JP2008191333A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely reduce flicker and harmonic current during heater control for a fixing device. <P>SOLUTION: The fixing device includes: a fixing member for fixing an image onto a recording material by heat; a heater having a main heater for heating the fixing member by generating heat with power supplied from an AC power source, and a sub-heater for heating the fixing member in an auxiliary manner by generating heat with power supplied from the AC power source; and a control section for controlling power supplied to the main heater and sub-heater from the AC power source. When two half waves composing one cycle of an AC input sinusoidal wave is assumed as one lighting duty, the control section exerts the heater control during the drive of the main heater and sub-heater such that if the lighting duties of the main heater and sub-heater are greater than 50%, each of the heaters is turned on for one of the two half waves of the heater and the main heater and sub-heater are turned on so that their half waves do not occur at the same time. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fixing device that heats a heater with AC power from an AC power source and fixes an image on a recording material, and an image forming apparatus including the fixing device.

2. Description of the Related Art Image forming apparatuses such as copying machines, printers, and facsimiles are generally provided with a heat roller type fixing device, and a toner image is fused and fixed on the surface of a recording material such as paper or a transparent film. This fixing device includes a fixing roller including a heat roller having a halogen heater (hereinafter referred to as a heater) disposed therein and a pressure roller pressed against the roller, and power supply to the heater is started during image formation. The heat roller and the pressure roller are gradually heated by the heat generated by the heater. The recording material after transfer of the toner image is nipped and conveyed to the nip portion of the heated heat roller and pressure roller in this way, whereby the toner image is fixed on the surface of the recording material. Such a fixing device is supplied with electric power from an AC power source. As a heater control method, one half of one cycle of the AC input sine wave to the heater is energized (all the half waves are energized). A half-wave control or a phase control for turning on or stopping (all off) is performed (for example, see Patent Document 1 below).
JP 2004-191710 A

  However, in the fixing device as described above, if the wattage of the heater is increased in order to shorten the stabilization time when the power is turned on, flicker (such as flickering of a fluorescent lamp) is caused in the power supply system in the case of heater control only by half-wave control. Is likely to occur). In addition, in the case of heater control based only on phase control, the flicker value decreases and flickering of the fluorescent lamp becomes inconspicuous, but the harmonic current may deteriorate. With respect to this problem, the fixing device described in Patent Document 1 exhibits a suitable effect, but further improvement is desired.

  The present invention has been made to solve the above-described problem, and an object thereof is to more reliably reduce the generation of flicker and harmonic current during heater control of a fixing device.

According to a first aspect of the present invention, there is provided a fixing member for thermally fixing an image on a recording material;
A heater unit having a main heater that generates heat with power from an AC power source and heats the fixing member; and a sub-heater that generates heat with power from an AC power source and supplementarily heats the fixing member;
Control means for controlling the power supplied from the AC power source to the main heater and the sub heater,
When the main heater and the sub-heater are driven, the control means uses one half of the AC input sine wave as one lighting duty, and the lighting duty of both the main heater and the sub-heater is larger than 50%. When one half of the two half-waves of each heater is fully lit, heater control is performed so that the half-waves of the main heater and the sub-heater do not overlap with each other in the same period. It is a fixing device.

  According to this configuration, when the main heater and the sub heater are driven, the control means sets one lighting duty in two half waves forming one cycle of the AC input sine wave, and the lighting duty of both the main heater and the sub heater is 50%. If it is larger, the phase control in which one half of the two half-waves is fully lit is used to reduce flicker more reliably, and the half-waves of the main heater and sub-heater are all simultaneously. By not overlapping the lighting half-waves, the generation of harmonic current is further reduced.

  Further, the invention according to claim 2 is the fixing device according to claim 1, wherein the control unit is configured to drive the main heater and the sub heater instead of the heater control or together with the heater control. When the lighting duty of both the main heater and the sub heater is less than 50% as one lighting duty with two half waves forming one cycle of an AC input sine wave, one of the two half waves of each heater is Half-waves are completely turned off, and heater control is performed so that the half-waves of the main heater and the sub heater are not overlapped with each other in the same period.

  According to this configuration, when the control unit drives the main heater and the sub-heater and the lighting duty of both the main heater and the sub-heater is less than 50%, of the two half waves forming one cycle of each heater. By controlling the half-waves of the main heater and sub-heater so that they do not overlap each other at the same time, while reducing flicker more reliably by phase control that turns off one half-wave completely, harmonics The generation of current is further reduced.

