JPH09305059A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce influence such as flickering of a lamp and deformation of an image on a CRT display respectively connected onto the same power source line as the heating source caused by conducting electricity to the heating source of a fixing device in the image forming device of heat-fixing system. SOLUTION: In the temp. control at the time of printing with use of plural heaters (heating sources) 41 to 44, this device is controlled so that one or more heaters are put on even if all plural heaters come to the worst lighting state, and that more than two heaters are simultaneously conducted, by setting the minimum lighting time in ON/OFF cycle of respective heater and the energizing timing. Moreover, the heater is driven in <=1sec cycle of energizing state and unenergizing state. As a result, a load fluctuation for one heater corresponding to the power source line is suppressed, and the influence such as flickering of the lamp connected onto the same power source line can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat fixing type image forming apparatus, and more particularly to a pair of heat fixing means and pressure means for fixing by carrying a transfer material having a toner image on its surface at its nip portion. And an image forming apparatus including a heat fixing device having a plurality of heat sources for heating the heat fixing means.

The image forming apparatus of the present invention is a laser beam printer adopting a heat fixing system, a printer such as an LED (light emitting diode) printer, an analog copying machine, a digital copying machine, a facsimile machine having a printer mechanism built therein, a ticket issuing machine and the like. Applicable to

[0003]

2. Description of the Related Art Conventionally, a fixing device used in an electrophotographic image forming apparatus that transfers a toner image onto a transfer material and heat-fixes the toner image to obtain a permanent image is generally shown in FIG. It had a simple structure.

In FIG. 1, reference numeral 1 denotes a fixing roller, which is, for example, a mold release member such as PFA (phenol formaldehyde) or PTFE (polytetrafluoroethylene) on a hollow cylindrical core metal 11 such as aluminum or iron. The resin layer 12 is formed, and is heated from the inside by the heater 4 disposed therein.

The temperature of the fixing roller 1 is detected as the surface temperature of the fixing roller 1 by the temperature detecting element 3 abutting on the fixing roller 1, and the heater 4 is intermittently turned on by a temperature control circuit (not shown). By operating, the surface temperature is controlled to a predetermined temperature. In a fixing device having a cleaning unit (not shown), the temperature detecting element 3 can be installed in the paper passing area on the surface of the fixing roller 1, but in the fixing device having no cleaning unit, image contamination is avoided. In general, the temperature detecting element 3 is generally installed in the non-image area (which is also the non-sheet passing area) on the surface of the fixing roller 1.

On the other hand, 2 is a pressure roller which rotates while being in pressure contact with the fixing roller 1. For example, a silicone having a heat resistance and a low hardness is provided on a metal core metal 13 such as aluminum or iron. An elastic layer 14 such as rubber or silicone sponge is formed, and P is formed on the surface of the elastic layer 14.
Coating layer 15 made of a resin having a high releasability such as FA or PTFE
It has a structure that has formed.

A transfer material (also referred to as a transfer sheet, a transfer paper, a recording paper, a paper, etc.) P carrying a toner image T is guided to a nip portion between the fixing roller 1 and the pressure roller 2 by an entrance guide 6. Then, the toner image is fixed on the transfer material by being heated and pressed between the rollers. The inlet guide 6 is made of a resistance control material (10E8Ω to 10E10Ω) such as PBT (polybutylene terephthalate), or a guide surface is made of metal such as stainless steel, and the resistance control is performed at a contact point with a fixing frame (not shown). It is common to use wood. This is because when the inlet guide 6 is formed of an insulator or the like, its guide surface is charged by sliding friction with the transfer material, which causes adverse effects such as toner scattering.

Further, in order to prevent wrinkles from occurring when the transfer material P passes through the nip portion, an appropriate inverted crown shape is formed in the longitudinal direction (rotational axis direction) of the fixing roller 1 and the pressure roller 2. Generally, the entrance guide 6 is used to optimize the entry position to the fixing nip.

In such a fixing device, the thickness of the fixing roller 1 may be 1.0 mm or less in order to reduce the heat capacity of the fixing roller 1 for the purpose of shortening the warm-up time. In such a case, when a single heater is used as the heater 4, an excessive temperature rise in the non-sheet passing area becomes a problem when printing small size paper. Particularly in a high speed machine, the printing speed must be remarkably reduced when printing small size paper.

