a half-wave cycle of the AC power source. When switching the turn on/off pattern, the controller sets a control cycle that is a switching period of the turn on/off pattern to be longer than a first period of time that does not affect a flicker value and to be shorter than a second period of time that does not affect temperature control responsivity or selects, as the above turn on/off pattern, a third turn on/off pattern with which the power difference between a first turn on/off pattern, which is an old pattern, and a second turn on/off pattern, which is a new pattern, is smaller than a predetermined reference power difference. 
     SUMMARY 
     Aspects of non-limiting embodiments of the present disclosure relate to providing a heating device, a fixing device, and an image forming apparatus capable of, when a shared power source that supplies power to the heating device also supplies power to another device, reducing a probability that the power supplied to the other device will be brought into a flickering state compared with the configuration in which a rated power is supplied from an early period of supply of power to the heat-generating member. 
     Aspects of certain non-limiting embodiments of the present disclosure address the above advantages and/or other advantages not described above. However, aspects of the non-limiting embodiments are not required to address the advantages described above, and aspects of the non-limiting embodiments of the present disclosure may not address advantages described above. 
     According to an aspect of the present disclosure, there is provided a heating device including at least one heat-generating member that generates heat by being supplied with power supplied by a shared power source and a controller that performs control in such a manner that, when the shared power source starts supplying power to the heat-generating member, a rated power is supplied to the heat-generating member after power that is 33% output or 67% output of the rated power has been supplied to the heat-generating member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present disclosure will be described in detail based on the following figures, wherein: 
         FIG. 1  is a front view of an image forming apparatus according to a first exemplary embodiment; 
         FIG. 2  is a schematic diagram of a fixing device according to each of the first, second, and third exemplary embodiments; 
         FIG. 3  is a block diagram illustrating a configuration of the fixing device according to the first exemplary embodiment; 
         FIG. 4  is a graph illustrating the relationship between control power and flicker value in the fixing device according to each of the first and second exemplary embodiments; 
         FIG. 5  is a timing chart illustrating changes in the temperature of a heater in the fixing device according to the first exemplary embodiment; 
         FIG. 6  is a diagram illustrating a turn on/off pattern of the heater in the fixing device according to the first exemplary embodiment; 
         FIG. 7  is a diagram illustrating a turn on/off pattern of a heater in the fixing device according to the second exemplary embodiment; 
         FIG. 8  is a diagram illustrating a turn on/off pattern of a heater in the fixing device according to the third exemplary embodiment; 
         FIG. 9  is a schematic diagram of a fixing device according to a fourth exemplary embodiment; 
         FIG. 10  is a diagram illustrating a turn on/off pattern of a heater in the fixing device according to the fourth exemplary embodiment; and 
         FIG. 11  is a diagram illustrating a turn on/off pattern of a heater in a fixing device according to a modification. 
     
    
    
     DETAILED DESCRIPTION 
     First Exemplary Embodiment 
     An image forming apparatus  20  and a fixing device  30  according to a first exemplary embodiment will be described as an example of an image forming apparatus and an example of a fixing device. 
     [Overall Configuration] 
       FIG. 1  illustrates a distribution switchboard  10 , an interior lighting  12 , and the image forming apparatus  20 . The distribution switchboard  10  and the interior lighting  12  are connected to each other by a wiring line  14 . The distribution switchboard  10  and the image forming apparatus  20  are connected to each other by a wiring line  16 . The distribution switchboard  10  supplies power that is supplied by a system power source (e.g., a commercial power source provided by an electric-power company) to the interior lighting  12  and the image forming apparatus  20 . Note that the distribution switchboard  10  is an example of a shared power source. As an example, the power supplied by the distribution switchboard  10  is alternating-current (AC) power. 
     The interior lighting  12  is an example of an apparatus that is different from the image forming apparatus  20 . The interior lighting  12  lights up by being supplied with power that is at least smaller than the power supplied to the image forming apparatus  20  when a fixing operation is performed. Note that, when the image forming apparatus  20  is activated (here, when the fixing device  30  that will be described later starts operating), the interior lighting  12  may sometimes shine unsteadily (the brightness of the interior lighting  12  may sometimes repeatedly change in a short time). This is because a large current flows to the side of the image forming apparatus  20  when the fixing device  30  starts operating, so that a voltage drop occurs in the distribution switchboard  10 , and the voltage on the side of the interior lighting  12  decreases. This “unsteady shining” will hereinafter be referred to as “flicker”. 
