JP2000242133A - Fixing temperature control method for electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately control the heating with heater even in the case of using plural heaters and to optimally set the fixing temperature by setting the turning-on pattern of a sub heater according to the length of the reference turning-on time of a main heater in the case of non-nipping. SOLUTION: The heater 3 is controlled to be turned on when the surface temperature of a heating roller 2 is equal to or under a control temperature according to a signal from a temperature sensor 8. Whether recording material 7 is nipped or not is judged based on a detection signal from a fixing detection sensor 22. When the material 7 is nipped, the heaters 4 and 5 are turned on/off synchronously with the on/off timing of the heater 3. When the material 7 is not nipped, the turning-on time of the heater 4 gets longer by specified additional turning-on time when the turning-on time of the heater 3 is longer than the specified criterion time Ts1. The heater 5 is turned on only when the turning-on time of the heater 3 is longer than a specified criterion time Ts2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus such as a copying machine, a printer, and a facsimile, and more specifically, to an unfixed toner image on a recording material while nipping the recording material over a pair of heat fixing rollers. The present invention relates to a fixing temperature control method for an electrophotographic apparatus, comprising: a heat fixing unit for performing heat fixing, wherein the heat fixing unit includes two or more heaters and one or more fixing temperature detecting sensors.

[0002]

2. Description of the Related Art Conventionally, as a technique for thermally fixing an unfixed toner image formed by an electrophotographic apparatus or the like, there are a hot roller system in contact with toner, a surf system using a seamless belt, and a hot plate in non-contact with toner. There are a system, a flash system, an infrared lamp system, an oven system, a dielectric heating system, and the like, and the toner contact system is mainly used in terms of thermal efficiency.

On the other hand, in a toner contact system, particularly a heat roller system, in order to reduce power consumption, a thin fixing roller system in which the heat capacity of the roller is reduced is often used. However, in the case of the thin fixing roller type, the heat flow in the longitudinal direction is deteriorated due to the reduction in thickness, and for example, heat stays in a non-sheet passing area or the like. Temperature rises excessively, and an offset phenomenon or the like is likely to occur.

In order to solve such a drawback, the number of heaters inserted into the heating roller is arranged in a plural number of about two to several, and the energization control of each heater is performed according to the size of paper to be passed. Was. The technique of controlling the energization by interposing a plurality of heaters is applicable not only to the thin fixing roller method but also to other heat roller methods, surf methods, and toner non-contact heating methods. Kaisho 5
No. 7-148779 is a heat fixing method using a preheating plate, which includes a plurality of heating heaters and first and second temperature control elements, and controls the heat fixing temperature by the first temperature control element.
The second temperature control element controls temperature unevenness caused by the sheet width.

[0005]

However, controlling a plurality of heaters while different heating controls are performed by the two temperature control elements complicates the control circuit and easily causes a malfunction.

In Japanese Patent Application Laid-Open No. Sho 62-124581, attention is paid to the fact that the fixing roller not only radiates heat to the transfer material but also radiates heat to the peripheral portion. This is a technique in which heat is applied to both ends of the roller so as to be large, and one heater is used to control this heater to be turned off with a delay from other heaters. However, such a technology is based on the premise that a large amount of heat is radiated to the peripheral portion of the roller. Particularly in the case of a thin fixing roller method, the heat capacity of the roller itself is small, and therefore, the influence of the size type or the thickness of the recording material is affected. As a result, the amount of heat removed from the fixing roller is not constant, and accurate control cannot be performed.

For this reason, for example, Japanese Patent Application Laid-Open No. Sho 62-189488.
No., when manual paper feed is performed, forcibly energize the heat source of the fixing device for a predetermined time at a predetermined timing,
A technique for increasing the heat capacity of the fixing device has been proposed.

However, this technique is based on the premise that the thickness of the recording material fed from the manual paper feeder is large and the amount of heat absorbed by the recording material is large. When the paper is fed, the temperature of the fixing roller becomes unnecessarily high, which causes problems such as offset.