Therefore, as a conventional means for solving this problem, an example in which two heaters having different light distributions are used as heating sources is known, and a cross section of a configuration example in this case is shown in FIG. The relationship between the light distribution of the heater and the segment arrangement is shown in FIG. It should be noted that FIG. 3 shows the heater light distribution when the paper conveyance is the central reference. In FIG. 3, the curve in the upper part of the drawing represents the value of the light intensity for each position of the heater, and the thick line in the lower part of the drawing represents the lighting position of the heater (that is, the position of the light emitting segment).

The one heater 4a of FIG. 2 is used when printing small size paper, and as shown in FIG. 3, the light distribution is largely distributed to the part where the paper absorbs heat. The other heater 4b in FIG. 4 is used in combination with the heater 4a as shown in FIG. 3 when printing large size paper. Further, since these two heaters correspond to those obtained by dividing one heater in the past into two heaters, it is general that the electric power per heater is set to be approximately half.

As a heater control method at the time of printing in this case, as shown in Table 1 below, two heaters were driven at a duty (lighting ratio) corresponding to the paper size.

[0013]

[Table 1]

[0014]

However, in the above-mentioned prior art, in the temperature control (temperature control) using only one heater as shown in FIG. 1, when the power supply to the heater is turned ON / OFF. Causes a large voltage fluctuation. FIG. 4 shows the waveform of the current flowing through the heater during the printing operation with the single heater (the configuration of FIG. 1). In this configuration, the heater is turned on in a cycle of 2 to 3 seconds, and the rush current (hatched portion in FIG. 4) when the heater is energized flows more than twice as much as usual. This is because the temperature of the energized portion of the halogen heater is lowered when it is not energized, so that the resistance value is lowered.

On the other hand, in the case of the temperature control using the two heaters as shown in FIGS. 2 and 3, the inrush current is reduced because the electric power per one is reduced, but the two heaters are used. Is turned on alternately to turn on the heater
When the / OFF cycle becomes long, the inrush current does not disappear.

Both of the two heaters are turned off at the same time.
In some cases, there are three states of the heater (1) both heaters are ON, (2) one heater is ON, and (3) both heaters are OFF (see Fig. 13). Since it appears as a fluctuation, an electric lamp or the like on the same power line also flickers in response to this fluctuation.

The present invention has been made in view of the above points, and an object thereof is to provide an image forming apparatus of a heat fixing type,
It is possible to reduce the load fluctuation of the power supply line when the heater, which is a heating source for heating the heat fixing unit, is energized, and to reduce the adverse effects on the electric lamp, the CRT display and the like on the same power supply line.

[0018]

In order to achieve the above object, according to the present invention, in the printing state, both heaters (heating sources) are not extinguished, and either heater is turned on. By driving the heater, the lighting state of the heater can be set to only two states (1) both ON and (2) one ON. Also,
By driving the two heaters with an ON / OFF cycle of 1 second or less, almost no rush current is generated when the heaters are energized. This is because there is almost no decrease in the temperature of the energized portion of the heater due to the short OFF time, and the resistance value does not decrease.

With such a configuration, the present invention can reduce the load fluctuation of the power supply line when the heater is energized, and reduce the harmful effects on the electric lamp, the CRT display and the like on the same power supply line.

More specifically, the present invention has a pair of heat fixing means and a pressure means for fixing by carrying a transfer material carrying a toner image on the surface in a nip portion, and the heat fixing means is provided. In an image forming apparatus provided with a heat fixing device having a plurality of heating sources for heating, at least one of the plurality of heat sources is at least one of the plurality of heating sources when the heat fixing device is in a temperature control control state during printing. It has a heating source drive control means for controlling the timing of energization so that two or more are in the energized state and are not energized simultaneously.

In a preferred embodiment of the present invention, the heating source drive control means drives the heating source in a cycle of energized state and de-energized state of 1 second or less to detect the temperature of the heat fixing means. The heat fixing unit is controlled to a predetermined temperature by increasing or decreasing the energization time within the cycle according to the temperature detected by the temperature detecting unit. The heat fixing unit has a fixing roll having a release layer on the surface of a cylindrical metal roll, and a plurality of halogen heaters as the heating source arranged inside the fixing roll. The control means corresponds to the size of the transfer material to be passed when the thermal fixing device is in the temperature control control state during printing,
Lighting source lighting ratio and ON / OFF of the halogen heater
Temperature control is performed by adjusting the length of the cycle.

