JP2000098794A - Image fixing controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute highly accurate fixing temperature control by suppressing the excessive rise of fixing temperature due to the successive passing of paper and the passing of the paper of a small size, and also stabilizing controlled temperature at the time of switching the feeding speed to a low speed when passing the paper. SOLUTION: A fixing part 11 is provided with a heat roller 13, a pressure roller 14, a cleaning roller 17 and a thermistor 18 at the outside of the heat roller 13. A controlling part 21 fetches the signal of the number of sheets of the passing paper and suppresses the excessive rise of the fixing temperature due to the successive passing of the paper, especially at both end parts of the heat roller 13 by current control from a heater driving part 22 to the heat roller 13 based on pulse width modulation control by a pulse width corresponding to the number of sheets of the passing paper. Also at the time of passing the paper of the small size and lowering the feeding speed of the paper, energizing of the heat roller 13 is controlled based on the pulse width modulation control.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a laser printer,
The present invention relates to an image fixing control device for controlling a fixing temperature of a toner image or the like in an electronic copying apparatus or the like, and in particular, to an image in which a heater provided in a heat roller is energized by controlling a fixing temperature by pulse width modulation (PWM). The present invention relates to a fixing control device.

[0002]

2. Description of the Related Art Conventionally, in an electronic copying apparatus or the like, in order to form a high quality image, a heater provided in a heat roller is turned on / off to control the image fixing temperature. This on / off control is described in JP-A-6-3 / 1994.
The example disclosed in JP 08855 is well known. In this example, the temperature detecting elements are arranged at two places of the high temperature part and the low temperature part of the heat roller, and when the temperature of the low temperature part rises and becomes stable, the control reference temperature is switched, and the low temperature part is switched. Insufficient fixing and fixing trouble due to excessive temperature are prevented.

In this example, although the occurrence of a fixing failure due to insufficient fixing at a low temperature or an excessive temperature can be prevented, the fixing state fluctuates depending on a sheet passing state. For example, the fixing temperature fluctuates depending on the sheet size of the sheet passing, the continuous (sheet number) state of the sheet passing, the state of overshoot or heat dissipation. When a small paper size is continuously passed with respect to the maximum paper size, only the ends of the heat roller (portions where the small paper size does not come into contact with the heat roller when the paper is passed) increase in temperature. In other words, it is not possible to control the fixing temperature accurately corresponding to the paper passing state.

[0004]

As described above, in the above-mentioned conventional example, there is a problem that it is difficult to control the fixing temperature accurately in correspondence with the paper passing state.

SUMMARY OF THE INVENTION The present invention solves such a problem in the prior art, and suppresses an excessive increase in the fixing temperature due to continuous paper passing and small-sized paper passing.
It is an object of the present invention to provide an image fixing control device capable of stabilizing a fixing temperature when a sheet feeding speed is switched to a low speed and performing high-precision temperature control.

[0006]

According to a first aspect of the present invention, a sheet on which an image generated in an electrostatic image forming process is transferred is heated and fixed by a heat roller. An image fixing control device that controls the fixing temperature of the heat roller, and when the number of passed sheets reaches a predetermined specified value, the heat roller is intermittently controlled by pulse width modulation control corresponding to the specified value. And a fixing control means for supplying power to the power supply.

According to the first aspect of the present invention, when the fixing temperature due to continuous paper passing is excessively increased, for example, the number of paper passing is divided step by step, and the number of paper passing at this stage is reduced. The current is suppressed by energization based on the pulse width modulation control by the corresponding pulse width, and high-precision fixing temperature control becomes possible.

According to a second aspect of the present invention, when a sheet on which an image generated by an electrostatic image forming process is transferred is heated by a heat roller to fix the image, the fixing temperature of the heat roller is controlled. An image fixing control device that includes a fixing control unit that intermittently energizes the heat roller by pulse width modulation control corresponding to the small sheet size when the sheet size of the sheet passing is smaller than the maximum sheet size. It is characterized by having.