The present invention has been made in order to solve such a problem.
Even when a plurality of heaters are used, even if the amount of heat deprived to the heat fixing roller fluctuates greatly due to the size and thickness of the recording material inserted (nip) through the fixing roller, the heating control of the heater can be performed accurately. It is an object of the present invention to provide a thermal fixing temperature control method for an electrophotographic apparatus which can perform an appropriate fixing temperature setting properly and accurately. Another object of the present invention is to
An object of the present invention is to provide a thermal fixing temperature control method in an electrophotographic apparatus capable of accurately and surely controlling the temperature with a simple control circuit or software control.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the invention according to claim 1 performs thermal fixing of an unfixed toner image on a recording material while nipping the recording material over a pair of heat fixing rollers. In the heat fixing means, in other words, a heat fixing roller pair system composed of a heat roller and a pressure roller or a combination of heat rollers, two or more heaters are provided inside at least one heat roller constituting the heat fixing roller pair. The present invention is applied to a fixing temperature control method of an electrophotographic apparatus comprising one or more fixing temperature detecting sensors on the surface of the heat generating roller and the like, and a feature of the present invention is that the heater Has a main heater that performs lighting time control based on a temperature detected by a temperature detection sensor, and performs lighting time control by increasing or decreasing the lighting time based on a reference lighting time of the main heater. And one or more sub-heaters, wherein the reference lighting time of the main heater is measured when the recording material is not nipped, and the length of the reference lighting time when the recording material is not nipped is one or more sub-heaters. Is set.

The present invention will be specifically described. The main heater, whose lighting time is set based on the temperature sensor, fluctuates during the fixing operation of the recording material, in other words, during the nip operation, according to the heat capacity of the recording material to be inserted. In this case, as in the case of a postcard size, only a part of the entire width of the fixing roller is nipped, and when a part of the fixing roller is thick and has a large amount of heat removal, if the main heater is located in a portion of the large amount of heat removal, Although the temperature of the portion where the sub-heater is located is sufficiently high, the lighting time of the main roller is long.
As a result, heat energy is excessively applied to the roller portion corresponding to the sub-heater, and heat fusion such as offset may occur at that portion.

Conversely, if the main heater is located in a portion where the amount of heat loss is small, the lighting time of the main heater is shortened even though the temperature of the portion where the sub-heater is located is low. When the lighting control is performed, additional lighting is not performed even though additional lighting of the sub-heater is required. As a result, heat energy of the roller portion corresponding to the sub-heater becomes insufficient, and insufficient fixing occurs in that portion. May occur.

Therefore, at the time of the nip, since the heat capacity of the recording material greatly varies, even if the lighting control of the sub-heater is performed based on the lighting time of the main heater at the time of the nip, an accurate and accurate optimal fixing temperature setting can be performed. I can't. Therefore, the present invention measures the reference lighting time of the main heater in a non-nip state where there is no influence of noise due to the recording material without setting the reference lighting time in a nip state where the recording material has a large thermal fluctuation. The lighting pattern of the sub heater is set according to the length of time. This makes it possible to accurately and accurately control the heating of the heater and to realize an optimal fixing temperature setting.

The present invention is preferably applied particularly to a thin-wall roller system, but is not limited to this, and can also be applied to a thick-wall roller system and surf heat fixing.

The invention described in claim 2 is characterized in that the lighting start timing of the sub-heater is set in synchronization with or delayed from the lighting start timing of the main heater. In the present invention, in particular, the main heater is stretched over the entire length of the heating roller, and the sub-heater is superimposed on the local position of the main heater in order to prevent a temperature drop in the peripheral portion, the central portion and other local portions of the heating roller. In such a case, it may be better not to turn on the sub heater disposed only in the local portion of the main heater when sufficient heat absorption is performed during non-nip, such as in the intermittent operation state. After the heat absorption is sufficiently performed, the lighting time of the main heater is shortened. In such a case, the lighting start timing of the sub-heater is set to be delayed from the lighting start timing of the main heater. The off-control can be performed without turning on the sub-heater after sufficient heat absorption. Note that the delay time can be varied based on a fixing load, an environmental temperature, and other factors that change the fixing temperature.

