JP2004212510A - Image forming device - Google Patents

Abstract

An image forming apparatus including a fixing device that heats and fixes a toner image formed on a recording material has an object to reduce flicker even when power consumption during printing is small.
An image forming unit that forms a toner image on a recording material, a fixing device that heats the toner image and fixes the recording material on the recording material, and power control that controls electric power supplied to the fixing device. In the image forming apparatus including the device, the power control device has two kinds of power control means of phase control and wave number control, and further has a power control switching means for switching these two kinds of power control means, An image forming apparatus, wherein wave number control is set in the power control device as normal power control means, and the power control means is switched from wave number control to phase control in accordance with printing conditions.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention includes an image forming unit that forms a toner image on a recording material, a fixing device that heats the toner image to fix the toner image on the recording material, and a power control device that controls power supplied to the fixing device. The present invention relates to an image forming apparatus provided.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a laser beam printer, a heat roller type using a halogen heater as a heat source has been used as a fixing device (heating device) for heating and fixing a toner image formed on a recording material such as paper. And a film heating type heat fixing device using a ceramic heater as a heat source.
[0003]
Generally, the heater is connected to an AC power supply via a switching element such as a triac, and power is supplied from the AC power supply. The fixing device (fixing device) is provided with a temperature detecting element, for example, a thermistor temperature sensing element. The temperature of the fixing device is detected by the temperature detecting element, and based on the detected temperature information, the engine controller switches the switching element. Is turned on / off, the power supply to the heater is turned on / off, and the temperature of the fixing device is temperature-controlled to a target constant temperature. On / off control of the ceramic heater is performed by phase control or wave number control of a commercial power supply.
[0004]
It includes a point at which the input commercial power supply switches from positive to negative or from negative to positive, and triggers based on a signal (hereinafter referred to as a "zero-cross signal") that reports that the power supply voltage has dropped below a certain value. Phase control or wave number control. Generally, a zero-cross signal is a pulse signal, and a heater is controlled by triggering at a rising edge at which the zero-cross signal changes from off to on.
[0005]
For example, Patent Literature 1 discloses a system in which two heating elements are independently controlled by phase control and wave number control. Patent Document 2 discloses a system in which phase control and wave number control are switched by a power supply voltage.
[Patent Document 1]
JP 2000-268939 A
[Patent Document 2]
JP-A-10-20711
[0006]
[Problems to be solved by the invention]
The commercial power supply has a certain level of line impedance R. When the image forming apparatus is connected to a commercial power supply and a current I flows in the image forming apparatus, a voltage V calculated from R × I is generated in this power supply line. That is, the commercial power supply has a value obtained by dropping the voltage from the original voltage value by the voltage V generated in the power supply line. When the current flowing through the ceramic heater fluctuates, the voltage drop also fluctuates, and as a result, the voltage value of the commercial power supply also fluctuates.
[0007]
Here, when lighting equipment such as a desk lamp is connected to a commercial power supply to which the image forming apparatus is connected, the brightness of the lighting equipment fluctuates due to the fluctuation of the voltage value of the commercial power supply as described above, so-called flickering. The phenomenon occurs. This flicker phenomenon is called flicker, and depending on the degree of flicker, humans may feel uncomfortable. Factors that make people feel uncomfortable include the degree of flicker (the magnitude of voltage fluctuation) and the cycle of the flicker.
[0008]
When comparing the phase control and the wave number control, which are power supply means to the ceramic heater, the wave number control turns ON / OFF the commercial power supply voltage in half-wave units, so that the voltage fluctuation becomes larger than the phase control.
[0009]
When wave number control is performed as a countermeasure, a lighting pattern is set such that the ON / OFF cycle is advantageous for flicker within a predetermined control unit (for example, 20 half-waves of the power supply waveform). The power supply Duty to the ceramic heater is set so that the power supply Duty is about 50% at the time of normal printing, which is frequently used, in consideration of variations in the power supply voltage, the ceramic heater, and the like.
