JP6739209B2 - Fixing device and image forming apparatus - Google Patents

Description

The present invention relates to a fixing device for heating and fixing a developer image formed on a recording material, and an image forming apparatus such as an electrophotographic device or an electrostatic recording device having the fixing device.

In recent years, a film heating fixing type fixing device has been proposed in order to save power and shorten the time from power-on to image output (for example, Patent Documents 1 and 2). The fixing device of the film heating fixing type has a heater and a heater unit composed of a fixing film that rotates while being in pressure contact with the heater, and a pressing member that brings a recording material into close contact with the heater unit. The fixing device of the film heating fixing system heats and fixes the toner image formed on the surface of the recording material by applying the heat of the heater to the recording material through the fixing film.

The film heat fixing type fixing device can reduce the heat capacity of the film, which is a fixing member, to several tenths of that of the heat roller, as compared with the heat roller type fixing device. Therefore, such a film heat fixing type fixing device can shorten the time required to raise the temperature of the portion for heating the recording material to the fixing possible temperature to several seconds, which is realized by the heat roller type fixing device. This makes it possible to carry out so-called on-demand fixing, which was difficult.

Conventionally, the fixing device of the film heating fixing system has a problem that the non-sheet passing portion of the heater becomes extremely high in temperature and the members of the fixing device are destroyed by heat. On the other hand, in the conventional film heating and fixing type fixing device, measures such as detecting the temperature of the non-sheet passing portion and lowering the target fixing temperature based on the detected temperature or increasing the paper interval to radiate heat are taken. Has been given.

JP-A-63-313182 JP-A-2-157878

However, in the conventional fixing device, even if the above measures are taken, when the temperature is raised from the room temperature to the target temperature at the time of fixing or when the recording material is continuously passed, the non-sheet passing portion of the heating element is not used. Becomes high temperature, the film surface layer near the non-sheet passing portion of the heating element also becomes high temperature. As a result, in the conventional fixing device, the surface layer of the film near the non-sheet passing portion of the heating element deteriorates, and when the conveyed recording material comes into contact with the deteriorated surface layer of the film, the film deteriorates. There is a problem that the formed surface layer is scraped. In particular, since the edge of the recording material is always in contact with the edge of the paper passing area through which the recording material passes, it is subjected to stronger stress than other paper passing areas and is more easily scraped.

Also, if the deteriorated surface layer of the film is scraped off, an offset image will be generated without being able to perform normal fixing in the part where the surface layer of the film has been scraped, so it will be necessary to replace the film, and the film will have a long life. There is a problem that can not be.

An object of the present invention is to control a non-passage portion of a recording material so that the temperature does not become unnecessarily high and suppress deterioration of the surface layer of the film, and thus a fixing device capable of suppressing abrasion of the surface layer of the film. An image forming apparatus is provided.

A fixing device according to the present invention is a fixing device that applies heat and pressure to a recording material having a developer image formed on its surface in a fixing region to fix the developer image on the recording material, and a pressure unit. A film that forms the fixing area between the pressing means, a heating means that heats the fixing area through the film, and a heating means that controls the fixing area to fix the developer. a control means for a required temperature or more, and the heating means, upon heating, in the width direction perpendicular to the conveying direction of the recording material of the fixing area, the end of the recording material of a predetermined size a first heating means than the temperature of the position the temperature is high the temperature distribution of the position of the central portion of the recording material of the predetermined size, the position of the end portion than the temperature of the position of the central portion of the front Symbol fixing area A second heating unit having a high temperature distribution of the first heating unit and the second heating unit in advance when fixing the recording material of the predetermined size. In the room temperature state, the first heating unit starts heat generation before the leading edge of the recording material of the predetermined size in the transport direction enters the fixing area, and after the leading edge enters the fixing area. To start heating by the second heating means, and keep the first heating means and the second heating means in a heating state until the trailing edge of the recording material of the predetermined size in the transport direction passes through the fixing area. It is characterized by

The image forming apparatus according to the present invention forms a latent electrostatic image on the photosensitive drum by irradiating the photosensitive drum, a charging unit that charges the photosensitive drum, and the photosensitive drum charged by the charging unit with a light beam. Exposure means, developing means for supplying a developer to the electrostatic latent image to form a developer image on the photosensitive drum, and transferring the developer to the recording material to develop the surface of the recording material. It is characterized by comprising a transfer means for forming an agent image and the above-mentioned fixing device.

According to the present invention, it is possible to suppress the abrasion of the surface layer of the film by controlling the non-passage portion of the recording material so as not to have an excessively high temperature and suppressing the deterioration of the surface layer of the film.

1 is a sectional view of an image forming apparatus according to Embodiment 1 of the present invention. FIG. 3 is a sectional view of the fixing device according to the first embodiment of the present invention. FIG. 3 is a bottom view and a plan view of the ceramic substrate according to the first embodiment of the present invention. FIG. 6 is a flowchart showing a fixing process according to the first embodiment of the present invention. FIG. 6 is a diagram showing a temperature transition in the fixing process according to the first embodiment of the present invention. It is a figure which shows the voltage waveform applied to the heating resistor which concerns on Embodiment 1 of this invention. It is a figure which shows the temperature distribution of the width direction of the heater which concerns on Embodiment 1 of this invention. FIG. 6 is a diagram showing a temperature transition in a fixing process when constantly supplying electric power to a heating resistor. It is a figure which shows the relationship between the temperature of the edge part of the width direction of the heater which concerns on Embodiment 1 of this invention, and the life of a film. FIG. 6 is a flowchart showing a fixing process according to Embodiment 2 of the present invention. FIG. 6 is a diagram showing a temperature transition in the fixing process according to the second embodiment of the present invention. FIG. 6 is a diagram showing a temperature transition in a fixing process when constantly supplying electric power to a heating resistor. It is a figure which shows the temperature distribution of the width direction of the heater which concerns on Embodiment 3 of this invention. FIG. 11 is a flowchart showing a fixing process of recording material passing through a sheet passing area R1 according to the third embodiment of the present invention. FIG. 13 is a diagram showing a temperature transition when the falling temperature gradient in the fixing process of the recording material passing through the paper passing area R1 according to the third embodiment of the invention is gentle. It is a figure which shows the table used by the fixing process of the recording material which passes the paper feeding area|region R1 which concerns on Embodiment 3 of this invention. FIG. 16 is a diagram showing a temperature transition when a falling temperature gradient in a fixing process for a recording material passing through a sheet passing region R1 according to the third embodiment of the invention is steep. FIG. 6 is a diagram showing a temperature transition in a fixing process when constantly supplying electric power to a heating resistor. FIG. 11 is a diagram showing a temperature transition in the fixing process when the sheet interval is widened and the energization ratio of the heat generating resistor is reduced between the sheets when the non-sheet passing portion is heated, as compared with the third embodiment. FIG. 11 is a diagram showing a temperature transition in a fixing process for a recording material passing through a paper passing area R2 according to the third embodiment of the present invention. FIG. 11 is a diagram showing a table used in a fixing process for a recording material passing through a paper passing area R2 according to the third embodiment of the present invention. FIG. 13 is a flowchart showing a fixing process for a recording material passing through a paper passing area R3 according to the third embodiment of the present invention. FIG. 13 is a diagram showing a temperature transition in a fixing process for a recording material passing through a paper passing area R3 according to the third embodiment of the present invention. FIG. 13 is a diagram showing a table used in a fixing process for a recording material passing through a paper passing area R3 according to the third embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
<Structure of image forming apparatus>
The configuration of the image forming apparatus S1 according to Embodiment 1 of the present invention will be described in detail with reference to FIG.