Regarding the turn-off timing of the sub-heater,
As described in claim 4, it is preferable to compare the lighting time of the main heater during non-nip with a predetermined determination time, and set the lighting off timing based on the result of the determination. That is, to specifically explain, it is assumed that, for example, one temperature detection sensor is disposed close to the main heater, and the sub-heater removes heat from the main heater as in the center position of the center sheet feeding. Assuming that it is located at a position where
For example, when a thick recording material is inserted by center feeding,
When controlled by the lighting time of the main heater at that nip,
As described above, the sub heaters are not accurately applied with heat.

On the other hand, in the non-nip state, the temperature of the entire heat generating roller including the heater is substantially constant, or the temperature curve is one-sided inclined in the axial direction due to the influence of the exhaust fan and the like. There is a correlation between the temperature of the sub heater and the required heat capacity. In other words, during non-nip time, energy is not usually taken from the recording material,
This is a cycle in which the lighting time of the main heater is short. In this case, it is preferable to synchronize the lighting time of the sub-heater with that of the main heater in order to achieve a uniform heat distribution.

When the lighting time of the main heater is longer than the predetermined judgment time when the nip is not nipped, for example, when the sub-heater is disposed at the center position of the center sheet feeding position, the lighting time of the main heater is reduced. The lighting time of the sub-heater is further increased. On the other hand, when the main heater is disposed at the center position of the center sheet feeding position, the lighting control of the sub-heater is performed by reducing the lighting time of the sub-heater from the lighting time of the main heater. Is good.

According to a fifth aspect of the present invention, the determination time is varied based on a fixing load and other factors that cause a change in the fixing temperature. That is, the deviation of the temperature distribution between the main heater and the sub-heater is not always constant, and differs depending on the fixing temperature rise, the difference in environmental temperature due to seasonal differences, the difference between continuous or intermittent passing, and the like. Even when the fixing temperature is raised, the fixing is performed in winter, and the printing and fixing is performed on a recording material that is continuously fed even in the non-nip state, the deviation is likely to increase. The frequency at which the lighting time of the heater is increased from the lighting time of the main heater is increased.

On the other hand, in the case of normal fixing, fixing in summer, and printing and fixing recording paper of intermittent passing, the deviation tends to be small. In this case, the determination time is lengthened and the lighting time of the sub heater is increased. The frequency of increasing (decreasing) the lighting time of the main heater is reduced. This makes it possible to more accurately perform heating control with uniform distribution in the axial direction, and by combining the inventions of the second and fourth aspects, it is possible to control both the lighting ON timing and the OFF timing of the sub-heater. It is possible.

Therefore, according to the present invention, since only the time management of the heater is performed, the control is easy in terms of hardware and software, and there is no room for malfunction. Moreover, according to the present invention, the determination is made not at the time of the nip where the heat capacity is indefinite but at the time of the non-nip where the heat capacity is stable, so that accurate temperature control is possible with a simple control circuit or software control.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the drawings. However, unless otherwise specified, the types of components, circuits, their relative arrangements and the order of operation described in this embodiment are not intended to limit the scope of the present invention thereto, but are merely illustrative examples. It's just