  Further, the invention according to claim 3 is the fixing device according to claim 1, wherein the control unit is configured to drive the main heater and the sub-heater instead of the heater control or together with the heater control. When only one of the main heater or the sub heater is larger than the lighting duty 50%, one half wave of the two half waves of the heater whose lighting duty is larger than 50% is fully lit, and the lighting duty is 50%. One half of the two half-waves of the heaters less than the total is turned off, and the heater control is performed so that the full turn-on half-wave of the one heater and the full turn-off half-wave of the other heater are overlapped at the same time It is.

  According to this configuration, when the control unit is operating the main heater and the sub-heater and only one of the main heater or the sub-heater has a lighting duty of more than 50%, the lighting means of the heater having a lighting duty greater than 50% The generation of harmonic current is further reduced by overlapping the wave and the half-turn-off half wave of the other heater at the same time.

According to a fourth aspect of the present invention, there is provided image forming means for forming a toner image on the recording material,
4. An image forming apparatus, wherein the toner image on the recording material formed by the image forming means is melted and fixed on the recording material by the fixing device according to claim 1.

  According to this configuration, when the toner image on the recording material formed by the image forming unit is fixed on the recording material, the effects obtained by the inventions according to the first to third aspects are exhibited.

  According to the first to fourth aspects of the present invention, it is possible to further reliably reduce the occurrence of flicker and harmonic current during the heater control of the fixing device.

  Hereinafter, a fixing device and an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view illustrating a schematic configuration of a multifunction peripheral as an example of an image forming apparatus according to the present embodiment.

  The multi-function device 1 employs an electrophotographic printing method and has functions such as a copy function, a printer function, a scanner function, and a facsimile function. The multi-function device 1 includes a reader unit 2 that reads an image and a printer unit 3 (main body M) that forms an image based on the read image information.

  The reader unit 2 includes a platen glass 11, a pressing plate 12, an irradiation lamp 13, reflection mirrors 14, 15, 16, a lens 17, a CCD (light receiving element) 18, and an image processing unit 19. . In the reader unit 2, the document D is placed on the platen glass 11 with its image surface facing downward, and is pressed against the platen glass 11 by the pressing plate 12. The document D is irradiated with an image surface by an irradiation lamp 13. The reflected light from the document surface at this time is further reflected by the reflecting mirrors 14, 15, 16, passes through the lens 17, and is input to the CCD 18, where it is photoelectrically converted into an electrical signal and then input to the image processing unit 19. Is done. The electrical signal input to the image processing unit 9 is subjected to various corrections such as density correction and shading correction, and then subjected to pulse width modulation and input to an exposure apparatus (described later).

  The printer unit 3 includes a drum-type photosensitive drum 21 and a primary charger 22, an exposure device 23, a developing device 24, a transfer device 25, a cleaning device 26, and the like disposed around the drum-type photosensitive drum 21. In addition, a sheet feeding cassette 27, a conveying belt 28, and a fixing device 29 are sequentially arranged from the upstream side in the conveying direction (direction of dotted arrow B) of a sheet-like recording material (for example, paper, transparent film) P as a recording medium. A paper discharge tray 30 and the like are provided.

  In the printer unit 3, the photosensitive drum 21 is rotationally driven in the direction of arrow A at a predetermined process speed (circumferential speed) by a drive mechanism (not shown), and the surface thereof is uniformly set to a predetermined polarity and potential by the primary charger 22. Charged. An electrostatic latent image is formed by the exposure device 23 on the surface of the photosensitive drum 21 after charging. The exposure device 23 irradiates laser light that is turned on / off based on the image information input from the image processing unit 19 described above, removes the charge on the surface of the photosensitive drum 21 where the laser light is irradiated, and converts it into image information. A corresponding electrostatic latent image is formed. The electrostatic latent image formed on the surface of the photosensitive drum 21 is developed as a toner image by electrostatically adhering charged toner to the developing device 24.

  The recording material P stored in the paper feed cassette 27 is supplied to a transfer nip portion between the photosensitive drum 21 and the transfer device 25 by a feed roller, a transport roller, and a registration roller (not shown). At this time, the recording material P is supplied to the transfer nip portion by the registration roller so as to be synchronized with the toner image formed on the photosensitive drum 21. The toner image on the photosensitive drum 21 is electrostatically transferred to the recording material P by the transfer device 25 while the supplied recording material P is nipped and conveyed by the transfer nip portion.