According to the second aspect of the present invention, the excessive rise of the fixing temperature every time the paper size of the paper passing becomes smaller than the maximum paper size is caused by the pulse width modulation by the pulse width corresponding to each small paper size. It is suppressed by the energization based on the control, and high-precision fixing temperature control becomes possible.

Further, according to the third aspect of the present invention, when the transport speed of the paper at the time of paper passing is switched to a low value, the pulse width modulation control corresponding to the transport speed intermittently causes
It is characterized in that it has a fixing control means for supplying electricity to the heat roller.

According to the third aspect of the present invention, the excessive rise of the fixing temperature every time the paper transport speed is switched to low is based on the pulse width modulation control by the corresponding pulse width every time the transport speed is reduced. It is suppressed by the current flow, and high-precision fixing temperature control becomes possible.

[0012]

Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram illustrating a side configuration of an image forming apparatus to which an embodiment of the present invention is applied. In FIG. 1, the image forming apparatus is, for example, a laser printer or an electronic copying apparatus. The image forming apparatus is a paper feed cassette 1 in which sheets for copying are stored, and a pickup roller for sending out the sheets from the paper feed cassette 1. 2 and a belt-shaped photoreceptor 3 supported and driven by three rollers.

The image forming apparatus includes three rollers 4 for supporting and driving the photosensitive member 3, a transfer charger 5 for transferring a toner image obtained by developing the latent image on the photosensitive member 3 with toner, onto a conveyed sheet. A registration roller 6 for transporting the paper sent from the paper feed cassette 1 by the pickup roller 2 to the photoconductor 3 at a proper timing; a toner developing unit 7 for developing the latent image of the photoconductor 3 with toner; Charger 8 for uniformly charging the photosensitive member 3, a cleaning unit 9 for removing the residual toner on the photosensitive member 3 and removing the charged charges, and exposing the photosensitive member 3 to laser light L emitted from a laser light source (not shown). An optical writing unit 10 for forming an electrostatic latent image by pressing, and a fixing unit 11 for pressing the sheet onto which the toner image has been transferred and fixing the toner image by heat melting.

The fixing unit 11 includes a heat roller 13 having a heater 12 such as a halogen lamp therein, a pressure roller 14 that comes into contact with the heat roller 13 with pressure, and a discharge roller 15 that discharges fixed paper. And a paper discharge tray 16 for holding the paper from the discharge roller 15. Although the heat roller 13 has the heater 12 disposed inside, the same operation is performed in an example in which the entire heater is formed of a ceramic heater.

The image forming apparatus shown in FIG. 1 controls the entire apparatus, takes in a sheet passing number signal from a sheet passing detecting section for counting the number of sheets passing through the fixing section 11, and outputs a signal to a display panel (not shown). Is provided with a device control unit for controlling the display. The device control unit also performs control to capture a document size detection signal from a document detection unit that detects a size of a document placed on a document table (not shown) and display the signal on a display panel (not shown). Further, the device control unit executes control for switching the sheet conveying speed. The apparatus control unit executes various controls other than the control corresponding to the embodiment of the present invention, such as a laser printer, an electronic copying apparatus, and the like.

FIG. 2 is a cross-sectional / block diagram showing a configuration of an embodiment of the present invention, and FIG. 3 is a block diagram showing an electrical configuration thereof. 2, this embodiment has a heat roller 13 in contact with a pressure roller 14 in the fixing unit 11 of FIG. 1, and further has a cleaning roller 17 for cleaning the surface of the heat roller 13. Also, the fixing unit
It has a discharge roller 15 for discharging the paper on which the toner image has been fixed at 11. The heater 12 is provided inside the heat roller 13, and a thermistor 18 as a temperature detecting element for detecting a temperature is provided at a central portion outside the heat roller 13.

