JP2011164387A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heater capable of suppressing flickers and harmonic currents generated by wave number control thereof or a phase control thereof, with a simpler, low-cost configuration, and capable of preventing other lighting devices and electronic devices from inducing flickers or malfunctions, and to provide an image forming apparatus which includes the heater. <P>SOLUTION: The heater includes a heat-generating body 109c, a power supply means 401 configured to supply power to the heat generating body, and a control means 126 configured to perform the on/off control of the power supply means. The control means includes a plurality of power control patterns to switch to the prescribed power and input the power to the heat generating body. Weighted values corresponding to the characteristics of each of the power control patterns are made to correspond to each of the power control patterns, and at on/off control, the weighted values corresponding to the power control patterns used in a prescribed period are integrated; and when the integrated value reaches a prescribed threshold, the power control pattern is switched. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a heat fixing device and an image forming apparatus such as a copying machine, a facsimile, or a printer including the heat fixing device, and more particularly to a heating device that heats and fixes an unfixed toner image transferred onto a transfer material.

  A thermal fixing device in an image forming apparatus using an electrophotographic process such as a copying machine, a facsimile machine, or a printer heat-fixes an unfixed toner image transferred onto a transfer material onto the transfer material with a heating roller or a ceramic heater. Is for the purpose. A heat roller type heat fixing device using a halogen heater as a heat source and a film heating type heat fixing device using a ceramic heater as a heat source are used.

  In these thermal fixing devices, generally, the heater is connected to an AC power source via a switching control element such as a triac, and power is supplied by the AC power source. The thermal fixing device is provided with a temperature detecting element, for example, a thermistor temperature sensitive element. Based on the temperature information detected by the temperature detection element, the engine controller performs ON / OFF control of the switching element by wave number control or phase control, thereby turning ON / OFF the power supply to the heater, and the thermal fixing device The temperature is controlled so that the temperature of the target becomes the target constant temperature.

  The phase control described above is a method of supplying power to the heater by turning on the heater at an arbitrary phase angle within one half wave of the AC power supply. On the other hand, the wave number control is a power control method in which the heater is turned on and off in units of half wave of the AC power source. Conventionally, in most cases, either phase control or wave number control is used.

  The reason for selecting the phase control is mainly to suppress flickering of lighting equipment, so-called flicker. Flicker is a voltage fluctuation in an AC power source due to a load current fluctuation of an electric device connected to the same power source as the lighting device and an impedance of a distribution line, thereby causing the lighting device to flicker. Since the phase control changes the input power by changing the ON phase every half wave, the current change amount and change cycle can be reduced, and the occurrence of flicker can be suppressed.

  On the other hand, since the wave number control is ON / OFF controlled in units of half wave of the AC power supply, the control cycle is longer than the phase control, current fluctuation is large, and flicker is likely to occur.

  Reasons for selecting wave number control include suppression of harmonic current and switching noise. In the phase control, harmonic current and switching noise are generated due to a rapid current fluctuation that occurs when the heater is turned ON / OFF. On the other hand, the wave number control in which the heater ON / OFF control is always performed at the zero cross point is less likely to generate harmonic current and switching noise than the phase control that switches in the middle of the half wave of the AC power supply. This harmonic current and switching noise tend to be generated more greatly when the voltage of the AC AC power supply used is higher.

  Therefore, the control method is fixed in accordance with the AC commercial power supply voltage in the region where the image forming apparatus is used. For example, the phase control method advantageous to flicker is used for the region of 100 to 120V, and the wave number control method advantageous to the harmonic current and switching noise is used for the region of 220V to 240V. Generally, it is fixed to this control method.

  In addition, there is a method that proposes a method that combines phase control and wave number control. For example, in Patent Document 1, some half waves of one half-wave as one control period are set as phase control, and the rest are wave numbers. Control. As a result, generation of harmonic currents and switching noise can be suppressed as compared with the case of only phase control. Furthermore, flicker can be reduced compared to the case of only wave number control, and power control to the heater can be controlled in more stages.

  Some have proposed a method in which phase control and wave number control are combined using two heating elements. For example, in Patent Document 2, harmonic current and flicker are improved by making the energization patterns different between at least two heaters.