The image forming apparatus S1 is exemplified by a laser printer here. The image forming apparatus S1 includes a photosensitive drum 1, a charging roller 2, a laser exposure unit 3, a developing device 4, a transfer roller 5, a cleaning blade 8, a supply roller 10, a cassette 11, and a fixing device 12. ,have.

The photosensitive drum 1 is in a state of being uniformly charged by the charging roller 2. An electrostatic latent image is formed on the surface of the photosensitive drum 1 by being irradiated with laser light from the laser exposure unit 3. The photosensitive drum 1 conveys the electrostatic latent image formed on its surface to the developing device 4 by rotating.

The charging roller 2 is applied with a predetermined bias voltage and comes into contact with the surface of the rotating photosensitive drum 1 to rotate, thereby uniformly charging the surface of the photosensitive drum 1.

The laser exposure unit 3 irradiates the charged surface of the photosensitive drum 1 with laser light, which is a light beam, to form an electrostatic latent image on the surface of the photosensitive drum 1.

The developing device 4 supplies toner to the electrostatic latent image formed on the surface of the photosensitive drum 1 to form a toner image, which is a developer image, on the photosensitive drum 1.

The transfer roller 5 transfers the toner image formed on the photosensitive drum 1 to the recording material 20 by nipping and conveying the recording material 20 at a portion facing the photosensitive drum 1 and applying a transfer voltage.

The heater unit 6 heats and presses the recording material 20 on which the toner image is transferred by the transfer roller 5 with the pressing roller 7 to fix the toner image transferred on the recording material 20 to the recording material 20.

The pressure roller 7 is pressed against the heater unit 6 with a predetermined nip pressure to form a fixing nip. The pressure roller 7 is driven to rotate by rotating the pressure roller 7, and also conveys the recording material 20 introduced into the fixing nip.

The cleaning blade 8 cleans the surface of the photosensitive drum 1 by removing the toner or paper dust remaining on the surface of the photosensitive drum 1 after the toner image is transferred onto the recording material 20.

The supply roller 10 conveys the recording material 20 contained in the cassette 11 to a portion where the photosensitive drum 1 and the transfer roller 5 face each other.

The fixing device 12 is a film heating fixing type fixing device, and includes a heater unit 6 and a pressure roller 7. The fixing device 12 applies heat between the heater unit 6 and the pressure roller 7 to the recording material 20 having a toner image formed on the surface conveyed from the facing portion of the photosensitive drum 1 and the transfer roller 5. By applying pressure, the toner image formed on the recording material 20 is fixed on the recording material 20. The fixing device 12 conveys the recording material 20 on which the toner image is fixed toward the outside of the image forming apparatus S1.

<Structure of fixing device>
The configuration of the fixing device 12 according to the first embodiment of the present invention will be described in detail with reference to FIGS. 2 and 3.

The fixing device 12 includes a heater unit 6, a pressure roller 7, a triac 51, a triac 52, and a CPU 100.

The heater unit 6 presses the pressure roller 7 to form a fixing nip N, and nips and conveys the recording material 20 at the fixing nip N to fix the toner image on the recording material 20.

Specifically, the heater unit 6 includes a heater 600, a film 650, a film guide 660, and a reinforcing metal plate 670.

In the heater 600, the width direction orthogonal to the conveying direction of the recording material 20 corresponds to the width of the recording material 20, and in the fixing nip N which is a fixing area, the heater 600 is applied to the recording material 20 on which the developer image is formed. Give heat. Specifically, the heater 600 includes a ceramic substrate 601, a glass coat layer 605, a resistance heating element 610, an electrode 615, an electrode 616, an electrode 617, and an electrode 618. Further, the heater 600 includes a resistance heating element 620, a thermistor 630, a thermistor 631, and a thermistor 632.

The ceramic substrate 601 has insulation and heat resistance, and has a low heat capacity. A resistance heating element 610 and a resistance heating element 620 are provided on one surface of the ceramic substrate 601. A thermistor 630, a thermistor 631, and a thermistor 632 are provided in contact with the surface of the ceramic substrate 601 opposite to the surface on which the resistance heating element 610 and the resistance heating element 620 are provided.

The glass coat layer 605 covers the resistance heating element 610 and the resistance heating element 620, and also covers a part of the electrode 615, the electrode 616, the electrode 617, and the electrode 618. The glass coat layer 605 rubs against the film 650 when the film 650 rotates. The thickness of the glass coat layer 605 is, for example, 60 μm here.

The resistance heating element 610, which is the first heating unit, is provided on the ceramic substrate 601. The resistance heating element 610 is formed with a uniform width along the width direction. When the resistance heating element 610 generates heat, the heat generation amount becomes uniform in the width direction orthogonal to the conveyance direction of the recording material 20 (left-right direction in FIG. 3A), and the widthwise end portion of the fixing nip N is formed. The temperature distribution in the center is higher than that in the center. The length of the resistance heating element 610 in the width direction is exemplified by 320 mm here. The resistance heating element 610 has a width of 2 mm, for example.

The electrode 615 is provided on the ceramic substrate 601 and connects the power source 30 and the resistance heating element 610.

The electrode 616 is provided on the ceramic substrate 601 and connects the triac 51 and the resistance heating element 610. The resistance value between the electrodes 615 and 616 is 10Ω.