[0010]
Here, the normal printing which is frequently used is intended to print A4 or letter size plain paper at an ambient temperature of normal temperature (15 to 30 ° C.). When the environmental temperature is high, the duty is low, and when the environmental temperature is low, the duty is high. When the paper size is small, the duty is low, and when the paper size is large, the duty is high. In the case of thick paper, the duty is higher than that of plain paper. That is, the greater the amount of heat applied from the fixing device to the paper, the higher the duty.
[0011]
However, when the power supplied to the ceramic heater may be small (for example, when the process speed is low, the temperature control temperature is low, or when printing on small-size paper), a predetermined control unit (for example, 20 half-waves of the power supply waveform) may be used. Therefore, the ON / OFF cycle which is advantageous for flicker cannot be created because the number of times of ON is reduced, resulting in a problem that flicker deteriorates.
[0012]
The present invention has been proposed in view of the above, and in an image forming apparatus including a fixing device that heats and fixes a toner image formed on a recording material, flicker is reduced even when power consumption during printing is small. The purpose is to make
[0013]
[Means for Solving the Problems]
The present invention includes an image forming unit that forms a toner image on a recording material, a fixing device that heats the toner image to fix the toner image on the recording material, and a power control device that controls power supplied to the fixing device. In the image forming apparatus provided with the power control device, the power control device has two kinds of power control means of phase control and wave number control, and further has a power control switching means for switching between these two kinds of power control means. The apparatus is an image forming apparatus in which wave number control is set as power control means in a normal state, and the power control means is switched from wave number control to phase control in accordance with printing conditions.
[0014]
More specifically,
1) The image forming apparatus has a plurality of process speeds of two or more, and a process speed switching means for switching these process speeds. When the process speed is lower than a predetermined process speed, the image forming apparatus includes the power control means. It switches from wave number control to phase control.
[0015]
2) When the fixing temperature in the fixing device is equal to or lower than a predetermined temperature, the power control means is switched from wave number control to phase control.
[0016]
3) When the size of the recording material is smaller than a predetermined size, the power control means is switched from wave number control to phase control.
[0017]
4) When the duty of the power supplied to the fixing device is equal to or less than a predetermined duty, the power control means is switched from wave number control to phase control.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described below with reference to the drawings.
[0019]
[Example 1]
Hereinafter, this embodiment will be described with reference to the drawings.
[0020]
(1) Example of image forming apparatus
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the present embodiment. The image forming apparatus of this embodiment is a laser beam printer using a transfer type electrophotographic process.
[0021]
A laser beam printer main body 101 (hereinafter, main body 101) has a cassette 102 for storing recording paper S, a cassette presence / absence sensor 103 for detecting the presence or absence of the recording paper S in the cassette 102, and a size of the recording paper S in the cassette 102. A cassette size sensor 104 (consisting of a plurality of micro switches) for detecting, a paper feed roller 105 for feeding out the recording paper S from the cassette 102, and the like are provided.
[0022]
A registration roller pair 106 for synchronously transporting the recording paper S is provided downstream of the paper feed roller 105. A cartridge 108 that forms a toner image on the recording paper S based on a laser beam from the laser scanner unit 107 is provided downstream of the registration roller pair 106.
[0023]
Further, a fixing device (fixing device) 109 for thermally fixing the toner image formed on the recording paper S is provided downstream of the cartridge 108, and a conveyance state of a paper discharge unit is detected downstream of the fixing device 109. A paper ejection sensor 110, a paper ejection roller 111 for ejecting the recording paper S, and a loading tray 112 for loading the recording paper S on which recording has been completed are provided.
[0024]
The laser scanner 107 includes a laser unit 113 that emits a laser beam modulated based on an image signal (image signal VDO) sent from an external device 128, and a laser beam from the laser unit 113 on a photosensitive drum 117 described later. A polygon motor 114, an image forming lens 115, a turning mirror 116, and the like for scanning the image are formed.
