JP2003295685A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrict flickers, to effectively suppress a power source higher harmonic current and a noise terminal voltage, and to optimally adjust temperature in an image forming apparatus including two or more heaters for fixing heat rollers. <P>SOLUTION: The apparatus includes: a roller temperature adjusting means which comprises the two heaters for heating the pair of upper and lower fixing rollers arranged in a fixer, detects the temperature of the rollers, drives the heaters by a heater control means based on the detected temperature signal, and performs adjustment to allow the temperature of the rollers to be the determined temperature; and a phase control means for performing the phase control of the supplied power source in each heater when the two heaters are driven in a roller heating heater control means. When a situation occurs where the two heaters are simultaneously started to be driven based on the control result of the roller temperature adjusting means, the phase control means performs phase control in only one of the two heaters. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION An image forming apparatus for forming an image on a transfer material by applying a heat and pressure to a toner image formed on the transfer material by a heat and pressure fixing device by an electrophotographic method. The present invention relates to an image forming apparatus that controls the electric power of a heater for heating a heating / pressurizing roller provided in a heating / pressurizing device and performs optimum temperature adjustment.

[0002]

2. Description of the Related Art Conventionally, in a copying machine, a toner image is transferred onto a transfer material by means of a photosensitive drum, and then a heat roller for fixing using a temperature sensor such as a thermistor is used to apply heat and pressure to form an image. ing. Further, a halogen heater is generally used as the heating means of the heat roller. In recent years, with the increase in speed and color of image forming apparatuses, in order to stably heat and fix the toner on the transfer material, the power of the heating means of the heat roller is increased, and at the same time, a plurality of heating means are installed. It had a configuration that made it possible by driving.

[0003]

However, in the above-described conventional example, it is necessary to significantly increase the power supply amount of the halogen lamp used for the heating means of the heat roller as the image forming apparatus operates at a higher speed. ing. Further, it has been pointed out that the halogen heater has a possibility that a large rush current flows when power is supplied to the heating means due to its characteristics and a temporary voltage drop of a commercial power source to be used has an influence. Therefore, in general, as a measure against a load with a large inrush current, the conduction angle of a triac, a thyristor, an SSR, etc., that controls the heating means during the ten-odd cycles affected by the inrush current, with respect to the frequency of the commercial power source. Measures such as phase control to reduce the are taken. However, there is a problem in that there are a plurality of heating means for the heat roller, and if the phase control is sequentially performed for each of them, radio noise occurs during switching such as triac, thyristor, and SSR.

[0004]

In view of the above problems, according to the present invention, a latent image formed on a photoconductor is developed with toner, the toner image on the photoconductor is transferred onto a transfer material, and then heated. In an image forming apparatus that forms an image on a transfer material by being heated and pressed by a pressure fixing device, at least two heating heaters for heating a heating pressure roller provided in the heating pressure fixing device are provided. One or more heating / pressurizing roller temperature detecting means for detecting the temperature of the heating / pressurizing roller, and a heating / pressurizing fixing roller heater based on the temperature signal detected by the temperature detecting means of the heating / pressurizing roller. The roller heating heater control means drives the heating heater to adjust the temperature of the heating / pressurizing roller to a specified temperature, and the roller heating heater control means has at least two or more. A phase control means for controlling the phase of the power supply for preheating the respective heaters when driving the heaters, and at least two based on the control result of the roller temperature adjusting means. When a situation occurs in which at least two or more of the above heaters are started to be driven at the same time, the phase control means performs the phase control on only one of the at least two or more heaters. It is the one.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a schematic configuration of a digital image forming apparatus as an example of the image forming apparatus according to the present invention. First, the configuration and operation will be described with reference to FIG. The image forming apparatus shown in FIG. 1 includes a reader unit 1 at the top of the main body of the device and a printer unit 2 at the bottom.

