JP2000242132A - Fixing temperature control method in electrophotographic apparatus provided with manual feed unit - Google Patents

Abstract

(57) Abstract: The present invention relates to a fixing device for an electrophotographic apparatus capable of realizing an optimum fixing temperature setting by accurately and accurately controlling heating of a heater in manual sheet feeding or the like even when a plurality of heating heaters are used. It is an object to provide a temperature control method. A recording device includes a main heater that controls lighting time based on a temperature detected by a temperature detection sensor, and a sub-heater that controls lighting time by increasing or decreasing the lighting time based on the lighting time of the main heater. During manual paper feeding or when feeding a fixed-size recording material whose material size cannot be specified, the lighting pattern of one or a plurality of sub-heaters is set according to the lighting time of the main heater.

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, a facsimile, and the like, which includes a plurality of paper feeding units each comprising a fixed recording material feeding unit and a manual feeding unit. Specifically, the image forming apparatus further includes a heat fixing unit configured to thermally fix an unfixed toner image carried on a recording material selectively fed from the plurality of paper feeding units, wherein the heat fixing unit includes two or more heat fixing units. The present invention relates to a fixing temperature control method for an electrophotographic apparatus including a heater 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 inserting such 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. Showa 57
No. 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 the two temperature control elements perform different heating controls tends to complicate the control circuit and cause a malfunction.

In Japanese Patent Application Laid-Open No. Sho 62-124581, noting that the fixing roller not only radiates heat to the transfer material but also radiates heat to the peripheral portion, one of the plurality of heaters is This is a technique in which heat is applied to both ends of a 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, this technique is based on the premise that a large amount of heat is radiated to the peripheral portion of the roller. For example, when an irregular-shaped recording material is inserted from a manual sheet feeding section, accurate temperature distribution control cannot always be performed.

That is, in order to form an image on a nonstandard recording material that is not stored in a paper cassette, such as a postcard size, letter size, or thick paper recording material, a manual paper feed unit is provided. I have. When a recording material of unknown size or thickness is inserted from such a manual sheet feeding unit, it is unknown whether the amount of heat removed by the fixing roller is large or small, and accurate control cannot be performed. For example, JP-A-62-189
No. 488 proposes a technique for increasing the heat capacity of the fixing device by forcibly energizing the heat source of the fixing device for a predetermined time at a predetermined timing when manual sheet feeding is performed.

[0008]

However, this technique is based on the premise that the recording material fed from the manual paper feeder is thick and the amount of heat absorbed by the recording material is large, and therefore the heat capacity is large. When non-standard paper having a small value is supplied, the temperature of the fixing roller becomes unnecessarily high, which causes a problem such as offset.

The present invention is directed to an electrophotographic apparatus capable of realizing an optimum fixing temperature setting by accurately and accurately controlling the heating of a heater in a manual sheet feeding or the like even when a plurality of heating heaters are used in order to solve such a problem. An object of the present invention is to provide a fixing temperature control method. Another object of the present invention is to provide a heat fixing temperature control method in an electrophotographic apparatus capable of performing accurate temperature control with a simple control circuit even when a non-standard recording material having an undetermined heat capacity is manually fed. It is in.

[0010]

In order to solve the above-mentioned problems, the invention according to claim 1 is directed to a plurality of paper feeding units including a standard recording material paper feeding unit and a manual paper feeding unit, and the plurality of paper feeding units. A heat fixing unit for thermally fixing an unfixed toner image carried on a recording material selectively fed from a paper unit, wherein the heat fixing unit includes two or more heaters and one or more heaters; In a fixing temperature control method for an electrophotographic apparatus comprising a fixing temperature detection sensor, the heating heater controls a lighting time based on a temperature detected by a temperature detection sensor, and a reference is made to a lighting time of the main heater. And a sub-heater that controls the lighting time by increasing or decreasing the lighting time. In manual feeding or when feeding a fixed-size recording material in which the recording material size cannot be specified, 1 or depending on the length of the lighting time of the main heater. Lighting of multiple sub heaters And sets the over down.

