JP3123291B2 - Fixing device temperature control device of image forming apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device temperature control device for an image forming apparatus, and more particularly, to a fixing process in image formation immediately after completion of a warm-up after turning on a power supply, and an image after a relatively long image forming operation pause. The present invention relates to a fixing device temperature control device of an image forming apparatus that does not cause a fixing defect in a fixing process in forming.

[0002]

2. Description of the Related Art In an image forming apparatus of an electrophotographic system, a fixing device of a roller system is widely used for fixing a formed toner image. This type of fixing device has two rows
The upper roller is a heating roller consisting of a metal roller with good heat conduction and small heat capacity, and the lower roller applies pressure evenly to the recording material with a wide contact surface. Rubber with a suitable material covered with rubber on the surface.
A pressure roller made of a rubber is used. The heating roller has a heater lamp inside, and the surface temperature is detected by a thermistor or the like to control the temperature so as to be within a predetermined fixing temperature range. Those without a tar are common.

[0003] In the above-mentioned fixing device of the roller type,
Since the heater lamp is energized when the power is turned on, the heating roller reaches the predetermined fixing temperature in a short time, but the pressure roller requires a long time to reach the predetermined fixing temperature. And
In particular, there are cases where the portion in contact with the heating roller reaches the fixing temperature but the other portions do not reach the fixing temperature.

For this reason, when it is determined that the surface temperature of the heating roller detected by a thermistor or the like has reached a predetermined fixing temperature and the printing operation is started, the heating roller and the pressure roller are started. With the contact rotation of, the heat of the heating roller is taken by the pressure roller, and the surface temperature of the heating roller falls below the fixing temperature.
Fixing failure will occur.

[0005] To solve this inconvenience, several methods have already been proposed. The first method is a method in which the heating roller and the pressure roller are preliminarily rotated before the start of the printing operation, and heat is applied to the pressure roller in advance.

[0006] In addition, the following three methods have been proposed as methods that do not perform preliminary rotation. In the first method, a heating lamp and a temperature detecting means are provided also in the pressure roller, and the heating roller and the pressure roller are set to a predetermined fixing temperature range before the printing operation is started. How to keep it.

In the second method, at the start of a printing operation, a fixing temperature higher than a normal fixing temperature is set on a heating roller to execute a fixing process, and printing after the printing operation is started. In this method, the number of sheets is counted, and after the number of sheets reaches a predetermined number, the temperature of the heating roller is returned to the normal fixing temperature to continue the fixing process (Japanese Patent Laid-Open No. 52-389).
No. 38).

A third method is to heat the heating roller to a temperature higher than a normal fixing temperature for a fixed time from the start of the printing operation.

[0009]

Although the above-described solving means can solve the above-mentioned disadvantages, the following new disadvantages arise. That is, in the method in which the heating roller and the pressure roller are preliminarily rotated, a time for a predetermined preliminary rotation after turning on the power is required, and the rise time is long.

[0010] Further, in the first method in which the pre-rotation of the heating roller and the pressure roller is not performed, the number of parts of the apparatus increases, resulting in an increase in cost.

According to the above-mentioned second method in which the pre-rotation of the heating roller and the pressurizing roller is not performed, no particular inconvenience occurs in the printing operation of the predetermined number or more, but the printing operation of the predetermined number or less is interrupted. The following inconveniences occur when performing the operation in a proper manner.

In other words, in the configuration in which the number of prints is newly started each time the print button is pressed, if the printing operation of a predetermined number or less is repeatedly performed in a short time, the fixing temperature is higher than the normal fixing temperature each time. Because the temperature is set,
The temperature inside the machine and the temperature of the roller gradually rises abnormally.

Further, in the configuration in which the number of prints is accumulated and counted, there is no particular problem when the interval between print operations to be repeatedly performed is sufficiently long, but when the print operation is repeatedly performed in a short time. In this case, the temperature inside the machine and the temperature of the rollers rise abnormally. For example, if it is assumed that a high fixing temperature is set until four sheets are printed, there is no problem when four sheets are printed one by one at a sufficient time interval. When a sheet is printed, a high fixing temperature is set during this time, so that the in-machine temperature and the roller temperature rise abnormally.