The reader unit 1 is a document table 1 on which a document is placed.
1. A document pressure plate 12 for pressing a placed document from above,
A light source 13 for illuminating the image surface of the original, a plurality of mirrors 14 and lenses 15 for guiding the reflected light from the image surface, a CCD for the reflected light
An image processing / photoelectric conversion unit 16 that performs photoelectric conversion on the obtained electric signal and performs various image processing on the obtained electric signal is configured as a main constituent member. Further, the image processing unit 16 includes a CCD, A / D conversion, S / H, shading correction,
It has image processing functions such as masking correction, scaling, and LOG conversion.

The operation of the reader unit 1 having the above-described structure is as follows. A document is placed on the document table 11 with its image surface facing downward, and is pressed by the document pressure plate 12 from above. The light source 13 moves in the direction of arrow K1 while irradiating light, and scans the image surface of the document. The reflected light image from the image plane is passed through a plurality of mirrors 14 and lenses 15 to the CCD.
An image is formed on the surface, and photoelectrically converted into an electric signal. The image signal, which has become an electric signal, is subjected to various kinds of image processing in the image processing section 16 and then sent to the next printer section 2.

As shown in FIG. 1, the printer section 2 converts an electric signal sent from the reader section 1 into a signal for driving a laser, and a laser element 1.
8, a polygon scanner 19 for scanning the surface of a photosensitive drum described later with a laser beam, an image forming unit including a photosensitive drum described later, and a fixing unit 39 arranged on the most downstream side are main components.

In the image forming section, the surface of the photosensitive drum 30 is rotatably supported in the direction of the arrow, and the surface of the photosensitive drum 30 is uniformly charged around the photosensitive drum 30. The primary charger 31, the developing device 20 for developing the electrostatic latent image on the photosensitive drum 30, the transfer charger 35 for transferring the toner image on the photosensitive drum 30 to the transfer material P, and the transfer residual toner on the photosensitive drum 30 are removed. A cleaner 34, a cleaner blade 34a, an auxiliary charger 33 for removing charge, and a pre-exposure lamp 32 for removing residual charge are provided.

Further, the developing device 20 includes a developing roller 20a.
Is provided, and the developing roller 20a rotates in the opposite direction to the photosensitive drum 30 to develop a toner image on the photosensitive drum 30.

The transfer material P on which the toner image is transferred in this manner
Is conveyed to the fixing unit 39 by the pre-fixing belt 38, where the fixing rollers 39a and 39b rotate to convey the transfer material P, and the pressure is applied, and the toner image on the surface is fixed by being heated and pressed. It Finally, the transfer material P after fixing is discharged to the paper discharge tray 41 outside the apparatus main body via the post-fixing conveyance belt 42.

The feeding / conveying unit for feeding and transferring the transfer material P has a conveyance path for the transfer material P, and a paper feed cassette 36, a paper feed roller 36a, and a paper feed roller 36a are provided on the most upstream side in the conveyance direction of the transfer material P.
It is provided with a sheet feeding device having a conveyance roller 36b and the like. In addition to this paper feeder, multi-paper feeder 4
3 is provided. Since the multi-paper feeding device 43 has a straight paper feeding path, it is possible to feed various transfer materials P having different properties such as material and size to the image forming unit.

Next, FIG. 2 shows a block diagram of a control system of this apparatus. All of the present devices are comprehensively controlled by the system controller 71. The system controller 71 mainly drives the respective loads in the device, collects and analyzes the information of the sensors, and the above-mentioned image processing unit 16 and laser driving unit 1.
In addition to 7, it also plays a role of exchanging data with the operation unit 102, that is, the user interface. The internal configuration of the system controller 71 is equipped with a CPU 71a for performing the above-mentioned role, and the CPU 71a is
Similarly, the ROM 7 mounted on the system controller 71
Various sequences related to a predetermined image forming sequence are executed by the program stored in 1b. At that time, in order to store rewritable data that needs to be temporarily or permanently stored, the RAM 7 is used.
1c is also installed. The RAM 71c stores, for example, a high voltage set value for the high voltage control unit 105, which will be described later, various data described later, image formation command information from the operation unit 102, and the like.

