JPH11161095A - Fixing device and image forming device equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make virtually permissible electric power possible to be supplied, even when both of halogen heaters for a fixing roller and the pressure roller are not allowed to fully turn up, for the sake of a counter measure with respect to the higher harmonic and flicker such as at the waiting time or the returning time after completion of processing jamming, and to make the waiting time or the returning time to the virtually permissible time in view thereof. SOLUTION: This device, provided with a fixing device 18 capable of fix- processing while transporting in holding a recording material P between the fixing roller 29 and the pressure roller 30 respectively incorporating the halogen heaters 36 and 37, and the controlling device 39 capable of controlling the surface temp. on rollers 29 and 30 by controlling conduction to the halogen heaters 36 and 37, is allowed to perform the time division control that the controlling device 39 is successively energizing the respective halogen heater 36 and 37. At this time, for the controlling device 39, one cycle of the time division control after the waiting time or the returning time after the completion of processing jamming is set to 0.01<=T<=2 sec.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device provided in an electrophotographic image forming apparatus such as a copying machine or a laser beam printer, and an image forming apparatus having the fixing device.

[0002]

2. Description of the Related Art Normally, a full-color image forming apparatus can select a full-color mode or a mono-color mode. When the full-color image mode is selected, the full-color image forming apparatus forms an electrostatic latent image on an image carrier (photosensitive drum) according to a color separation signal of a document image, and develops the latent image with a colored toner. Then, each time one-color development is performed, the toner image is transferred to a recording material on a transfer device (transfer drum) to form a full-color toner image, and then the toner image on the recording material separated from the transfer device is fixed by a fixing device. On the other hand, when the mono-color mode is selected, fixing is performed after development and transfer for one color. Further, the fixing device includes a fixing roller and a pressure roller, and both of the rollers have built-in heating means such as a halogen heater.

For the fixing roller and the pressure roller, it is desirable to simultaneously turn on (full light) halogen heaters having large power consumption and to obtain a sufficient amount of generated heat in order to improve the fixing property. However, at the time of the copy sequence, it is necessary to simultaneously supply electric power not only to cause the fixing device to generate heat but also to turn on the heater for reading the original image and to rotate the driving motor of each section of the main body. Therefore, at the time of the copy sequence, there is no margin in the supplied power, and it is impossible to fully turn on the halogen heaters of both the fixing roller and the pressure roller.

[0004]

As described above, in the full-color image forming apparatus, at the time of waiting or at the time of restoration after the completion of the jam processing, the halogen of the fixing roller and the pressure roller is reduced to prevent harmonics and flicker. The heater could not be fully turned on, and as a result, there was a possibility that the wait time or the return time would become long. Further, at the time of monocolor continuous printing, a difference in fixing temperature between the first recording sheet and a plurality of recording materials becomes large, which may cause a gloss difference.

A first object of the present invention is to provide a method for controlling the heating of both the fixing roller and the pressing roller when full lighting is not desirable, such as during a wait or at the time of recovery after the end of jam processing. A fixing device capable of supplying power that is practically acceptable, and having a practically negligible wait time or recovery time, or
An object of the present invention is to provide an image forming apparatus having the fixing device.

A second object of the present invention is to provide a fixing device in which the temperature difference between the first sheet and a plurality of sheets is reduced as much as possible during the formation of a monocolor continuous image, thereby eliminating the gloss difference.
Another object is to provide an image forming apparatus having the fixing device.

[0007]

According to the present application, the first object is to provide a cylindrical or substantially cylindrical rotatable fixing roller heated by a plurality of heating means and pressed against each other. A fixing device configured to perform a fixing process by passing a sheet-shaped recording material carrying an unfixed image between the pressure roller and a pressure roller, wherein at least one of a fixing roller and a pressure roller is provided. A temperature detector that detects the temperature of the roller is provided, and the ratio of the energizing time from the commercial power supply to each heating means within a specified cycle is set according to a comparison between the detected temperature of the temperature detector and the target temperature. In the fixing device, the removal of the recording material jammed in the nip formed between the start of each heating unit and the time when both rollers are heated to the target temperature or between the two rollers pressed against each other. rear In the time of return, the length T of the defined cycle is achieved by the first invention of is set to 0.01 ≦ T ≦ 2 seconds.