Further, in the third method in which the heating roller is heated to a normal fixing temperature or higher for a certain period of time from the start of the printing operation, when the printing operation within the above-mentioned predetermined period is repeatedly executed, each printing is performed. Since the fixing process is performed at a temperature higher than the normal fixing temperature each time the operation is performed, the inside temperature and the temperature of the roller gradually increase abnormally. An object of the present invention is to solve the above-mentioned disadvantages.

[0015]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems. According to the first aspect of the present invention, there is provided a heating roller having a built-in heating element, a pressure roller pressed against the heating roller, and an intermittent heat roller. A timer for counting the cumulative time after turning on the power of the heating roller rotation time during the image forming operation that is repeatedly performed, and the cumulative time measured by the timer is set in advance.
Until the specified value is reached, the heating roller is
At the time of image formation
To maintain a higher temperature than during non-image formation.
And temperature control means for controlling the temperature .

According to the second aspect of the present invention, a heating roller having a built-in heating element, a pressure roller which presses against the heating roller, and an image forming operation pause time in an intermittently repeated image forming operation are measured. A first timer that measures the cumulative time of the rotation time of the heating roller during an image forming operation that is intermittently repeated, and the first timer
The image forming operation pause time measured in the step exceeds the first predetermined value.
When the timer has been set, the timer starts counting by the second timer,
The accumulated time measured by the second timer is set in advance.
Until the specified value is reached, the heating roller is
Maintain a temperature that allows fixing during image formation, and
Maintain a higher temperature during cropping than during non-image formation
Temperature control means for controlling the temperature as described above .

[0017]

According to the first aspect of the present invention, the temperature control means includes :
During intermittently repeated image forming operations
The cumulative time after turning on the power of the heating roller rotation time is set in advance.
Until the specified value is reached, the heating roller is
At the time of image formation
To maintain a higher temperature than during non-image formation.
Temperature control. As a result, the pressure roller is not sufficiently warmed as in the start-up of the image forming apparatus , and the temperature is reduced.
Even when the temperature is low, no fixing failure occurs.

According to the second aspect of the present invention, the temperature control means is configured to stop the image forming operation measured by the first timer.
Intermittently with the second timer when the time exceeds the first predetermined value
Of heating roller rotation time during image forming operation repeated
Start timing of accumulated time, measured by second timer
Until the cumulative time reaches the preset value, heating
Roller temperature to a temperature that can be fixed during non-image formation
Maintained during image forming operation than during non-image forming.
Control temperature to maintain high temperature. This allows
Even when the image forming operation has been suspended for a long time and the temperature of the pressure roller has dropped , no fixing failure occurs in the restarted image forming operation .

In any one of the first and second aspects of the present invention, after the accumulated time of the rotation time of the heating roller reaches a predetermined value, the heating roller is set to the first fixing temperature at the normal fixing temperature. Is maintained at the predetermined set temperature, there is no possibility that the temperature inside the apparatus and the temperature of the heating roller and the pressure roller rise abnormally.

[0020]

Embodiments of the present invention will be described below.
FIG. 1 is a sectional view schematically illustrating the configuration of a laser printer embodying the present invention. In FIG. 1, 1 is a photosensitive drum, 2 is a semiconductor laser oscillator, 3 is a polygon mirror, 3a is a polygon mirror driving motor, 4 is a reflection mirror, 5 is a charging brush, and 6 is a developing device. , 7 is a transfer roller, 8
Denotes a cleaning blade, 9 denotes a paper feed roller, and 10 denotes a paper feed sensor. Reference numeral 11 denotes a fixing device, and a heating roller 12
And a pressure roller 13. 14 is a paper ejection sensor, 1
Reference numeral 5 denotes a paper discharge roller. The CP is a recording paper, which may be stored in a known paper feeding cassette or may be fed from a manual paper feeding port.