Data exchange with the image processing unit 16, the ray control unit 17, and the operation unit 102, which is the first role of the system controller 71, will be described. As described above, the image processing unit 16 A / D converts an image signal from a CCD (not shown).
Conversion, S / H, shading correction, masking correction,
Image processing such as scaling and LOG conversion is performed. In addition to sending the specification setting value data of each unit necessary for these image processes, it receives a signal from each unit, for example, a document image density signal, and controls the high-voltage control unit 105 and the laser control unit 17, which will be described later. Then, settings for optimal image formation are performed. The image control unit 17 controls the laser optimally based on the definition of the image size for forming an image and the digital video data subjected to the image processing, that is, in the present device, it performs the PWM processing of the laser emission. Make the required settings. The operation unit 102 obtains information such as a copy magnification and a density setting value set by the user, and also the state of the image forming apparatus, for example, information on the number of images formed or whether images are being formed, and occurrence of a jam. It sends out data to show the user and its location to the user.

Next, the driving of each load in the apparatus and the information collection and analysis of the sensors, which is the second role, will be described. In this device, a DC load such as a motor and a clutch / solenoid, and a sensor such as a photo interrupter and a micro switch are arranged at various places inside the device. In other words, various sensors are used to convey the transfer material and drive each unit by appropriately driving the motor and each DC load, and monitoring the operation thereof. Therefore, the system controller 71 causes the motor control unit 107 to control each motor based on signals from various sensors 109, and at the same time, causes the DC load control unit 108 to operate the clutch / solenoid to smoothly perform the image forming operation. Is proceeding to.

By sending various high-voltage control signals to the high-voltage control unit 105, the primary charger 31, the auxiliary charger 33, the transfer charger 35, and the developing roller 20a, which are various chargers constituting the high-voltage unit 106, are sent. Appropriate high pressure is applied. Further, the fixing roller 39 in the fixing device 39 described above
A heaters 39c and 39d for heating the rollers are incorporated in a and 39b, respectively, and an oil heater 40b for heating oil to be applied to the fixing roller is provided.
The heater control section 45 controls ON / OFF of each heater. At this time, the fixing rollers 39a and 39b are also provided with thermistors 39e and 39f for measuring the temperature thereof, and the oil heater 40a is also provided with a thermistor 40c for measuring the temperature thereof.
The A / D 103 converts the resistance value change of each thermistor according to the temperature change of each of the fixing rollers 39a and 39b and the oil heater 40a into a voltage value, which is then input to the system controller 71 as a digital value. The heater control unit 45 described above is controlled based on this temperature data.

The system controller 71 has a commercial power source 3
Zero cross detection 71e for detecting the zero cross of the voltage of
And heaters 39c, 39 for heating the rollers.
A trigger signal for controlling the electric power supplied to d is generated.

Next, FIG. 3 shows a block diagram of the above-mentioned image forming apparatus. This block diagram is a block diagram for performing image formation on the transfer material P and optimal image fixing. The system controller 71 performs various controls of the image forming apparatus, and is totally controlled by an internal CPU. In the figure, 72 is an image input section which constitutes a part of the reader section 1, 16 is an image processing section, 17 is a laser drive section which modulates and drives a semiconductor laser based on image data, and 18 is driven by the laser drive section 17. Semiconductor laser (laser element).

Further, 30 is a photosensitive drum on which an electrostatic latent image is formed by the output light of the semiconductor laser 18, 20 is a developing device for developing according to the latent image on the photosensitive drum 30, and 35
Is a transfer charger that transfers the toner image on the photosensitive drum 30 onto the transfer material P.