JP 2003-123941 A JP-A-10-91017

  However, with the recent increase in printing speed, the power supply required for the thermal fixing device is steadily increasing, and it is becoming difficult to suppress flicker and harmonic current. Furthermore, not only the regulation for the current integer harmonic current component but also the strengthening of the harmonic regulation that newly regulates the harmonic current component other than the integer order, it is more and more necessary to satisfy each regulation. It has become difficult.

  For example, when the control is performed by simply combining the heater lighting pattern of the phase control and the wave number control as exemplified in Patent Document 1 or the like, in the heat fixing device with the increased power, between the integer order harmonics It is not possible to suppress the harmonic component between orders which is a component of. If the control is performed so as to suppress the inter-order harmonic component, flicker becomes a problem this time, and it is very difficult to satisfy both regulations.

  Further, in the configuration exemplified in Patent Document 2, etc., two or more heaters and their control circuits are used and individually controlled to suppress flicker and harmonic current as the entire heat fixing device. . However, in such a configuration, it is necessary to provide two or more heaters and their control circuits, resulting in an increase in cost and an increase in space.

  The present invention has been devised in view of the above problems of the prior art. And with a simpler and lower cost configuration, it suppresses flicker and harmonic current generated by the wave number control and phase control of the heater, preventing flickering and malfunctioning in other lighting equipment and electronic equipment It is an object of the present invention to provide a heating device capable of performing the above.

The present invention has the following configuration in order to solve the above-described problems.
In a heating apparatus having a heating element, power supply means for supplying power to the heating element, and control means for ON / OFF control of the power supply means,
The control means includes
Having a plurality of power control patterns for switching and supplying predetermined power to the heating element;
Associating the plurality of power control patterns with weight values according to the characteristics of each power control pattern,
When the ON / OFF control is performed, the weight values corresponding to the plurality of power control patterns used within a predetermined period are integrated,
The heating apparatus, wherein the power control pattern is switched when the integrated value reaches a predetermined threshold value.

  As described above, according to the present invention, it is possible to provide a heating apparatus that is advantageous for harmonic regulation and that can suppress flicker low.

1 is a configuration diagram illustrating an image forming apparatus according to the present invention. The figure which showed the cross-sectional structure of the heater in 1st Example The block diagram which showed the cross-sectional structure of the heater part in a 1st Example. The block diagram which showed the circuit structure of the heater control circuit in a 1st Example. The figure which showed the heater control waveform (phase control) in 1st Example The figure which showed the heater control waveform (phase control) in 1st Example The figure which showed the heater control pattern in 1st Example The block diagram which showed the harmonic level between orders in 1st Example of this invention Table showing weight values of each pattern in the first embodiment The image figure which showed the weighting value of each pattern and mode in 2nd Example The figure which showed the flow in 2nd Example

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the accompanying drawings.

  Hereinafter, a first embodiment of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a schematic configuration diagram of an image forming apparatus using an electrophotographic process, and shows, for example, a laser beam printer.

  The laser beam printer main body 101 (hereinafter referred to as the main body 101) has a paper feed cassette 102 for storing the recording paper S, and has a cassette presence / absence sensor 103 for detecting whether or not the recording paper S is in the paper feed cassette 102. Also, a cassette size sensor 104 (consisting of a plurality of micro switches) that detects the size of the recording paper S in the paper feeding cassette 102, a paper feeding roller 105a that feeds the recording paper S from the paper feeding cassette 102, and a pair of conveying rollers. 105b, 105c, 105d and the like. A registration roller pair 106 that synchronously conveys the recording paper S is provided downstream of the paper feed roller 105a and the conveyance roller pairs 105b, 105c, and 105d. Further, on the downstream side of the registration roller pair, the leading edge and the trailing edge of the recording sheet S are detected, and the sheet feeding sensor 124 for taking the image writing timing, and the laser beam 118 from the laser scanner unit on the recording sheet S. A process cartridge 108 for forming a toner image is provided. Further, a fixing device 109 that thermally fixes the toner image formed on the recording paper S is provided downstream of the process cartridge 108, and the conveyance state of the paper discharge unit is provided downstream of the heat fixing portion in the fixing device 109. A paper discharge sensor 110 for detection is provided. A pair of paper discharge rollers 111 for conveying the recording paper S, a pair of face-up paper discharge rollers 140 for discharging the recording paper S, and a stacking tray 112 for stacking the recording paper S on which recording has been completed are also provided. The conveyance reference of the recording paper S is set so as to be centered with respect to the length of the recording paper S in the direction orthogonal to the conveyance direction of the image forming apparatus, that is, the width of the recording paper S.