  After the toner image is transferred, the cleaning device 26 removes the toner (residual toner) remaining on the surface without being transferred to the recording material P at the time of transfer. Thereafter, the surface of the photosensitive drum 21 is ready for the next image formation. After the toner image has been transferred, the recording material P is separated from the surface of the photosensitive drum 21, and then conveyed to the fixing device 29 by the conveying belt 28, where it is heated and pressurized to fix the toner image on the surface. Details of the fixing device 29 will be described later. The recording material P having the toner image fixed on the surface thereof by the fixing device 29 is discharged onto the paper discharge tray 30. Thereby, the image formation on one recording material P is completed.

  A fixing device 29 according to an embodiment of the present invention will be described. FIG. 2 is an enlarged view of the fixing device 29 shown in FIG. As shown in FIG. 2, the fixing device 29 includes a heat roller 31 and a pressure roller 32, a heater 33, a thermistor 34, and a control unit 36. The heat roller 31 and the pressure roller 32 are fixing members (fixing rollers) that heat-fix the image on the recording material. The heater 33 is disposed in the heat roller 31 in order to heat the heat roller 31. The thermistor 34 detects the temperature of the heat roller 31. The control unit (CPU) 36 controls the overall operation of the multifunction device 1 including control of the fixing device 29.

  Further, the multi-function device 1 includes a zero cross detection unit 37 and a supply power adjustment unit 38. The zero cross detection unit 37 detects the timing at which the AC power becomes 0 (zero). The supplied power adjustment unit 38 adjusts AC power supplied from the AC power supply. The control unit 36 controls a thyristor, a triac, or the like constituting the supply power adjustment unit 38 based on the zero cross detection signal input from the zero cross detection unit 37. The supply power adjustment unit 38 includes a phase control circuit configured by connecting thyristors in reverse parallel or a triac, a photo triac, and the like, and supplies the heater 33 as described below based on a control signal from the control unit 36. The power to be controlled (phase control, etc.) is performed.

  The heat roller 31 forming the fixing member is formed of a cylindrical metal member, and is rotationally driven in the direction of arrow E by a drive mechanism (not shown). The pressure roller 32 is formed of a cylindrical elastic member, and is disposed below the heat roller 31 in a posture in which the rotation axes of both rollers are parallel to the heat roller 31.

  The pressure roller 32 is pressed against the heat roller 31 from below. As a result, a belt-like fixing nip portion N is formed between the heat roller 31 and the rotation axis of the heat roller 31 and the pressure roller 32. The pressure roller 32 is rotationally driven in the direction of arrow F by a drive mechanism (not shown) at substantially the same peripheral speed as that of the heat roller 31 described above.

  The heat roller 31 is heated by a heater 33, and the heat roller 31 and the pressure roller 32 rotate in the directions of the arrow E and the arrow F, respectively, so that the recording material P is nipped and conveyed by the fixing nip portion N. The recording material P is conveyed to the fixing device 29 in a state where an unfixed toner image is carried on the surface, and the toner is melted and fixed on the surface of the recording material P by pressing and heating of the heat roller 31 and the pressure roller 32. The The heat roller 31 and the pressure roller 32 are used for recording on each recording material P and toner image so that the toner image can be continuously fixed on a plurality of recording materials P, that is, even during continuous image formation. It has a relatively large heat capacity that can apply a sufficient amount of heat to fix the toner image on the surface of the material P.

  The heater 33 includes a main heater 331 and a sub-heater 332 each made of a halogen heater extending in the direction of the rotation axis of the heat roller 31. The main heater 331 and the sub heater 332 are supplied with electric power from the AC power source 35 under the control of the control unit 36 and the supply power adjustment unit 38. The main heater 331 and the sub heater 332 are disposed in the center of the heat roller 31 as viewed from the side, and heat the heat roller 31 from the inside. For example, the main heater 331 is provided so as to increase the amount of heat generated at the center of the heat roller 31 in the rotation axis direction, and the sub heater 332 increases the amount of heat generated at the end of the heat roller 31 in the rotation axis direction. Is provided. The power supplied to the main heater 331 and the sub-heater 332 is controlled by a supply power adjustment unit 38 that is controlled by the control unit 36 according to the temperature of the heat roller 31 detected by the thermistor 34. As the main heater 331 and the sub heater 332, those having a large heat generation amount, that is, those having a large resistance are used so that the heat roller 31 and the pressure roller 32 can be heated in a relatively short time.