As a preferred embodiment of the present invention, the plurality of heating sources are composed of two heaters, and the heating source drive control means is such that each heater is driven ON / O for 1 second or less.
FF cycle is set as 1 unit, and ON / O during printing
Turn on the two heaters so that the FF cycle is continuous,
Also, by shifting the ON timing of the two heaters by 1/2 cycle and setting the minimum lighting time of each heater to a value equal to or larger than the shift amount of the ON timing, the two heaters are At the same time, control so that it does not turn off. Further, as a specific example thereof, the heating source drive control means turns on the two heaters at a cycle of 600 msec when printing the maximum size transfer material.
The two heaters are turned off at the same time by turning on / off the two heaters and the other heaters with their ON timings shifted by 300 msec from each other, and by controlling energization so that both heaters are turned on for at least 300 msec. To avoid becoming ON, and ON / OF for 600 msec.
Temperature control is performed by increasing or decreasing the lighting time within a range of 300 msec to 600 msec in the F cycle.
Then, the heating source drive control means changes the lighting ratio of the two heaters according to the size of the transfer material when printing a small-sized transfer material.

Further, preferably, the two heaters are further divided into two, the electric power of each heater is halved, and the minimum fall time of each heater is halved. Further, when the heating source drive control means determines that the temperature detected by the temperature detection means is lower than a predetermined target temperature, the heating source drive control means increases the lighting time within the ON / OFF cycle, and If it is also determined to be high, the lighting time within the ON / OFF cycle is reduced.

As another preferred embodiment of the present invention, in the case of one-sided reference in which the transfer material is conveyed with one side of the apparatus as a reference surface, the one having the temperature detecting means as a reference surface, The plurality of heating sources includes three heaters, and two light distribution peaks of the three heaters are 10% to 30% of the light distribution peaks of the remaining heaters 402.
It is characterized by making it larger. Further, as a specific example thereof, when using the three heaters, the heating source drive control means divides an ON / OFF cycle of 600 msec into three, and sets a shift amount of the minimum lighting time and energization timing to 200 msec. . Then, the heating source drive control means reduces the lighting ratio of the heater for a small-sized transfer material, and sets the ON / OFF cycle to 500 mse.
The minimum lighting time is set to 100 msec for only one of the three heaters. In addition, the heating source drive control means increases or decreases the lighting time by 20 msec for each of the three heaters and 10 msec for each of the remaining heaters during the temperature control, thereby responding to the size of the transfer material. Temperature control is performed without changing the lighting ratio.

[0025]

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

(First Embodiment) FIG. 5 shows a first embodiment of the present invention.
1 shows a schematic configuration of an image forming apparatus according to an embodiment. Reference numeral 101 denotes a digital latent image type image forming apparatus main body using an electrophotographic technique common to copiers, printers, facsimiles and the like. Inside the main body 101 of the image forming apparatus, a primary charger 10 for charging the photoconductor 102 is charged.
4, a developing device 105 that applies toner (development material) to the charging portion (latent image) on the photoconductor, a transfer separation charging device 106 that transfers the toner image to the transfer paper and removes the transfer paper, and excess residual toner on the photoconductor A cleaner 107 for removing the charge and a pre-exposure lamp 103 for removing the charge are sequentially arranged around the photoconductor 102 rotating in the direction of the arrow in the drawing. The toner image charged and developed on the photoconductor 102 is transferred onto the transfer paper carried in from the transfer paper deck 109 by the transfer separation charger 106, and the transfer paper on which the toner image is transferred is fixed by the conveyor belt 110. It is heat-fixed through the container 108 and is discharged onto the discharge tray 111 outside the apparatus.