  The paper discharge sensor 110 is provided inside the fixing device 109 and detects the timing at which the recording paper S has passed through the thermal fixing unit. The recording paper S passes through the conveyance roller pair 111 and is then discharged to the stacking tray 112 via the face-up paper discharge roller pair 140. The full load detection sensor 142 provided in the paper discharge unit is a sensor that detects whether the recording paper S on the stacking tray 112 is full and detects the movement of the recording paper S in the paper discharge unit.

  The laser scanner unit 107 includes a laser unit 113 that emits a laser beam modulated based on an image signal (image signal / VDO) from the external device 131. Further, a polygon motor 114, an imaging lens 115, a folding mirror 116, and the like for scanning the laser beam on the photosensitive drum 117 are also provided.

  The process cartridge 108 includes a photosensitive drum 117, a primary charging roller 119, a developing device 120, a transfer roller 121, a cleaner 122, and the like necessary for a known electrophotographic process. The fixing device 109 includes a fixing film 109a, a pressure roller 109b, a ceramic heater 109c provided inside the fixing film, and a thermistor 109d that detects the surface temperature of the ceramic heater 109c.

  The main motor 123 applies driving force to the paper feed roller 105a via the paper feed roller clutch 125, and to the transport roller pairs 105b, 105c, 105d and to the registration roller pair 106 via the registration roller clutch 129. Yes. Further, a driving force is also applied to each unit of the process cartridge 108 including the photosensitive drum 117, the fixing device 109, the discharge roller pair 111, and the face-up discharge roller pair 140.

  An engine controller 126 controls the electrophotographic process by the laser scanner unit 107, the process cartridge 108, and the fixing device 109, and controls the conveyance of the recording paper S in the main body 101.

  Reference numeral 127 denotes a video controller, which is connected to an external device 131 such as a personal computer via a general-purpose interface 130 (Centronics, RS232C, USB, etc.). The image information sent from the general-purpose interface 130 is expanded into bit data, and the bit data is sent to the engine controller 126 as a / VDO signal.

  A line 128 connecting the engine controller 126 and the video controller 127 includes a command / status signal line, a clock signal line, a / VDO signal line, a synchronization signal line, and the like between the controllers.

  FIG. 2 and FIG. 3 show the ceramic heater 109c and its peripheral outline in the present embodiment. FIG. 2 is a sectional view of a ceramic surface heater. FIG. 3 is a sectional view around the fixing film 109a, the pressure roller 109b, and the ceramic heater 109c.

The ceramic heater 109c protects the ceramic insulating substrate 201 such as SiC, AlN, Al ₂ O ₃ , the heating element 203 formed by paste printing or the like on the surface of the insulating substrate 201, and the heating element 203. It is composed of a protective layer 202 such as glass.

  The ceramic heater 109c is supported by the film guide 301 as shown in FIG. The fixing film 109a is a high heat conductive film made of a heat-resistant material such as cylindrical metal or polyimide, and is externally fitted to a film guide 301 that supports a ceramic heater 109c on the lower surface side. Then, the ceramic heater 109c on the lower surface of the film guide 301 and the pressure roller 109b as an elastic pressure member are pressed against each other with a predetermined pressure against the elasticity of the pressure roller 109b with the fixing film 109a interposed therebetween. A fixing nip portion that is a heating portion is formed. Further, the thermo switch 302 is in contact with the back surface of the insulating substrate 201 of the ceramic heater 109c as an excessive temperature rise prevention means. The position of the thermo switch 302 is corrected by the film guide 301, and the heat sensitive surface of the thermo switch 302 is in contact with the back surface of the ceramic heater 109c. Although not shown, the thermistor 109d as a temperature detecting element is also in contact with the back surface of the ceramic heater 109c. Further, in order to improve the slidability of the fixing film 109a, slidable grease may be applied to the interface between the fixing film 109a and the ceramic heater 109c.