     An index that indicates the degree of flicker is “flicker value”. A flicker value (Pst) in the first exemplary embodiment refers to a value measured by a measurement method based on the flicker standard (IEC 61000-3-11). In the first exemplary embodiment, Pst is set to 1.0 as a standard flicker value. 
     &lt;Image Forming Apparatus&gt; 
     The image forming apparatus  20  includes an image forming unit  26  that forms a toner image G onto one of sheets P and the fixing device  30 . More specifically, the image forming apparatus  20  includes a power source  22  to which power is supplied by the distribution switchboard  10 , an accommodating unit  23  that accommodates the sheets P, a transport unit  24  that transports the sheets P, the image forming unit  26 , and the fixing device  30 . Each of the sheets P is an example of a recording medium. The toner image G is an example of a developer image. 
     The image forming unit  26  illustrated in  FIG. 3  is an example of an image forming unit. The image forming unit  26  includes a charging unit  26 A that charges the outer peripheral surface of a photoconductor (not illustrated), an exposure unit  26 B that exposes the charged outer peripheral surface to light so as to form a latent image, a developing unit  26 C that develops the latent image with toner, and a transfer unit  26 D that transfers the developed toner image G onto one of the sheets P. 
     [Configuration of Principal Portion] 
     The fixing device  30  will now be described. 
     The fixing device  30  illustrated in  FIG. 2  includes an operation unit  32  that performs a fixing operation and a controller  50  that controls each operation of the operation unit  32 . 
     &lt;Operation Unit&gt; 
     As an example, the operation unit  32  includes a fixing roller  34 , which is an example of a fixing member, a heater  36 , which is an example of a heat-generating member, a pressure roller  38 , which is an example of a pressing member, a temperature sensor  42  that detects the temperature of the fixing roller  34 , and a motor  44  that causes the fixing roller  34  to rotate. Note that the heater  36  and the controller  50  are included in a heating device  40 . 
     The fixing roller  34  includes a cylindrical shaft portion  34 A, an elastic layer  34 B, and a release layer  34 C. The heater  36  is inserted in the shaft portion  34 A. The fixing roller  34  and the pressure roller  38  form a nip part N. The fixing roller  34  and the pressure roller  38  are caused to rotate by the motor  44 , so that one of the sheets P is transported. The toner image G is heated and pressurized at the nip part N by the fixing roller  34  that has been heated by the heater  36  and the pressure roller  38 , so that the toner image G is fixed onto the sheet P, which has been transported. 
     As an example, the heater  36  is formed as a halogen lamp that is long in one direction and generates heat by being supplied with power. In addition, the heater  36  is electrically connected to the power source  22 . Furthermore, the heater  36  generates heat by being supplied with the power supplied by the power source  22  (the distribution switchboard  10 , see  FIG. 1 ) so as to heat the fixing roller  34  in such a manner that the toner image G is fixed onto one of the sheets P. 
     &lt;Controller&gt; 
     As an example, the controller  50  illustrated in  FIG. 3  is configured to also function as a main controller that controls the operation of each unit of the image forming apparatus  20 . Note that the controller  50  may be configured as a discrete controller for the fixing device  30 . 
     The controller  50  includes a central processing unit (CPU)  52 , read only memory (ROM)  54 , random access memory (RAM)  56 , and a storage  58 . The units included in the controller  50  are connected to one another via a bus. The ROM  54  stores various programs and various data items. The RAM  56  serves as a work area and temporarily stores a program or a data item. The storage  58  stores various programs including an operating system and various data items. The CPU  52  runs various programs recorded in the ROM  54  or the storage  58 . 
     When supply of power to the heater  36  is started by the power source  22  (the distribution switchboard  10 , see  FIG. 1 ), the controller  50  performs control in such a manner that power that is 33% output of a rated power WA (see  FIG. 4 ) is supplied to the heater  36 , after which the rated power WA is supplied to the heater  36 . Note that the arrow in  FIG. 3  that extends from the power source  22  to the heater  36  indicates the supply of power. In the first exemplary embodiment, the rated power WA is power that is necessary for the temperature of the heater  36  to reach a temperature T 5  (see  FIG. 5 ) within a predetermined period of time (within a predetermined range). The reason why the power that is 33% output of the rated power WA is supplied to the heater  36  will be described later. 