On the other hand, laser light emitted from a semiconductor laser 121 for converting an input electric image signal into an optical signal is scanned by a polygon mirror 123 which is directly connected to a polygon motor 122 and rotates, and a light beam is emitted by an imaging lens 124. Are corrected to have equal intervals, the reflection mirror 125 irradiates the photoconductor 102 with the image information, and a latent image is formed on the photoconductor 102. The image signal supplied to the semiconductor laser 121 is obtained by reading a document with a scanner (not shown; also referred to as a document reading device or a reader), a printer,
In the case of a facsimile or the like, it is transmitted as an electric signal through an interface (not shown).

As a first embodiment of the present invention of the fixing device 108, a fixing device having the same structure as that described with reference to FIG. 2 is used, and the same heater light distribution and segment arrangement as described with reference to FIG. 3 are used. This fixing device is A3 size (2
97mm) Transfer material with maximum width of paper (transfer paper)
This is an example of a central reference apparatus that conveys the sheet with the sheet passing center of the apparatus as a reference, and the heater light distribution also has a symmetrical distribution with respect to the sheet passing reference.

Here, the heaters 4a and 4b are both 50
It is driven with a rated power of 0W. The fixing roller 1 has a core metal 11 of aluminum and a diameter of 40 mm and a thickness of 1.0 mm.
Roller of which the surface layer is covered with a release layer 12 of PFA. The pressure roller 2 has a silicone sponge elastic layer 14 on a stainless steel core 13 and a PFA release layer 15 on the surface, and has a diameter of 30 mm and a product hardness of 50 °. By applying pressure, a nip width of 5.0 mm can be created between the fixing roller 1 and the fixing roller 1. Since the temperature detecting element 3 is installed outside the image area, toner does not adhere to the temperature detecting element 3,
No cleaning means is required.

Reference numeral 16 denotes a heater drive control device, which is a central processing unit (CP) that controls the overall operation of the image forming apparatus.
(U) Information such as the size of the transfer material is received from 17 and the heaters 4a and 4b are energized and controlled according to this information and the detected temperature input from the temperature detecting element 3.

In particular, in this example, the fixing devices similar to those shown in FIGS. 2 and 3 are used to heat the heaters 4a and 4b during printing.
The heater drive control device 16 controls as described below so that both are not turned off at the same time.

First, the heaters 4a and 4b are driven with an ON / OFF cycle of 1 second or less as one unit, and the heaters 4a and 4b are controlled so that the ON / OFF cycle is continuous during printing.
Turn on 4b. The temperature control is performed by increasing or decreasing the lighting time of the heaters 4a and 4b within the ON / OFF cycle. That is, when it is determined that the temperature detected by the temperature detection element 3 is lower than the predetermined target temperature, the lighting time within the ON / OFF cycle is increased, and when it is determined that the temperature is higher than the predetermined target temperature. Reduces the lighting time.

By shifting the ON timings of the two heaters 4a and 4b by 1/2 cycle, it is possible to prevent the inrush currents of the two heaters 4a and 4b from overlapping with each other and to turn on the heaters 4a and 4b at the minimum. By setting the time to be equal to or larger than the shift amount of the ON timing, the two heaters 4a and 4b are simultaneously turned off.
Try not to be F.

FIG. 6 shows the heater ON / OFF state when printing the maximum size paper (A3 size paper).
At this time, the heaters 4a and 4b are turned on / off at a cycle of 600 msec to turn the heaters 4a and 4b off.
The driving is performed by shifting the timing of N by 300 msec from each other. Then, set both heaters 4a and 4b to a minimum of 300 mse.
By controlling the energization so that c is lit, two lines are turned on at the same time.
Avoiding the FF state.

The power required for printing is 2
In the device configuration that requires 1000W in total, half of 500W is insufficient in terms of electric power, so 600m
Temperature control is performed by increasing or decreasing the lighting time in the range of 300 msec to 600 msec within the ON / OFF cycle of sec.

For example, as shown in FIG. 7, both heaters 4
a and 4b are in a lighting state of 400 msec (200 msec
When printing is started from (overlap), the lighting time of the heaters 4a and 4b is decreased by 20 msec if the temperature detected by the temperature detection element 3 is equal to or higher than the target temperature, and conversely, if the temperature is lower than the target temperature, the lighting time is increased by 20 msec. Temperature control is performed by increasing.

However, the range of increase and decrease of the lighting time of this heater is in the range of 300 msec to 600 msec, and 16 steps of adjustment can be performed.