Further, 39 is a fixing unit for fixing the toner image on the transfer material P by heating and pressing. Next, the area around the fixing unit in the image forming apparatus having the above-described configuration will be described with reference to the block diagram of FIG. Fixing roller 39
Halogen heaters 39c and 39d for heating the rollers are provided inside a and 39b, and as described above, the system controller 71 performs ON / OFF control of each heater via the heater controller 45. Be seen.
Further, ON / OFF of each heater is turned on / off by a thermistor 39e for temperature monitoring, which is attached in contact with each roller.
Based on the temperature measured by 9f, it is controlled so as to reach the specified temperature. Further, the fixing unit 39 is coated with silicone oil for the purpose of improving the releasability of the upper fixing roller 39a and the transfer material P, and the oil coating unit is 40. The oil coating unit includes an oil pan 40e for storing oil and an oil heater 4 for adjusting the oil temperature for keeping the viscosity of the oil constant.
0b and a heater mounting plate 40a for transferring the heat of the oil heater to the silicon oil, an oil thermistor 40c for measuring the temperature of the oil heater, and an oil coating for applying an appropriate amount of oil to the upper fixing roller. It is composed of a roller 40d.

Similarly to the temperature control of the fixing roller, the system heater 71 of the oil heater 40b controls the ON / OFF of each heater through the heater controller 45. ON / OFF of the heater is controlled so as to reach the specified temperature based on the temperature measured by the thermistor 40c for temperature monitoring attached to the oil heater 40b. A primary power supply 44 for supplying primary side power to each of the above-mentioned heaters is connected to the heater control section, and an SSR inside the heater control section 45 turns ON / OFF power supply.
F is carried out. In addition, signals from the thermistors are sent directly to the system controller 71 via the heater controller 45.
At the same time, the abnormality detection of each thermistor is performed inside the heater control unit 45, the abnormality output is detected by the thermistor disconnection, abnormal temperature detection, etc., and a signal to that effect is output to the system controller 71. It has become.

The details of the oil applying unit 40 inside the fixing unit 39 will be described with reference to FIG. As described above, the oil application unit 40 includes the oil heater mounting sheet metal 40a, the oil heater 40b, the oil application roller 40d, the oil pan 40e, and two oil temperature monitoring thermistors 40c-1 and 40c-2. . The oil pan 40e is filled with silicone oil up to the dotted line in the figure, and by rotating the roller from below the oil application roller 40d in the direction of the arrow in the figure, an appropriate amount of oil is applied to the upper fixing roller 39a. Has become. The lower part of the oil heater mounting plate 40a is soaked in the silicone oil that the oil heater 40b is attached to the part that is not soaked in oil. This is because the oil is heated by a relatively inexpensive heater without using an expensive oil resistant heater.
Indirectly via 0a. As means for detecting the temperature of the oil, in addition to the oil temperature detecting thermistor 40c-2 which directly detects the temperature of the oil by immersing it in the oil, an oil heater temperature detecting thermistor 40c which also detects the temperature of the oil heater. -1 is used.

Next, the internal structure of the heater controller 45 will be described in detail with reference to FIG. The heater control unit 45 is responsible for ON / OFF control of each heater as described above.
ON / OFF of the primary power supplied to the heater is SSR
(Solid-state relay) 45a, 45b, 45c, respectively. A signal for controlling the SSR is sent from the system controller 71. Also SS
A state signal indicating whether or not the SSR is actually conducting the primary power source is output from R, and "H" is output when the SSR is conducting, and "L" is output when the SSR is not conducting. Therefore, the status signal is sent to the SSR abnormality detection circuits 45e, 45.
Input to f and 45g respectively, and system controller 7
When the control signal from the system controller 71 and the status signal are defective by comparing with the control signal from 1 (ON with "H", OFF with "L"), for example, the system controller If the SSR is conducting even though the OFF signal is output from the SSR,
Abnormalities are detected. This abnormality detection signal is ANDed with each detection signal output, and if any one of them has a problem, the power supply to the SSR is stopped. In addition, a signal for forcibly stopping the power supply to the SSR is also input from the system controller 71.