     The controller  50  performs “half-wave control” for controlling AC power (power having an AC waveform) that is supplied to the heater  36  by the distribution switchboard  10  (see  FIG. 1 ) in units of a half-wavelength (a half of one wavelength) of the AC power. The half-wave control is an example of thinning-out control, which will be described later. Note that, in the following description, the power (AC power) that is supplied to the heater  36  will hereinafter be referred to as “control power”. 
     The thinning-out control is control for thinning out the AC power that is supplied to a heat-generating member (the heater  36 ) with respect to the rated power WA by maintaining the amplitude of the AC power as the rated power WA and by changing a period during which power is supplied to the heat-generating member in a period within one cycle of the AC power. 
     In  FIG. 6 , a graph G 1  of an AC waveform representing a turn on/off pattern of the heater  36  is illustrated as an example of control of supplying power to the heater  36  (see  FIG. 2 ), the control being performed by the controller  50  (see  FIG. 2 ). Note that the graph G 1  is indicated by a bold solid line. The dashed line indicates a state in which the heater  36  is temporarily turned off (the amplitude is zero). 
     In the graph G 1 , with a half-wavelength as a unit, 0.5 cycle out of 1.5 cycles is set to be a supply period S 1 , and the remaining 1.0 cycle is set to be a non-supply period S 2 , so that control with 33% output is performed. As seen from the graph G 1 , here, as an example, a power supply pattern in which supply of power is performed (ON) in the first 0.5 cycle out of the 1.5 cycles and in which the supply of power is not performed (OFF) in the subsequent 1.0 cycle is repeated. 
     [Singular Points of Control Power] 
     Singular points of the control power when power is supplied to the heater  36  according to the first exemplary embodiment will now be described. 
       FIG. 4  illustrates a graph G 2  illustrating a relationship between the control power [W] supplied to the heater  36  (see  FIG. 2 ) and the flicker value of the interior lighting  12  (see  FIG. 1 ) when the control power is supplied thereto. Each point in the graph G 2  is a flicker value that is measured when the heater  36  is activated at a set turn on/off duty ratio. In other words, the graph G 2  is obtained by measuring the flicker value while changing the setting of the turn on/off duty ratio. As illustrated in the graph G 2 , it is confirmed that a singular point A and a singular point B at each of which the flicker value is sharply decreased appear when the control power (the setting of the turn on/off duty ratio) is varied. 
     Here, it is found that, when the above-mentioned rated power WA [W] is 100%, the control power [W] at the singular point A is equivalent to 33%. It is found that, when the above-mentioned rated power WA [W] is 100%, the control power [W] at the singular point B is equivalent to 67%. It is confirmed that, by setting the control power supplied to the heater  36  to at least one of 33% and 67% as mentioned above, the flicker value decreases more than that in the case of using the control power that is set to neither 33% nor 67%. Note that a measurement error of the control power is set within a range of ±1%. 
     In other words, it is confirmed that the flicker value decreases as a result of thinning out (reducing) the control power supplied to the heater  36  to 33% or 67% of the rated power WA. Accordingly, in the fixing device  30  (see  FIG. 2 ) according to the first exemplary embodiment, as an example, control power that is 33% output of the rated power WA is supplied to the heater  36  in an early period of printing (from time tc to time te, see  FIG. 5 ) in which flicker occurs. The period from time tc to time te is about 1 second as an example. The rated power WA is set to be supplied to the heater  36  after the early period of printing. 
     [Temperature of Heater] 
     A set temperature and a detected temperature of the heater  36  according to the first exemplary embodiment will now be described. 
       FIG. 5  illustrates a graph G 3  of a set temperature of the heater  36  (see  FIG. 2 ) at each point in time, the set temperature having been set in advance in the controller  50  (see  FIG. 2 ), and a graph G 4  of the detected temperature of the heater  36  detected by the temperature sensor  42  (see  FIG. 2 ). The graph G 3  is indicated by a dashed line. The graph G 4  is indicated by a solid line. In  FIG. 5 , temperatures T 1 , T 2 , T 3 , T 4 , and T 5  [° C.] of the heater  36  are illustrated. The temperature T 1  is the lowest temperature, followed by the temperature T 2 , the temperature T 3 , the temperature T 4 , and the temperature T 5  in ascending order. Note that temperature differences between the temperatures T 1 , T 2 , T 3 , T 4 , and T 5  of the heater  36 , which are illustrated in  FIG. 5 , do not represent the absolute values of the actual temperature differences. 