In this embodiment, the A / D converter 20 outputs a temperature detection signal obtained by sampling / quantizing (digital signal conversion) a detection signal indicating a temperature change of the thermistor 18.
And the heat roller 13 based on the temperature detection signal from here.
And a control unit 21 for controlling the surface temperature of the heat roller 13 to a set temperature when heating and pressing the sheet on which the toner image is transferred between the pressure roller 14 and a drive for setting the heater 12 to the set temperature. And a heater drive unit 22 for sending a signal (on / off signal) to the heater 12. This controlled surface temperature of the heat roller 13 is appropriately referred to as a fixing temperature.

In the electrical configuration of FIG.
Is connected to a power supply line at one end and the other end is connected to a resistor R1.
The connection point between the other end of the thermistor 18 and the resistor R1 is connected to the input terminal of the A / D converter 20. A voltage drop due to a change in the resistance value of the thermistor 18 due to a change in the temperature of the heater 12 (the divided voltage between the resistance value of the thermistor 18 and the resistor R1) is detected as a temperature change, and A
/ D converter 20 which outputs a temperature detection signal converted into a digital signal.

The control unit 21 includes a CPU 30 for executing control according to the present invention and a P / P having a different pulse width under the control of the CPU 30.
A PWM signal generating circuit 31 for generating a WM signal (duty signal); an OR gate 32 for performing an OR process on a PWM signal from the PWM signal generating circuit 31 and a duty control switching signal from the CPU 30; Signal and O
An AND gate 33 that sends a heater control output signal obtained by AND processing the logical value from the R gate 32 to the heater driving unit 22
And

The CPU 30 executes (1), (2), and (3) corresponding to the first, second, and third embodiments described below as control particularly corresponding to the present invention. (1) Excessive increase in the fixing temperature due to continuous paper passing is suppressed by energization based on pulse width modulation control based on a pulse width corresponding to the number of sheets passed, thereby enabling highly accurate fixing temperature control. (2) An excessive rise in the fixing temperature every time the paper size of the paper passing becomes smaller is suppressed by energization based on pulse width modulation control by a pulse width corresponding to each smaller paper size,
Enables highly accurate fixing temperature control. (3) Excessive increase in the fixing temperature every time the paper transport speed is switched low is suppressed by energization based on pulse width modulation control by a corresponding pulse width every time the transport speed is reduced, and the high-precision fixing temperature Enable control.

The CPU 30 is provided in the fixing unit 11 and the like.
A sheet passing number signal obtained by counting the number of sheet passing detected by an optical counter (light emitting element / light receiving element) not shown is input. Also, the CPU 30 receives a document size detection signal obtained by detecting the paper size (for example, the paper size of B5, A4, B4) sent from the paper feed cassette 1 with a photodetector (light emitting element / light receiving element) or the like. Is done. Further, the CPU 30
Is supplied with a paper transport speed switching signal when the transport speed of the paper is changed by switching the operation mode.

The heater driving section 22 supplies a heater power supply 40 for supplying AC power to the heater 12 and an electric power supply from the heater power supply 40 for setting the heater 12 to a set temperature in response to a heater control signal from the control section 21. And a power supply control circuit 41 using a relay for turning on / off.

Next, the operation of this embodiment will be described. First, the general operation of the image forming apparatus shown in FIG. 1 will be described. The photoconductor 3 is uniformly charged by the charging charger 8 and moves in the direction of the arrow. The optical writing unit 10 converts the original into XY
It is driven based on an image signal scanned and read out by a CCD or the like, and forms a latent image on the photoconductor 3 by the laser beam L. The latent image is developed with toner by a toner developing unit 7, and the toner image is transferred by a transfer charger 5 to a sheet being conveyed at a timing by a registration roller 6.

After the toner is transferred to the paper, the photosensitive member 3
After the residual toner is removed by the cleaning unit 9, the residual charge is removed. Further, the photoconductor 3 is charged by the charging charger 8 so as to form the next latent image. Further, the sheet on which the toner image has been transferred by the photoconductor 3 is conveyed to the fixing unit 11, heated and pressed between the heat roller 13 and the pressure roller 14, and the discharge roller is fixed after the transfer image is fixed. The paper is discharged onto a paper discharge tray 16 at 15.