At this time, a relay 45d is provided between the SSR and the primary side power source from which power is supplied, and when there is an abnormality,
The output of 5h turns off the transistor 45i,
As a result, the power supply is stopped by turning off the relay. In addition, each thermistor 39e, 39
f, 40c-1 and 40c-2 are pulled up by a resistor R in order to detect a change in resistance value with respect to temperature as a change in voltage. Furthermore, the temperature data converted into voltage is
After being sent to the A / D 103, the system controller 71
At the same time, the result is compared with the specified voltage and the result is also sent to the system controller 71. This is for the purpose of notifying the system controller 71 of the occurrence of some abnormality in the thermistor when the temperature detected by each thermistor becomes equal to or higher than the specified temperature (the temperature which largely deviates from the temperature adjustment temperature). In the figure, 45j is an abnormal temperature detection circuit, which is configured to be compared with a specific set voltage by each thermistor.

Next, the structure for detecting the zero cross of the commercial power source will be described with reference to FIG. FIG. 5 shows the internal structure of the zero-cross detection 71e. The commercial power supply 3 is full-wave rectified by the diode bridge 110 and drives the photocoupler 111 via the resistor 112. A full-wave rectified commercial power source current flows through the LED side of the photocoupler 111, and the LED emits light in a full-wave rectified pulsating flow, that is, the LED hardly emits light when the commercial power source voltage is near 0V. There is. As a result, on the transistor side of the photocoupler 111, the collector is pulled up to 5 V, so that “H” is output when the voltage of the commercial power source 3 is near zero cross, and “L” is output in other cases, and the zero cross timing is set by the system controller. The CPU 71a in 71 is notified.

Here, the zero-cross control of this apparatus will be described with reference to FIG. In the figure, (a) shows the voltage waveform of the commercial power supply 3. As described above, the zero-cross signal of the commercial power source 3 is detected by the zero-cross detection 71e, and the result is shown in FIG. FIG. 7C shows a heater ON signal, which is a signal for continuously outputting "H" during the period in which the heaters 39c and 39d are driven. This device uses a halogen heater as a heat roller heating means,
The halogen heater has a characteristic that a large rush current flows when it is started. When a large inrush current flows, the SSR for driving the heater deteriorates and a temporary voltage drop of the commercial power source occurs, affecting not only the device but also other devices connected to the commercial power source. Is concerned.

Therefore, in this apparatus, 300 mS, which is considered to have a large inrush current and corresponds to a dozen cycles of a commercial power source.
During the period, SS is used to preheat the halogen heater.
Phase control is performed to reduce the energization angle to R. Regarding the phase control method, the CPU 71a in the system controller 71 is based on the zero-cross signal in FIG.
Generates the SSR drive pulse shown in FIG. SS
The R drive pulse is a triac gate trigger signal inside the SSR, and the CPU 71a causes the zero-cross signal (b) immediately after the timing when the heater ON signal (c) becomes "H".
Is detected, the signal is delayed so that the energization time is 3 mS in order to reduce the energization angle of the SSR. After performing such an operation for 300 mS, the preheating is terminated and the normal zero-cross energization is reset. The heater energizing current phase at this time is shown in FIG. As described above, the phase control is performed for each of the fixing halogen heaters 39c and 39d independently at the beginning of energization, and the inrush current is minimized.

Next, when the phase of the halogen heater is controlled, generation of radio noise due to switching of the SSR becomes a problem depending on the magnitude of the conduction angle. Generally, the noise terminal voltage is maximized when the phase of the conduction angle is around 90 degrees, but even at a small conduction angle, the noise terminal voltage also increases as the power consumption of the heater increases. Also, when a plurality of heaters are driven at the same time and the phase control periods at that time overlap, the noise terminal voltage also increases, as in the case of using a heater with high power. Normally, we try to suppress the noise terminal voltage by using a noise filter, etc., but when the value is large, a noise filter with an extremely large constant is adopted, but it is not feasible because it is extremely large. In addition, it is extremely difficult to drop it completely. Therefore, the present apparatus is configured to perform phase control on only one of the upper and lower halogen heaters. Since the toner image is formed on the upper surface of the transfer material, in order to properly fix the toner image, the temperature of the upper heat roller is adjusted to be higher than the temperature of the lower heat roller, and at the same time, the temperature of the upper heater is adjusted. It is necessary to set the electric power larger than the electric power of the lower heater. In this device, the upper heater is 800
Since the lower heater is set to W and the lower heater is set to 400 W, the ratio of noise terminal voltage generated by phase control is large in the upper heater, and the inrush current value is extremely higher in the upper heater than in the lower heater. I know it's big.