  The thermistor 34 described above is disposed so as to face the surface of the heat roller 31 and is not in contact with the heat roller 31. The thermistor 34 detects the temperature of the surface of the heat roller 31 and sends a temperature detection signal indicating the detection result to the control unit 36. A plurality of thermistors 34 are provided in the direction of the rotation axis of the heat roller 31 for the center and end portions in the direction of the rotation axis of the heat roller, and are sandwiched between the nip portions of the heat roller 31 and the pressure roller 32. The temperature of the heat roller 31 that changes according to environmental changes, such as the size of the recording material and the ambient temperature, is detected, and a temperature detection signal is transmitted to the control unit 36. As the AC power source 35, a general household power source is used.

  The control unit 36 controls the supply power adjustment unit 38 based on the temperature detection signal from the thermistor 34. The control unit 36 includes a storage unit 361 composed of a ROM or an EEPROM. In the storage unit 361, tables of respective lighting duties (described later) set in advance according to the temperatures of the heat roller 31 are stored for each of the main heater 331 and the sub heater 332. The control unit 36 determines a lighting duty table for each of the main heater 331 and the sub-heater 332 according to the temperature indicated by the temperature detection signal received from the thermistor 34, and supplies power adjustment unit according to the determined lighting duty table 38 is controlled. In this manner, the supply power adjustment unit 38 controls the power supplied from the AC power source 35 to the main heater 331 and the sub heater 332 to adjust the temperature of the heat roller 31.

  In the fixing device 29 having the above-described configuration, the temperature of the heat roller 31 is maintained at the standby temperature or the fixing temperature by controlling the power supplied to the main heater 331 and the sub heater 332 by the power supply adjusting unit 38. In the present embodiment, the control unit 36 and the supply power adjustment unit 38 function as control means in the claims.

  Next, control of the heater 33 of the fixing device 29 will be described. FIGS. 3A and 3B, FIGS. 4A and 4B, and FIGS. 5A and 5B are diagrams illustrating waveforms of control of the heater 33. FIG.

  In the fixing device 29, the supply power adjustment unit 38 controls the power supplied to each of the main heater 331 and the sub heater 332, and the lighting duty is set to one cycle of the AC input sine wave for each of the main heater 331 and the sub heater 332. 2 half-waves, and one half-wave forming the two half-waves is fully lit or completely off, and the other half-wave is phase-controlled. Further, the supply power adjustment unit 38 performs control so that the half-waves of the main heater 331 and the sub-heater 332 are not overlapped with each other between all the lighting half-waves or all the lighting-off half-waves at the same time.

  The “lighting duty” here is the percentage of the lighting time TON with respect to the blinking cycle (= lighting time TON + lighting time TOFF) in the two half waves forming one cycle of the AC input sine wave. To do.

  Hereinafter, description will be given with reference to the drawings. The power supply control when both the main heater 331 and the sub heater 332 have a lighting duty greater than 50% will be described. 3A and 3B are diagrams showing waveforms of power supply control when the lighting duty is larger than 50% for both the main heater 331 and the sub heater 332, FIG. 3A is a diagram showing the waveform of the main heater 331, and FIG. It is a figure which shows the waveform of 332;

  For example, when the lighting duty of the main heater 331 is 80% and the lighting duty of the sub-heater 332 is 60%, the supply power adjusting unit 38, as shown in FIGS. 3 (a) and 3 (b), the main heater 331 and the sub-heater 332 For each of the above, one half wave of two half waves forming one cycle of the AC input sine wave is always turned on. Looking at the main heater 331, the power supply adjustment unit 38 sets the lighting duty for one half wave of two half waves forming one cycle to 100%, and the lighting duty for the other half wave to 60%. The lighting duty is 80% for two half-waves forming one cycle. Looking at the sub-heater 332, the power supply adjustment unit 38 sets the lighting duty for one half wave of one half wave forming one cycle to 20% and the lighting duty for the other half wave to 100%. The lighting duty is 60% with two half waves forming a cycle.