The electrode 617 is provided on the ceramic substrate 601 and connects the triac 52 and the resistance heating element 620.

The electrode 618 is provided on the ceramic substrate 601 and connects the power source 30 and the resistance heating element 620. The resistance value between the electrodes 617 and 618 is 10Ω.

The resistance heating element 620, which is the second heating unit, is formed such that both ends in the width direction are narrowed so that the widths at both ends in the width direction are narrower than the width at the central portion. The resistance heating element 620 has a temperature distribution in which the temperature of the end portion of the fixing nip N is higher than that of the central portion thereof in the width direction when heat is generated.

The thermistor 630 is connected to the CPU 100.

The thermistor 631 is connected to the CPU 100.

The thermistor 632 is connected to the CPU 100.

The film 650 is a cylindrical heat resistant film. The film 650 is formed of a metal such as polyimide or stainless steel (SUS) having a thickness of about 40 μm. The film 650 is configured as a composite layer film in which the outer peripheral surface is coated with PFA (tetrafluoroethylene perfluoroalkyl vinyl ether copolymer) or the like or a PFA tube is coated. The film 650 is in close contact with the pressure roller 7 and rotates around the film guide 660 by being rotated by the rotation of the pressure roller 7.

The film guide 660 has a semicircular trough shape in cross section, and fixes the ceramic substrate 601 with the resistance heating element 610 and the resistance heating element 620 exposed.

The reinforcing sheet metal 670 has an inverted U-shaped cross section and is provided so as not to be deformed when the heater unit 6 is pressed by the pressing roller 7.

The pressure roller 7 presses the heater unit 6 with a predetermined pressure by a pressure means (not shown), and is rotationally driven by a drive means (not shown) to convey the recording material 20. Here, the predetermined pressure is exemplified by a total pressure of 9 kgf. Specifically, the pressure roller 7 is composed of a core metal 71, an elastic layer 72 made of silicone rubber, and a surface layer 73 made of a fluorine resin.

The CPU 100, which is a control unit, controls the driving of the triac 51 and the triac 52 according to the temperatures detected by the thermistor 630, the thermistor 631, and the thermistor 632. As a result, the CPU 100 controls the power supplied from the power supply 30 to the resistance heating element 610 or the resistance heating element 620.

When the recording material 20 does not pass through the fixing nip N, the CPU 100 reduces the amount of heat generated by the resistance heating element 620 compared to when the recording material 20 passes through the fixing nip N. When the recording material 20 does not pass through the fixing nip N, typically, the start-up period of the printing operation for starting the heating of the fixing device 12 before the first recording material 20 passes through the fixing nip N, or the fixing nip N This is a sheet interval when the recording material 20 continuously passes through.

The control for reducing the heat generation amount of the resistance heating element 620 in the CPU 100 is typically control for controlling the triac 52 to stop the power supply from the power supply 30 to the resistance heating element 620.

<Fixing process>
The fixing process according to the first embodiment of the present invention will be described in detail with reference to FIGS. 4 to 7.

The fixing process in the fixing device 12 is started by the CPU 100 receiving a request signal for a printing operation.

After the start of the fixing process, first, the CPU 100 controls the drive of the triac 51 to supply power from the power supply 30 to the resistance heating element 610 (S1).

As shown in FIG. 5, the temperature L6 of the central portion in the width direction of the heater 600 is resistance heat generation during the start-up period of the printing operation in which the fixing device 12 is heated before the first recording material 20 passes through the fixing nip N. Since power is supplied only to the body 610, the temperature rises to the required fixing temperature in a short time. On the other hand, the temperature L7 of the end portion of the heater 600 in the width direction gradually rises because power is not supplied to the resistance heating element 620 during the start-up period of the printing operation.

Next, the CPU 100 determines whether the temperature detected by the thermistor 632 has reached the target temperature (S2).

As a result of the determination, the CPU 100 repeats the process of S2 when the temperature detected by the thermistor 632 has not reached the target temperature (S2: No).

On the other hand, as a result of the determination, when the temperature detected by the thermistor 632 reaches the target temperature (S2: Yes), the CPU 100 starts feeding the recording material 20 (S3).

Then, the CPU 100 controls the drive of the triac 51 so that the temperature detected by the thermistor 632 maintains the target temperature, and causes the power supply 30 to supply power to the resistance heating element 610 (S4).

As described above, during the start-up period of the printing operation before the leading end of the recording material 20 reaches the fixing nip N, power is supplied only to the resistance heating element 610, and the surface of the film 650 is at the end portion in the width direction of the film 650. Is controlled so that the temperature does not rise above the softening temperature at which the softens. In this embodiment, since the outer surface of the film 650 is covered with PFA, the CPU 100 controls the surface of the film 650 so as not to exceed 260°C. Therefore, when the recording material 20 enters the fixing nip N, it is possible to prevent the surface layer of the film 650 from being scraped. The allowable ultimate temperature of the widthwise end of the film 650 is preferably changed according to the material of the surface layer of the film 650.

Next, the CPU 100 determines whether the leading end of the recording material 20 in the transport direction has reached the fixing nip N (S5).

As a result of the determination, the CPU 100 returns to the process of S4 when the leading end of the recording material 20 has not reached the fixing nip N (S5: No).

On the other hand, when the front end of the recording material 20 reaches the fixing nip N (S5: Yes), the CPU 100 controls the drive of the triac 52 and causes the power source 30 to supply power to the resistance heating element 620 (S6).

As described above, during the paper passing period after the leading end of the recording material 20 reaches the fixing nip N, the power source 30 supplies power to both the resistance heating element 610 and the resistance heating element 620. Accordingly, the temperature of the end portion of the heater 600 in the width direction can be set to a high temperature distribution, and the fixing property of the end portion of the recording material 20 in the width direction can be improved. At this time, the temperature of the end portion of the heater 600 in the width direction is equal to or higher than the temperature required for fixing the developer and is equal to or lower than a predetermined temperature which is higher than the temperature required for fixing. Here, the predetermined temperature is exemplified by the temperature of the central portion of the heater 600 in the width direction when the recording material 20 reaches the fixing nip N.

On the other hand, when the leading edge of the recording material 20 reaches the fixing nip N, the temperature of the widthwise end of the film 650 is lower than the temperature of the widthwise center as shown in FIG. Therefore, it is difficult for the surface layer to be scraped by the end portion (edge) in the width direction of the recording material 20.