FIG. 1 shows an electrophotographic apparatus incorporating a thin fixing type heat fixing roller applied to the present invention. FIG. 1 (A) is a schematic sectional view of a main part thereof, and FIG. 1 (B) shows an internal structure of a heating roller 2. It is a longitudinal cross-sectional view. In FIG. 1, 1 is a pressure roller,
A low hardness pressurized rubber layer 1b is wound around the outer periphery of the roller shaft 1a. Reference numeral 2 denotes a heating roller which is formed by coating the outer peripheral surface of a thin roller member 2a made of carbon steel with a fluorine coat or a thin silicon rubber layer 2b. Further, the fixing device employs a so-called center sheet feeding in which different size papers are inserted symmetrically around the center of the heating roller 2 so as to be symmetrically distributed right and left. Heaters A (3) each consisting of a halogen lamp having heating coils 3a, 4a, and 5a positioned on the right, center, and left sides, respectively, in the figure.
And three heaters B (4) and C (5) in total.

That is, the three heaters A (3), B
(4) and C (5) are symmetrically arranged around the center axis of the roller and parallel to the axial direction.
On the left side of the heating coil 3a in FIG.
The heating coil 4a of (4) is located at the central portion, and the heating coil 5a of the heater C (5) is located on the left side in the figure to facilitate temperature control described later. The number of turns of the heating coil 5a of the heater C (5) (left side in the figure) is small, and the number of turns of the heating coil 3a of the right side heater A (3) is large. This is because the heat-generating coil 3a on the right side in the figure has a larger heat removal energy to be removed along the exhaust flow.

In the present embodiment, a thermistor or other temperature sensor 8 is disposed on the right side of the outer peripheral surface of the heating roller 2 facing the heating coil 3a on the right side of the drawing where the heat absorbed by the exhaust gas is the largest. I have. Accordingly, the temperature sensor 8 is configured to directly perform on / off control for the heater A (3) facing the heater heater 2 while the heaters B (4) and C (5) are connected to the heater A (3). The on / off control is performed in synchronization with the lighting time of 3) or delayed as necessary. In the drawing, reference numeral 6 denotes an unfixed toner image carried on the recording material 7.

In this embodiment, the photosensitive drum 11 and the transfer roller 12 are arranged along the recording material conveying path on the upstream side of the fixing device, the registration roller 13 and the registration sensor 14 are provided at the entrance thereof, Sensor 1
(4) The paper feed path on the upstream side functions as a cassette paper feed path that guides the fixed-form plain paper stored in the paper feed cassette 17 to the entrance of the registration roller 13 by the driving rotation of the paper feed roller 16, and feeds paper on the paper feed path. A sensor 15 is provided so that the paper feed type can be determined. The registration sensor 14 detects the start end of the recording material 7 that has reached the entrance end of the registration roller 13 and the rear end of the recording material 7 that has passed through the registration roller 13. Lumber 7
By measuring the time interval from the detection of the trailing edge of the next recording material 7 to the detection of the length of the recording material 7, it is possible to set the fixing interval time between intermittent sheet feeding and continuous sheet feeding. Also, a fixing detection sensor 22 is provided on the entrance side of the fixing device, and it can be determined whether or not the recording material 7 has been inserted into the fixing roller pair, more specifically, whether the recording material 7 is in the nip state or the non-nip state. .

Next, the operation of this embodiment will be described in detail with reference to FIG. FIG. 2 is a time chart showing a state in which the surface temperature distribution of the heating roller 2 and the lighting times of the heaters A (3), B (4), and C (5) are controlled. In FIG. 2, the heater A (3) is controlled by a signal from the temperature sensor 7 to be turned on when the surface temperature of the heating roller 2 becomes equal to or lower than the control temperature Tc. Based on a detection signal from the fixing detection sensor 22, it is determined whether the nip is not nip or nip. In the case of nip, the heater A (3) is turned on / off with respect to the heating heater B (4) and the heating heater B (4). C (5) turns on / off synchronously.

In the case of non-nip, the process proceeds to a determination routine. In the determination routine, the heater A (3) described later is turned on.
After the heater B (4) and the heater C (5) turn on in synchronization with the timing, the heater A (3)
It is determined whether or not the lighting time TA of the heater B (4) has exceeded the predetermined determination time Ts1. If the lighting time TA is longer than the predetermined determination time Ts1, the lighting time (TB =
TA + Tp) becomes longer.