[0025]
The main motor 123 applies a driving force to the sheet feeding roller 105 via a sheet feeding roller clutch 124 and a driving force to the pair of registration rollers 106 via a registration roller 125. Further, each unit of the cartridge 108 including the photosensitive drum 117 , The fixing device 109 and the paper discharge roller 111.
[0026]
Reference numeral 126 denotes an engine controller which controls the electrophotographic process by the laser scanner unit 107, the cartridge 108, and the fixing device 109, and controls the conveyance of the recording paper in the main body 101.
[0027]
Reference numeral 127 denotes a video controller, which is connected to an external device 131 such as a personal computer by a general-purpose interface (Centronics, RS232C, etc.) 130, expands image information sent from the general-purpose interface into bit data, and The data is sent to the engine controller 126 as a VDO signal.
[0028]
In the cartridge 108, a photosensitive drum 117, a primary charging roller 119, a developing device 120, a cleaner 122, a non-contact IC memory unit 201 with an antenna, and the like necessary for a known electrophotographic process are incorporated. The cartridge 108 is detachably attached to the main body 101 and can be replaced. Further, in the main body 101, a coil antenna 202 for communicating with the non-contact IC memory unit 201 on the cartridge 108 side, and a communication control board 203 equipped with a modulation / demodulation circuit for performing communication control are provided.
[0029]
The recording paper S fed from the cassette 102 is introduced by a registration roller 106 at a predetermined control timing into a transfer nip portion, which is a pressure contact portion between the photosensitive drum 117 and the transfer charging roller 121, and is formed on the surface of the photosensitive drum 117. The transferred toner images are sequentially transferred, separated from the photosensitive drum surface, and introduced into the fixing device 109. Since an electrophotographic process for forming a toner image on the surface of the photosensitive drum 117 is known, its description is omitted. The recording paper S introduced into the fixing device 109 is heated and fixed by the unfixed toner image, and is discharged as a print by a discharge roller 111 to a stack tray 112.
[0030]
(2) Fixing device 109
FIG. 2 is a schematic configuration diagram of the fixing device 109. The fixing device of this embodiment is a heating device of a film heating system of a pressure rotating body driving system (tensionless type) disclosed in, for example, JP-A-4-44075-44083.
[0031]
109c is a ceramic heater as a heat source. The ceramic heater 109c basically has an elongated thin plate-shaped ceramic substrate having a longitudinal direction perpendicular to the drawing, and a current-generating resistor layer (heating element) provided on the substrate surface. This is a heater with a low heat capacity, the temperature of which rises sharply as a whole by energizing the heater.
[0032]
A holder 109e fixedly supports the heater 109c. The holder 109e is a heat-resistant resin member having a substantially semicircular gutter-shaped cross section and having a longitudinal direction perpendicular to the drawing. The heater 109c is fitted in a groove formed along the length of the lower surface of the holder 109e so as to expose the heater surface side downward and fixed with a heat-resistant adhesive or the like.
[0033]
A cylindrical heat-resistant film 109a is loosely fitted to the holder 109e having the heater 109c.
[0034]
Reference numeral 109f denotes a pressing stay having an inverted U-shaped cross section, which is a rigid member whose longitudinal direction is perpendicular to the drawing. The pressure stay 109f is disposed so as to pass through the inside of the holder 109e.
[0035]
An elastic pressure roller 109b is a pressure member. The pressure roller 109b is disposed such that both ends of the metal core are rotatably supported by bearings. The above-mentioned assembly of the heater 109c, the holder 109e, the film 109a, and the stay 109f is arranged above the pressure roller 109b in parallel with the pressure roller 109b with the heater 109c facing downward. Is pressed downward by an urging member (not shown), so that the lower surface of the heater 109c is pressed against the upper surface of the pressure roller 109b via the film 109a against the elasticity of the roller elastic layer, so that the nip portion N having a predetermined width is formed. Is formed.