The operation of the above configuration will be briefly described. First, the surface of the photosensitive drum 1 is charged to a predetermined potential by the charging brush 5. Laser light modulated by the image signal emitted from the semiconductor laser oscillator 2 is scanned in the main scanning direction by the polygon mirror-3, reflected by the reflection mirror-4, and incident on the photosensitive drum 1. The scanning in the sub-scanning direction is performed by the rotation of the photosensitive drum 1 in the direction of arrow a.
A latent image of the image is formed thereon. The latent image is developed by the developing device 6 to form a toner image.

On the other hand, the paper feed roller 9 is operated by a paper feed command to feed the recording paper CP, and the toner on the photosensitive drum 1 is turned on.
The image is conveyed to the transfer position at the timing when the image comes to the transfer position. Since a bias potential having a polarity opposite to that of the toner image on the photosensitive drum 1 is applied to the transfer roller, the toner image on the photosensitive drum 1 is transferred to the recording paper CP. Recording paper C
The toner image transferred to P is fixed by the fixing device 11 and is discharged out of the apparatus by the discharge roller 15.

FIG. 2 shows a heating roller 1 constituting the fixing device 11.
2 and FIG. 3 are longitudinal sectional views of the pressure roller 13 and FIG. 2 and 3, reference numeral 12 denotes a heating roller. The roller body is composed of a metal tube 12a made of a material such as aluminum having a good heat conduction and a small heat capacity. It is coated with easy and heat resistant Teflon (trade name).

The heating roller 12 has a heater inside.
A lamp 21 is provided, and an engine control C described later is provided.
It is heated to a predetermined temperature by electric power supplied under temperature control by the PU. The surface temperature of the heating roller 12 is
Temperature sensor 2 such as a thermistor arranged in contact with the surface
2 and a detection signal is output from an engine control C to be described later.
It is input to PU34.

Reference numeral 13 denotes a pressure roller, which has an elastic silicon rubber 13 on the surface of a core material 13b made of an appropriate material so that a pressure can be applied evenly to the recording material over a wide contact surface.
a, and the surface may be coated with Teflon (trade name) if necessary.

The heating roller 12 and the pressure roller 13 are rotatably supported in a state in which they are in contact with each other, and are heated by a suitable transmission mechanism such as a chain motor from a main motor (not shown). The pressure roller 13 is driven by driving the pressure roller 13.
Also rotates following the heating roller 12.

The recording paper CP on which the toner image is formed passes between the heating roller 12 and the pressure roller 13 with the surface (front surface) on which the toner image is located on the heating roller 12 side. Then, the toner is melted by the heat of the heating roller 12 and pressed against the recording paper CP by the pressure roller 13 to complete the fixing.

FIG. 4 is a circuit block diagram of a control circuit of a laser printer, showing components related to the present invention. 31 is a host computer, 32 is a printer controller, 33 is an operation panel, 34 is an engine control CPU that controls each part of the printer based on instructions from the printer controller. -T3
5. A transport control unit 36 for controlling the feeding of the recording paper, a scanner control unit 37 for controlling the scanning by the polygon mirror, and a high voltage for controlling the high voltage such as charging the photosensitive drum, applying a developing bias, and applying a transfer bias. A control unit 38, a laser control unit 39 for performing modulation control of laser light, a heater lamp 21,
The temperature sensor 22, the paper feed sensor 10, the paper discharge sensor 14, and the like are connected.

From the operation panel 33, printer control information such as recording paper size and the like is input to the printer controller 32. The printer controller 32 is a host computer.
When a print request signal is received from the data
A print command is output to U34. Thus, the engine control CPU 34 instructs the conveyance control unit 36 to start feeding paper, instructs the scanner control unit 37 to prepare for scanning, and charges the photosensitive drum via the high-voltage control unit 38, develops a bias, and transfers a transfer bias. And prepare for printing.