According to the present application, the second object is to
By passing a sheet-shaped recording material carrying an unfixed image between a cylindrical or substantially cylindrical rotatable fixing roller and a pressure roller which are heated by a plurality of heating means and pressed against each other, A fixing device adapted to perform a fixing process, comprising: a temperature detector that detects a temperature of at least one of a fixing roller and a pressure roller; When performing a fixing process on a recording material carrying a monocolor unfixed image in a fixing device in which the ratio of the energization time from the commercial power supply to each heating unit within a specified period is set according to the comparison. According to the second aspect of the present invention, the length T of the prescribed period is set to 0.01 ≦ T ≦ 2 seconds.

Further, according to the present application, the first object or the second object is that in the first invention or the second invention according to the present application, the fixing roller is heated from a commercial power supply within a prescribed period. The third invention that the energizing time to the heating means for heating the pressure roller from the commercial power supply in the above-mentioned specified period is taken longer than the energizing time to the heating means for the above-mentioned specified cycle is also achieved. You.

Further, according to the present application, the first object or the second object is that, in the first invention or the second invention according to the present application, consumption of heating means for heating the fixing roller is achieved. This is also achieved by the fourth invention in which the power is set to be larger than the power consumption of the heating means for heating the pressure roller.

Further, according to the present application, the first object is to provide a cylindrical or substantially cylindrical or cylindrical or substantially cylindrical rotatable latent image carrier which is formed on a peripheral surface of a rotatable latent image carrier by exposure. A developing device that visualizes the latent image with a developer, a transfer device that transfers the visible image formed on the outer peripheral surface to a sheet-shaped recording material, and the fixing device according to claim 1.
The present invention is also achieved by the fifth invention having a control means for controlling the supply of electricity from a commercial power supply to each heating means provided in the fixing device.

According to the present application, the second object is to
A developing device for visualizing, by a developer, an electrostatic latent image formed on an outer peripheral surface of a rotatable latent image carrier having a cylindrical or substantially cylindrical shape or a cylindrical or substantially cylindrical shape by exposure, and the outer peripheral surface; A transfer device for transferring the visible image formed on the sheet to a sheet-shaped recording material; a fixing device according to claim 2; and a control device for controlling energization from a commercial power supply to each heating device provided in the fixing device. This is also achieved by the sixth invention having:

Further, according to the present application, the first object or the second object is that in the fifth invention or the sixth invention according to the present application, the fixing roller is heated from a commercial power supply within a prescribed period. The present invention is also achieved by the seventh invention in which the energizing time to the heating means for the heating means is set to be longer than the energizing time to the heating means for heating the pressure roller from the commercial power supply within the specified period. You.

Further, according to the present application, the first object or the second object is that in the fifth invention or the sixth invention according to the present application, the consumption of the heating means for heating the fixing roller is achieved. The present invention is also achieved by the eighth invention in which the power is set to be larger than the power consumption of the heating means for heating the pressure roller.

That is, in the first invention according to the present application, the ratio of the energizing time from the commercial power supply to each heating means within a specified period is determined in accordance with the comparison between the detected temperature of the temperature detector and the target temperature. In addition to the setting, a period from when each heating unit is started to when both rollers are heated to a target temperature, or after a recording material jammed in a nip formed between both rollers pressed against each other is removed. The length T of the specified cycle at the time of return is set to 0.01 ≦ T ≦ 2 seconds.

In the second invention according to the present application,
According to the comparison between the detected temperature of the temperature detector and the target temperature, the ratio of the energizing time from the commercial power supply to each heating means within the specified period is set, and the fixing process is performed on the recording material carrying the unfixed monocolor image. Is set to 0.01 ≦ T ≦ 2 seconds.