According to this invention, the lighting time of the main heater whose lighting time is set based on the temperature sensor becomes longer in proportion to the heat capacity of the recording material to be inserted during the fixing operation. Therefore, even if the heat capacity of the manually fed recording material is uncertain, the heat capacity can be easily determined by judging from the lighting time. By setting the lighting pattern of one or a plurality of sub-heaters, it is possible to precisely and accurately control the heating of the heater in the manual sheet feeding, thereby realizing the optimum fixing temperature setting. Although the present invention is suitably applied to manual sheet feeding, the present invention is not limited to this, and is also applicable to fixing of fixed-size sheets such as ordinary cassette sheet feeding.

The invention according to 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. When the heat supply capacity of the manual sheet feeding is small, it may be better not to turn on the sub heater disposed only in the local portion of the main heater. The small heat capacity means that the lighting time of the main heater is short,
In such a case, by setting the lighting start timing of the sub-heater to be delayed from the lighting start timing of the main heater, it is possible to control without turning on the sub-heater superimposed on the main heater when the heat removal capacity is small. I can do it. Note that the delay time can be varied based on a fixing load 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 that the lighting time of the main heater is compared with a predetermined determination time, and the lighting off timing is set based on the determination result. That is, to specifically explain, for example, it is assumed that one temperature detection sensor is disposed close to the main heater, and a position where the amount of heat removal is larger than that of the main heater when the sub-heater is manual feed. For example, when a thick recording material is inserted by manual paper feeding, if the main heater is turned on, the amount of heat of the sub heaters may be insufficient.
In such a case, the lighting time of the main heater is long. On the other hand, in the case of normal temperature control in which the lighting time of the main heater is short, such as when a small-sized recording material is inserted even in manual sheet feeding, the lighting time of the sub heater is synchronized with that of the main heater. This is preferable for achieving a uniform heat distribution. Therefore, when the lighting time of the main heater is longer than the predetermined determination time, the lighting time of the sub heater is increased (decreased) from the lighting time of the main heater. On the other hand, when the lighting time of the main heater is within the predetermined determination time, it is preferable to perform the lighting control in synchronization.

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. In addition, even in the case of the manual sheet feeding, when the fixing temperature rises, the fixing is performed in winter, and the printing and fixing is performed on the recording material of the continuous paper, the deviation tends to be large. 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 intermittent recording paper, the deviation is likely to be small. In this case, the determination time is lengthened and the lighting time of the sub heater is increased. The frequency of decreasing (increasing) the lighting time of the main heater is increased. 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 hardware and software, and there is no room for malfunction. Therefore, according to the present invention, even when a non-standard recording material having an indeterminate heat capacity is manually fed, accurate temperature control can be performed with a simple control circuit or software control.

[0017]

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).

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.
The heating coil 3a of (3) is located on the left side
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 heating coil 5a of the heater C (5) has a small number of turns (left side in the figure), and the heating coil 3a of the right heater A (3) has a large number of turns. This is because the heat-generating coil 3a on the right side in the drawing has larger heat-removal energy along the exhaust gas flow because the fan 9 is provided.

In the present embodiment, the heating coil 3 on the right side of the drawing having the largest heat removal energy by the exhaust gas flow is used.
A thermistor and other temperature sensors 8 are arranged on the right side of the outer peripheral surface of the heating roller 2 facing a. Therefore, the temperature sensor 8 is connected to the heater A via the heating roller 2.
On / off control is directly performed for (3), while the heaters B (4) and C (5) are turned on / off by synchronizing with the lighting time of the heater A (3) or by delaying as necessary. Are doing. In the drawing, reference numeral 6 denotes an unfixed toner image carried on the recording material 7.

In the present embodiment, the photosensitive drum 11 extends along the recording material conveying path on the upstream side of the fixing device.
And a transfer roller 12, a registration roller 13 and a registration sensor 14 at an entrance side thereof, and a paper supply path upstream of the registration sensor 14 is branched into upper and lower two parts. The stored standard plain paper functions as a cassette paper feed path that guides to the entrance of the registration roller 13 by the driving rotation of the paper feed roller 16, while the other paper feed path feeds nonstandard paper stored by the manual paper feed plate 20. Roller 1
9 functions as a manual paper feed path that guides to the entrance of the registration roller 13 by the rotation of the drive roller 9, and paper feed sensors 15 and 18 are provided on the respective paper feed paths 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.
1 (described later) makes it possible to detect the length of the recording material 7.