Next, heater control during printing of small size paper will be described below. When printing small size paper, the lighting ratio of the heaters 4a and 4b is changed as shown in Table 1 above. For example, when printing B5 size paper, the lighting ratio of the heater is 4a: 4b.
= 5: 1, 600 mse as shown in FIG.
The c cycle is divided into 6 equal parts, and the heater 4a is 5/6 (500 ms).
ec) is the minimum lighting time, heater 4b is 1/6
Energize so that the minimum lighting time is (100 msec). At this time, the lighting time of the heater 4b is set to ON / OF.
By increasing / decreasing with respect to the rear of the F cycle, the state in which both the heaters 4a and 4b are simultaneously lit decreases.
As described above, when the thermal fixing unit is configured by two heaters, it can be said that it is more desirable to increase or decrease the lighting time of one of the heaters based on the time after the ON / OFF cycle.

Next, an example for a high speed machine will be described below. The higher the speed of the machine, the more the electric power required for printing increases. Therefore, even with the configuration of the two heaters 4a and 4b, the heater power per one becomes the same value as that of the low speed machine of the one heater configuration. Therefore, 2 more each of the above-mentioned heaters
The heater control method in the case of division will be described below.

When each of the heaters shown in FIGS. 2 and 3 is further divided into two, as shown in FIG.
Of the 3,44 heaters, 41 and 42 correspond to the above-mentioned heater 4a, and 43 and 44 correspond to the above-mentioned heater 4b. Here, the electric power of each heater 41-44 is 250
W. The power of one heater is 500W to 250
By reducing to W, the inrush current of the heater is also reduced, which is advantageous for voltage fluctuations.

FIG. 10 shows an example of driving each of these heaters 41 to 44 in the same manner as in the case of the above-mentioned two heaters. As shown in FIG. 10, 600 msec
Based on the ON / OFF cycle of, the minimum lighting time per one is set to 150 msec, and the energization timing of the heater is shifted by 150 msec.
One of the four heaters is lit. Here, as a temperature control method, 50 m
150 ms by increasing or decreasing the lighting time in units of sec
The strength of the heater can be changed in 10 steps from ec to 600 msec. As shown in Table 2 below, when the lighting state of the heater changes from 1 to 2, 4 to 5, and 7 to 8 in the figure, only a voltage drop corresponding to a maximum power fluctuation of 250 W occurs, and the 500 W heater It is possible to reduce the voltage fluctuation as compared with the case of two lines.

[0042]

[Table 2]

(Second Embodiment) In the above-described first embodiment of the present invention, the case of the central reference in which the transfer material is conveyed with the sheet passing center of the apparatus as the reference has been described, but the second embodiment of the present invention is described. In the embodiment, the case of one-sided reference in which the transfer material is conveyed with one side of the apparatus as the reference surface will be described below.

In the case of the one-sided reference, as shown in FIG.
With the one with the temperature detection element 3 as the reference surface, the heater is distributed to the small size paper as two
There are three distributions. Letter size (LETTER)
When the width (216 mm) is set to the maximum size, it is appropriate to distribute two lines. When the A3 width (297 mm) is set to the maximum size, distribution to three lines is more suitable for temperature control. It is possible.

The structure of the fixing device is the same as that of the central reference described above in the first embodiment of the present invention except for the heater. Here, the heater 401 is an envelope size (90 to 10
0 mm), heater 401 and heater 402
Target legal size (LEGAL) (216 mm). The sizes of B5 and A5 are controlled by the lighting ratio of the heater 401 and the heater 402. Also,
For heaters 401 and 402, further heater 403
Is added to target B4 to A3 sizes. The electric power of each heater 401 to 403 is 30
0W.

In the light distribution in this case, the heights of the high light distribution areas may be all equal, but in consideration of heat leakage at the end of the fixing roller 1, the light distribution peaks of the heaters 401 and 402 are set as heaters. 10% to 3 with respect to the light distribution peak of 402
It is desirable to increase it by 0%.