Therefore, in the present apparatus, at the timing when the upper and lower heaters are driven simultaneously, phase control is performed only on the upper heaters, so that the inrush current is reduced and the noise terminal voltage is generated as much as possible. It is controlled to hold down. The algorithm will be specifically described below with reference to FIG. FIG. 8 shows the temperatures TU and TL of the upper and lower heat rollers.
Shows the temperature change and the driving signal of each heater. TUS and TLS are threshold temperatures at which the heaters are turned on / off, and are turned off when the temperature is higher than TUS and TLS, and turned on when the temperature is lower. Here, the temperatures of the upper and lower heat rollers are both TU.
When the values are lower than S and TLS, the upper and lower heaters are normally turned on at the same time, but as a result, the phase control of the heaters overlaps with each other, and the above-mentioned problem of the noise terminal voltage occurs. Therefore, in this device, the upper and lower heaters are turned on simultaneously.
At the timing when the above situation occurs, the phase control of the lower heater is controlled to be turned off.

The above-mentioned control is centrally controlled by the system controller 71, and the heater control algorithm will be described with reference to FIG. FIG. 9 shows an algorithm for controlling the heater of the heat roller, but this sequence is regularly performed at intervals of 500 mS.

When the temperature control is started (S101), the upper heater ON status SU is reset (S10).
2). Then, the temperatures of the upper and lower heat rollers are measured by the thermistors 30e and 39f (S103). Therefore, first, it is determined whether or not the temperature TU of the upper heat roller exceeds the threshold temperature TUS (S104), and if the temperature TU of the upper heat roller is higher than the threshold temperature TUS, at that time point. It is determined whether the upper heat roller is ON or not (S105), and if it is ON, the upper heat roller is OFF (S106). Further, if the temperature TU of the upper heat roller is lower than the threshold temperature TUS, it is determined whether or not the upper heat roller is ON at that time (S110). The roller is turned on (S110), and the upper heater ON status SU is set (S112). Subsequently, it is determined whether the temperature TL of the lower heat roller exceeds the threshold temperature TLS (S107), and the temperature T of the lower heat roller is determined.
If L exceeds the threshold temperature TLS, it is determined whether or not the lower heat roller is ON at that time (S
108), if it is ON, turn the lower heat roller OF
F (S109).

If the temperature TL of the lower heat roller is lower than the threshold temperature TLS, it is determined whether or not the upper heater ON status SU is set (S11).
3) If not set, after the phase control flag of the lower heater is turned on (S117), it is determined whether the lower heat roller is turned on at that time (S11).
4) If not turned on, the lower heat roller is turned on (S115). When the upper heater ON status SU is set, the phase control flag of the lower heater is turned off (S118) in order to prevent the upper and lower heaters from being phase-controlled at the same time (S118). It is determined whether the roller is ON (S11
4) If not turned on, the lower heat roller is turned on (S115), and this sequence is finished (S11).
6). That is, only the upper heater performs the phase control when driving the heater.

[Other Embodiments] In the first embodiment, the ON condition of the upper heater is prioritized in order to prevent simultaneous ON of each heater, but the heater control is prioritized by the ON condition of the lower heater. It is possible to obtain the same effect by performing. Further, in the first embodiment, the phase control signal is digitally created by the CPU, but it is possible to obtain the same effect by analogically creating the phase control signal based on the zero-cross signal.