  Furthermore, the supply power adjustment unit 38 controls the half-waves of the main heater 331 and the sub-heater 332 whose lighting duty for one half-wave is 100% (full lighting) so that they do not overlap at the same time. . That is, as shown in FIGS. 3A and 3B, the supply power adjustment unit 38 has one half wave of the lighting duty 100% (full lighting) of the main heater 331 and one half of the lighting duty 20% of the sub heater 332. From the AC power source, the wave overlaps at the same time and one half wave of the main heater 331 lighting duty 60% and one half wave of the sub heater 332 lighting duty 100% (full lighting) overlap at the same time. Control power supply.

  Next, power supply control when the lighting duty is less than 50% for both the main heater 331 and the sub heater 332 will be described. FIG. 4 is a diagram showing a waveform of power supply control when the lighting duty is less than 50% for both the main heater 331 and the sub heater 332, (a) is a diagram showing the waveform of the main heater 331, and (b) is a sub heater. It is a figure showing the waveform of 332.

  For example, when the lighting duty of the main heater 331 is 40% and the lighting duty of the sub-heater 332 is 25%, the supply power adjusting unit 38, as shown in FIGS. 4 (a) and 4 (b), the main heater 331 and the sub-heater 332 For each of these, one half wave of two half waves forming one cycle of the AC input sine wave is always turned off. Looking at the main heater 331, the supply power adjustment unit 38 sets the lighting duty for one half wave of one half wave forming one cycle to 80%, and the lighting duty for the other half wave to 0%. The lighting duty is 40% with two half waves forming one cycle. Looking at the sub-heater 332, the supply power adjustment unit 38 sets the lighting duty for one half wave of one half wave forming one cycle to 0% and the lighting duty for the other half wave to 50%. The lighting duty is 25% with two half waves forming a cycle.

  Further, the supply power adjustment unit 38 prevents the half waves of the main heater 331 and the sub heater 332 that have the lighting duty for one half wave being 0% (all off) from overlapping at the same time. That is, as shown in FIGS. 4 (a) and 4 (b), the supplied power adjustment unit 38 is one half of the lighting duty 80% of the main heater 331 and one half of the lighting duty 0% (all off) of the sub heater 332. From the AC power source so that the wave overlaps at the same time and one half wave of the lighting duty of the main heater 331 0% (all off) and one half wave of the sub heater 332 lighting duty 50% overlap at the same time Control power supply.

  Next, power supply control when only one of the main heater 331 and the sub heater 332 is larger than the lighting duty 50% will be described. FIG. 5 is a diagram showing a waveform of power supply control when only one of the main heater 331 and the sub heater 332 is larger than the lighting duty 50%, (a) is a diagram showing the waveform of the main heater 331, (b). FIG. 4 is a diagram illustrating a waveform of a sub heater 332.

  For example, when the lighting duty of one cycle of the main heater 331 is 80% and the lighting duty of one cycle of the sub-heater 332 is 10%, the supply power adjustment unit 38, as shown in FIGS. One half of the two half-waves that make up one cycle of the main heater 331 with a lighting duty greater than 50% is set to full lighting, and of the two half-waves that make up one cycle of the sub-heater 332 with a lighting duty of less than 50% One half wave of is completely extinguished. Looking at the main heater 331, the power supply adjustment unit 38 sets the lighting duty for one half wave of two half waves forming one cycle to 100%, and the lighting duty for the other half wave to 60%. The lighting duty is 80% with two half waves forming one cycle. With regard to the sub-heater 332, the power supply adjustment unit 38 sets the lighting duty for one half wave of two half waves forming one cycle to 0% and the lighting duty for the other half wave to 20%. The lighting duty is 10% for two half-waves forming a cycle.

  Further, as shown in FIGS. 5A and 5B, the supply power adjustment unit 38 is configured such that one half wave of the main heater 331 in which the lighting duty for one half wave is 100% (full lighting), 1 One half wave of the sub heater 332 whose lighting duty for the half wave is 0% (all off) overlaps at the same time, one half wave of the lighting duty of the main heater 331 is 60%, and the lighting duty of the sub heater 332 is 20%. The power supply from the AC power supply is controlled so that 1% of half wave overlaps at the same time.

  As described above, when the main heater 331 and the sub heater 332 of the fixing device 29 are controlled, the supply power adjusting unit 38 controls the phase of each of the main heater 331 and the sub heater 332 to reliably reduce flicker, and further, supply power The adjustment unit 38 controls the half-waves of the main heater 331 and the sub-heater 332 so that they do not overlap with each other when they are all turned on or all turned off, thereby further reliably reducing the generation of harmonic currents. it can.