Further, in the third invention according to the present application, the energization time from the commercial power supply to the heating means for heating the fixing roller in the specified cycle is increased by the application time from the commercial power supply in the specified cycle. It is taken longer than the energizing time to the heating means for heating the pressure roller.

Further, in the fourth invention according to the present application,
The power consumption of the heating means for heating the fixing roller is set to be greater than the power consumption of the heating means for heating the pressure roller.

Further, according to the fifth invention of the present application, the commercial power supply within a specified period is determined in accordance with a comparison between a target temperature and a detected temperature of a temperature detector provided in a fixing device of the image forming apparatus. To set the ratio of the energizing time to each heating means, and formed between the start of each heating means and the time when both rollers rise to the target temperature, or between both rollers pressed against each other. The length T of the specified period at the time of restoration after the removal of the recording material jammed in the nip portion is set to 0.01 ≦ T ≦ 2 seconds.

In the sixth invention according to the present application,
According to the comparison between the detected temperature of the temperature detector provided in the fixing device of the image forming apparatus and the target temperature, the ratio of the energizing time from the commercial power supply to each heating means within the specified period is set, and the mono-color is set. The length T of the above-mentioned specified period when the fixing process is performed on the recording material carrying the unfixed image is set to 0.01 ≦ T ≦ 2 seconds.

Further, in the seventh invention according to the present application, the energization time from the commercial power supply to the heating means for heating the fixing roller provided in the fixing device of the image forming apparatus within a prescribed period is set. The power supply time for the heating means for heating the pressure roller from the commercial power supply within the specified period is taken longer.

In the eighth invention according to the present application,
The power consumption of the heating means for heating the fixing roller provided in the fixing device of the image forming apparatus is set to be larger than the power consumption of the heating means for heating the pressure roller.

[0023]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) First, a first embodiment of the present invention will be described with reference to FIGS.

FIG. 2 shows a full-color image forming apparatus according to the present embodiment. The image forming apparatus includes a document scanning and reading unit A, a photosensitive drum 6 as an image carrier on which an electrostatic latent image is formed by image information read by the document scanning and reading unit A, A developing device 9 for supplying toner to the upper latent image to develop the latent image; a transfer drum 11 as a transfer device for holding the recording material P and transferring the toner image from the photosensitive drum 6 to the recording material P; And a fixing device 18 for fixing the toner image on the recording material separated from the recording material 11.

The developing device 9 includes a cyan developing device 9C, a magenta developing device 9M, a yellow developing device 9Y, a black developing device 9
K is provided. The surface of the rotating photosensitive drum 6 is charged, and is exposed by a laser beam modulated by a cyan image signal among color separation image signals of a target color image. The electrostatic image formed on the photosensitive drum 6 is developed by the cyan developing device 9C. Then, the cyan toner image on the photosensitive drum 6 is transferred to the transfer drum 11.
Is transferred to the recording material P held in the printer. This operation is repeated for magenta, yellow, and black, and a full-color toner image corresponding to the target color image is formed on the recording material P. In the case of the mono-color mode, one of the colors is selected, and a mono-color image is formed on the recording material P.

The fixing device 18 is shown enlarged in FIG.

The fixing device 18 includes a fixing roller 29, a pressure roller 30 pressed against the fixing roller 29, and a control device 39 as control means for controlling the temperatures of the fixing roller 29 and the pressure roller 30. Have. The fixing roller 29 and the pressure roller 30 are in pressure contact with each other by a pressure mechanism (not shown), and are configured to sandwich and convey the recording material P onto which the unfixed toner image has been transferred.

The fixing roller 29 includes a cylindrical or substantially cylindrical core metal 31 made of aluminum, and an HTV (high temperature vulcanization type) silicone rubber layer 32 formed on the core metal 31.
And an RTV (low-temperature vulcanization type) silicone rubber layer 33 formed on the HTV silicone rubber layer 32. The total thickness of the silicone rubber layers 32 and 33 is 2.
4 mm and a diameter of 60 mm.