     A period before time ta is a non-operating period during which the fixing device  30  is in an OFF state. A period from time ta to time tb is a first standby period of the fixing device  30 . A period from time tb to time tc is a first idling period of the fixing roller  34  and the pressure roller  38  (see  FIG. 2 ). A period from time tc to time tg (including time td, time te, and time tf) is a printing (fixing operation) period. A period from time tg to time th is a second idling period of the fixing roller  34  and the pressure roller  38 . A period after time th until the image forming apparatus  20  (see  FIG. 1 ) is brought into an OFF state is a second standby period of the fixing device  30 . 
     As illustrated in the graph G 3 , in the non-operating period, the first standby period, the first idling period, and the early period of printing, which is the period from time tc to time te, the set temperature of the heater  36  is set to the temperature T 3 . In a printing period from time te to time tg, the set temperature of the heater  36  is set to the temperature T 5 , which is as an example of a target temperature. In the early period of printing, the turn on/off pattern of the heater  36  is changed from a normal turn on/off pattern as will be described later. 
     As illustrated in the graph G 4 , the detected temperature of the heater  36  is the temperature T 1  in the non-operating period (OFF). The detected temperature of the heater  36  is the temperature T 2  in the first standby period and the first idling period (from time to to time tc). The detected temperature of the heater  36  is the temperature T 4  in the early period of printing. The detected temperature of the heater  36  increases from time te to time tf and is the temperature T 5  in a later period of printing that is a period from time tf to time tg. After time tg, the detected temperature of the heater  36  decreases from the temperature T 5 . 
     Here, in the fixing device  30  according to the first exemplary embodiment, the controller  50  is set to perform control such that the above-mentioned power supply pattern (see  FIG. 6 ) in which the output is 33% of the rated power WA is repeated in the early period of printing (from time tc to time te). 
     Comparative Example 
     As a comparative example of the fixing device  30  according to the first exemplary embodiment, the control power supplied to the heater  36  is set to the rated power WA from the early period of printing, and in this case, it is confirmed that a flicker phenomenon (unsteady shining) occurs in the interior lighting  12 . 
     [Effects] 
     Effects of the first exemplary embodiment will now be described. 
     Assume that a main power switch (not illustrated) of the image forming apparatus  20  illustrated in  FIG. 1  is in an ON state and that the interior lighting  12  is in a lit-up state. In this state, assume that an image forming process is started. In the fixing device  30 , in the first standby period and the first idling period (see  FIG. 5 ), the control power that causes the temperature of the heater  36  to increase to the temperature T 2  is supplied to the heater  36 . The control power supplied to the heater  36  during these periods is smaller than the rated power WA. Thus, the flicker phenomenon rarely occurs in the interior lighting  12 . 
     Next, in the early period of printing, the controller  50  causes the control power that is 33% output of the rated power WA to be supplied to the heater  36 . Here, 33% output of the rated power WA is one of the singular points as mentioned above, and the degree of decrease in the flicker value of the interior lighting  12  is higher than that in the case where the control power that is not 33% output of the rated power WA is supplied. As a result, a voltage drop is less likely to occur in the distribution switchboard  10 , and thus, the probability that the power supplied to the interior lighting  12  will be brought into a flickering state is reduced compared with the configuration in which the rated power WA is supplied to the heater  36  from an early period of supply of power to the heater  36 . 
     In addition, in the fixing device  30 , the controller  50  performs the half-wave control on the AC power that is supplied to the heater  36 . More specifically, when the control power is supplied to the heater  36 , the controller  50  makes the control power smaller than the rated power WA by performing the half-wave control with ON/OFF switching in units of a half-wavelength of the AC power (the thinning-out control for reducing the output with respect to the rated power WA). As a result, compared with the configuration in which the amplitude of the AC power is changed, a device for changing the amplitude is not necessary, and the control power may easily be reduced, so that the control power that is supplied to the heater  36  may easily be controlled. 