On the other hand, the heater C (5)
It turns on with a delay from the ON timing of (3), that is,
The heating time of the heater A (3) is T for the heater C (5).
It is determined whether or not A has exceeded a predetermined determination time Ts2, and is turned on only when it is longer than the predetermined determination time Ts2. Accordingly, the lighting time of the heater C (5) becomes (TC = TA−Ts2), and the heater A (3) is turned off in synchronization with the off timing.

This will be described with reference to the flowchart shown in FIG. For example, the fixing detection sensor 2 shown in FIG.
According to (2), it is determined whether the nip state or the non-nip state (S1). If the nip state, the process proceeds to an automatic on / off routine (S15), and the heating heater B ( 4) and heater C
(5) performs control to turn on / off synchronously. (S1
6, S17, S7 ', S8', S11 ')

In the case of non-nip, the process shifts to a determination routine (S2), and the heater A (3) sets the temperature sensor 8
Is turned on when the surface temperature of the heater 2 becomes equal to or lower than the control temperature Tc, and the heater A (3)
In synchronization with the N timing (S3), the heater B
(4) is turned on, and in (S4) the heater A (3)
It is determined whether or not the lighting time TA of the heater A exceeds the predetermined determination time Ts2, and when the lighting time (TA) of the heater A (3) exceeds the determination time (Ts2), the heater C (5) is turned on. If not, the heater C (5) is kept off (S5). Further, in (S6), the heater A
It is determined whether the lighting time TA of (3) has exceeded a predetermined determination time Ts1. If the lighting time TA is longer than the predetermined determination time Ts1, the additional lighting is performed after the heater A (3) is turned off (S7). The timer for setting the time Tp is turned on (S9), and when the lighting time (TB) of the heater B (4) exceeds (TA + Tp) (S10), the heater B (4) is turned off (S9).
11). The heater C (5) is turned off at the same time as the heater A (3) is turned off (S7).

On the other hand, the lighting time TA of the heater A (3)
Is shorter than the determination time Ts, the heaters B (4) and C are synchronized with the off operation (S7 ') of the heater A (3) without turning on the timer for setting the additional lighting time Tp. (5) is simultaneously turned off (S8 ') (S1)
1 ').

Next, experimental results of a specific prototype are shown. The inventors have developed an electrophotographic printer shown in FIG. 1 having a linear velocity of 100 mm / sec. Figure 3 shows the experimental results.
It is shown in (B). As an evaluation method, A4
The surface temperature of the heating roller immediately before the nip when an image was fixed by intermittently passing a thin recording material of size and an A3 size thick recording material by continuous passing of paper was measured.

Then, the determination time Ts1 of the heater B (4) is set to 5
Second, the determination time Ts2 of the heater C (5) was 0.7 seconds, and the additional lighting time Tp was 3 seconds. That is, as shown in (A),
The heater B (4) is additionally lit for the time Tp when it is longer than the determination time Ts1 (5 seconds). Further, the heater C (5)
Lighting timing Ts2 (0.7 seconds) from heater A (3)
By delaying, the heater is not turned on when it is shorter than the determination time Ts2. Also, for the fixing device,
Since the exhaust heat fan 9 is provided on the heater C side, the heater A (3)
The air whose temperature has been increased by each heater is discharged from the heater side to the heater C (5) side. Therefore, during intermittent printing or thin paper fixing where only a small amount of heat is taken during fixing, the heater C
(5) The high-temperature air is trapped on the side, and the fixing temperature tends to rise.