  FIG. 4 shows a ceramic heater driving and control circuit according to the present invention. Reference numeral 401 denotes a commercial AC power source for connecting the main body 101. The main body 101 generates heat by supplying the AC power to the ceramic heater 109c via the AC filter 402, the relay 413, the triac 404, and the thermo switch 302. The power supply to the ceramic heater 109c is energized / interrupted by the triac 404. The thermo switch 302 is placed between the triac 404 and the ceramic heater 109c, and is always energized at normal times. When the ceramic heater 109c reaches high heat due to some abnormality, it is turned OFF, and the supply of input power to the ceramic heater 109c is cut off. This OFF state is continued without returning. Under the control of the engine controller 126, the relay 413 turns on / off the transistor 423, thereby energizing / cutting off the 24V power source and turning on / off the power supply to the ceramic heater 109c. Turns on when the fuser is energized and turns off when the fuser stops. The resistors 405 and 406 are bias resistors for the triac 404, and the phototriac coupler 407 is a device for securing an insulation distance between the primary and secondary. The triac 404 is turned on by energizing the light emitting diode of the phototriac coupler 407. The resistor 408 is a resistor for limiting the current flowing through the light emitting diode of the phototriac coupler 407, and the transistor 409 turns on / off the light emitting diode of the phototriac coupler 407. The transistor 409 operates according to the ON signal from the engine controller 126 via the resistor 410.

  The commercial AC power supply 401 is input to the zero cross detection terminals Neutral and Hot of the engine controller 126 via the AC filter 402. The zero cross detection terminal of the engine controller 126 notifies the CPU (not shown) as a pulse signal that the commercial power supply voltage is below a certain threshold value. Hereinafter, this pulse signal sent to the CPU in the engine controller 126 is referred to as a ZEROX signal.

  The engine controller 126 turns on / off the triac 404 by phase control or wave number control in accordance with the pulse edge of the ZEROX signal.

  Reference numeral 109d denotes a temperature detection element for detecting the temperature of the ceramic heater 109c, for example, a thermistor temperature sensing element. The temperature detected by the temperature detection element 109d is detected as a divided voltage between the resistor 415 and the temperature detection element 109d, and A / D is input to the engine controller 126 as a TH signal. The temperature of the ceramic heater 109c is monitored by the engine controller 126 as a TH signal and is compared with the set temperature of the ceramic heater 109c set in the engine controller 126. Then, the power to be supplied to the ceramic heater 109c is calculated, converted into a phase angle corresponding to the supplied power, and the engine controller 126 sends an ON signal to the transistor 409 through the resistor 410 according to the control condition.

  Next, phase control and wave number control, which are heater power control methods, will be described. FIG. 5 shows an example in the case of phase control. The logic of the ZEROX signal switches at the point where the AC power supply switches from positive to negative and from negative to positive. When the heater drive signal is turned on after ta time from the rising and falling edges, the heater is energized at the shaded area in FIG. Power is supplied. Since the heater is turned off at the next zero cross point after the heater is turned on, the same power is supplied to the heater in the next half-wave by turning on the heater drive signal again after time ta from the edge of the ZEROX signal. Is supplied. When the heater drive signal is turned on after a time tb different from the time ta, the energization time for the heater changes, so that the power supplied to the heater can be changed. Thus, the power supplied to the heater is controlled by changing the time for which the heater drive signal is turned ON from the edge of the ZEROX signal for each half wave. Here, it is assumed that the heater driving signal is turned on for the same time in two consecutive half waves.

  In the phase control, as shown in FIG. 5A, since the energization to the heater is turned on in the half of the AC power supply waveform, the current flowing through the heater rises sharply and a large harmonic current flows. Since the harmonic current increases as the amount of current rise increases, the harmonic current becomes maximum when the phase angle is 90 °, that is, when the supplied power is 50%. The harmonic current increases as the phase angle approaches 90 °, and decreases as the phase angle approaches 0 °. Therefore, the higher the number of patterns with a stricter phase angle, the more the harmonic current increases, which is more disadvantageous for harmonic regulation. On the other hand, since the phase control can suppress the current change amount of each half wave to be small, flicker can be suppressed to a low level. However, actually, in addition to the heater, a low-voltage power supply (not shown) that supplies power to the engine controller 126, the video controller 127, and the like is also connected to the commercial AC power supply 401, as shown in FIG. Current is flowing. As a result, the current waveform flowing through the main body 101 becomes a waveform of the total current including these currents, for example, a waveform as shown in FIG. Therefore, it cannot be generally said that the harmonic current increases when a pattern having a phase angle close to 90 ° is used.