     Furthermore, in the fixing device  30 , 0.5 cycle out of 1.5 cycles is set to be a supply period of the AC power that is supplied to the heater  36 , and the remaining 1.0 cycle is set to be a non-supply period of the AC power, so that control (supply) for 33% output is performed. In other words, when performing output control (power supply) of 33%, which is not a nice round figure, it is not necessary to adjust the output level to exactly 33%, and the output may be obtained only by setting 0.5 cycle out of 1.5 cycles to be the supply period. As a result, it becomes easier to control the control power that is supplied to the heater  36  compared with the configuration in which the control power is supplied during a period when zero crossing of the AC waveform does not occur. 
     According to the image forming apparatus  20 , by providing the fixing device  30 , a voltage drop is less likely to occur in the distribution switchboard  10  as mentioned above. As a result of a voltage drop being less likely to occur in the distribution switchboard  10 , a reduction in the power that is supplied to the image forming apparatus  20  is suppressed. Consequently, compared with the configuration in which the rated power WA is supplied to the heater  36 , occurrence of a flickering state in each unit (e.g., the image forming unit  26 ) excluding the fixing device  30  included in the image forming apparatus  20  is suppressed. 
     Second Exemplary Embodiment 
     Next, the image forming apparatus  20  and the fixing device  30  according to a second exemplary embodiment will be described. Note that members and portions that are basically the same as those of the image forming apparatus  20  and the fixing device  30  according to the first exemplary embodiment, which have been described above, will be denoted by the same reference signs as used in the first exemplary embodiment, and descriptions thereof will be omitted. Descriptions of effects that are similar to those of the first exemplary embodiment will also be omitted. 
     In the fixing device  30  according to the second exemplary embodiment that is illustrated in  FIG. 2 , the turn on/off pattern of the heater  36  set in the controller  50  is different from that in the first exemplary embodiment. The configuration excluding this turn on/off pattern is similar to that of the first exemplary embodiment. 
     In  FIG. 7 , a graph G 5  representing a turn on/off pattern of the heater  36  is illustrated as an example of control of supplying power to the heater  36 , the control being performed by the controller  50 . Note that the graph G 5  is indicated by a bold solid line. The dashed line indicates a state in which the heater  36  is turned off (the amplitude is zero). 
     In the graph G 5 , with a half-wavelength as a unit, 1.0 cycle out of 1.5 cycles is set to be a supply period S 3 , and the remaining 0.5 cycle is set to be a non-supply period S 4 , so that control with 67% output is performed. Here, as an example, a power supply pattern in which supply of power is performed (ON) in the first 1.0 cycle out of the 1.5 cycles and in which the supply of power is not performed (OFF) in the subsequent 0.5 cycle is repeated. 
     [Effects] 
     Effects of the second exemplary embodiment will now be described. 
     In the fixing device  30  according to the second exemplary embodiment, in the early period of printing, the controller  50  causes the control power that is 67% output of the rated power WA to be supplied to the heater  36 . Here, 67% output of the rated power WA is one of the singular points as mentioned above, and the degree of decrease in the flicker value of the interior lighting  12  is high. As a result, a voltage drop is less likely to occur in the distribution switchboard  10 , and thus, the probability that the power supplied to the interior lighting  12  will be brought into a flickering state is reduced compared with the configuration in which the rated power WA is supplied from the early period of supply of power to the heater  36 . 
     In addition, in the fixing device  30  according to the second exemplary embodiment, 1.0 cycles out of 1.5 cycles is set to be the supply period S 3  of the AC power that is supplied to the heater  36 , and the remaining 0.5 cycle is set to be the non-supply period S 4  of the AC power, so that control (supply) of 67% output is performed. In other words, when performing output control (power supply) of 67%, which is not a nice round figure, it is not necessary to adjust the output level to exactly 67%, and the output may be obtained only by setting 1.0 cycle out of 1.5 cycles to be the supply period. As a result, it becomes easier to control the control power that is supplied to the heater  36  compared with the configuration in which the AC power is supplied during a period when zero crossing of the AC waveform does not occur. 