Next, the operation of this embodiment will be described in detail with reference to FIG. FIG. 2 shows the surface temperature distribution of the heating roller 2 and the heaters A (3), B (4), C
It is a time chart figure showing the state which controls lighting time of (5). In FIG. 2, the heater A (3)
The signal from the temperature sensor 8, the surface temperature of the heating roller 2 is controlled temperature T ₀ is controlled to be turned ON and becomes equal to or less than the. With respect to the ON timing of the heater A (3),
After the heater B (4) is turned on synchronously, it is determined whether the lighting time TA of the heater A (3) has exceeded a predetermined determination time Ts1, and if it is longer than the predetermined determination time Ts1, The lighting time (TB = TA + Tp) of the heater B (4) becomes longer by the additional lighting time Tp.

The heater C (5) turns on with a delay from the ON timing of the heater A (3), that is, the heater C (5) determines that the lighting time TA of the heater A (3) is a predetermined value. It is determined whether or not the time has exceeded the time Ts2, and is turned on only when the time is longer than the predetermined time Ts2, and is not turned on when the time is shorter than the predetermined time Ts2.
-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. By (S1), for example, it is detected whether or not manual fixing is performed by the manual paper feed sensor 18 shown in FIG. 1, and in the case of manual fixing, the process proceeds to (S2).
(3) is turned on when the surface temperature of the heater 2 becomes equal to or lower than the control temperature Tc according to a signal from the temperature sensor 8. Then, in synchronization with the ON timing of the heater A (3), the heater B (4) is turned on in (S3), and the lighting time TA of the heater A (3) is further determined in (S4) by a predetermined determination time. It is determined whether or not Ts2 has been exceeded.
When the lighting time (TA) in (3) exceeds the determination time (Ts2), the heater C (5) is turned on. If not, the heater C (5) is kept off (S).
5). Further, in (S6), it is determined whether or not the lighting time TA of the heater A (3) has exceeded a predetermined determination time Ts1, and if it is longer than the predetermined determination time Ts1, the heater A
After (3) is turned off (S7), the timer for setting the additional lighting time Tp is turned on (S9), and when the lighting time (TB) of the heater B (4) exceeds (TA + Tp), (S1)
0), the heater B (4) is turned off (S11). The heater C (5) is turned off at the same time when the heater A (3) is turned off (S7) (S8).

On the other hand, the lighting time TA of the heater A (3)
Is shorter than the determination time Ts1, the heater A (3) is turned on without turning on the timer for setting the additional lighting time Tp.
In synchronization with the off operation (S7 ') of the heater B (4)
And C (5) are simultaneously turned off (S8 ') (S1
1 ').

Next, experimental results of a specific prototype are shown. An electrophotographic printer having a linear velocity of 100 mm / sec as shown in FIG. 1 was developed. The result of the experiment is shown in FIG. As an evaluation method, the surface temperature of the heating roller in a stable state when an image was fixed on a letter-size and postcard-size plain paper by horizontal paper feeding at room temperature and normal humidity was measured.

The determination time Ts1 of the heater B (4) is set to 6
Second, the determination time Ts2 of the heater C (5) was 2 seconds, and the additional lighting time Tp was 3 seconds. Further, as shown in (A), when the heater B (4) is longer than the determination time Ts1 (6 seconds), the time T
Turn on additional light by p. The heater C (5) is not turned on when the lighting timing is delayed by Ts2 (2 seconds) from the heater A (3) when it is shorter than the determination time Ts2. Further, a heater C is provided to the fixing device.
Side, the air whose temperature has been increased by each heater is discharged from the heater A (3) side to the heater C (5) side, so that a small amount of paper is fixed and only a small amount of heat is taken. In the case of intermittent printing,
(5) The high-temperature air is trapped on the side, and the fixing temperature tends to rise.

In the case where the letter size paper is continuously fed and fixed from the manual paper feed unit by the horizontal feed, since the paper is passed near the entire width of the heating roller, high-temperature air is not trapped on the heater C (5) side. On the other hand, since the paper is passed through the center, the heat loss of the heater B (4) is large. In such a case, if the lighting time of the heaters B (4) and C (5) is set in synchronization with the lighting time of the heater A (3) as in the related art, as shown in FIG. Since the heat loss of the heater B (4) portion is large, the fixing temperature of that portion decreases to 175 ° C., and insufficient fixing occurs. In such a case, at the time of printing in which the heater A is controlled at 180 ° C. by the temperature detector 8, the heater B (4) is additionally turned on for 3 seconds longer when the lighting time of the heater A (3) is 6 seconds or longer. 185
It is possible to control at a temperature of ° C.