Then, the CPU 100 controls the temperature detected by the thermistor 630, the thermistor 631, and the thermistor 632 to maintain the target temperature during the sheet passing period (S7). The CPU 100 controls the driving of the TRIAC 51 and the TRIAC 52 to supply power from the power supply 30 to the resistance heating element 610 and the resistance heating element 620 so as to maintain the target temperature.

FIG. 6 shows a case where the resistance heating element 610 and the resistance heating element 620 are controlled at the same energization ratio (40% in two cycles of the power supply voltage waveform). In addition, FIG. 6 illustrates a voltage when the power consumption of each of the resistance heating element 610 and the resistance heating element 620 is about 400 W when a voltage of 100 V is applied to the resistance heating element 610 and the resistance heating element 620. The waveform is shown.

The power supply 30 applies the voltage having the voltage waveform shown in FIG. 6A to the resistance heating element 610, and applies the voltage having the voltage waveform shown in FIG. 6B to the resistance heating element 620. In addition, in FIG. 6, the filled portion is an area to which a voltage is applied.

The CPU 100 controls the resistance heating element 610 and the resistance heating element 620 so that power is supplied by phase control in which ON and OFF are switched at a phase angle within one half wave. Further, the CPU 100 sets both the resistance heating element 610 and the resistance heating element 620 so that the ON timing of the voltage waveform of the resistance heating element 610 does not overlap with the ON timing of the voltage waveform of the resistance heating element 620. It is controlled so that power is supplied evenly. As a result, electrical noise can be prevented from increasing.

FIG. 7 shows the temperature distribution (no load state) in the width direction (horizontal axis direction) of the heater 600 when the voltage having the voltage waveform of FIG. 6 is applied. In FIG. 7, L1 indicates the temperature distribution of the resistance heating element 610, L2 indicates the temperature distribution of the resistance heating element 620, and L3 is the temperature obtained by combining the temperature distributions of the resistance heating element 610 and the resistance heating element 620. The distribution is shown.

From FIG. 7, the resistance heating element 610 has a temperature distribution in which the temperature of the central portion of the resistance nip N is higher than that of the end portion of the fixing nip N in the width direction when heat is generated. Further, the resistance heating element 620 has a temperature distribution in which the temperature of the end portion of the fixing nip N is higher than that of the center portion thereof in the width direction when heat is generated.

As described above, by using the two resistance heating elements 610 and 620 having different heat distributions in the width direction of the heater 600, the heat distribution of the resistance heating elements 610 and 620 is intended. It is possible to change the distribution. In FIG. 7, A indicates the arrangement position of the thermistor 630, B indicates the arrangement position of the thermistor 631, and C indicates the arrangement position of the thermistor 632.

Returning to FIG. 4, next, the CPU 100 determines whether the trailing end of the recording material 20 in the transport direction has passed through the fixing nip N (S8).

If the result of determination is that the trailing edge of the recording material 20 has not passed through the fixing nip N (S8: No), the processing returns to S7.

On the other hand, when the trailing edge of the recording material 20 passes through the fixing nip N (S8: Yes), the CPU 100 ends the fixing operation.

As described above, in the fixing operation in the present embodiment, the electric power supplied to each of the two resistance heating elements 610 and 620 is independently controlled, and the recording material 20 does not pass when the printing operation is started. The temperature of the portion is controlled to be lower than the temperature of the passage portion of the recording material 20.

For comparison with the fixing process according to the present embodiment, FIG. 8 shows a temperature transition when power is constantly supplied to the resistance heating element 610 and the resistance heating element 620 from the start to the end of the fixing process. Is shown.

From FIG. 8, the temperature L4 of the central portion of the heater 600 in the width direction is stable near the target temperature during the start-up period of the printing operation. On the other hand, the temperature L5 of the end portion of the heater 600 in the width direction is higher than the target temperature during the start-up period of the printing operation because the heat generation amount is increased to improve the fixing property of the end portion of the heater 600 in the width direction. It is hot. Therefore, in the case of FIG. 8, when the temperature is raised from the room temperature to the target temperature, the temperature of the non-passing portion of the recording material 20 becomes high, so that the surface layer of the film near the non-passing portion is deteriorated, and When the recording material 20 is conveyed, the surface layer of the film is easily scraped.

As shown in FIG. 9, in the fixing device 12 according to the present exemplary embodiment, the temperature of the end portion in the width direction of the heater 600 can be lowered by Q as compared with the related art, so that the film 650 has a long life by U. Can be

As described above, in the present embodiment, when the recording material 20 enters the fixing area, the temperature of the end portion is equal to or higher than the temperature required for fixing the developer and higher than the temperature required for fixing. The resistance heating element 610 and the resistance heating element 620 are controlled so that the temperature becomes equal to or lower than a predetermined temperature. Thus, the non-passage portion of the recording material 20 is controlled so as not to have an unnecessarily high temperature and the deterioration of the surface layer of the film is suppressed, so that the surface layer of the film can be prevented from being scraped and the film has a long life. Can be

In the present embodiment, the power supply from the power source 30 to the resistance heating element 620 is stopped to reduce the heat generation amount of the resistance heating element 620. However, in the state where the power supply from the power source 30 to the resistance heating element 620 is continued. The amount of heat generated by the resistance heating element 620 may be reduced.

(Embodiment 2)
Since the configurations of the image forming apparatus and the fixing apparatus according to the second embodiment of the present invention are the same as those in FIGS. 1 to 3, the description thereof will be omitted.

<Fixing process>
The fixing process according to the second embodiment of the present invention will be described in detail with reference to FIGS. 10 to 12. It should be noted that the present embodiment will be described using the reference numerals of FIGS. 1 to 3.

The fixing process in the fixing device 12 is started by the CPU 100 receiving a request signal for a printing operation.

After the start of the fixing process, first, the CPU 100 controls the driving of the triac 51 to supply power from the power source 30 to the resistance heating element 610 (S11).

As shown in FIG. 11, since the temperature L16 of the central portion of the heater 600 in the width direction is supplied only to the resistance heating element 610 during the start-up period of the printing operation in which the fixing device 12 starts to be heated, the temperature required for the fixing is reduced in a short time. Going up. On the other hand, the temperature L17 of the end portion of the heater 600 in the width direction gradually rises because power is not supplied to the resistance heating element 620 during the start-up period of the printing operation.

Next, the CPU 100 determines whether the temperature detected by the thermistor 632 has reached the target temperature (S12).