     Third Exemplary Embodiment 
     Next, the image forming apparatus  20  and the fixing device  30  according to a third exemplary embodiment will be described. Note that members and portions that are basically the same as those of the image forming apparatuses  20  and the fixing devices  30  according to the first and second exemplary embodiments, which have been described above, will be denoted by the same reference signs as used in the first and second exemplary embodiments, and descriptions thereof will be omitted. Descriptions of effects that are similar to those of the first and second exemplary embodiments will also be omitted. 
     In the fixing device  30  according to the third exemplary embodiment that is illustrated in  FIG. 2 , the turn on/off pattern of the heater  36  set in the controller  50  is different from those in the first and second exemplary embodiments. The configuration excluding this turn on/off pattern is similar to those in the first and second exemplary embodiments. 
     In  FIG. 8 , a graph G 6  representing a turn on/off pattern of the heater  36  is illustrated as an example of control of supplying power to the heater  36 , the control being performed by the controller  50  according to the third exemplary embodiment. Note that the graph G 6  is indicated by a bold solid line. The dashed line indicates a state in which the heater  36  is turned off (the amplitude is zero). 
     As an example, the graph G 6  illustrates a state in which control for a first period SA corresponding to 4.5 cycles (from time tc to time td) is performed followed by control for a second period SB corresponding to 4.5 cycles (from time td to time te). In the first period SA, the control with 33% output is performed. In the second period SB, the control with 67% output is performed. Note that each of the first period SA and the second period SB may correspond to any number of cycles that are multiples of 1.5 cycles. In this manner, the controller  50  is configured to control the heater  36 . The controller  50  performs control in such a manner that the control power that is 67% output of the rated power WA is supplied to the heater  36  after the control power that is 33% output of the rated power WA has been supplied to the heater  36  and before the rated power WA is supplied to the heater  36 . 
     [Effects] 
     Effects of the third exemplary embodiment will now be described. 
     In the fixing device  30  according to the third exemplary embodiment, in the early period of printing, the controller  50  causes the control power that is 33% output or 67% output of the rated power WA to be supplied to the heater  36 . Here, 33% output or 67% output of the rated power WA is one of the singular points as mentioned above, and the degree of decrease in the flicker value of the interior lighting  12  is high. As a result, a voltage drop is less likely to occur in the distribution switchboard  10 , and thus, the probability that the power supplied to the interior lighting  12  will be brought into a flickering state is reduced compared with the configuration in which the rated power WA is supplied from the early period of supply of power to the heater  36 . 
     In addition, in the fixing device  30  according to the third exemplary embodiment, the control power that is 67% output is supplied to the heater  36  after the control power that is 33% output has been supplied to the heater  36 . As a result, the amount of the control power that is supplied to the heater  36  increases more than that in the configuration in which the control power is switched in one step during the period from when supply of power is started until the fixing operation is performed, and thus, the time taken for the temperature of the heater  36  to reach the target temperature is reduced. 
     Fourth Exemplary Embodiment 
     Next, the image forming apparatus  20  and a fixing device  60  according to a fourth exemplary embodiment will be described. Note that members and portions that are basically the same as those of the image forming apparatuses  20  and the fixing devices  30  according to the first, second, and third exemplary embodiments, which have been described above, will be denoted by the same reference signs as used in the first, second, and third exemplary embodiments, and descriptions thereof will be omitted. Descriptions of effects that are similar to those of the first, second, and third exemplary embodiments will also be omitted. 
       FIG. 9  illustrates the fixing device  60  according to the fourth exemplary embodiment. The differences between the fixing device  60  and the fixing device  30  (see  FIG. 2 ) according to the third exemplary embodiment are that the fixing device  60  further includes a heater  62 , which is another example of a heat-generating member, in addition to the heater  36  and that the turn on/off patterns of the heaters  36  and  62  set in the controller  50  are different from the turn on/off pattern of the fixing device  30  set in the controller  50  in the third exemplary embodiment. In other words, the fixing device  60  includes a plurality of heat-generating members. The controller  50  is configured to control the control power that is supplied to the heater  36  and the heater  62 . In addition, the heaters  36  and  62  and the controller  50  are included in the heating device  40 . 