Further, a vertical synchronization request signal is output to the printer controller 32 to wait for reception of the vertical synchronization signal. When the vertical synchronization signal is output, the host controller 31 sends the printer controller 32 to the printer controller 32. The laser light is modulated on the basis of the image signal input to the laser control unit 39 via the laser controller 39, and a latent image of an image is formed on the photosensitive drum 1. The formed latent image is developed by the developing device 6, transferred to the recording paper CP, and the temperature of the fixing device 1 is controlled by the engine control CPU 34.
The toner is fixed at 1 and discharged.

Hereinafter, the temperature control of the fixing unit 11 by the engine control CPU 34, which is a feature of the present invention, will be described.

FIG. 5 is a timing chart for explaining the temperature control of the fixing unit 11 executed by the engine control CPU 34. When the power is turned on, the engine control CPU
By 34, the heater lamp 21 in the heating roller 12 is turned on, and the heating roller 12 is heated. Heating row
When the surface temperature of the laser 12 reaches the first predetermined temperature J1 at which the toner can be melted, the engine control CPU 34 controls the heater to maintain the first predetermined temperature J1.
The lamp 21 is controlled on / off, and the printer control is performed.
Then, the process shifts to a standby state waiting for a print command from the printer 32.

When a print command is output from the printer controller 32, the main motor is turned on by the engine control CPU 34, and the execution of a printing operation by a predetermined electrophotographic process is started. At the same time, the surface temperature of the heating roller 12 is raised to a second predetermined temperature J2 higher than the first predetermined temperature J1, so that the second predetermined temperature J2 is maintained during rotation of the main motor. On / off control of the heater lamp 21 is performed. In addition, timer TM1
Thus, the measurement of the rotation time t1 of the main motor is started.

When the printing operation is completed, the main motor is turned off by the engine control CPU 34, and the heating roller is turned off.
The surface temperature of the lamp 12 is lowered to a first predetermined temperature J1, and the heater lamp 21 is turned on / off so as to maintain the first predetermined temperature J1. At the same time, the timer TM3 starts counting the print operation suspension time t3 from the end of the print operation to the output of the next print command.

Thereafter, every time a print command is output, the main motor is turned on, the surface temperature of the heating roller 12 is maintained at the second predetermined temperature J2, and the rotation of the main motor by the timer TM1. Every time the printing operation is completed, the main motor is turned off and the surface temperature of the heating roller 12 is reduced to the first predetermined temperature J1.
And the measurement of the print operation suspension time t3 by the timer TM3 is repeated.

In the process of repeating the above control processing, the rotation time of the main motor (same as the rotation time of the heating roller) t1 (t1a, t1b, t1c) measured by the timer TM1.
Is accumulated by the timer TM2. The accumulated time Ta is equal to a predetermined value K.
It is determined whether 1 has been exceeded. As a result, the accumulated time T
When a exceeds a predetermined value K1, the printing operation being executed at that time is terminated without any change.
Thereafter, when a print command is output, the print operation is executed while maintaining the surface temperature of the heating roller 12 at the first predetermined temperature J1.

On the other hand, the timer TM3 measures the print operation suspension time t3 (t3a, t3b, t3c, etc.), but it is determined whether or not the time t3 exceeds a predetermined value K2. As a result, the print operation suspension time t3 is set to the predetermined value K.
When the temperature exceeds 2, the subsequent printing operation based on the print command is executed by raising the surface temperature of the heating roller 12 to the second predetermined temperature J2 and maintaining the same. In this case, the timer TM2 for measuring the accumulated time Ta of the rotation time t1 of the main motor is reset, and the accumulated time T1 is newly set.
Timing of a is started.

In FIG. 5, the rotation times t1a, t1b, and t of the main motor in the first to third printing operations are shown.
Since the accumulated time Ta of 1c has exceeded the predetermined value K1, in the fourth printing operation, the surface temperature of the heating roller 12 becomes the first temperature.
At a predetermined temperature J1. Also,
In the fifth print operation, the print operation pause time t3d
Has exceeded the predetermined value K2, the surface temperature of the heating roller 12 is raised to the second predetermined temperature J2, and this indicates that the operation is being performed while maintaining this temperature.