  FIG. 6A shows an example of wave number control. In the wave number control, ON / OFF control is performed in units of a half wave of the AC power supply. Therefore, the heater drive signal is turned on together with the edge of the ZEROX signal when turning on. Then, for example, twelve half waves are set as one cycle of control, and the power supplied to the heater is controlled by changing the number of half waves that are turned on in one control cycle. In FIG. 6, six half of the twelve half waves are ON, so the power supplied to the heater is 50%. Here, when turning on, it is assumed that two consecutive half waves are turned on at the same phase angle.

  In wave number control, the heater is always turned on / off at the zero cross point, so there is no sharp rising edge of current as in phase control, and the harmonic current is very small. On the other hand, since the current flows in half-wave units, the amount of change in the current is large and the change cycle is long, so the influence on flicker is large. Therefore, by devising the position (control pattern) of the half wave that is turned on within one control cycle, the influence of the current fluctuation cycle on flicker is minimized. However, here as well, in fact, in addition to the heater, a low-voltage power supply (not shown) that supplies power to the engine controller 126, the video controller 127, and the like is also connected to the commercial AC power supply 401, and the current waveform flowing through the main body 101 Has a waveform as shown in FIG. Therefore, it is necessary to confirm the influence of the total current waveform flowing through the main body 101 on the flicker.

  In the present embodiment, eight half waves of the AC power supply are set as one control period, a part of the half waves are phase controlled, and the remaining half waves are wave number controlled. Control is performed by a pattern in which the controls are appropriately combined. In such a control method, since the phase control is not turned ON every half wave, the flowing harmonic current can be reduced, and all the half waves are turned ON / OFF like the wave number control. This also eliminates flicker.

  FIG. 7 shows an example of the heater power control pattern in this embodiment. In FIG. 7, four full waves (= 8 half waves) are set as one control cycle, of which three full waves are controlled by wave number control and one full wave is controlled by phase control. Between 0% and 100% of the heater supply power is divided into 40, and the ON duty is determined at each level. Here, it is assumed that the adjacent positive half-wave and negative half-wave satisfy the same vertical symmetry of being turned on by the same amount. For example, in FIG. 7, when the ON duty is 1/40 (= 2.5%), the first two half-waves are set to phase control, and both the two half-waves are turned ON by 10% of the entire half-wave. After that, all the wave number control portions of the three full waves are turned off, so that 2.5% of power is supplied in one control cycle. The ON duty 10/40 (= 25%) is supplied with 25% power in one control cycle by turning on the first two half-waves with wave number control and turning on both of the two half-waves. In addition, when the ON duty is 25/40 (= 62.5%), the first two half-waves are set to wave number control, both of the two half-waves are turned on 100%, and the next two half-waves are turned on by 50% Further, after the next half wave is turned off, the next two half waves are turned on 100%, and the next half wave is turned off. By controlling in this way, 62.5% of electric power is supplied in one control cycle. As described above, 41 control pattern stages as shown in FIG. 7 are defined from ON duty 0/40 at which the supplied power is 0% to ON duty 40/40 at which the supplied power is 100%. The engine controller 126 switches these control patterns in an appropriate order, applies power to the heater 109c, and controls the temperature to reach a predetermined temperature. Note that the control pattern of FIG. 7 is created so as to be more advantageous to flicker than harmonic current.

  FIG. 8 shows a harmonic measurement result for the waveform shown in FIG. 7 as an example. The horizontal axis represents each pattern level (ON duty), the vertical axis represents the harmonic level (characteristic), and the highest value among the measurement orders is plotted. As described in the description with reference to FIGS. 5 and 6, the measured value here indicates the harmonic level in the waveform obtained by combining the heater control waveform in FIG. 7 and the current waveform of the low-voltage power supply (not shown). . Therefore, the ON duty including the phase control waveform with 50% duty does not necessarily indicate a high level even at the harmonic level. In the case of the present embodiment, depending on the pattern level, there is a pattern in which the harmonic level is at the limit level with respect to the standard limit, and a pattern having a relatively large margin. For example, in the level pattern of ON duty 6/40, there is almost no margin with respect to 0.9, which is the standard limit, and there is a possibility that the standard limit will be exceeded in consideration of variations and the like. That is, if this level pattern is continuously used, it means that the harmonic level exceeds the standard.