When the A3 size thick paper is continuously passed and fixed, high-temperature air is not trapped on the side of the heater C (5) because the heating roller is passed near the entire width of the heating roller. For this reason, the heat loss of the heater B (4) is large. In such a case, the heater A
In synchronization with the lighting time of (3), the heaters B (4), C
When the lighting time of (5) is set, as shown in FIG. 3B, the heat immediately before the fixing of the heater B (4) in the center portion is reduced to 175 ° C. because the heat is largely removed from the heater B (4). Sometimes insufficient fixing occurs. In such a case, when the heater A is controlled to 180 ° C. by the fixing temperature detection sensor 8 when the nip is not nipped, the heater B (4)
If the lighting time of (3) is 5 seconds or longer, additional lighting is performed for 3 seconds longer, so that it is possible to control at a necessary temperature of 190 ° C. as a pre-fixing temperature.

In the case of intermittent printing operation on A4 thin paper, the amount of heat taken is reduced by greatly reducing the frequency of printing on the paper, and the frequency of lighting when the paper is not fixed is increased. The lighting time of (3) becomes very short. Therefore, in the control according to the present invention, the heater C
Since the lighting time of (5) is much shorter than that of the heater A or does not light, the abnormal temperature rise of 205 ° C. before fixing as in the related art due to the heat retention on the heater C (5) side. No generation occurs, and the temperature of the heater C (5) can be maintained at 185 ° C. When the fixing device is not sufficiently heated, for example, immediately after the power is turned on, a large amount of heat is taken to the pressure roller and the surroundings. Therefore, the lighting time of the heater A (3) is 5 seconds even when the nip is not nipped. Even in such a case, it is preferable that the heating time of the heater B is additionally turned on for 3 seconds, so that the heat amount at the center of the heating roller does not become insufficient.

In an electrophotographic apparatus provided with manual paper feed and a plurality of cassette paper feeds, the paper length and paper width greatly fluctuate. In the case of manual paper feed, intermittent paper feed is generally used. May increase, and the printing speed may decrease significantly. In such a case, the determination time Ts1,
A more optimal temperature distribution can be realized by precisely controlling Ts2 to be variable.

In such a case, a technique of making the determination time variable in FIG. 4 may be used. The manual paper feed mechanism has a layout structure shown by imaginary lines in FIG. That is, the paper feed path on the upstream side of the registration sensor 14 is vertically branched into two, and one paper feed path is
The standard plain paper stored in 7 serves as a cassette paper feed path that is guided to the entrance of the registration roller 13 by the driving rotation of the paper feed roller 16, while the other paper feed paths are for nonstandard paper stored from the manual paper feed plate 20. The paper feed roller 19 functions as a manual paper feed path that guides to the entrance of the registration roller 13 by the rotation of the paper feed roller 19. Paper feed sensors 15 and 18 are provided on the respective paper feed paths, and the paper feed type can be determined.

In this device configuration, the determination time T
s1 and Ts2 are paper feed sensors 15, 1 provided in the electrophotographic apparatus.
8 and signals from the registration sensor 14 and the like are taken into the CPU 21, and predetermined judgment conditions are calculated on the CPU 21 side based on the measured values of the various sensors 14, 15, 18, and the like. Select the judgment time. For example, the determination times Ts1 and Ts2 are made different or the heater C (5) is determined based on the paper feed type by the paper feed sensors 15 and 18, the size detection of the recording material by the cassette selection, the paper feed interval of the registration sensor 14, and the like. Control such as not to be performed can be performed.

The operation will be described with reference to the flowchart of FIG. First, it is determined whether manual paper feed (S20) or cassette paper feed (S21) based on the manual paper feed sensor 18, and in the case of cassette paper feed, the process proceeds to (S21). In (S21), the CPU 21 detects the cassette type (size), and, for example, when the recording material size is B4 (S2).
2) is a determination time Ts1 for additionally lighting the heater B (4).
5 seconds, the determination time Ts1 is 6 seconds for the A4 size (S23), and the determination time Ts1 is 7 for the B5 size (S24).
Set to seconds. In other words, when fixing a small-sized sheet, the determination time is reduced from 5 to 6 to 7 seconds so that the uneven distribution of the heat load at the center does not become too large.
Note that the delay determination time Ts2 of the heater C (5) can be similarly varied as necessary.