In the fifth printing operation, a timer TM2 for counting the accumulated time of the rotation time t1 of the main motor.
Is reset and the counting of the accumulated time Ta is newly started, so that it is determined that the accumulated time Ta does not exceed the predetermined value K1 in the sixth printing operation, and the heating roller is also operated in the sixth printing operation. The surface temperature of No. 12 is raised to the second predetermined temperature J2, indicating that the operation is being performed while maintaining the same.

FIG. 6 is a flowchart for explaining the outline of the control operation executed by the engine control CPU 34.

First, the counters, timers, flags and the like are initialized (step P1). Next, the process waits until the printer is ready for operation (step P2), and waits for the output of a print command (step P3). When a print command is output, a print operation by an electrophotographic process is executed (step P4), a temperature control of the fixing unit is executed (step P5), and a timer management for managing operation times of various operation units of the apparatus. (Step P6) to determine the end of the printing operation (Step P7). If the printing operation has not been completed, return to Step P4 to continue the printing operation, and if the printing operation has been completed, perform the step. P
Return to step 2 and shift to the standby state.

FIG. 7 is a flowchart showing the details of the temperature control process of the fixing unit executed in step P5 of the flowchart shown in FIG. First, it is determined whether or not the content of the state counter that defines the processing order is 0 (step P).
11) If the contents of the counter are 0, the process proceeds to state 0.

First, the surface temperature T of the heating roller 12 becomes the first temperature.
It is determined whether the temperature is higher than the predetermined temperature J1.
If it is higher than 1, the heater lamp 21 is turned off, and if it is lower than the predetermined temperature J1, it is turned on (step P1).
2, P13, P14), control is performed to maintain the surface temperature of the heating roller 12 at the first predetermined temperature J1.

Next, it is checked whether or not the main motor has changed from OFF to ON, and the start of the printing operation is determined (step P15). If the print operation is not started, the main
Returning to the routine, if the printing operation is to be started, the timer TM3 for measuring the printing operation pause time t3 is stopped (step P16). If the print operation is started from the initial state, the content of the timer TM3 is 0.

Next, the state of the flag WUE is checked (step P17). The flag WUE is the same as the heating roller 12 described above.
A flag indicating a state of temperature control for raising and maintaining the surface temperature of the second surface to the second predetermined temperature J2. The flag is set when the temperature control is completed, and is in a reset state when the temperature control is continued. Also, when starting from an initial state, the flag WUE is reset.

If the flag WUE is reset in the judgment of step P17, the process proceeds to step P22 and thereafter. First, the content of the timer TM3 for measuring the print operation suspension time t3 is set to a value K indicating a predetermined time interval.
2 is determined (step P22), and if it is exceeded, the timer TM2 for measuring the accumulated time Ta of the rotation time t1 of the main motor is reset to 0 (step P22).
23). If the value does not exceed the value K2 in the judgment of step P22, step P23 is omitted.

Thus, after the printing operation suspension time exceeds the value K2 indicating the predetermined time interval, the surface temperature of the heating roller 12 is again raised to the second predetermined temperature J2, and the temperature control for maintaining the temperature is maintained. It can be carried out.

The process proceeds to the preparation process at the start of the printing operation.
First, the rotation time t1 of the main motor is determined by the timer TM1.
Is started (step P24), the timer TM3 is reset (step P25), the state counter is advanced to 2 (step P26), and the process returns to the main routine.

If the flag WUE is set in the judgment in step P17, the surface temperature of the heating roller 12 is set to the second temperature.
This means that the temperature control for raising and maintaining the predetermined temperature J2 has been completed, and the flow proceeds to the processing after step P18. First, it is determined whether or not the content of the timer TM3 has exceeded a value K2 indicating a predetermined time interval (step P18). If so, the surface temperature of the heating roller 12 is raised to a second predetermined temperature J2. The flag WUE is reset (step P19) to prepare for restarting the temperature control to be performed and maintained, and the routine goes to step P24 to prepare for starting the printing operation.