  Next, the operation will be described. First, when a main switch (not shown) of the main body 101 is turned on, a low voltage power supply (not shown) is activated. Then, a voltage supplied to the engine controller 126 and the video controller 127, for example, a relatively low voltage such as 3.3V or 5V, and a voltage for operating a drive system such as a relay or a motor, for example, 24V A relatively high voltage start-up is performed.

  Then, the engine controller 126 is activated and starts a pre-multi-rotation operation for warming up the main body 101. First, the transistor 423 is turned on to supply 24V voltage to the drive coil of the relay 413.

  When relay 413 is turned on, power is supplied to triac 404. The engine controller 126 controls the triac 404 by turning on / off the transistor 409 and supplies electric power to the ceramic heater 109c to perform predetermined preheating control. After the ceramic heater 109c is preheated, the main motor 123 starts to be driven by the engine controller 126, and each unit of the process cartridge 108, the fixing device 109, the paper discharge roller pair 111, and the face-up paper discharge roller pair 140 are rotationally driven. . Further, the triac 404 is controlled, the drive control of the ceramic heater 109c in the fixing device 109 is also performed, and a preparatory operation for a predetermined process device is executed.

  The engine controller 126 then raises the ceramic heater 109c to a predetermined temperature, finishes the preparation operation of each process device, and enters a standby state.

  At this time, the engine controller 126 stops driving the triac 404 by turning off the transistor 409, and stops the power supply to the ceramic heater 109c.

  Next, the printing operation will be described.

  When the engine controller 126 receives a print operation start command from the video controller 127, the engine controller 126 starts the print operation.

  After turning on the relay 413, the engine controller 126 controls the transistor 409 and supplies power to the ceramic heater 109c to perform predetermined preheating control. After the ceramic heater 109c is preheated, the main motor 123 is driven, and the transistor 409 is controlled to start up the ceramic heater 109c and start driving the polygon motor 114. By driving the main motor 123, the photosensitive drum 117 and the transfer roller 121, the fixing film 109a and the pressure roller 109b of the fixing device 109, the paper discharge roller pair 111, and the face-up paper discharge roller pair 140 start to rotate. Thereafter, the engine controller 126 starts the light amount control of the laser unit 113 and sequentially performs high-pressure driving of the primary charging roller 119, the developing device 120, and the transfer roller 121. The engine controller 126 detects that the rotation of the polygon motor 114 is in a steady state from the pulse interval of the / BD signal sent from the laser light detection sensor by a CPU (not shown). Then, the sheet feeding roller clutch 125 is turned on to drive the sheet feeding roller 105a, and the recording sheets S in the sheet feeding cassette 102 are fed out one by one. The paper feed roller clutch 125 is immediately turned off when one sheet of recording paper S is fed from the cassette. The fed recording sheet S is conveyed toward the registration roller pair 106 by the conveyance roller pairs 105b, 105c, and 105d rotated by the registration roller clutch 129 that is turned on together with the paper supply roller clutch 125. Then, the CPU detects that the recording paper S has reached the paper feed sensor 124 and starts outputting a synchronization signal to the video controller 127. At the same time, the registration roller clutch 129 is turned OFF, and the driving of the conveyance roller pairs 105b, 105c, 105d and the registration roller pair 106 is temporarily stopped.

  At that time, the video controller 127 has started developing the image information into a dot image, and has completed preparations for starting the output of the / VDO signal. The video controller 127 receives the synchronization signal from the engine controller 126 and starts outputting the / VDO signal as image data for one page.

  On the other hand, the engine controller 126 turns on the registration roller clutch 129 again at the same time as the output of the synchronization signal, and resumes driving of the conveying roller pairs 105b, 105c, 105d and the registration roller pair 106. The conveyance roller pairs 105 b, 105 c, 105 d and the registration roller pair 106 are driven until the trailing edge of the recording paper S passes the registration roller pair 106. During this time, the engine controller 126 drives the laser unit 113 according to the / VDO signal from the video controller 127. Laser light 118 emitted from the laser unit 113 is converted into linear scanning by the rotation of the polygon motor 114 of the laser scanner unit 107, and is irradiated onto the photosensitive drum 117 by the imaging lens 115 and the folding mirror 116.