[0036]
The pressure roller 109b is rotationally driven at a predetermined peripheral speed in a counterclockwise direction indicated by an arrow by driving means (not shown). A rotational force acts on the cylindrical film 109a due to the frictional contact between the pressure roller 109b and the film 109a at the nip portion N by the rotational drive of the pressure roller 109b, and the film 109a adheres to the downward surface of the heater 109c. The outer periphery of the holder 109e is driven and rotated in the clockwise direction of the arrow while sliding.
[0037]
The pressure roller 109b is driven to rotate, the cylindrical film 109a is driven to rotate accordingly, and the heater 109c is energized, and the heater rises quickly to a predetermined temperature and the temperature is controlled. Then, the recording paper S carrying the unfixed toner image t is introduced between the film 109a of the nip N and the pressure roller 109b, and the toner image carrying side of the recording paper S is placed on the outer surface of the film 109a in the nip N. The nip N is conveyed while being in close contact with the film 109a. In this nipping and conveying process, the recording paper S is heated by the heat of the film 109a heated by the heater 109c, and the unfixed toner image t on the recording paper S is heated and pressed onto the recording paper S to be fused and fixed. The recording paper S that has passed through the nip portion N is discharged from the surface of the film 109a with a curvature separated therefrom and conveyed.
[0038]
In the above-described film heating type fixing device, since a low heat capacity heater can be used as a heating element, power saving and shortening of the wait time can be achieved as compared with the conventional heat roller type and belt heating type devices. It becomes possible.
[0039]
FIG. 3 is a structural diagram of an example of the ceramic heater 109c. (A) is a partially cutaway plan model diagram on the heater front side, (b) is a plan model diagram on the heater back side, and (c) is an enlarged cross-sectional model along line (c)-(c) in (b). FIG.
[0040]
This heater 109c
▲ 1 ▼. A ceramic substrate (high insulating / high thermal conductive substrate) a made of ceramics such as alumina, aluminum nitride, and silicon carbide having a long side in a direction perpendicular to the conveying direction of the recording paper S;
▲ 2 ▼. Formed by coating and baking about 10 μm thick, about 1 to 3 mm wide linear or narrow strip by screen printing or the like along the length of the substrate at the center of the substrate width direction on the front side of the ceramic substrate a. Ag / Pd (silver palladium), RuO ₂ , Ta ₂ N or other resistance heating element layer (electric heating element) b,
(3). Electrode portions cc formed of Ag / Pt (silver / platinum), which are electrically connected to both ends in the longitudinal direction of the resistance heating element layer b,
▲ 4 ▼. An insulating protective layer d provided on the surface of the resistance heating element layer b, such as a thin glass coat or a fluororesin coat, which is electrically insulated and can withstand rubbing with the film 109a;
▲ 5 ▼. A thermistor 109d as a temperature detecting means provided on the back side of the ceramic substrate a,
Etc.
[0041]
In the heater 109c of this example, the heating element b is formed and provided on the front surface side of the ceramic substrate a so that the center of the width of the heating element b substantially coincides with the center of the heater width, as shown in FIG. The heater 109c is fitted into a heater fitting groove formed on the lower surface of the holder 109e along the longitudinal direction with the heater surface side outside, and is adhered and held with a heat resistant adhesive.
[0042]
The electrode portions c and c of the heater 109c are connected to a power control device, which is a heater drive circuit described in the following section (3), via power supply connectors 109g and 109g. , The entire heater 109c including the substrate a and the protective layer d rapidly rises in temperature. The thermistor 109d detects the temperature of the heater 109c and feeds back the temperature information to the power control device. The power control device controls and controls the power supply to the resistance heating element layer b based on the fed back temperature information so that the temperature of the heater 101c is maintained at a predetermined control target temperature.