If it is determined in step P18 that the content of the timer TM3 does not exceed the value K2 indicating the predetermined time interval, temperature control for maintaining the surface temperature of the heating roller 12 at the first predetermined temperature J1 is performed. To do so, the timer TM3 is reset (step P20), the state counter is advanced to 1 (step P21), and the process returns to the main routine.

FIG. 8 is a continuation of the flowchart shown in FIG. If it is determined in step P11 of the flowchart shown in FIG. 7 that the state counter is not 0, step P11 is executed.
It moves to 31 and determines whether or not the state counter is 1.
If the content of the counter is 1, the processing shifts to state 1.

First, the surface temperature T of the heating roller 12 becomes the first temperature.
It is determined whether the temperature is higher than the predetermined temperature J1.
If it is higher than 1, the heater lamp 21 is turned off, and if it is lower than the predetermined temperature J1, it is turned on (step P3).
(2, P33, P34), control is performed to maintain the surface temperature of the heating roller 12 at the first predetermined temperature J1.

Next, it is determined whether or not the main motor has changed from ON to OFF, and the end of the printing operation is determined (step P35). If the printing operation has not been completed, the routine returns to the main routine. If the printing operation has been completed, the timer TM3 for counting the printing operation pause time t3 is started (step P36), and the state counter is reset to 0. (Step P37), and return to the main routine.

If it is determined in step P31 that the state counter is not 1, the surface temperature of the heating roller 11 is set to the second value.
Then, the process proceeds to the state 2 for executing the temperature control for raising and maintaining the predetermined temperature J2.

First, the surface temperature T of the heating roller 12 is set to the second
It is determined whether the temperature is higher than a predetermined temperature J2.
When the temperature is higher than the predetermined temperature J2, the heater lamp 21 is turned off. When the temperature is lower than the predetermined temperature J2, the heater lamp 21 is turned on (step P4).
1, P42, P43), control is performed to maintain the surface temperature of the heating roller 12 at the second predetermined temperature J2.

Next, it is determined whether or not the main motor has changed from ON to OFF, and the end of the printing operation is determined (step P44). If the printing operation is not completed, the operation returns to the main routine. If the printing operation is completed, the timer TM3 terminates the measurement of the rotation time t1 of the main motor by the timer TM1 and the timer TM3 which measures the printing operation suspension time t3. (Step P45), and the timer TM
The total time t2 of the main motor measured by the timer TM1 is added to the content t2 of 2 to obtain an accumulated time Ta (step P46).

It is determined whether or not the content of the timer TM2 is larger than a predetermined value K1 (step P4).
7) If it is larger than the predetermined value K1, the heating roller 2
The timer TM2 and the timer TM1 are reset to end the control for maintaining the first surface temperature at the second predetermined temperature J2 (step P48). Further, the flag WUE is set (step P49), the state counter is reset to 0 (step P50), and the process returns to the main routine.

If it is determined in step P47 that the content of the timer TM2 is smaller than the predetermined value K1, the heating roller 1
Since the control for maintaining the surface temperature of No. 2 at the second predetermined temperature J2 is continued, only the timer TM1 is reset (step P51), the state counter is reset to 0 (step P50), and the main loop is reset. Return to Chin.

FIG. 9 is a flowchart showing a second embodiment of the temperature control process of the fixing device, which is shown in FIGS. 7 and 8.
In the first embodiment shown in the flowchart, the processing after step P31 (after the state when the state counter is not 0) is different, so that the different part will be described below as the processing after step P61.