Next, an outline of the control of the fixing temperature of the heat roller 13 when heating and pressing the sheet on which the toner image has been transferred between the heat roller 13 and the pressure roller 14 will be described. The fixing temperature is controlled by turning on / off the power supply to the heater 12.
When the power supply is turned off, the temperature is controlled to the set temperature by the energization / non-energization time interval (particularly, the energization time interval control by the PWM control in the first to third embodiments described in detail below). For example, 180 degrees is a common set temperature.

FIG. 4 is a flowchart showing a schematic processing procedure of fixing temperature control. 1 to 4, the control unit 21 takes in a temperature detection signal from the thermistor 18 provided at the center outside the heat roller 13 through the A / D converter 20 (step S41). The control unit 21 compares the detected value Tc of the received temperature detection signal with the control value Td (corresponding to the current fixing temperature) currently sent to the heater driving unit 22 (step S42).

In this comparison, if the control value Td is smaller than the detected value Tc (No), that is, if the fixing temperature of the heater 12 is lower than the set temperature, the control unit 21 causes the heater drive unit 22 to supply power to the heater 12. A control value Td to be turned on (ON) is set (step S43). If the control value Td is larger than the detection value Tc in the comparison in step S42 (Yes), that is, if the fixing temperature of the heater 12 is higher than the set temperature, the control unit 21 sends the heater driving unit 22 Turn off the power (O
The control value Td to be set to FF) is set (step S44).

Next, fixing temperature control by PWM control will be described. FIG. 5 is a flowchart showing a temperature control processing procedure in the operation of the first embodiment of the present invention.
FIG. 6 is a timing chart for explaining fixing temperature control by PWM control. In the first embodiment, the PWM is controlled so as to suppress an excessive increase in the fixing temperature due to continuous paper passing.
The fixing temperature is controlled by the control.

In FIGS. 1 to 3, 5 and 6, the CPU 30 in the control unit 21 shown in FIG. 3 takes in a signal of the number of sheets passed (page counter) and counts the number of prints from the start of the sheet passing ( Step S51). This count value P
In step 1, the heater drive unit 22 is controlled by the control of the control unit 21, and the heater 12 is continuously energized from there. With this continuous energization, the fixing temperature of the heater 12 rises. For this reason, the control unit 21 performs the fixing temperature control by the PWM control (duty control) on the heater driving unit 22 so as to suppress the excessive rise of the fixing temperature. The specified value S1 and the count value P1, which are the count values of the number of sheets to be subjected to the duty switching, are continuously taken in each time the number of passed sheets is counted, and the CPU 30 compares each of the taken-in numbers to determine S1 ≦ P1 ( Steps S52 and S53).

In this operation, the page counter is incremented until S1 ≦ P1 (step S5).
4), the CPU 30 controls the PWM signal generation circuit 31 as shown in FIG. 6 (a), and the duty signal (PW
M signal) is output by the PWM signal generation circuit 31. That is, during S1 ≦ P1, a low (L) level duty control switching signal shown in FIG. 6C is transmitted, and the CPU 30 sends the heater control signal shown in FIG. Then, a low (L) level heater control output signal during the "normal control time" shown in FIG. 6D is output to the power supply control circuit 41 of the heater drive unit 22 through the OR gate 32 and the AND gate 33. The power supply control circuit 41 of the heater drive unit 22 is turned on, and the heater power supply 40 continuously supplies power to the heater 12.

When the CPU 30 determines that S1.ltoreq.P1, the duty control switching signal shown in FIG. 6C is set to the high (H) level, and the CPU 30 sets the duty control switching signal shown in FIG. L) A heater control signal of a level is sent to one of the AND gates 33. Then, the PWM is supplied to the power supply control circuit 41 of the heater driving unit 22 through the OR gate 32 and the AND gate 33.
The duty signal (PWM signal) from the signal generation circuit 31 is supplied to the power supply control circuit 41 of the heater drive unit 22 by “d” shown in FIG.
is output as a heater control output signal during the “uty control time”. The power supply control circuit 41 of the heater drive unit 22 is turned on intermittently by the duty signal (PWM signal),
The heater 12 is intermittently energized from the heater power supply 40, and this d
The fixing temperature is controlled to correspond to the Uty signal (PWM signal) (step S55).