On the other hand, the pressure roller 30 has a cylindrical or substantially cylindrical core metal 34 made of aluminum and a silicone rubber layer 35. The silicone rubber layer 35 has a thickness of 1.8 mm and a diameter of 60 mm.

The fixing roller 29 has a halogen heater 36 as heating means disposed in a hollow portion of the cored bar 31.
The pressure roller 30 also has a halogen heater 37 as heating means disposed in the hollow portion of the metal core 34.
Thereby, both sides of the recording material P are heated. Further, the pressure roller 30 is arranged such that a thermistor 38 as a temperature detector contacts the surface thereof. The thermistor 38 detects the temperature of the pressure roller 30 and sends a detected temperature signal to the control device 39. The control device 39 controls the temperature of the halogen heaters 36 and 37 based on the temperature detected by the thermistor 38 and
9 and the temperature of the pressure roller 30 are kept constant (17 in this example).
0 ° C.).

Reference numeral 50 denotes a release agent (oil) coating device for the fixing roller 29, reference numeral 60 denotes a cleaning device for removing deposits on the surface of the fixing roller 29, and reference numeral 70 denotes a cleaning device for the pressure roller 30. ing.

By the way, at the time of full-color fixing, the fixing roller 29 and the pressure roller 30
It is desirable that the halogen heaters 36 and 37 are fully lit. However, since the generation of high frequency must be regulated, there is a restriction that it must be kept within 700 w. In order to cope with this, in the present embodiment, the inrush current at the time of the wait or at the time of recovery after the jam processing is used, and by taking advantage of the apparent power, the wait time or the recovery time that is practically acceptable will be achieved. It is assumed that. Inrush current means switch ON
It is a current that flows at the moment when it occurs and has a value larger than the specified current.

In this embodiment, the halogen heaters 36 and 37 of the fixing roller 29 and the pressure roller 30 are 600
A halogen heater of W was used. And the control device 39
Is 1 at the time of weighting as shown in the time chart of FIG.
The period was set to 0.4 second, and the time division ratio between the fixing roller 29 and the pressure roller 30 was set to 28:12. That is, the control was performed such that the fixing roller 29 was turned on for 0.28 seconds and the pressure roller 30 was turned on for 0.12 seconds in one cycle. The power supply voltage is 100V.

However, in the case where a plurality of recording materials are continuously formed in a monocolor image, instead of the full color mode described above, the number of recording materials passing through the fixing device per unit time is larger than that in the full color mode. Many. For this reason, the rollers 29 and 30 have been conventionally compared to the full color mode.
The temperature of the surface was easily lowered, and as a result, low-temperature offset was easily generated. In particular, since the fixing roller 29 is deprived of heat by the toner in addition to the recording material, the surface temperature of the fixing roller 29 is more likely to be lower than that of the pressure roller 30, and may be lower than the fixing temperature. This low-temperature offset of the fixing roller 29 was remarkable when the apparatus was placed in a low-temperature environment of 15 ° C. or lower.

Therefore, the energizing time of the fixing roller 29 to the halogen heater 36 within one cycle is set to be longer than that of the pressing roller 30 (time division ratio 28:12).
Low temperature offset was prevented. Further, in the present embodiment, in order to reduce a gloss difference caused by a large difference between the temperature of the first sheet and the temperature of the plurality of sheets during the continuous fixing of the mono-color, the same as in the above-described wait state Is controlled as follows.

In this embodiment, the halogen heaters 36 and 37 of the fixing roller 29 and the pressure roller 30 are 600
A halogen heater of W was used. At the time of mono-color continuous printing, as shown in FIG.
Seconds were turned on sequentially during image formation at a time division ratio of 28:12.

The change in gloss under the conditions shown in FIG. 1 was measured as follows. At that time, the gloss is DIN
It was measured by the 75-degree method.