[0043]
(3) Power control device (heater drive circuit)
FIG. 4 shows an example of a power control device (ceramic heater drive circuit) 100 for controlling the power supplied to the fixing device (ceramic heater).
[0044]
Reference numeral 1 denotes an AC power supply for connecting the image forming apparatus, and the image forming apparatus supplies commercial power to the ceramic heater 109c via the AC filter 2 to cause the ceramic heater 109c to generate heat. The power supply to the ceramic heater 109c is turned on and off by the triac 4. The resistors 5 and 6 are bias resistors for the triac 4, and the phototriac coupler 7 is a device for securing a creepage distance between the primary (the resistance heating element layer b side) and the secondary (thermistor 109d side). The triac 4 is turned on by energizing the light emitting diode of the phototriac coupler 7. The resistor 8 is a resistor for limiting the power supply of the phototriac coupler 7 and is turned on / off by the transistor 9. The transistor 9 operates according to an ON signal from the engine controller 126 via the resistor 10.
[0045]
Further, the AC power supply 1 via the AC filter 2 is transmitted to the engine controller 126 via the zero cross detection circuit 11 as a zero cross signal whose pulse width changes according to the voltage of the commercial power supply 1.
[0046]
The engine controller 126 detects the pulse width of the zero-cross signal, and turns on / off the triac 4 by wave number control based on the pulse width.
[0047]
The temperature detected by the thermistor 109d, which is a temperature detecting element for detecting the temperature of the ceramic heater 109c, is detected as a partial pressure between the resistor 13 and the thermistor 109d, and is input to the engine controller 126 as an A / D signal as a TH signal. Is done. The temperature of the ceramic heater 109c is monitored by the engine controller 126 as a TH signal, and the power to be supplied to the ceramic heater 109c is calculated by comparing the temperature with the set temperature of the ceramic heater 109c set inside the engine controller 126. The engine controller 126 sends an ON signal to the transistor 9 at a heater ON / OFF timing of a wave number pattern corresponding to the supplied power.
[0048]
Here, FIG. 5 is an example of wave number patterns for each supply power, and these patterns are determined so that the heater is turned ON / OFF at a cycle advantageous for flicker. Generally, a lighting pattern having a cycle advantageous for flicker can be formed because there are many lighting pattern options around Duty 50%, which is frequently used, but a low power supply side (around 20%) and a high power supply side (around 20%). (Around 80%), there are few choices of lighting patterns, and it is difficult to form a pattern having a cycle advantageous for flicker.
[0049]
Here, when the image forming apparatus is provided with a plurality of process speeds (two speeds of the full speed and half speed in the present embodiment), when printing is performed at a half speed with respect to a normal full speed, fixing is performed per unit time. The amount of heat taken by the paper in the apparatus is reduced, and as a result, the power supplied to the fixing device is reduced. That is, the result is that flicker gets worse.
[0050]
Therefore, in this embodiment, when the process speed is equal to or lower than a predetermined speed, the power control method is changed from wave number control to phase control advantageous for flicker. Although phase control is advantageous for flicker, it is disadvantageous in that harmonic currents increase. Particularly, in the phase control, when the duty of the supplied power is used around 50%, the harmonic current increases. However, in this embodiment, the phase control is performed only under the condition that the process speed is equal to or lower than a predetermined speed (the condition where the supplied power is small). Therefore, the harmonic current slightly increases as compared with the wave number control, but it can be kept at a level that does not cause a problem for the standard, and the flicker can be reduced without any adverse effect (see FIG. 6).
[0051]
Next, the flow in this embodiment will be described with reference to the flowchart in FIG.
[0052]
First, when the power of the main body 101 is turned on (S1), the main body performs a predetermined operation and enters a standby state (S2). Thereafter, if there is a print command (S3), the printing conditions (process speed) are checked (S4). If the process speed is higher than a predetermined speed, power is supplied to the fixing device by wave number control (S5), and the process speed is increased. Is less than the predetermined speed, power is supplied to the fixing device by phase control (S6). At the same time as the printing is completed (S7), the power supply is terminated.