As a result of the determination, the CPU 100 repeats the process of S12 when the temperature detected by the thermistor 632 has not reached the target temperature (S12: No).

On the other hand, as a result of the determination, when the temperature detected by the thermistor 632 reaches the target temperature (S12: Yes), the CPU 100 starts feeding the recording material 20 (S13).

Then, the CPU 100 controls the drive of the triac 51 so that the temperature detected by the thermistor 632 maintains the target temperature, and causes the power supply 30 to supply power to the resistance heating element 610 (S14). In this way, the widthwise end of the heater 600 and the widthwise end of the film 650 do not become hot because power is supplied only to the resistance heating element 610 during the start-up period of the printing operation. Therefore, when the recording material 20 enters the fixing nip N, it is possible to prevent the surface layer of the film 650 from being scraped.

Next, the CPU 100 determines whether the leading end of the recording material 20 has reached the fixing nip N (S15).

When the result of the determination is that the leading edge of the recording material 20 has not reached the fixing nip N (S15: No), the CPU 100 returns to the processing of S14.

On the other hand, when the leading end of the recording material 20 reaches the fixing nip N (S15: Yes), the CPU 100 controls the driving of the triac 52 and causes the power source 30 to supply power to the resistance heating element 620 (S16).

As described above, during the paper passing period after the leading end of the recording material 20 reaches the fixing nip N, the power source 30 supplies power to both the resistance heating element 610 and the resistance heating element 620. As a result, the temperature of the end portion of the heater 600 in the width direction can be set to a high temperature distribution, and the fixability of the end portion of the recording material 20 in the width direction can be improved. At this time, the temperature of the end portion of the heater 600 in the width direction is equal to or higher than the temperature required for fixing the developer and is equal to or lower than a predetermined temperature that is higher than the temperature required for fixing.

On the other hand, when the leading edge of the recording material 20 reaches the fixing nip N, the temperature of the end portion in the width direction of the film 650 is always lower than the temperature of the center portion in the width direction, as shown in FIG. Therefore, the surface layer is not easily scraped by the end portion of the recording material 20 in the width direction.

Then, the CPU 100 controls the temperature detected by the thermistor 630, the thermistor 631, and the thermistor 632 so as to maintain the target temperature (S17). The CPU 100 controls the driving of the triac 51 and the triac 52 to supply power from the power source 30 to the resistance heating element 610 and the resistance heating element 620, thereby controlling the target temperature.

Next, the CPU 100 determines whether the trailing edge of the recording material 20 has passed through the fixing nip N (S18).

When the result of the determination is that the trailing edge of the recording material 20 has not passed through the fixing nip N (S18: No), the CPU 100 returns to the processing of S17.

On the other hand, when the trailing edge of the recording material 20 has passed the fixing nip N (S18: Yes), the CPU 100 stops the drive control of the triac 52 and stops the power supply from the power source 30 to the resistance heating element 620 (S19). In this way, after the target temperature is reached, the resistance heating element 620 is reached in the space between the trailing edge of the recording material 20 passing through the fixing nip N and the leading edge of the next recording material 20 reaching the fixing nip N. Of the resistance heating element 610 is stopped and power is supplied only to the resistance heating element 610. Therefore, it is possible to prevent the temperature of the widthwise end of the heater 600 and the widthwise end of the film 650 from rising, and to keep the widthwise end of the film 650 at a low temperature when the recording material 20 enters the fixing nip N. can do. Accordingly, it is possible to prevent the surface layer of the film 650 from being scraped.

Next, the CPU 100 determines whether or not the requested number of sheets have been passed (S20).

If the result of determination is that the requested number of sheets have not been passed (S20: No), the CPU 100 returns to the processing of S14.

On the other hand, when the requested number of sheets have been passed (S20: Yes), the CPU 100 ends the fixing process.

For comparison with the fixing process according to the present embodiment, FIG. 12 shows a temperature transition when power is constantly supplied to the resistance heating element 610 and the resistance heating element 620 from the start to the end of the fixing process. Is shown.

As shown in FIG. 12, the temperature L15 of the central portion of the heater 600 in the width direction is equal to the temperature taken by the recording material 20 while the recording material 20 is passing through the fixing nip N and the temperature replenished between the sheets. The temperature change is constant. On the other hand, the temperature L14 at the end portion of the heater 600 in the width direction is higher than that of the center portion of the heater 600 in the width direction because the amount of heat generated is increased to improve the fixing property of the end portion of the heater 600 in the width direction. As a result, the temperature does not drop so much even when the recording material 20 passes through the fixing nip N. Then, the temperature L14 at the end portion of the heater 600 in the width direction increases upward as the printing operation continues because the heat is replenished between the sheets.

As described above, in the present embodiment, when the recording material 20 continuously passes through the fixing nip N, the non-passage portion of the recording material 20 is controlled so as not to have an excessively high temperature, so that the film Suppress deterioration of the surface layer. Thereby, even when the recording material 20 continuously passes through the fixing nip N, the abrasion of the surface layer of the film can be suppressed.

In the present embodiment, the power supply from the power source 30 to the resistance heating element 620 is stopped to reduce the heat generation amount of the resistance heating element 620. However, in the state where the power supply from the power source 30 to the resistance heating element 620 is continued. The amount of heat generated by the resistance heating element 620 may be reduced.

(Embodiment 3)
Since the configurations of the image forming apparatus and the fixing apparatus according to the third embodiment of the present invention are the same as those in FIGS. 1 to 3, the description thereof will be omitted.

<Fixing process>
The fixing process according to the third embodiment of the present invention will be described in detail. It should be noted that the present embodiment will be described using the reference numerals of FIGS. 1 to 3.

In FIG. 13, the horizontal axis is the width direction of the heater 600. Further, in FIG. 13, A shows the arrangement position of the thermistor 630, B shows the arrangement position of the thermistor 631, and C shows the arrangement position of the thermistor 632. In the present embodiment, each of the thermistor 630, the thermistor 631, and the thermistor 632 controls the temperature of the end portion in the width direction of each recording material 20 having a different sheet passing area when the recording material 20 having a different sheet passing area passes through. It is located so that it can be detected.

Specifically, the thermistor 630 detects the temperature of the end portion in the width direction of the recording material 20 that passes through the paper passing area R1. The thermistor 631 detects the temperature of the end portion in the width direction of the recording material 20 that passes through the paper passing area R2. The thermistor 632 detects the temperature of the end portion in the width direction of the recording material 20 that passes through the paper passing area R3.