In the first embodiment, the count value P1 is fetched continuously, and S1 ≦ P1 is determined based on one specified value S1, but the number of sheets passed (page counter) is gradually increased. For example, each time the number of passed sheets increases, the number of sheets is divided into three steps (for example, three steps of 5 to 30 sheets / 31 to 50 sheets / 51 to 70 or more), and a specified value S1 different for each of the divided count values P1. (3 steps), and the CP is set so that the pulse width of the PWM signal is gradually reduced in each step.
When U controls the PWM signal generation circuit 31, higher-precision fixing control becomes possible. That is, when the number of passed sheets increases, the temperature of the heat roller 13, particularly at both ends, tends to be excessively high. Therefore, as the number of passed sheets increases stepwise, the pulse width of the PWM signal is gradually reduced to shorten the energizing time. .

As described above, in the first embodiment, an excessive rise in the fixing temperature due to continuous paper passing is suppressed by the PWM control, and the fixing temperature can be controlled with high precision, and as a result, a high quality toner can be obtained. An image is formed.

FIG. 7 is a flowchart showing a temperature control processing procedure in the operation of the second embodiment of the present invention. In the second embodiment, the fixing temperature is controlled by the PWM control so that the fixing temperature is not excessively increased when the sheet size to be fixed is smaller than the maximum size sheet. In this case, the fixing temperature control by the continuous paper passing in the first embodiment is corrected by the detected sheet size (a sheet size smaller than the maximum sheet size), and the fixing temperature control by the PWM control is performed.

1 to 3, 6 and 7, the CPU 30 in the control unit 21 shown in FIG. 3 initially executes the same processing as in the first embodiment. That is, the number of prints from the start of sheet passing is counted (step S71). At this count value P1, the heater drive unit 22 is controlled by the control of the control unit 21, and the heater 12 is continuously energized from there. Since the fixing temperature of the heater 12 is increased by the continuous energization, the fixing temperature is controlled by PWM control (duty control). The CPU 30 compares the specified value S1 and the count value P1 in the count value of the number of sheets to be subjected to the duty switching every time the count value of the number of passed sheets is fetched, and determines S1 ≦ P1 (steps S72 and S73).

In this operation, the page counter is incremented until S1 ≦ P1 (step S7).
4), the CPU 30 controls the PWM signal generating circuit 31 as shown in FIG.
A signal (PWM signal) is output. During S1 ≦ P1, a low (L) level duty control switching signal shown in FIG. 6C is transmitted, and the CPU 30 sends a heater control signal shown in FIG. 6B to one of the AND gates 33. I do. And
Heater drive unit through OR gate 32 and AND gate 33
The "normal control time" shown in FIG.
, A low (L) level heater control output signal is output. The power supply control circuit 41 of the heater drive unit 22 is turned on by the heater control output signal, and the heater 12 is continuously energized from the heater power supply 40.

When the CPU 30 determines that S1.ltoreq.P1, it fetches a document size detection signal. Here, when the paper size to be fixed is smaller than the maximum size paper, its PWM is controlled so as to suppress an excessive rise in the fixing temperature.
The fixing temperature is controlled by the control. In this case, the fixing temperature control by the continuous paper passing in the first embodiment is corrected based on the paper size (the paper size smaller than the maximum paper size) to be passed, and the fixing temperature control by the PWM control is performed (step). S75).