[0053]
Here, in correspondence with the first aspect, the engine controller 126 sets the power control unit to a phase control from wave number control in accordance with “print control conditions” and “power control switching unit for switching between two types of power control units”. Means for switching to control ". The circuit portions 4 to 11 and 126 correspond to “power control means for wave number control” or “power control means for phase control”. Only the engine controller 126 switches from wave number control to phase control, and the other control means 4 to 11 are the same between them.
[0054]
[Example 2]
The present embodiment is almost the same in overall configuration as the first embodiment, except for the condition for switching from wavenumber control to phase control.
[0055]
When the fixing temperature is low, the electric power supplied to the fixing device naturally becomes small, which leads to the deterioration of flicker as in the first embodiment.
[0056]
Therefore, in this embodiment, when the fixing temperature is equal to or lower than a predetermined temperature, the power control method is changed from wave number control to phase control. The effect of changing to the phase control is the same as in the first embodiment.
[0057]
Next, the flow in this embodiment will be described with reference to the flowchart in FIG.
First, when the power of the main body 101 is turned on (S1), the main body performs a predetermined operation and enters a standby state (S2). Thereafter, when a print command is issued (S3), the printing conditions (fixing temperature) are checked (S4). If the fixing temperature is higher than a predetermined temperature, power is supplied to the fixing device by wave number control (S5), and the fixing temperature is set. Is lower than the predetermined temperature, power is supplied to the fixing device by phase control (S6). At the same time as the printing is completed (S7), the power supply is terminated.
[0058]
The switching of the fixing temperature is automatically performed by the engine controller 126 according to the printing conditions (environmental temperature, paper size, number of prints). The fixing temperature varies depending on the environmental temperature (the lower the environmental temperature, the higher the fixing temperature). The fixing temperature differs depending on the paper size (the larger the paper size, the higher the fixing temperature). When printing is performed continuously, the fixing temperature decreases every predetermined number of sheets (in a stepwise manner). The “predetermined temperature” in the present embodiment is assumed to be 170 to 180 ° C.
[0059]
[Example 3]
The overall configuration of this embodiment is almost the same as that of the first embodiment, but the conditions for switching from wave number control to phase control are different.
[0060]
When the size of the paper passing through the fixing device is small, the amount of heat taken by the fixing device is reduced, and the power supplied to the fixing device is also reduced, which leads to the deterioration of flicker as in the first embodiment.
[0061]
Therefore, in this embodiment, when the paper size to be printed is smaller than a predetermined size, the power control method is changed from wave number control to phase control. The effect of changing to the phase control is the same as in the first embodiment.
[0062]
Next, the flow in this embodiment will be described with reference to the flowchart in FIG.
[0063]
First, when the power of the main body 101 is turned on (S1), the main body performs a predetermined operation and enters a standby state (S2). Thereafter, when there is a print command (S3), the printing conditions (paper size) are checked (S4). When the size is larger than the predetermined size, power is supplied to the fixing device by wave number control (S5), and the paper size is reduced. If the size is smaller than the predetermined size, power is supplied to the fixing device by phase control (S6). At the same time as the printing is completed (S7), the power supply is terminated.
[0064]
In the present embodiment, the “predetermined size” is assumed to be a paper having a size of B5 size paper or less.
[0065]
[Example 4]
The overall configuration of this embodiment is almost the same as that of the first embodiment, but the conditions for switching from wave number control to phase control are different.
[0066]
In the first to third embodiments, the power supply method is switched from the wave number control to the phase control according to the printing conditions. In the present embodiment, the power supplied to the fixing device is constantly monitored, and the supplied power is reduced to a predetermined Duty or less. If this happens, the power supply method is switched from wave number control to phase control.