On the other hand, in the case of manual feeding, the flow shifts to (S25). In (S25), first, the point when the registration is turned on is detected by the registration sensor 14 or the like, and then the time until the trailing edge of the recording material passes through the registration sensor 14 or the time until the next recording material is registered (paper passing). Interval time) CPU
21 (S26), for example, if the recording material length is 25 cm
In the above case (S27), the determination time Ts1 for additionally lighting the heater B (4) is set to 5 seconds, the determination time Ts1 is set to 6 seconds for 15 to 25 cm, and the determination time Ts1 is set to 7 seconds for 15 cm or less. (S28).

[0042]

As is apparent from the above description, according to the present invention, even when a plurality of heaters are used, fluctuations in heat removal energy during a nip can be avoided and determination control can be performed during a non-nip. An electrophotographic apparatus that can accurately and accurately control the heating of the heater to achieve the optimal fixing temperature setting, and can perform accurate temperature control with a simple control circuit and software control because it is a time control called a mere judgment time. And a method for controlling the thermal fixing temperature in the above.

[Brief description of the drawings]

FIG. 1A is a schematic sectional view of a main part of a thin fixing type electrophotographic apparatus applied to the present invention, and FIG. 1B is a longitudinal sectional view showing an internal structure of a heating roller.

FIG. 2 is a graph showing an example of a lighting control pattern of each heater by a plurality of heaters according to the first embodiment.

FIG. 3 is a table showing experimental results of temperature rise in a specific electrophotographic printer according to the embodiment of FIG. 2;

FIG. 4 is a flowchart showing an overall operation procedure of the present invention.

FIG. 5 is a flowchart illustrating a subroutine procedure for controlling a determination time to be variable.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 pressure roller 2 heating roller 3 heating heater A 4 heating heater B 5 heating heater c 6 unfixed toner image 7 unfixed recording material 8 temperature sensor 11 photosensitive drum 12 transfer roller 13 registration roller 14 registration sensor 15, 18 paper feed Sensor 19 Feed roller 20 Manual feed plate 21 CPU 22 Fixing detection sensor

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H027 DA12 DA39 EA12 EC06 ED25 HB09 2H033 BA25 BB18 CA02 CA07 CA26 CA27 CA45 9A001 HH34 JJ35

Claims (5)

[Claims] 1. A thermal fixing device for thermally fixing an unfixed toner image on a recording material while nipping the recording material on a pair of thermal fixing rollers, the thermal fixing device comprising two or more heaters, A fixing temperature control method for an electrophotographic apparatus comprising at least one fixing temperature detection sensor, wherein the heating heater controls a lighting time based on a temperature detected by the temperature detection sensor, and a reference for the main heater. One or a plurality of sub-heaters for increasing or decreasing the lighting time based on the lighting time and performing lighting time control, and measuring the reference lighting time of the main heater when the recording material is not nipped, and A fixing temperature control method in an electrophotographic apparatus, wherein a lighting pattern of one or a plurality of sub-heaters is set according to a length of a reference lighting time. 2. The fixing temperature control method according to claim 1, wherein the lighting start timing of the sub heater is set in synchronization with or delayed from the lighting start timing of the main heater. 3. The fixing temperature control method according to claim 2, wherein the delay time is varied based on a fixing load and other factors that change the fixing temperature. 4. The lighting-off timing of the sub-heater is determined by comparing the lighting time of the main heater with a predetermined determination time, and setting the lighting-off timing based on the determination result. 3. The fixing temperature control method according to 1 or 2. 5. The fixing temperature control method according to claim 4, wherein the determination time is varied based on a fixing load and other factors that change the fixing temperature.