The copying apparatus was left under a low-temperature environment of 15 ° C. for 24 hours, and A3 (basis weight 8
0 g / m ² ) paper was continuously passed in a monocolor mode, and the surface temperature of the fixing roller 29 during the paper passing was monitored. The result was as shown in FIG. FIG. 4 also shows a conventional example for comparison.

As is apparent from the above, the lowest point was 130 ° C. in the related art, but in the present embodiment, it did not drop below 155 ° C. The gloss is also 10 in this embodiment.
It was 15 for the first sheet and 18 for the 100th sheet.

As described above, in the case of continuous printing in the mono-color mode, the apparent power has been increased.
Even when the copying apparatus was placed in a low-temperature environment, the gloss difference could not be visually discriminated.

During full-color copying, one cycle T of time division may be, for example, 4 seconds. This is because less power is required during full-color copying than when continuous monochrome printing is performed.

(Second Embodiment) Next, a second embodiment will be described.

In the second embodiment, continuous printing in the mono-color mode was performed under the same conditions as in the first embodiment except that the lighting cycle of the halogen heaters 36 and 37 was 0.2 seconds.

As a result, the same result as in the first embodiment was obtained. Furthermore, as a result of performing similar experiments with various lighting cycles, the lighting cycle T of the halogen heater was 0.01
It was found that the selection can be made arbitrarily within the range of ≦ T ≦ 2 seconds.

(Third Embodiment) Next, a third embodiment will be described.

In the first embodiment, the fixing roller 2
A halogen heater of 600 W was used for both the halogen heaters 9 and 9 and the pressure roller 30. And
One cycle was set to 0.4 seconds, and the lights were sequentially turned on at a time division ratio of 28:12. On the other hand, in the present embodiment, a heater of 700 W is used as the halogen heater 36 of the fixing roller 29, and a heater of 500 W is used as the halogen heater 37 of the pressure roller 30. Under the conditions, continuous printing in the monocolor mode was performed, and the fixing temperature and gloss at that time were confirmed.

As a result, the lowest point of the temperature was shifted only by ± 2 ° C. as compared with the case of the first embodiment, and the gloss difference could not be visually discriminated.

According to the present embodiment, since the electric power of the halogen heater 36 of the fixing roller 29 is made larger than the electric power of the halogen heater 37 of the pressing roller 30, low-temperature offset of the fixing roller 29 is prevented.

(Fourth Embodiment) Next, a fourth embodiment will be described.

In the first embodiment, the fixing roller 2
The thicknesses of the silicone rubber layers of the fixing roller 29 and the pressure roller 30 are set to 2.4 mm and 1.8 mm, respectively. Are changed to 2 mm and 1 mm, respectively, and the other conditions are the same as those in the first embodiment.
Continuous printing in the monocolor mode was performed, and the fixing temperature and gloss at that time were checked.

As a result, the lowest point of the temperature was only shifted by ± 2 ° C. from the case of the first embodiment, and the gloss difference could not be visually discriminated.

From this, it was confirmed that the fixing performance in the mono color mode was improved by the control of the present invention.

[0054]

As described above, according to the first invention of the present application, each of the commercial power sources within a specified period is set in accordance with the comparison between the detected temperature of the temperature detector and the target temperature. In addition to setting the ratio of the energizing time to the heating means, a nip formed between the time when each heating means is started and when both rollers are heated to the target temperature, or between the two rollers pressed against each other Since the length T of the specified period at the time of return after the removal of the recording material jammed is set to 0.01 ≦ T ≦ 2 seconds, the inrush current can be used and the apparent power can be gained. Therefore, during the period from the start of each heating means to the time when both rollers rise to the target temperature, or when returning after removing the recording material jammed in the nip formed between the two rollers pressed against each other. All heating means can be fully lit like Can supply power that is practically acceptable even under severe conditions.Therefore, between the time when each heating means is started and when both rollers are heated to the target temperature, or when both rollers are pressed against each other. The length from the removal of the recording material jammed in the nip formed between them to the return of the recording material can be set to a practically acceptable length.