First, the fixing process of the recording material 20 that passes through the paper passing region R1 will be described in detail with reference to FIGS. 14 to 17.

The fixing process in the fixing device 12 is started by the CPU 100 receiving a request signal for a printing operation.

After the start of the fixing process, first, the CPU 100 controls the driving of the triac 51 to supply power to the resistance heating element 610 from the power source 30 (S31).

As shown in FIG. 15, the temperature L27 of the central portion of the recording material 20 in the width direction is supplied only to the resistance heating element 610 during the start-up period of the printing operation in which the fixing device 12 starts to be heated, and thus the fixing temperature is required for a short time. Will continue to rise. On the other hand, the temperature L28 of the end portion of the recording material 20 in the width direction gradually rises because power is not supplied to the resistance heating element 620 during the start-up period of the printing operation.

Next, when the temperature detected by the thermistor 632 reaches the target temperature, the CPU 100 starts feeding the recording material 20 (S32).

Next, when the front end of the recording material 20 reaches the fixing nip N (S33), the CPU 100 controls the drive of the triac 52 and causes the power source 30 to supply power to the resistance heating element 620 (S34).

As described above, during the paper passing period after the leading end of the recording material 20 reaches the fixing nip N, the power source 30 supplies power to both the resistance heating element 610 and the resistance heating element 620. As a result, the temperature of the end portion of the heater 600 in the width direction can be set to a high temperature distribution, and the fixability of the end portion of the recording material 20 in the width direction can be improved. At this time, the temperature of the end portion of the heater 600 in the width direction is equal to or higher than the temperature required for fixing the developer and is equal to or lower than a predetermined temperature that is higher than the temperature required for fixing.

On the other hand, the temperature of the widthwise end of the film 650 when the leading end of the recording material 20 reaches the fixing nip N is lower than the temperature of the widthwise center of the film 650, as shown in FIG. Therefore, the surface layer is not easily scraped by the end portion of the recording material 20 in the width direction.

Then, the CPU 100 controls the temperature detected by the thermistor 630, the thermistor 631, and the thermistor 632 so as to maintain the target temperature (S35). The CPU 100 controls the driving of the TRIAC 51 and the TRIAC 52 to supply power to the resistance heating element 610 and the resistance heating element 620 from the power supply 30 to maintain the target temperature during the sheet passing period.

Next, the CPU 100 determines whether the trailing edge of the recording material 20 has passed through the fixing nip N (S36).

As a result of the determination, the CPU 100 returns to the process of S35 when the trailing edge of the recording material 20 does not pass through the fixing nip N (S36: No).

On the other hand, when the trailing edge of the recording material 20 passes through the fixing nip N (S36: Yes), the CPU 100 stops the drive control of the triac 51 and stops the power supply from the power supply 30 to the resistance heating element 610. Further, the CPU 100 stops the drive control of the triac 52 and stops the power supply from the power source 30 to the resistance heating element 620 (S37).

Next, the CPU 100 monitors the temperature detected by the thermistor 630 (S38).

Next, the CPU 100 determines the temperature gradient ΔT in a predetermined time from the temperature detected by the thermistor 630 to determine the heat storage state of the fixing device 12 (S39). When the fixing device 12 is not warm, the temperature drop at the widthwise end of the recording material 20 is large, and when the fixing device 12 is warm, the temperature drop at the widthwise end of the recording material 20 is high. Becomes loose. Therefore, by determining the temperature gradient ΔT, it is possible to accurately predict the heat storage state of the fixing device 12.

Next, the CPU 100 refers to the table shown in FIG. 16 in which the predetermined temperature gradient ΔT and the energization ratio are associated with each other, and determines the energization ratio associated with the obtained temperature gradient ΔT (S40). ). The energization ratio is the energization ratio of the resistance heating element 610 and the resistance heating element 620 until the leading edge of the next recording material 20 enters the fixing nip N.

Here, as shown in FIG. 17, when the temperature gradient of the trailing edge temperature L10 of the recording material 20 in the width direction is large, the CPU 100 can determine that the heat storage state of the fixing device 12 is low. In this case, since the CPU 100 determines a large energization ratio, it is possible to raise the temperature of the end portion of the recording material 20 in the width direction and prevent the fixing property of the end portion of the recording material 20 in the width direction from being deteriorated. ..

As a result, the temperature of the heater 600 can be raised to a temperature for fixing the next recording material 20 at an optimum energization ratio that does not cause overshoot. Further, even after the recording material 20 enters the fixing nip N, it is possible to prevent the temperature of the end portion of the heater 600 in the width direction from being too low, and the end portion of the recording material 20 in the width direction of the heater 600 can be prevented. The fixability can be improved.

Next, the CPU 100 causes the power supply 30 to supply power to the resistance heating element 610 and the resistance heating element 620 at the determined energization ratio (S41).

Next, when the front end of the recording material 20 reaches the fixing nip N (S42), the CPU 100 controls the temperature detected by the thermistor 630, the thermistor 631, and the thermistor 632 so as to maintain the target temperature (S43). The CPU 100 controls the driving of the triac 51 and the triac 52 to supply power from the power source 30 to the resistance heating element 610 and the resistance heating element 620, thereby controlling the target temperature.

Next, the CPU 100 determines whether the trailing edge of the recording material 20 has passed through the fixing nip N (S44).

If the result of determination is that the trailing edge of the recording material 20 has not passed through the fixing nip N (S44: No), the CPU 100 returns to the processing of S43.

On the other hand, when the trailing edge of the recording material 20 has passed the fixing nip N (S44: Yes), the CPU 100 determines whether or not the designated number of sheets have been passed (S45).

If the result of determination is that the specified number of sheets have not been passed (S45: No), CPU 100 returns to the process of S37.

On the other hand, if the result of determination is that the specified number of sheets have been passed (S45: Yes), the CPU 100 ends the fixing processing.

As described above, the CPU 100 stops the heat generation of the resistance heating element 610 and the resistance heating element 620 during the paper interval, and the heat storage state of the fixing device 12 from the falling temperature gradient ΔT of the heater 600 in the predetermined time at that time. Predict. Then, the CPU 100 raises the temperature of the heater 600 at an energization ratio that does not cause overshoot based on this prediction result. Accordingly, when the recording material 20 enters the fixing nip N, it is possible to prevent the temperature of the end portion in the width direction of the recording material 20 from rising, and the surface of the film 650 by the end portion in the width direction of the recording material 20. It is possible to prevent the scraping of.