In the case of plain paper of postcard size, the paper is manually fed after the trailing edge is detected by the registration sensor. In this case, since the printing frequency of the sheet is greatly reduced, the amount of heat taken is reduced, and the frequency of turning on the sheet other than when fixing the sheet is increased, so that the lighting time of the heater A (3) is 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 temperature is 200 ° C. as in the related art due to the heat retention on the heater C (5) side during intermittent printing as described above. Abnormal temperature rise does not occur and heater C
The temperature of (5) can be maintained at 175 ° C. Note that, even in the case of normal cassette sheet feeding, if the fixing device is not sufficiently heated, such as immediately after the power is turned on, a large amount of heat is taken to the pressure roller and the surroundings, so that the heater A (3) is turned on. The time is longer than 6 seconds, and even in such a case, it is preferable that the lighting time of the heating 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 manual paper feeding in which an unspecified paper size is used, since a wide paper length is taken into consideration, the interval between the papers becomes large, and the printing speed may be greatly reduced. In such a case, a more optimal temperature distribution can be realized by precisely controlling the determination time so as to be variable.

In such a case, a technique of making the determination time variable in FIG. 4 may be used. The determination times Ts1 and Ts2 are obtained by taking signals from the registration sensor 14 and the like provided in the electrophotographic apparatus into the CPU 21 and determining Cs based on the measurement values of the various sensors 14 to 16 and the like.
A predetermined determination condition is calculated on the PU 21 side, and the memory map 2
A determination time based on the determination condition is selected from 2 and the like. For example, control can be performed such that the determination times Ts1 and Ts2 are made different based on the detection of the recording material size and the fixing interval of the registration sensor 14, or the heater C (5) is not determined.

The operation will be described with reference to the flowchart of FIG. First, it is determined whether or not manual feeding is performed based on the manual paper feed sensor 18 in (S20), and in the case of manual feeding, the process proceeds to (S21). In (S21), first, the point in time when the registration is turned on is detected by the registration sensor 14 or the like, and thereafter, the time until the rear end of the recording material passes through the registration sensor 14 or the time until the next recording material is registered (paper passing). The interval time is detected by the CPU 21 (S22). For example, when the recording material length is 25 cm or more (S23), the determination time Ts1 for additionally lighting the heater B (4) is set to 5 seconds, 15 to 15 seconds.
In the case of 25 cm, the determination time Ts1 is set to 6 seconds, and in the case of 15 cm or less, the determination time Ts1 is set to 7 seconds (S24).
That is, when fixing a large-size sheet, the uneven distribution of the heat load at the center does not become too large, so that the determination time is reduced from 5 to 6 to 7 seconds. The heater C
The delay determination time Ts2 of (5) can be similarly varied.

[0033]

As is apparent from the above description, according to the present invention, even when a plurality of heaters are used, the heating of the heaters in manual sheet feeding or the like is controlled accurately and accurately to set the optimum fixing temperature. To provide a thermal fixing temperature control method in an electrophotographic apparatus which can be realized and which can perform accurate temperature control with a simple control circuit and software control even when a non-standard recording material having an indeterminate heat capacity is manually fed, for example. Can be.

[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 Paper feed roller 20 Manual paper feed plate 21 CPU

Claims (5)

[Claims] 1. A plurality of paper feed units each comprising a fixed-form recording material paper feed unit and a manual paper feed unit, and an unfixed sheet carried on a recording material selectively fed from the plurality of paper feed units. A fixing temperature control method for an electrophotographic apparatus, comprising: a heat fixing unit for performing heat fixing of a toner image, wherein the heat fixing unit includes two or more heaters and one or more fixing temperature detection sensors. A recording material comprising: a main heater for controlling the lighting time based on the temperature detected by the temperature detection sensor; and a sub-heater for controlling the lighting time by increasing or decreasing the lighting time based on the lighting time of the main heater. A fixing 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 lighting time of a main heater at the time of manual paper feeding or a fixed-size recording material whose size cannot be specified. Temperature control Law. 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 heating 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 1, wherein the determination time is varied based on a fixing load and other factors that change the fixing temperature.