Further, according to the second invention of the present application, the ratio of the energizing time from the commercial power supply to each heating means within the specified period is determined in accordance with the comparison between the detected temperature of the temperature detector and the target temperature. In addition to the setting, when the fixing process is performed on a recording material carrying a monocolor unfixed image, the length T of the specified period is set to 0.01 ≦ T ≦ 2 seconds, so that the rush current can be used. You can earn apparent power,
Therefore, even in a situation where all the heating means cannot be fully turned on, such as when a fixing process is performed on a recording material carrying a monocolor unfixed image, it is possible to supply power that is practically acceptable, and The length during which the fixing process is performed on the recording material carrying the color unfixed image can be set to a practically acceptable length.

Further, according to the third invention of the present application,
The energization time from the commercial power supply to the heating means for heating the fixing roller in the specified cycle is taken longer than the energization time from the commercial power supply to the heating means for heating the pressure roller in the specified cycle. Therefore, low-temperature offset to the fixing roller can be prevented.

In the fourth invention according to the present application,
Since the power consumption of the heating means for heating the fixing roller is set to be larger than the power consumption of the heating means for heating the pressure roller, low-temperature offset to the fixing roller can be prevented.

Further, according to the fifth invention of the present application, the commercial power supply within a prescribed period is determined in accordance with a comparison between a target temperature and a temperature detected by a temperature detector provided in a fixing device of the image forming apparatus. To set the ratio of the energizing time to each heating means, and formed between the start of each heating means and the time when both rollers rise to the target temperature, or between both rollers pressed against each other. Since the length T of the above specified period at the time of return after the removal of the recording material jammed in the nip portion is set to 0.01 ≦ T ≦ 2 seconds, it is possible to use the rush current and to gain apparent power. Can, and therefore,
From the start of each heating means to the time when both rollers rise to the target temperature, or when returning after removing the recording material jammed in the nip formed between the two rollers pressed against each other. Even in a situation where all the heating means cannot be fully turned on, it is possible to supply power that is practically acceptable, and thus, from the start of each heating means until both rollers rise to the target temperature, Alternatively, it is possible to provide an image forming apparatus that can be set to a practically acceptable length from the time when the recording material clogged in the nip formed between the two rollers pressed against each other is returned to the time when it is returned.

Further, according to the sixth aspect of the present invention, the commercial power supply within a specified period is determined according to a comparison between the target temperature and the temperature detected by the temperature detector provided in the fixing device of the image forming apparatus. , The ratio of the energizing time to each heating means is set, and the length T of the specified cycle when the fixing process is performed on the recording material carrying the monocolor unfixed image is 0.
Since 01 ≦ T ≦ 2 seconds, the inrush current can be used and the apparent power can be gained. Therefore, when the fixing process is performed on the recording material carrying the unfixed monocolor image, Even under the condition that all heating means cannot be fully lit, it is possible to supply power that is practically acceptable,
Thus, it is possible to provide an image forming apparatus capable of setting the length of the recording material carrying a monocolor unfixed image to a practically acceptable length while the fixing process is performed.

Further, in the seventh invention according to the present application, the energization time from the commercial power supply to the heating means for heating the fixing roller provided in the fixing device of the image forming apparatus within the specified period is set. The present invention provides an image forming apparatus capable of preventing a low-temperature offset from being applied to a fixing roller because a longer time is taken for energizing a heating unit for heating a pressure roller from a commercial power supply within the specified period. Can be.

In the eighth invention according to the present application,
Since the power consumption of the heating means for heating the fixing roller provided in the fixing device of the image forming apparatus is set to be larger than the power consumption of the heating means for heating the pressure roller, An image forming apparatus in which low-temperature offset is prevented can be provided.

[Brief description of the drawings]

FIG. 1 is a timing chart showing lighting timing of a halogen heater of a fixing device provided in an embodiment of an image forming apparatus according to the present application.

FIG. 2 is a cross-sectional view illustrating the entire image forming apparatus according to the present application.