Next, a method for controlling temperature control during printing will be described below. Since paper sizes other than LEGAL can be realized by the same control as in the case of the central reference two-heater configuration described above, the case of using three heaters will be described below. When the three heaters 401 to 403 having the light distribution characteristics shown in FIG. 11 are used, 600 ms
By dividing the ec ON / OFF cycle into three and setting the minimum lighting time and energization timing shift amount to 200 msec, it is possible to perform control in the same manner as in the above examples.

Since it is possible to cope with small-sized paper by lowering the lighting ratio of the heater 403, as shown in FIG. 12, the ON / OFF cycle is shortened to 500 msec, and the minimum lighting time of only the heater 403 is set to 100 msec. .

As a result, the lighting ratio of the heater is 40.
The ratio is 1: 402: 403 = 2: 2: 2: 1, which corresponds to the B4 size. In this state, the temperature control is controlled by the heater 4
01 and 402 are 20 msec each, and heater 403 is 1
By increasing or decreasing the lighting time by 0 msec, the control can be performed without changing the lighting ratio corresponding to the paper size.

(Other Embodiments) In the above-described embodiment of the present invention, the case where the heater as the heating source has two to four heaters has been exemplified. The invention is likewise applicable.

The heater drive control device 16 can be composed of an energization pattern generation circuit and a heater drive circuit. This energization pattern generation circuit may have either a hardware configuration or a software configuration.

Furthermore, the present invention may be applied to a system composed of a plurality of devices or an apparatus composed of a single device. Further, it goes without saying that the present invention can be applied to the case where it is achieved by supplying a program to a system or an apparatus. In this case, by reading a storage medium storing a program represented by software for achieving the present invention into the system or the apparatus, the system or the apparatus can enjoy the effects of the present invention. Becomes

[0053]

As described above, according to the present invention,
In the temperature control during printing when multiple heaters (heating sources) are used, all heaters are set to the minimum lighting state by setting the minimum lighting time and the energization timing within the ON / OFF cycle of each heater. Even if one or more heaters are turned on, it is configured so that two or more heaters are not energized at the same time, so by controlling the load fluctuation of one heater to the power supply line, the same power supply line It is possible to reduce the influence of the flicker of the electric lamp connected to the CRT and the distortion of the screen of the CRT display.

[Brief description of drawings]

FIG. 1 is a sectional view showing a structure of a conventional heat fixing device having a single heater structure.

FIG. 2 is a sectional view showing the structure of a heat fixing device having a two-heater structure to which the present invention can be applied.

FIG. 3 is a characteristic diagram showing the relationship between the light distribution in the longitudinal direction and the segment arrangement of the two-heater configuration of FIG.

FIG. 4 is a waveform diagram showing a current waveform of a heater having the single heater configuration of FIG.

FIG. 5 is a sectional view with a block diagram showing the configuration of the image forming apparatus of the first embodiment of the present invention.

FIG. 6 is a timing diagram showing a minimum lighting state of the heater according to the first embodiment of the present invention when printing with a two-heater configuration.

FIG. 7 is a timing diagram showing the relationship between the output of the temperature detection element and the lighting state of the heater in the first embodiment of the present invention during printing in the two-heater configuration.

FIG. 8 is a first example of the present invention when printing small size paper.
It is a timing chart which shows the lighting state of two heaters in an embodiment.

FIG. 9 is a characteristic diagram showing a relationship between a longitudinal light distribution and a segment arrangement of four heaters when the heater power is divided into two in the configuration of FIG. 2 in the first embodiment of the present invention.

FIG. 10 is a timing diagram showing heater driving timing in the heater configuration of FIG.

FIG. 11 is a characteristic diagram showing the relationship between the heater light distribution in the longitudinal direction and the segment arrangement in the one-sided reference device configuration according to the second embodiment of the present invention.

FIG. 12 is a timing chart showing the driving timing of the heater in the heater configuration of FIG.

FIG. 13 is a waveform diagram showing a current waveform in a lighting state of two heaters according to conventional temperature control.