  The present invention is not limited to the configuration of the above embodiment, and various modifications can be made. For example, in the above embodiment, the fixing device 29 shown in FIG. 2 has been described as an embodiment of the present invention. However, the present invention is not limited to the fixing device shown in FIG. The present invention can be applied to a fixing device that fixes a toner image on a recording material P by heating with a heater, that is, a so-called heat fixing fixing device. Similarly, the present invention is not limited to the image forming apparatus shown in FIG. 1 but can be applied to a general image forming apparatus having a heat fixing type fixing device.

  In the above embodiment, the control unit 36, the zero cross detection unit 37, and the supply power adjustment unit 38 are described as being provided in the fixing device 29. However, the control unit 36, the zero cross detection unit 37, and the supply power are described. The adjusting unit 38 is not necessarily provided in the fixing device 29. In addition, a control unit (control unit) that controls the operation of the multifunction device 1 may function as the control unit 36, the zero-cross detection unit 37, and the supply power adjustment unit 38. That is, the control unit (control unit) that controls the operation of the multifunction device 1 functions as the control unit 36, the zero-cross detection unit 37, and the supply power adjustment unit 38 is also included in the fixing device and the image forming apparatus according to the present invention. .

  Further, the image forming apparatus according to the present invention is not limited to the above-described multifunction peripheral, and may be various types of image forming apparatuses such as a fax machine, a printer, and a copying machine.

1 is a cross-sectional view illustrating a schematic configuration of a multifunction peripheral that is an example of an image forming apparatus according to an exemplary embodiment. FIG. 2 is an enlarged view of the fixing device shown in FIG. 1. It is a figure which shows the waveform of electric power supply control in case a lighting duty is larger than 50% in both a main heater and a sub heater, (a) is a figure which shows the waveform of a main heater, (b) is a figure which shows the waveform of a sub heater. . It is a figure which shows the waveform of electric power supply control in case a lighting duty is less than 50% in both a main heater and a sub heater, (a) is a figure which shows the waveform of a main heater, (b) is a figure which shows the waveform of a sub heater. . It is a figure which shows the waveform of electric power supply control in case only one of a main heater and a sub heater is larger than lighting duty 50%, (a) is a figure which shows the waveform of a main heater, (b) is a figure which shows the waveform of a sub heater. It is.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Printer 29 Fixing device 31 Heat roller 32 Pressure roller 33 Heater 331 Main heater 332 Sub heater 34 Thermistor 35 AC power supply 36 Control part 361 Storage part 38 Supply electric power adjustment part

Claims (4)

A fixing member for thermally fixing an image on a recording material;
A heater unit having a main heater that generates heat with power from an AC power source and heats the fixing member; and a sub-heater that generates heat with power from an AC power source and supplementarily heats the fixing member;
Control means for controlling the power supplied from the AC power source to the main heater and the sub heater,
When the main heater and the sub-heater are driven, the control means uses one half of the AC input sine wave as one lighting duty, and the lighting duty of both the main heater and the sub-heater is larger than 50%. When one half of the two half-waves of each heater is fully turned on, heater control is performed so that the half-waves of the main heater and the sub-heater do not overlap with each other in the same period. Fixing device.   The control means, instead of the heater control, or together with the heater control, when driving the main heater and the sub heater, the main heater and the sub heater as one lighting duty with two half waves forming one cycle of the AC input sine wave When the lighting duty of both of the sub heaters is less than 50%, one half wave of the two half waves of each heater is completely turned off, and each half wave of the main heater and the sub heater is simultaneously turned on. The fixing device according to claim 1, wherein the heater control is performed so as not to overlap each other with all the light-off half waves.   Instead of the heater control or together with the heater control, when only one of the main heater or the sub heater is larger than the lighting duty 50% when the main heater and the sub heater are driven, the lighting duty is One half of the two half-waves of the heater larger than 50% is fully lit, and one half of the two half-waves of the heater whose lighting duty is less than 50% is completely unlit, and the one heater The fixing device according to claim 1, wherein heater control is performed such that the full lighting half-wave and the other heater half-extinguishing half-wave are overlapped at the same time. Image forming means for forming a toner image on the recording material;
An image forming apparatus for fixing a toner image on the recording material formed by the image forming means on the recording material by the fixing device according to claim 1.

Images