FIG. 18 shows, as a comparison with the fixing process according to the present embodiment, a temperature transition when power is constantly supplied to the resistance heating element 610 and the resistance heating element 620 from the start to the end of the fixing process. Is shown.

From FIG. 18, the temperature L25 at the widthwise central portion of the recording material 20 is a balance between the temperature taken by the recording material 20 while the recording material 20 is passing through the fixing nip N and the temperature replenished between the sheets. , The temperature has become constant. On the other hand, the temperature L24 at the widthwise end of the recording material 20 increases the amount of heat generation to improve the fixability of the widthwise end of the recording material 20, so the widthwise central portion of the recording material 20 is increased. Compared with, the temperature does not drop much even when the recording material 20 passes through the fixing nip N. Then, the temperature L25 of the widthwise end portion of the recording material 20 rises upward as the printing operation continues because the heat is replenished between the sheets.

On the other hand, when measures are taken such as widening the space between the sheets to radiate heat or suppressing the temperature rise by reducing the energization ratio of the resistance heating element between the sheets, the next recording material 20 will be fed to the fixing nip N. In order to secure the fixing property when approaching, it is necessary to increase the energization ratio of the resistance heating element again.

FIG. 19 is a comparison with the fixing process according to the present embodiment, in which the sheet interval is widened when the temperature of the non-passing portion of the recording material 20 is increased and the sheet-to-paper energization is performed without obtaining the temperature gradient ΔT. It shows the temperature transition between the central portion and the end portion in the width direction of the recording material 20 when the ratio is lowered.

From FIG. 19, the temperature L34 of the widthwise central portion of the recording material 20 is a balance between the temperature taken by the recording material 20 while the recording material 20 is passing through the fixing nip N and the temperature replenished between the sheets. , The temperature has become constant. On the other hand, the temperature L35 of the end portion of the recording material 20 in the width direction suppresses the temperature rise by reducing the energization ratio between the sheets, but the temperature L35 is adjusted according to the timing when the recording material 20 enters the fixing nip N again. To raise. However, when the fixing device 12 is in a state where the fixing device 12 is easily warmed by continuous use, the temperature of the end portion in the width direction of the recording material 20 is excessively raised, and as a result, the recording material is kept in a state where the temperature of the surface layer of the film 650 is high. You will come into contact with 20.

Next, the fixing process for the recording material 20 passing through the paper passing area R2 will be described in detail with reference to FIGS.

In the fixing process for the recording material 20 passing through the sheet passing region R2, the temperature of the thermistor 631 is monitored instead of the temperature of the thermistor 630 in the process of S38 of FIG. Further, in the fixing process for the recording material 20 passing through the sheet passing region R2, instead of obtaining the temperature gradient ΔT from the temperature detected by the thermistor 630 in the process of S39 of FIG. 14, the temperature gradient ΔT is obtained from the temperature detected by the thermistor 631. Ask. The processes other than the above in the fixing process of the recording material 20 passing through the paper passing area R2 are the same as those in FIG.

In the fixing process for the recording material 20 that passes through the paper passing region R2, the temperature L42 at the end portion in the width direction of the recording material 20 while power is not supplied is detected by the thermistor 631, and the detection result of the recording material 20 is detected. The temperature gradient ΔT at a predetermined time at the end portion in the width direction is calculated. Further, the energization ratio associated with the obtained temperature gradient ΔT is determined with reference to the table in FIG. 21 in which the temperature gradient and the energization ratio are associated in advance. Then, when the next recording material 20 enters the fixing nip N, the temperature of the heater 600 is raised at a determined energization ratio so that the temperature of the end portion of the recording material 20 in the width direction does not increase.

As described above, even when the recording material 20 having a relatively short width in the width direction of the sheet passing area is continuously fixed, the heat storage state of the fixing device 12 is predicted from the falling temperature gradient of the heater 600, and the overshooting occurs. The heater temperature is raised at an energization ratio that does not occur. As a result, it is possible to prevent the temperature of the end portion of the recording material 20 in the width direction from rising when entering the recording material 20, and prevent the surface of the film 650 from being scraped by the end portion of the recording material 20 in the width direction. It will be possible.

Finally, the fixing process for the recording material 20 passing through the paper passing region R3 will be described in detail with reference to FIGS. 22 to 24.

The fixing process in the fixing device 12 is started by the CPU 100 receiving a request signal for a printing operation.

After the start of the fixing process, first, the CPU 100 controls the driving of the triac 51 to supply power to the resistance heating element 610 from the power supply 30 (S51).

As shown in FIG. 23, since the temperature L53 of the central portion in the width direction of the recording material 20 is supplied only to the resistance heating element 610 during the start-up period of the printing operation in which the fixing device 12 starts to be heated, the temperature required for fixing is short. Will continue to rise. On the other hand, the temperature L54 of the widthwise end portion of the recording material 20 gradually rises because power is not supplied to the resistance heating element 620 during the start-up period of the printing operation.

Next, when the temperature detected by the thermistor 632 reaches the target temperature, the CPU 100 starts feeding the recording material 20 (S52).

Next, when the recording material 20 reaches the fixing nip N (S53), the CPU 100 controls the temperature detected by the thermistor 630, the thermistor 631, and the thermistor 632 so as to maintain the target temperature during the sheet passing period (S54). .. The CPU 100 controls the driving of the TRIAC 51 so that the power source 30 supplies power to the resistance heating element 610 to maintain the target temperature.

Next, the CPU 100 determines whether the recording material 20 has passed through the fixing nip N (S55).

As a result of the determination, the CPU 100 returns to the process of S54 when the recording material 20 does not pass through the fixing nip N (S55: No).

On the other hand, when the recording material 20 passes through the fixing nip N (S55: Yes), the CPU 100 stops the drive control of the triac 51 and stops the power supply from the power source 30 to the resistance heating element 610 (S56).

Next, the CPU 100 monitors the temperature detected by the thermistor 632 (S57).

Next, the CPU 100 determines the heat storage state of the fixing device 12 by obtaining the temperature gradient ΔT in a predetermined time from the temperature detected by the thermistor 632 (S58). When the fixing device 12 is not warm, the temperature drop at the widthwise end of the recording material 20 is large, and when the fixing device 12 is warm, the temperature drop at the widthwise end of the recording material 20 is high. Becomes loose. Therefore, by determining the temperature gradient ΔT, it is possible to accurately predict the heat storage state of the fixing device 12.