  The photosensitive drum 117 is rotationally driven in the clockwise direction in FIG. 1 at a predetermined peripheral speed (process speed). The photosensitive drum 117 is uniformly charged to a predetermined polarity and potential by a primary charging roller 119 as a charging means during the rotation process. Scanning exposure using a laser beam modulated and controlled (ON / OFF control) with respect to a time-series electric digital pixel signal of target image information output from the laser scanner unit 107 to the uniformly charged surface of the photosensitive drum 117. Is made. As a result, an electrostatic latent image of target image information is formed on the surface of the photosensitive drum 117. The electrostatic latent image formed on the photosensitive drum 117 is developed with a developer (toner) and visualized by a developing device 120 as a developing unit.

  On the other hand, the recording paper S fed out one by one is subjected to predetermined control to a transfer nip portion, which is a pressure contact portion between the photosensitive drum 117 and the transfer roller 121 as a transfer means, by the conveyance roller pairs 105b, 105c, 105d and the registration roller pair 106. It is fed at the timing. The toner image on the surface of the photosensitive drum 117 is sequentially transferred onto the surface of the recording paper S. The recording sheet S exiting the transfer nip is sequentially separated from the surface of the photosensitive drum 117 during the rotation process, and is introduced into the fixing device 109 for fixing the toner image. Toner on the recording paper S is applied to the recording paper S passing between the fixing film 109a and the pressure roller 109b by applying heat from the ceramic heater 109c through the fixing film 109a and applying pressure by the pressure roller 109b. The image is heat-fixed.

  FIG. 9 shows the result of weighting each pattern level according to the harmonic current value of FIG.

  When controlling the temperature of the heater 109c, the engine controller 126 appropriately selects an ON duty from the control pattern of FIG. 7, and changes each ON duty value for each control period. Then, each weight value of the selected ON duty value is added. This weighting value is added every 10 control periods (every 800 msec. If 50 Hz). If the addition value within 10 control periods (within a predetermined period) exceeds 6.0, the weighting value is Use of patterns of 0.8 or higher is prohibited. When the addition of 10 control cycles is completed while the pattern having the weight value of 0.8 or more is prohibited, the addition value is reset again, and the addition of the weight value is started from zero. If the addition value of 10 control cycles does not exceed 6.0, the addition value of the weighting value is reset as it is, and the addition of the weighting value of the next 10 control cycles is started.

  When the added value of the weight value exceeds 6.0, the pattern with the weight value of 0.8 or more cannot be used until 10 control cycles thereafter. Therefore, for example, when it is desired to use the level pattern of ON duty 6/40, the level pattern of ON duty 5/40 (minus side) and the level pattern of ON duty 7/40 (plus side) are alternately used. By performing such control, it is possible to use a level pattern of ON duty 5/40 and a level pattern of ON duty 7/40 having a low harmonic level, thereby preventing the harmonic level from becoming a problem. I can do it.

  On the other hand, if the level pattern of the ON duty 5/40 and the level pattern of the ON duty 7/40 are alternately used, the temperature of the heater 109c may be rippled because it deviates from the ON duty that is originally desired. Therefore, it is not desirable to use a method of alternately using upper and lower level patterns as much as possible. However, in this embodiment, it is allowed to use the level pattern of ON duty 6/40 until the added value of the weighting value reaches 0.40, and the occurrence of temperature ripple can be suppressed as much as possible. Harmonic current can also be suppressed.

  The recording paper S exiting the fixing device 109 is printed out on the stacking tray 112 by the conveying roller pair 111 and the face-up paper discharge roller pair 140.

  The photosensitive drum 117 after the recording paper S is separated is cleaned by a cleaner 122 as a cleaning unit to remove adhered contaminants such as transfer residual toner, and the electrophotographic image is started repeatedly by charging. Served for formation.

  When the printing operation is finished, the engine controller 126 stops the heater driving circuit to stop the power supply to the ceramic heater 109c, and stops the main motor, the laser scanner, and other series of printing process processing.