[0067]
In the present embodiment, even if the control is once switched to the phase control, the control may be switched from the phase control to the wave number control when the supplied power becomes equal to or higher than a predetermined duty.
[0068]
FIG. 10 shows a lighting pattern of a heater that supplies power by phase control only for a duty of 30 or less and fraction control otherwise.
[0069]
As a supplement, in each of the first to fourth embodiments, each of the process speed, the fixing temperature, the paper size, and the power is described as the print condition. However, two, three, or four AND conditions of these four items are required. It is needless to say that a flicker countermeasure can be similarly performed.
[0070]
Although various examples and embodiments of the present invention have been shown and described, those skilled in the art will appreciate that the spirit and scope of the present invention is not limited to the specific description and figures herein. It will be appreciated that various modifications and changes are set forth which are all set forth in the following claims.
[0071]
Examples of embodiments of the present invention are listed below.
[0072]
[Embodiment 1] An image forming unit that forms a toner image on a recording material, a fixing device that heats the toner image and fixes the recording material, and a power control device that controls power supplied to the fixing device An image forming apparatus comprising:
The power control device has two kinds of power control means of phase control and wave number control, and further has a power control switching means for switching between these two kinds of power control means.
The power control device is set to wave number control as power control means at normal time,
An image forming apparatus characterized in that said power control means is switched from wave number control to phase control in accordance with printing conditions.
[0073]
[Embodiment 2] The image forming apparatus has a plurality of process speeds equal to or higher than two speeds, and further includes a process speed switching unit that switches these process speeds. When the switched process speed is equal to or less than a predetermined process speed, The image forming apparatus according to the first embodiment, wherein the power control unit is switched from wave number control to phase control.
[0074]
[Embodiment 3] The image forming apparatus according to Embodiment 1, wherein when the fixing temperature in the fixing device is equal to or lower than a predetermined temperature, the power control unit is switched from wave number control to phase control.
[0075]
[Embodiment 4] The image forming apparatus according to Embodiment 1, wherein the power control unit is switched from wave number control to phase control when the size of the recording material is equal to or smaller than a predetermined size.
[0076]
[Embodiment 5] The image forming apparatus according to Embodiment 1, wherein when the duty of the power supplied to the fixing device is equal to or less than a predetermined duty, the power control unit is switched from wave number control to phase control.
[0077]
【The invention's effect】
As described above, according to the present invention, in an image forming apparatus including a fixing device that heats and fixes a toner image formed on a recording material, even when power consumption during printing is small (at low power). The purpose is to reduce flicker.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment.
FIG. 2 is a schematic configuration diagram of a fixing device.
FIG. 3 is a schematic configuration diagram of an example of a ceramic heater as a heat source.
FIG. 4 is a drive circuit diagram of a ceramic heater.
FIG. 5 is a wave number pattern with respect to supplied power.
FIG. 6 shows the relationship between the phase angle of the phase control and the harmonic current.
FIG. 7 is a control flowchart.
FIG. 8 is a control flowchart according to the second embodiment.
FIG. 9 is a flowchart according to a third embodiment.
FIG. 10 illustrates a heater lighting pattern according to a fourth embodiment.
[Explanation of symbols]
109 is a fixing device, 109a is a fixing film, 109b is a pressure roller, 109c is a ceramic heater, 109d is a thermistor, 1 is a commercial power supply, 4 is a triac, 7 is a phototriac coupler, 11 is a zero-cross detection circuit, and 126 is an engine controller.

Claims (1)

Image forming apparatus including: an image forming unit that forms a toner image on a recording material; a fixing device that heats the toner image to fix the recording material; and a power control device that controls power supplied to the fixing device. At
The power control device has two kinds of power control means of phase control and wave number control, and further has a power control switching means for switching between these two kinds of power control means.
The power control device is set to wave number control as power control means at normal time,
An image forming apparatus characterized in that said power control means is switched from wave number control to phase control in accordance with printing conditions.

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