     As an example, the heater  62  is formed as a halogen lamp that is long in one direction and generates heat by being supplied with the control power. In addition, the heater  62  is electrically connected to the power source  22 . Furthermore, the heater  62  generates heat by being supplied with the control power supplied by the power source  22  (the distribution switchboard  10 , see  FIG. 1 ) so as to heat the fixing roller  34  in such a manner that the toner image G is fixed onto a recording medium. As an example, the output of the heater  62  is lower than the output of the heater  36 . 
     The controller  50  performs control in such a manner that supply of the control power to the heater  36  and supply of the control power to the heater  62  are started at different points in time. More specifically, the controller  50  performs control in such a manner that supply of the control power to the heater  36  that has a larger capacity than the heater  62  is started before supply of the control power to the heater  62  that has a smaller capacity is started. Note that the “capacity” of each of the heaters  36  and  62  refers to the amount of heat [J/s=W] required to raise the temperature of an object to be heated. 
     In  FIG. 10 , a graph G 7  illustrating the turn on/off pattern of the heater  62  and a graph G 6  illustrating the turn on/off pattern of the heater  36  are respectively illustrated as an example of control of supplying power to the heater  62  and an example of control of supplying power to the heater  36  (see  FIG. 9 ), each of the control being performed by the controller  50  according to the fourth exemplary embodiment. Note that the graph G 6  is similar to that of the third exemplary embodiment, and thus, description thereof will be omitted. The graph G 7  is indicated by a bold solid line. 
     As an example, the graph G 7  illustrates a state in which control for a first period SC corresponding to 4.5 cycles is performed followed by control for a second period SD corresponding to 4.5 cycles. In the first period SC, the control with 33% output is performed. In the second period SD, the control with 67% output is performed. Note that each of the first period SC and the second period SD may correspond to any number of cycles that are multiples of 1.5 cycles. In this manner, the controller  50  controls the control power that is supplied to the heater  62  in such a manner that the control power that is 67% output of the rated power WA is supplied to the heater  62  after the control power that is 33% output of the rated power WA has been supplied to the heater  62  and before the rated power WA is supplied to the heater  62 . 
     In  FIG. 10 , time t 1  is the start point of the first period SA. Time t 2  is a point in time after 1.5 cycles have passed from time t 1  and is the start point of the first period SC. Time t 3  is the start point of the second period SB and is a point in time after 3.0 cycles have passed from time t 2 . Time t 4  is a point in time after 1.5 cycles have passed from time t 3  and is the start point of the second period SD. Time t 5  is the end point of the second period SB and is a point in time after 3.0 cycles have passed from time t 4 . Time t 6  is a point in time after 1.5 cycles have passed from time t 5  and is the end point of the second period SD. In this manner, the controller  50  performs control in such a manner that supply of the control power to the heater  36  is performed first, and supply of the control power to the heater  62  is performed 1.5 cycles (the period from time t 1  to time t 2 ) later. 
     [Effects] 
     Effects of the fourth exemplary embodiment will now be described. 
     The controller  50  of the fixing device  60  illustrated in  FIG. 9  causes the control power that is 33% output or 67% output of the rated power WA to be supplied to the heaters  36  and  62  in the early period of printing. Here, 33% output or 67% output of the rated power WA supplied to each of the heaters  36  and  62  is one of the singular points as mentioned above, and the degree of decrease in the flicker value of the interior lighting  12  is high. As a result, a voltage drop is less likely to occur in the distribution switchboard  10 , and thus, the probability that the power supplied to the interior lighting  12  will be brought into a flickering state is reduced compared with the configuration in which the rated power WA is supplied from the early period of supply of power to the heaters  36  and  62 . 
     According to the fixing device  60 , at least the control power that is supplied to the heater  36 , which has a larger capacity than the heater  62 , is controlled. As a result, compared with the configuration in which only supply of power to the heater  62  having a smaller capacity is controlled, supply of a large amount of power that affects flicker is managed, and thus, occurrence of the flickering state in the interior lighting  12  is suppressed. 
     In addition, according to the fixing device  60 , time t 1 , which is a point in time at which supply of the control power to the heater  36  is started, and time t 2 , which is a point in time at which supply of the control power to the heater  62  is started, differ from each other. As a result, the amount of the control power that is supplied to the fixing device  60  at time t 1  is smaller than that in the configuration in which power is simultaneously supplied to the heaters  36  and  62 , and thus, occurrence of the flickering state in the interior lighting  12  is suppressed. 