The duty control switching signal shown in FIG. 6C is set to the high (H) level, and the CPU 30 sends the low (L) level heater control signal shown in FIG.
To one of them. Then, PW is supplied to the power supply control circuit 41 of the heater drive unit 22 through the OR gate 32 and the AND gate 33.
Duty signal (PWM signal) from M signal generation circuit 31
Is output as a heater control output signal during the “duty control time” as shown in FIG. This duty
The power supply control circuit 41 of the heater drive unit 22 is turned on intermittently by a signal (PWM signal), and the heater power supply 40
Power is supplied intermittently to the fixing temperature 12 so that the fixing temperature corresponding to the duty signal (PWM signal) is controlled (step S7).
6).

In the second embodiment, following the fixing temperature control similar to that of the first embodiment, if the size of the sheet to be fixed is smaller than the maximum size sheet, the fixing temperature is not excessively increased. However, the same fixing temperature control as in the first embodiment may not be performed. That is, when the CPU recognizes that the paper passing is smaller than the maximum size paper by the paper size detection signal to be fixed at the start of the operation,
Immediately, the fixing temperature is controlled by the PWM control.

Further, in the second embodiment, when the paper size is smaller than the maximum size paper, one-stage control is performed to prevent the fixing temperature from excessively increasing.
In the case of a plurality of paper sizes smaller than the maximum size paper, when the CPU controls the PWM signal generation circuit 31 so as to gradually reduce the pulse width of the PWM signal in a stepwise manner for each of the smaller paper sizes, higher accuracy can be achieved. Fixing control becomes possible. That is, in the case of a smaller paper size, the heat roller 13, especially at both ends, is likely to be overheated.
The pulse width of the PWM signal is sequentially reduced for each small sheet size to shorten the energization time.

As described above, in the second embodiment, an excessive rise in the fixing temperature due to the passage of a small sheet size is suppressed, and the fixing temperature can be controlled with high accuracy, and the high quality toner image is formed. Is done.

FIG. 8 is a flowchart showing a temperature control processing procedure in the operation of the third embodiment corresponding to the present invention. In the third embodiment, the temperature control by the PWM control is performed so that the fixing temperature at the time of changing the sheet conveying speed at the time of sheet passing is low is stabilized. In FIGS. 1 to 3, 6 and 8, the CPU 30 takes in a paper transport speed switching signal when the transport speed of the paper is changed by switching the operation mode (step S81). Next, it is determined whether or not the sheet transport speed switching signal is a low-temperature operation mode for reducing the speed (step S82). If it is not the low-temperature operation mode (No), the process ends. In this case, the heater driving unit 22 is controlled by the control of the control unit 21, and the heater 12 is continuously energized from here. Since the fixing temperature of the heater 12 is increased by the continuous energization, the fixing temperature is controlled by PWM control (duty control).

In this case, a low (L) level duty control switching signal shown in FIG. 6C is sent, and the CPU 30 sends a heater control signal shown in FIG. 6B to one of the AND gates 33. Then, a low (L) level heater control output signal during the normal control time shown in FIG. 6D is output to the power supply control circuit 41 of the heater drive unit 22 through the OR gate 32 and the AND gate 33. Power supply control circuit 41 of heater drive unit 22
Is turned on, and power is continuously supplied to the heater 12 from the heater power supply 40.

If it is determined in step S82 that the operation mode is the low-temperature operation mode (Yes), the fixing temperature is controlled by the PWM control so as to suppress an excessive rise in the fixing temperature. The duty control switching signal shown in FIG. 6C is set to a high (H) level, and the CPU 30 sends a low (L) level heater control signal shown in FIG. 6B to one of the AND gates 33. .

Further, the signal is output to the power supply control circuit 41 of the heater drive unit 22 through the OR gate 32 and the AND gate 33 as a heater control output signal in the "duty control time" shown in FIG. The power supply control circuit 41 of the heater driving unit 22 is turned on intermittently by the duty signal (PWM signal), and the heater 12 is intermittently energized from the heater power supply 40.
The fixing temperature is controlled to correspond to the duty signal (PWM signal) (step S83).