  In the above embodiment, the weighting value addition cycle is shown as 10 control cycles, but it goes without saying that this cycle may be appropriately changed or may be changed according to the frequency of the commercial power source. Further, the point where one control cycle is set to 4 full waves may be changed as appropriate. Furthermore, the ON duty control pattern of this embodiment is not limited to this pattern, and may be changed as appropriate. In addition, in this pattern, a pattern advantageous to flicker is assembled and control is switched as appropriate by weighting the harmonic current. Conversely, a pattern advantageous to harmonic current is created and controlled appropriately by weighting the flicker value. There is no problem even if the method of switching is taken.

  As described above, the heating device of this embodiment satisfies the harmonic level standard and can suppress flickers to a low level.

  Next, a second embodiment of the present invention will be described with reference to the flowcharts of FIGS. Since the main configuration and operation are the same as those described in the first embodiment of the present invention, a description thereof will be omitted.

  In this embodiment, a plurality of weight values corresponding to the operation mode of the main body 101, loads such as options to be connected, and the area (AC voltage) to be used are associated (FIG. 10), and the operation modes and options to be connected are set. The weighting value is switched according to the load condition of the first embodiment, and the same operation as in the first embodiment is performed.

  The load of the low-voltage power supply changes mainly depending on the operation mode and connected options. Accordingly, the waveform of the AC current flowing through the low-voltage power source changes, and as a result, the inter-order harmonic level of each pattern level also changes. In some operation modes, there is a case where a pattern level having a margin with respect to inter-order harmonics becomes a stricter value than the standard in another operation mode. Therefore, it is necessary to change the weight value of each level pattern of the inter-order harmonics according to the operation mode and the load state.

  Therefore, a plurality of weight value tables are stored in the storage element in the engine controller 126 of the main body 101 in accordance with each operation mode and each option setting, and the weight value table in accordance with each operation mode and option setting is stored. change.

  First, when the engine controller 126 receives a print instruction (S101), the presence / absence of an option is confirmed (S102). Then, when there is an option (S104) and when there is no option (S103), the process proceeds to the next step. Therefore, the weight value table is selected according to the print mode such as double-sided / single-sided (S105 to S108). Next, a printing operation is performed according to the selected weighting value (S109). Then, after finishing the printing operation, the next operation is selected (S110). When printing is continued, the process returns to the option presence / absence confirmation step again (S102). If the printing is not continued, the process ends as it is (S111).

  In the printing operation, the weighting value integration method during printing, the control method when the integration value reaches a predetermined value, and the like are as described in the first embodiment.

  In this configuration, the case where there is only one option is shown, but of course, when there are a plurality of option settings, the table may be changed according to the number of options. Other configurations and operations are the same as those in the first embodiment.

  As described above, in the heating apparatus of the present embodiment, it is possible to satisfy the harmonic level standard even in various print modes and to keep flicker low.

109 Fixing device 109c Heater (corresponding to heating element)
126 Engine controller (corresponding to control means)
401 Commercial AC power supply (corresponding to power supply means)
413 Relay

Claims (6)

In a heating apparatus having a heating element, power supply means for supplying power to the heating element, and control means for ON / OFF control of the power supply means,
The control means includes
Having a plurality of power control patterns for switching and supplying predetermined power to the heating element;
Associating the plurality of power control patterns with weight values according to the characteristics of each power control pattern,
When the ON / OFF control is performed, the weight values corresponding to the plurality of power control patterns used within a predetermined period are integrated,
The heating apparatus, wherein the power control pattern is switched when the integrated value reaches a predetermined threshold value.   The heating device according to claim 1, wherein the weighting value is a value associated with the flicker value of the plurality of power control patterns.   The heating device according to claim 1, wherein the weighting value is a value associated with a harmonic current value included in the plurality of power control patterns. The switching of the power control pattern of the control means is
The use of a power control pattern having a large weight value among the plurality of power control patterns is temporarily stopped, or the power control pattern is switched to a power control pattern having a small weight value among the plurality of power control patterns. Item 4. The heating device according to any one of Items 1 to 3. The switching of the power control pattern of the control means is
5. When the threshold is reached, the positive power control pattern and the negative power control pattern can be alternately selected and switched with respect to a required predetermined input power. The heating apparatus of any one of Claims. The heating device is a heating device used in an image forming apparatus,
The control means includes
A plurality of weight values are associated with each of the power control patterns according to an operation mode and configuration of the image forming apparatus, and the weight value is selected according to the operation mode and configuration of the image forming apparatus. The heating device according to any one of claims 1 to 4.

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