Step P1 of the flowchart shown in FIG.
If it is determined in step 1 that the state counter is not 0, FIG.
The procedure then moves to step P61 of the flowchart shown in FIG. First,
It is determined whether or not the state counter is 1 (step P6).
1) If the content of the counter is 1, the process proceeds to state 1;

It is determined whether or not the surface temperature T of the heating roller 12 is higher than the first predetermined temperature J1. If the surface temperature T is higher than the predetermined temperature J1, the heater lamp 21 is turned off, and the predetermined temperature J1 is set. If it is lower than this, it is turned on (steps P62 and P62).
63, P64), control is performed to maintain the surface temperature of the heating roller 12 at the first predetermined temperature J1.

Next, it is determined whether or not the main motor has changed from ON to OFF, and the end of the printing operation is determined (step P65). If the printing operation has not been completed, the routine returns to the main routine. If the printing operation has been completed, the timer TM3 for measuring the printing operation pause time t3 is started (step P66), and the state counter is reset to 0. (Step P67), and returns to the main routine.

If it is determined in step P61 that the state counter is not 1, the surface temperature of the heating roller 12 is changed to the second temperature.
Then, the process proceeds to the state 2 for executing the temperature control for raising and maintaining the predetermined temperature J2. First, it is determined whether or not the surface temperature T of the heating roller 12 is higher than a second predetermined temperature J2.
Is turned off, and when it is lower than the predetermined temperature J2, it is turned on (steps P71, P72, P73), and the heating roller 12 is turned off.
Is controlled to maintain the surface temperature at the second predetermined temperature J2.

Next, it is determined whether or not the accumulated time Ta of the rotation time of the main motor measured by the timer TM2 is larger than a predetermined value K1 (step P7).
4) If it is not larger than the predetermined value K1, it is checked whether the main motor has changed from ON to OFF, and the end of the printing operation is determined (step P75). If the printing operation has not been completed, the routine returns to the main routine. If the printing operation has been completed, the timer TM1 terminates the measurement of the rotation time t1 of the main motor (step P76), and sets the printing operation pause time t3. The timer TM3 starts counting time (step P77), and the content of the timer TM2 t
2 is added to the rotation time t1 of the main motor measured by the timer TM1 to obtain an accumulated time Ta (step P
78).

In this case, the accumulated time Ta of the rotation time of the main motor has not reached the predetermined value K1, and the heating roller 1
Since the control for maintaining the surface temperature of No. 2 at the second predetermined temperature J2 is continued, the timer TM1 is reset (step P79), the state counter is reset to 0 (step P80), and the main routine is executed. Return to

If it is determined in step P74 that the accumulated time Ta of the rotation time of the main motor is larger than the predetermined value K1, the surface temperature of the heating roller 12 is reduced to the second predetermined temperature J2.
In order to end the control to maintain the state, the timer TM2 and the timer TM1 are reset, the flag WUE is set (steps P81 and P82), the state counter is reset to 0 (step P80), and the process returns to the main routine. .

In the first embodiment of the temperature control of the fixing device described above, the set temperature is not changed during the printing operation (see step P44), so that the temperature of the heating roller fluctuates during the continuous printing operation. There is no possibility that the quality of the recorded image will change. In the second embodiment of the temperature control of the fixing unit, when it is considered that the pressure roller is already sufficiently heated by the continuous recording operation (see step P74), the second setting higher than the normal setting is performed. Since the temperature is not maintained, there is no risk that the heating roller will be too hot.

In the embodiment of the present invention described above, the heating roller and the pressure roller are rotated during the warm-up period until the surface temperature of the heating roller of the fixing device reaches a predetermined temperature. However, the present invention does not provide a fixing device in which the heating roller and the pressure roller rotate during the warm-up period, or the heating roller and the pressure roller during the warm-up period. The present invention can be applied to a fixing device configured to rotate intermittently. In the case of applying to such a fixing device, the rotation time of a heating roller and a pressure roller during a warm-up period is determined by a printing operation. Cumulative time Ta of the rotation time of the main motor at the time of
May be added.