     Furthermore, according to the fixing device  60 , supply of power to the heater  36  having a larger capacity is started before supply of power to the heater  62  having a smaller capacity is started. As a result, a relatively large amount of power is supplied from the start point of supply of power, and heat is generated. Thus, the time taken for reaching the target temperature is reduced compared with the configuration in which supply of power to the heater  62  is started first. 
     Note that the present disclosure is not limited to the above-described exemplary embodiments. 
     &lt;Modification&gt; 
       FIG. 11  illustrates a graph G 8  as a modification of a control graph of the control power in the fixing device  30  (see  FIG. 2 ). In the graph G 8 , half-value control is not performed, and when the rated power WA is 100%, the output ratio for the heater  36  is changed to 33%, 67%, and 100% in a stepwise manner. In the graph G 8 , the output ratio for the heater  36  is changed to 33% and then to 67% in the early period of printing. In the present modification, for example, the output ratio is changed to 33%, 67%, and 100% by changing the duty ratio between a turned-on section in which the heater  36  is in an ON state and a turned-off section in which the heater  36  is in an OFF state (by performing pulse width modulation). In this manner, even if the control power that is 33% output or 67% output is supplied to the heater  36  by using a method that does not perform the half-value control, the probability that the power supplied to the interior lighting  12  will be brought into a flickering state is reduced. 
     &lt;Other Modifications&gt; 
     The turn on/off pattern in the case of obtaining the 33% output by performing the half-wave control is not limited to a turn on/off pattern of ON, OFF, and OFF and may be a turn on/off pattern of OFF, ON, and OFF or a turn on/off pattern of OFF, OFF, and ON. In addition, the turn on/off pattern for obtaining the 67% output by performing the half-wave control is not limited to a turn on/off pattern of ON-ON-OFF and may be a turn on/off pattern of ON-OFF-ON or a turn on/off pattern of OFF-ON-ON. 
     For example, assume that a fixing device includes a heater H 1  having the largest capacity W 1 , a heater H 3  having the smallest capacity W 3 , and a heater H 2  having a capacity W 2  that is smaller than the capacity W 1  of the heater H 1  and larger than the capacity W 3  of the heater H 3 . The heaters H 1 , H 2 , and H 3  are each an example of a heat-generating member. Here, when a relationship of W 1 &lt;(W 2 +W 3 ) is satisfied, the above-described control may be performed on the control power supplied to the heater H 2  and the control power supplied to the heater H 3 , and the above-described control may not be performed on the control power supplied to the heater H 1 . Note that the number of the heat-generating members may be four or more. 
     When the sum of the control power supplied to the heater  36  and the control power supplied to the heater  62  is smaller than the rated power WA, supply of the control power to the heater  36  and supply of the control power to the heater  62  may be simultaneously started. Alternatively, supply of the control power to the heater  62  may be started before supply of the control power to the heater  36  is started. 
     Each of the heat-generating members is not limited to being a halogen lamp and may be a flash lamp. Note that a flickering state will become notable in the case where a halogen lamp is used. 
     As a measure of flicker, the above-described power supply control is not limited to being performed in the early period of printing. For example, assume the case where the first fixing operation has been completed, and the temperature of the heater  36  has decreased due to a long interval between the sheets P. In this case (an intermediate period of printing), the above-described power supply control may be performed at the start of the second fixing operation. 
     The method for controlling the control power supplied to the heaters  36  and  62  is not limited to the half-wave control and may be a control method using an AC waveform in which zero crossing does not occur at least one of a turn-on point and a turn-off point. In addition, the method for controlling the control power supplied to the heaters  36  and  62  is not limited to a method in which a period is changed while keeping the amplitude constant and may be a method in which the amplitude of the AC power is changed. 
     The present disclosure is not limited to the above-described exemplary embodiments, and various modifications and applications may be made within the gist of the present disclosure. For example, the heating device  40  is not limited to being configured to be applied to the fixing device  30 . 
     The foregoing description of the exemplary embodiments of the present disclosure has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The exemplary embodiments were chosen and described in order to best explain the principles of the disclosure and its practical applications, thereby enabling others skilled in the art to understand the disclosure for various exemplary embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the disclosure be defined by the following claims and their equivalents.