In the third embodiment, one-step control is performed to prevent the fixing temperature from excessively increasing when the sheet conveyance speed is reduced. In the case where the lowering is performed, if the CPU controls the PWM signal generating circuit 31 so that the pulse width of the PWM signal is gradually reduced at each stage, more accurate fixing control becomes possible. That is, in the case of paper passing at a lower speed, since the temperature at both ends of the heat roller 13 is likely to be excessive, the pulse width of the PWM signal is sequentially reduced for each low-speed paper passing to shorten the energizing time.

As described above, in the third embodiment, an excessive increase in the fixing temperature when the sheet conveyance speed at the time of sheet passing is switched to a low speed is suppressed by the PWM control, and a high-precision fixing temperature control is performed. And the high quality toner image is formed.

[0048]

As is apparent from the above description, according to the first aspect of the present invention, an excessive rise in the fixing temperature due to continuous paper passing is caused by a pulse width corresponding to the pulse width corresponding to each increase in the number of sheets passed. The current is suppressed by the power supply based on the modulation control, so that the fixing temperature can be controlled with high accuracy. As a result, a high-quality toner image can be formed.

According to the second aspect of the present invention, the excessive increase in the fixing temperature every time the sheet size of the sheet passing becomes smaller than the maximum sheet size is caused by the pulse width corresponding to the pulse width corresponding to each small sheet size. The current is suppressed by the power supply based on the modulation control, and the fixing temperature can be controlled with high accuracy, and as a result, a high-quality toner image can be formed.

Further, according to the third aspect of the present invention, the excessive rise of the fixing temperature every time the paper transport speed is switched to the low speed is controlled by the pulse width modulation control by the corresponding pulse width every time the transport speed is lowered. Based on the power supply based on this, the fixing temperature can be controlled with high precision, and as a result, a high quality toner image can be formed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a side configuration of an image forming apparatus to which an embodiment of the present invention is applied.

FIG. 2 is a cross-sectional / block diagram showing a configuration of an embodiment of the present invention.

FIG. 3 is a block diagram showing an electrical configuration of the embodiment of the present invention shown in FIG.

FIG. 4 is a flowchart showing a processing procedure of heater temperature control in the embodiment.

FIG. 5 is a flowchart illustrating a processing procedure of temperature control according to the first embodiment of the present invention.

FIG. 6 is a timing chart for explaining fixing temperature control by a PWM method in the embodiment.

FIG. 7 is a flowchart illustrating a processing procedure of temperature control according to a second embodiment of the present invention.

FIG. 8 is a flowchart illustrating a processing procedure of temperature control according to a third embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 3 photoreceptor 5 transfer charger 6 registration roller 7 toner developing unit 8 charging charger 9 cleaning unit 11 fixing unit 12 heater 13 heat roller 18 thermistor 20 A / D converter 21 control unit 22 heater driving unit 30 CPU 31 PWM signal generation circuit 32 OR gate 33 AND gate 40 Heater power supply 41 Power supply control circuit

Claims (3)

[Claims] An image fixing control device for controlling a fixing temperature of a heat roller when heating and fixing a sheet on which an image generated by an electrostatic image forming process is transferred by a heat roller. An image fixing control device comprising: a fixing control unit that, when a predetermined value reaches a predetermined value, intermittently supplies current to the heat roller by pulse width modulation control corresponding to the predetermined value. 2. An image fixing control device for controlling a fixing temperature of a heat roller when a sheet on which an image generated in an electrostatic image forming process is transferred is heated by a heat roller to fix the image. When the paper size of the paper is smaller than the maximum paper size, a fixing control means for intermittently energizing the heat roller by pulse width modulation control corresponding to the small paper size is provided. Control device. 3. An image fixing control device for controlling a fixing temperature of a heat roller when a sheet on which an image generated in an electrostatic image forming process is transferred is heated by a heat roller to fix the image. An image fixing control comprising a fixing control means for intermittently energizing the heat roller by pulse width modulation control corresponding to the conveying speed when the conveying speed of the paper is switched to a low speed. apparatus.