[0035]

The latent image formed on the photoconductor is developed with toner, the toner image on the photoconductor is transferred onto the transfer material, and then the paper is heated and pressurized by the heat and pressure fixing device. In an image forming apparatus for forming an image on a transfer material, at least two heating heaters for heating the heating / pressurizing roller provided in the heating / pressurizing fixing device are provided, and the temperature of the heating / pressurizing roller. Based on the temperature signal detected by the heating / pressurizing roller temperature detecting means and the temperature detecting means of the heating / pressurizing roller, the heating heater is driven by the roller heating heater control means of the heating / pressurizing fixing roller heating heater, The roller temperature adjusting means for adjusting the temperature of the heating / pressurizing roller to a specified temperature and the roller heating heater control means heat each of them when driving the at least two or more heating heaters. And a phase control means for controlling the phase of the power supply in order to perform the preheating against over data, on the basis of the control result by the roller temperature adjusting means,
When a situation occurs in which at least two or more heating heaters are simultaneously driven to start, at least two or more heating heaters are subjected to phase control by the phase control means for only one of them. By implementing the invention, it is possible to provide a device capable of reducing the inrush current to the heater and suppressing the generation of radio noise at the same time.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a schematic configuration of an image forming apparatus according to the present invention.

2 is a block diagram showing an example of a control system of the copying machine shown in FIG.

3 is a block diagram showing an example of a printer unit control system and a fixing unit of the copying machine shown in FIG.

FIG. 4 is a block diagram showing an example of an oil coating system of the fixing unit shown in FIG.

5 is a block diagram showing an example of a zero-cross detection circuit in the system controller shown in FIG.

FIG. 6 is a block diagram showing an example of a heater controller of the fixing unit shown in FIG.

FIG. 7 is a graph illustrating an SSR drive signal for supplying electric power to a heater.

FIG. 8 is a diagram showing a relationship between a heater driving signal and a temperature of a heat roller.

FIG. 9 is a flowchart showing a procedure for controlling driving of each heater.

[Explanation of symbols]

1 Reader section 11 Platen 12 Original plate 13 Light source 15 lenses

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H033 AA41 BA25 BB18 BB30 CA07                       CA30 CA46 CA48                 3K058 AA26 AA46 BA18 DA02                 5H323 AA36 BB03 BB20 CB04 CB42                       DA03 DB04 FF01 GG04 HH02                       KK05 MM02 MM12

Claims (4)

[Claims] 1. A latent image formed on a photoconductor by an electrophotographic method is developed with toner, the toner image on the photoconductor is transferred onto a transfer material, and then heated and pressed by a heating and pressure fixing device. In the image forming apparatus for forming an image on the transfer material, at least two heating heaters for heating the heating / pressurizing roller provided in the heating / pressurizing fixing device are provided, and A heating pressure roller temperature detecting means for detecting the temperature of the pressure roller, and a roller heating heater control of the heating heater of the heating pressure fixing device based on the temperature signal detected by the temperature detecting means of the heating pressure roller. Means for driving the heating heater to adjust the temperature of the heating / pressurizing roller to a specified temperature, and the roller heating heater control means for the at least two heating heaters. A phase control means for controlling the phase of the power supply for preheating each heater when driving the heater, and based on the control result by the roller temperature adjusting means, the at least two When a situation occurs in which at least two or more of the above heaters are simultaneously driven, the phase control means performs the phase control on only one of the at least two or more heaters. An image forming apparatus comprising: 2. The heating / pressurizing roller provided in the heating / pressurizing fixing device according to claim 1, wherein the heating / pressurizing roller has a pair of upper and lower portions sandwiching a transfer material, and each heating / pressurizing roller is independently heated. An image forming apparatus comprising a heater. 3. The image forming apparatus according to claim 2, wherein the heating means provided in the heating / pressurizing roller independently adjusts the temperature so that each roller reaches the specified temperature. . 4. The phase control means in the roller heating heater control means according to claim 1, wherein the electric power conduction angle to the heater is reduced for a certain period with reference to the zero cross timing of the commercial power source. A characteristic image forming apparatus.