[Explanation of symbols]

 1 Fixing Roller 2 Pressure Roller 3 Temperature Detection Element 4, 4a, 4b Heater 5 Separation Claw 6 Fixing Entrance Guide 11 Core Bar 12 Releasable Resin Layer (Release Layer) 13 Metal Core Bar (Stainless Bar) 14 Elastic Layer 15 coating layer (release layer) 16 heater drive control device 17 central processing unit 41-44, 401-403 heater P transfer material T toner

Claims (12)

[Claims] 1. A pair of heat fixing means for fixing by fixing a transfer material carrying a toner image on the surface in a nip portion, and a pressure means, and a heating source for heating the heat fixing means. In an image forming apparatus including a plurality of heat fixing devices, when the heat fixing device is in a temperature control control state during printing, at least one or more of the plurality of heat sources are in a conductive state, and 2 An image forming apparatus comprising: a heating source drive control unit that controls the timing of energization so that three or more are not energized simultaneously. 2. The heating source drive control means drives the heating source in a cycle of an energized state and a non-energized state of 1 second or less,
2. The thermal fixing unit is controlled to a predetermined temperature by increasing or decreasing an energization time within the cycle according to a temperature detected by a temperature detecting unit detecting the temperature of the thermal fixing unit. Image forming device. 3. The heat fixing unit has a fixing roll having a release layer on the surface of a cylindrical metal roll, and a plurality of halogen heaters arranged inside the fixing roll as the heat source. The heating source drive control means, when the thermal fixing device is in a temperature control control state during printing, corresponds to the size of the transfer material to be passed, and the heating source lighting ratio and the ON / OFF cycle of the halogen heater. The image forming apparatus according to claim 2, wherein the temperature control is performed by adjusting the length of the image forming apparatus. 4. The plurality of heating sources are composed of two heaters, and the heating source drive control means sets each ON / OFF cycle of one second or less for driving each heater to be ON during printing. The two heaters are turned on so that the ON / OFF cycles are continuous, and the ON timings of the two heaters are shifted by 1/2 cycle, and the minimum lighting time of each heater is the same as the ON timing shift amount. 4. The image forming apparatus according to claim 1, wherein the two heaters are controlled so as not to be turned off at the same time by setting a value larger than that. 5. The heating source drive control means drives the two heaters ON / OFF at a cycle of 600 msec to print the maximum size transfer material, thereby switching between the one heater and the other heater of the two heaters. It is avoided that two heaters are turned off at the same time by driving the heaters with their ON timings shifted by 300 msec, and controlling the energization so that both heaters are turned on for at least 300 msec.
300m in ON / OFF cycle of 600msec
The image forming apparatus according to claim 4, wherein the temperature control is performed by increasing or decreasing the lighting time in the range of sec to 600 msec. 6. The heating source drive control means changes the lighting ratio of the two heaters according to the size of the transfer material when printing a small-sized transfer material. Alternatively, the image forming apparatus according to item 5. 7. The two heaters are further divided into two,
7. The image forming apparatus according to claim 4, wherein the electric power of each heater is halved and the minimum fall time of each heater is halved. 8. The heating source drive control means, when it judges that the temperature detected by the temperature detection means is lower than a predetermined target temperature, increases the lighting time in the ON / OFF cycle to set the predetermined temperature. 8. The image forming apparatus according to claim 4, wherein the lighting time within the ON / OFF cycle is reduced when it is determined that the temperature is higher than the target temperature. 9. In the case of one-sided reference in which the transfer material is conveyed with one side of the apparatus as a reference surface, the one on which the temperature detecting means is installed is used as a reference surface, and the plurality of heating sources are three.
4. A heater comprising three heaters, wherein two of the three heaters have light distribution peaks which are 10% to 30% larger than the light distribution peaks of the remaining heaters 402. The image forming apparatus according to any one of claims. 10. The heating source drive control means, when using the three heaters, turns on / off for 600 msec.
The image forming apparatus according to claim 9, wherein the OFF cycle is divided into three, and the minimum lighting time and the energization timing shift amount are set to 200 msec. 11. The heating source drive control means reduces the lighting ratio of the heater for a small-sized transfer material, and shortens the ON / OFF cycle to 500 msec.
The minimum lighting time is 1 for only one of the two heaters
The image forming apparatus according to claim 10, which is set to 00 msec. 12. The heating source drive control means, when temperature control is performed, two of the three heaters have 20 msec.
The image forming apparatus according to claim 11, wherein temperature control is performed without changing the lighting ratio corresponding to the size of the transfer material by increasing or decreasing the lighting time of the remaining heaters by 10 msec.