FIG. 3 is a sectional view of a fixing device included in the image forming apparatus of FIG. 2;

FIG. 4 is a graph showing a change in the surface temperature of a fixing roller when performing continuous monocolor printing under the control of FIG. 1;

[Explanation of symbols]

 Reference Signs List 6 photosensitive drum (latent image carrier) 9 developing device 11 transfer drum (transfer device) 18 fixing device 29 fixing roller 30 pressure roller 36 halogen heater of fixing roller (heating means) 37 halogen heater of pressure roller (heating means) ) 39 control device (control means) P recording material

Claims (8)

[Claims] 1. A sheet-like recording material carrying an unfixed image between a cylindrical or substantially cylindrical rotatable fixing roller and a pressure roller heated by a plurality of heating means and pressed against each other. A fixing device adapted to perform a fixing process by passing paper, comprising a temperature detector for detecting a temperature of at least one of a fixing roller and a pressure roller, and detecting a temperature of the temperature detector. In a fixing device in which the ratio of the energization time from the commercial power supply to each heating means within a specified period is set in accordance with the comparison between the heating means and the target temperature, both rollers are set to the target temperature from the start of each heating means. Until the temperature rises, or at the time of return after the removal of the recording material jammed in the nip formed between the two rollers pressed against each other, the length T of the specified period is set to 0.1. 01 A fixing device, wherein ≤ T ≤ 2 seconds. 2. A sheet-like recording material carrying an unfixed image between a cylindrical or substantially cylindrical rotatable fixing roller and a pressure roller heated by a plurality of heating means and pressed against each other. A fixing device adapted to perform a fixing process by passing paper, comprising a temperature detector for detecting a temperature of at least one of a fixing roller and a pressure roller, and detecting a temperature of the temperature detector. In the fixing device, the ratio of the energizing time from the commercial power supply to each heating means within a specified period is set in accordance with the comparison between the target temperature and the recording material carrying a monocolor unfixed image. When performing the fixing process, the fixing device is characterized in that the length T of the specified cycle is set to 0.01 ≦ T ≦ 2 seconds. 3. The energizing time from the commercial power supply to the heating means for heating the fixing roller in the specified cycle is the energizing time from the commercial power supply to the heating means for heating the pressure roller in the specified cycle. The fixing device according to claim 1, wherein the fixing device is longer than the fixing device. 4. The power consumption of the heating means for heating the fixing roller is set to be larger than the power consumption of the heating means for heating the pressure roller.
Or a fixing device according to claim 2. 5. A developing device for visualizing, by a developer, an electrostatic latent image formed on an outer peripheral surface of a rotatable latent image carrier having a cylindrical or substantially cylindrical shape or a cylindrical or substantially cylindrical shape by exposure. A transfer device for transferring a visible image formed on the outer peripheral surface to a sheet-like recording material; a fixing device according to claim 1; and a power supply from a commercial power supply to each heating unit provided in the fixing device. An image forming apparatus comprising: a control unit configured to control the image forming apparatus. 6. A developing device for visualizing, with a developer, an electrostatic latent image formed on an outer peripheral surface of a cylindrical or substantially cylindrical or cylindrical or substantially cylindrical rotatable latent image carrier by exposure. A transfer device for transferring a visible image formed on the outer peripheral surface to a sheet-like recording material; a fixing device according to claim 2; and power supply from a commercial power supply to each heating unit provided in the fixing device. An image forming apparatus comprising: a control unit configured to control the image forming apparatus. 7. The energizing time from the commercial power supply to the heating means for heating the fixing roller in the specified cycle is the energizing time from the commercial power supply to the heating means for heating the pressure roller in the specified cycle. The image forming apparatus according to claim 5, wherein the image forming apparatus is longer than the image forming apparatus. 8. The power consumption of the heating means for heating the fixing roller is set to be larger than the power consumption of the heating means for heating the pressure roller.
Or an image forming apparatus according to claim 6.