Next, the CPU 100 refers to the table shown in FIG. 24 in which the predetermined temperature gradient ΔT and the energization ratio are associated with each other, and determines the energization ratio associated with the obtained temperature gradient ΔT (S59). ). The energization ratio is the energization ratio of the resistance heating element 610 until the leading edge of the next recording material 20 enters the fixing nip N.

Next, the CPU 100 causes the power supply 30 to supply power to the resistance heating element 610 at the determined energization ratio (S60).

Next, when the recording material 20 reaches the fixing nip N (S61), the CPU 100 controls the temperature detected by the thermistor 630, the thermistor 631, and the thermistor 632 so as to maintain the target temperature (S62). The CPU 100 controls the driving of the TRIAC 51 so that the power source 30 supplies power to the resistance heating element 610 to maintain the target temperature.

Next, the CPU 100 determines whether the recording material 20 has passed through the fixing nip N (S63).

As a result of the determination, the CPU 100 returns to the process of S62 when the recording material 20 does not pass through the fixing nip N (S63: No).

On the other hand, when the recording material 20 has passed through the fixing nip N (S63: Yes), the CPU 100 determines whether the designated number of sheets have been passed (S64).

If the result of determination is that the specified number of sheets have not been passed (S64: No), the CPU 100 returns to the processing of S56.

On the other hand, as a result of the determination, the CPU 100 ends the fixing process when the designated number of sheets have been passed (S64: Yes).

As described above, even when the recording material 20 having a shorter width in the width direction of the paper passing area is continuously fixed, the heat storage state of the fixing device 12 is predicted from the falling temperature gradient of the heater 600 in a predetermined time, Raise the heater temperature at an energization ratio that does not cause overshoot. Accordingly, it is possible to prevent the temperature of the widthwise end portion of the recording material 20 from rising when the recording material 20 enters, and prevent the surface of the film 650 from being scraped by the widthwise end portion of the recording material 20. It will be possible.

When the recording material 20 having a relatively short width continuously passes through the fixing nip N, the temperature of the non-passage portion of the recording material 20 of the heater 600 becomes higher, so that the surface layer of the film 650 in the vicinity thereof is more scraped. It will be easier. According to the present embodiment, the abrasion of the surface layer of the film can be suppressed regardless of the width of the recording material 20, and the life of the film can be extended.

In the present embodiment, the amount of heat generated by the resistance heating element 620 is reduced by stopping the power supply from the power supply 30 to the resistance heating element 620 during the startup period. The amount of heat generated by the resistance heating element 620 may be reduced while power is continuously supplied to the resistance heating element 620.

In Embodiments 1 to 3 above, the resistance value of the resistance heating element 610 and the resistance value of the resistance heating element 620 may not be the same. For example, the resistance value of the resistance heating element 610 and the resistance value of the resistance heating element 620 are set to different values so that the heat generation amount on the upstream side in the transport direction of the recording material 20 with respect to the center of the fixing nip N becomes large. The fixing property may be improved.

Further, in the first to third embodiments described above, each resistance heating element does not necessarily have to generate heat over the entire width direction, and may generate heat in a part of the width direction.

S1 Image forming apparatus 1 Photosensitive drum 2 Charging roller 3 Laser exposure unit 4 Developing device 5 Transfer roller 6 Heater unit 7 Pressure roller 8 Cleaning blade 10 Supply roller 11 Cassette 12 Fixing device 20 Recording material 30 Power supply 51 Triac 52 Triac 71 Core bar 72 Elastic layer 73 Surface layer 600 Heater 601 Ceramic substrate 605 Glass code layer 610 Resistance heating element 615 Electrode 616 Electrode 617 Electrode 618 Electrode 620 Resistance heating element 630 Thermistor 631 Thermistor 632 Thermistor 650 Film 660 Film guide 670 Reinforcing plate

Claims (5)

A fixing device for applying heat and pressure to a recording material having a developer image formed on its surface in a fixing region to fix the developer image on the recording material,
Pressurizing means,
A film forming the fixing area between the pressing means,
Heating means for heating the fixing area through the film,
Control means for controlling the heating means to bring the fixing area to a temperature higher than that required for fixing the developer;
Have
The heating means, when heat is generated,
In the width direction perpendicular to the conveying direction of the recording material of the fixing area, the temperature is high the temperature distribution of the position of the central portion of the recording material of the predetermined size than the temperature of the position of an end portion of the recording material of a predetermined size It includes a first heating means, and a second heating means the temperature is high the temperature distribution of the position of the end portion than the temperature of the position of the central portion of the front Symbol fixing area,
The control means is
In fixing the recording material of the predetermined size, when the first heating means and the second heating means are in a room temperature state in advance,
The first heating means starts heat generation before the leading end of the recording material of the predetermined size in the transport direction enters the fixing region, and the second heating is performed after the leading end enters the fixing region. Means for starting heat generation and keeping the first heating means and the second heating means in a heat generating state until the trailing edge of the recording material of the predetermined size in the transport direction passes through the fixing area,
A fixing device characterized by the above. The control means is
According to claim 1, wherein the controller controls the first heating means and the second heating means so that the temperature of the position of said end portion is equal to or less than the temperature of the position of the central portion in the fixing area Fixing device. In fixing the recording material of the second predetermined size smaller than the predetermined size in the width direction, when the first heating unit and the second heating unit are in a room temperature state in advance,
The first heating unit is in a heat generating state before the leading edge of the second predetermined size recording material enters the fixing area until the rear edge of the second predetermined size recording material passes through the fixing area. And the second heating means is not brought into a heat generation state while the recording material having the second predetermined size passes through the fixing area.
The fixing device according to claim 1 or 2, characterized in that. When the first heating means and the second heating means are in a heat generation state, the voltage applied to the first heating means and the second heating means is phase-controlled.
The fixing device according to any one of claims 1 to 3, wherein: A photosensitive drum,
Charging means for charging the photosensitive drum,
Exposure means for irradiating the photosensitive drum charged by the charging means with a light beam to form an electrostatic latent image on the photosensitive drum;
Developing means for supplying a developer to the electrostatic latent image to form a developer image on the photosensitive drum;
Transfer means for transferring the developer to the recording material to form the developer image on the surface of the recording material;
A fixing device according to any one of claims 1 to 4,
An image forming apparatus comprising:

Images