[0069]

As described above, according to the first aspect of the present invention,
In the following, the intermittently repeated image form
Cumulative heating roller rotation time during power-up operation after power-on
Until the interval reaches the preset value, the heating roller
Maintains a temperature that can be fixed during non-image formation
However, during image forming operation, it is higher than during non-image forming.
Control the temperature to maintain the temperature. This allows the image
The pressure roller warms up sufficiently, such as when starting the forming equipment.
No fixing failure occurs even when the temperature is low . According to the second aspect of the present invention, the first tie
The image forming operation pause time measured by the timer is set to the first predetermined value.
When exceeded, the image form is repeated intermittently by the second timer
Start timing of cumulative time of heating roller rotation time during forming operation
And the accumulated time measured by the second timer is set in advance.
Until the specified value is reached, the heating roller temperature
Maintain a temperature that allows fixing during image formation, and
Maintain a higher temperature during cropping than during non-image formation
Temperature control. As a result, when the image forming operation is stopped
Even when the time is long and the temperature of the pressure roller is lowered , the fixing failure does not occur in the restarted image forming operation.

A period in which the fixing process is performed while the heating roller is maintained at a second predetermined temperature higher than the first predetermined temperature, which is a normal fixing temperature, is set as a time period for the heating roller. Cumulative value of rotation time (cumulative value of rotation time of main motor),
That is, since the heating roller is actually determined by the accumulated value of the time during which the heating roller is operated at the high second set temperature, the number of parts does not increase, unlike the configuration in which the fixing roller is preliminarily rotated. And the rise time of the apparatus can be shortened.

Further, the size of the recording paper and the image forming operation are repeated in a short time, or are repeated at intervals of time, as in the configuration determined by the number of recording papers and the elapsed time from the start of the printing operation. Depending on the operation mode of the image forming operation, such as the temperature of the heating roller and the pressure roller,
There is no risk of inconvenience such as an abnormal rise in the temperature inside the machine.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically illustrating the configuration of a laser printer to which the present invention is applied.

FIG. 2 is a cross-sectional view of a heating roller and a pressure roller constituting the fixing device.

FIG. 3 is a longitudinal sectional view of a heating roller and a pressure roller constituting the fixing device.

FIG. 4 is a block diagram of a control circuit of the laser printer.

FIG. 5 is a timing chart illustrating a temperature control operation of the fixing device.

FIG. 6 is a flowchart illustrating an outline of a control operation of an engine control CPU.

FIG. 7 is a flowchart showing a first embodiment of a temperature control process of the fixing device.

FIG. 8 is a flowchart (continued) showing a first embodiment of the temperature control processing of the fixing device.

FIG. 9 is a flowchart showing a second embodiment of a fixing device temperature control process.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photosensitive drum 2 laser oscillator 11 fixing device 12 heating roller 13 pressurizing roller 21 heater lamp 22 temperature sensor 31 host computer 32 printer controller 34 engine control CPU

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 15/20

Claims (2)

(57) [Claims] 1. A heating roller having a built-in heating element, a pressure roller pressed against the heating roller, and a cumulative time after power-on of a heating roller rotation time during an intermittently repeated image forming operation is measured. Timer and the accumulated time measured by the timer are set in advance.
Until the predetermined value is reached, the heating roller is
At a temperature that allows fixing at
To maintain a higher temperature than during non-image formation.
And a temperature controller for controlling the temperature of the fixing device. 2. A heating roller having a built-in heating element, a pressure roller pressed against the heating roller, a first timer for measuring an image forming operation pause time in an intermittently repeated image forming operation, and an intermittent operation. A second timer that counts the cumulative time of the rotation time of the heating roller during the image forming operation that is repeatedly performed, and an image forming operation pause time that is measured by the first timer.
When the value exceeds a first predetermined value, the second timer
Start timing, and the time counted by the second timer
Until the accumulated time reaches a predetermined value set in advance,
Keep the heating roller at a temperature that allows fixing during non-image formation.
Higher during non-image formation than during non-image formation.
Temperature control means for controlling the temperature to maintain
A fixing device temperature control device for an image forming apparatus, comprising: