JP2009075157A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To locally cool a fixing device when an abnormal rise of temperature or the like occurs therein. <P>SOLUTION: The image forming apparatus provided with an inside air cooling fan 101 and adapted to transfer an image formed on an image carrier and fix it by a fixing device 20 comprises a control means for sucking the outside air to the inside or discharging the inside air by changing a rotating direction. The control means rotates the internal cooling fan 101 in a direction of discharging the air from the inside until a predetermined condition is established, and rotates it in a direction of sucking and blowing the outside air to the inside when the predetermined condition is exceeded. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a digital multifunction machine having a combination of these functions.

  In an electrophotographic image forming apparatus such as a copying machine or a printer, an image formed with a heat-meltable toner formed on a recording medium such as transfer paper by an electrophotographic system is heated to form a permanently fixed image on the recording medium. It is necessary to fix. There are various methods for fixing, and a heat roller fixing method for fixing by heating and pressing is widely used. In this heat roller fixing method, a fixing roller and a pressure roller are pressed against each other, the fixing roller is heated, and a recording medium that supports the unfixed toner image is passed through the nip portion of the two rollers, whereby an unfixed toner image is formed. It is fixed on a recording medium.

  Such a fixing method heat-fixes on paper, so that the fixing device becomes high temperature. However, since heat adversely affects the image forming unit such as development and transfer, the internal temperature of the image forming apparatus is not desired to be high. Therefore, in order to prevent the heat generated from the fixing device from being filled in the apparatus, an air flow is created using means such as a fan, and the heat generated from the fixing device is discharged to the outside.

  However, the fixing device needs to be maintained at a certain temperature (fixing roller setting temperature example: 180 ± 15 ° C.), and it is desirable that the temperature distribution of the fixing device be uniform. One of the factors for making the temperature distribution of the fixing device uniform is air flow stabilization. Ideally, there is no airflow, or the airflow is infinitely small. In particular, when the wind blows directly on the fixing unit, the temperature of the part hit by the wind is pinpointed. Therefore, considering that the temperature of the fixing unit is kept uniform, it is not necessary to blow the wind directly.

  On the other hand, recent color laser printers and the like are strongly required to shorten the warm-up time, save space, and have high image quality. Therefore, it is essential to wrap rubber around the fixing roller to reduce the heat capacity. With this structure, the temperature difference between the surface layer temperature and the core metal closest to the heater increases, so the overshoot after the heat source is stopped increases. For this reason, even when an excessive temperature rise prevention device such as a thermostat works to prevent ignition, the temperature of the fixing roller may increase due to overshoot, and smoke may be generated. The overshoot can be alleviated by direct air blowing to the fixing device and air cooling at a pinpoint.

  Therefore, for example, Patent Document 1 proposes that when the fixing roller needs to be cooled, a propeller that rotates when the fixing roller is reversely rotated is provided, and the fixing roller is cooled by wind generated from the propeller. .

  As described above, it is more effective to blow the fuser directly to mitigate overshoot, but from the viewpoint of making the temperature distribution of the fuser uniform for image formation, the fuser is fixed. It is preferable that heat can be exhausted without directing air to the vessel.

FIG. 8 is a diagram for explaining cooling by a conventional fan. FIG. 8 (a) is a flowchart, FIG. 8 (b) is a front view showing the state of the cooling fan during the process of step S801, and FIG. ) Is a side view. In addition, the rotation direction of a cooling fan is shown in the figure (b), and the flow of a wind is shown in the figure (c) by the arrow, respectively. As shown in the figure, conventionally, when a cooling fan 101 is provided in a part of the apparatus main body, the power is turned on, and the fan operation is started (step S801), the blade 102 of the cooling fan 101 is indicated by an arrow 103. The wind of the arrow 104 which rotates in the direction and flows from the inside of the machine to the outside is generated. If the power is turned off, the cooling fan 101 stops. As a result, heat is exhausted without directing air to the fixing device.
JP 2007-47357 A

  However, in the technique of Patent Document 1, a dedicated fan for the fixing roller must be provided, and the configuration of the fixing device becomes complicated. Further, it is not possible to cope with emergency air cooling in the event of an abnormality simply by flowing air from the inside of the apparatus to the outside with the cooling fan shown in FIG.

  The present invention has been made in view of the actual situation of the prior art, and a problem to be solved is to enable local cooling when an abnormal temperature rise or the like occurs in the fixing device.

  In order to achieve the above object, the first means includes an in-machine air cooling fan, and changes the rotation direction in an image forming apparatus that transfers an image formed on the image carrier onto a recording medium and fixes the image on the recording medium. Thus, it has a control means for taking outside air into the machine or exhausting the air inside the machine.

  The second means is characterized in that, in the first means, the internal cooling fan is rotated in the direction of exhausting air from the inside of the apparatus until the control means reaches a predetermined condition.

  The third means is characterized in that, in the first means, when the control means reaches a predetermined condition, the inside cooling air is sucked into the inside of the machine and the inside cooling fan is rotated in a direction to blow the wind into the machine. To do.

  A fourth means is characterized in that, in the first means, when the control means is in a predetermined condition, the internal cooling fan is not rotated in any direction.

  A fifth means is characterized in that, in the second or third means, the predetermined condition is that the fixing temperature exceeds a preset value.

  The sixth means is characterized in that, in the second or third means, the predetermined condition is that the fixing temperature exceeds a preset value and exceeds a preset temperature rise gradient. .

  A seventh means is characterized in that, in the fifth means, the preset value is lower than a temperature at which smoke is emitted from the fixing means.

  According to an eighth means, in the sixth means, the preset value is a temperature lower than a temperature at which smoke is emitted from the fixing means, and a difference between the set value of the low temperature and a temperature at which the fixing means emits smoke. Is divided by a preset temperature rise gradient value, and is shorter than the time of temperature rise due to inertia even after the power supply to the fixing unit is cut off.

  The ninth means is that, in the seventh or eighth means, the temperature lower than the temperature at which the fixing means emits smoke is when there is no paper passing instruction compared to when the fixing means has a command to pass a recording medium. Is characterized by being set lower.

  According to a tenth means, in the fourth means, the predetermined condition is that the fixing temperature does not exceed a preset value.

  In the embodiments described later, the image carrier corresponds to the photoreceptors 1y, 1m, 1c, and 1k, the in-machine air cooling fan corresponds to the cooling fan 101, and the temperature detection means corresponds to the thermistor 207.

  According to the present invention, the airflow can be changed by arbitrarily changing the rotation direction of the in-flight cooling fan, and control can be performed to switch between a flow path that blows directly against the heat source and a flow path that discharges the atmosphere. . This makes it possible to achieve both rapid cooling at the time of abnormality and exhaust heat for temperature adjustment.

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

  FIG. 1 is a configuration diagram showing an outline of an example of an image forming apparatus to which the present invention is applied. This image forming apparatus is a color image forming apparatus capable of forming a color image with toners of four colors of yellow (Y), magenta (M), cyan (C), and black (K). That is, a photoreceptor 1y that is an image carrier that forms a yellow toner image, a photoreceptor 1m that forms a magenta toner image, a photoreceptor 1c that forms a cyan toner image, and a photoreceptor 1k that forms a black toner image. A light beam deflected by the polygon mirror 30 is irradiated on the surface to perform optical writing for each color. Since the photoreceptors 1y to 1k of the respective colors have the same configuration except for the color of the toner used, the photoreceptor 1y that forms a yellow toner image will be described as an example. Around the photoreceptor 1y, a charging roller 2y, a developing roller 3y, and a cleaning roller 4y are arranged, and the surface of the photoreceptor 1y between the charging rotor 2y and the developing roller 3y receives exposure light from the polygon mirror 30. It is the composition of. The toner in the toner cartridge 5y located above the developing roller 3y is supplied via the supply roller 6y. 7y is a paddle for stirring the toner.

  A transfer belt 8 for transferring the toner images on the photoconductors 1y to 1k is disposed so as to be in contact with the photoconductors 1y to 1k. This transfer belt 8 is stretched between a secondary transfer tension roller 9 and a secondary transfer drive roller 10. On the back surface of the transfer belt 8, primary transfer rollers 11y, 11m, 11c, and 11k for transferring the toner images on the photoreceptors 1y to 1k to the transfer belt 8 are provided. A toner sensor 12 that detects toner on the transfer belt 8 is disposed near the secondary transfer tension roller 9, and a belt cleaner 13 that cleans the transfer belt 8 is disposed near the secondary transfer drive roller 10. It is installed.

  A waste toner box 14 for storing waste toner is provided below the transfer belt 8. The waste toner box 14 is provided with a waste toner full detection sensor 15 for detecting that the waste toner is full.

  Below the waste toner box 14, a main body feeding unit 16 for storing paper is located. The paper 17 in the main body feeding unit 16 is pulled out one by one by a feeding roller 18 and transferred by a secondary transfer roller 19. The toner image on the belt 8 is transferred, and the toner image is fixed on the paper 17 by passing through the fixing device 20, and is discharged out of the apparatus by the paper discharge roller 21. Reference numeral 22 denotes a registration roller for adjusting the conveyance timing of the paper 17 sent out by the paper feed roller 18 to the fixing device 20, 23 denotes a registration sensor for detecting the paper 17 sent to the registration roller 22, and 24 denotes paper discharge. A paper discharge sensor for detecting paper. Further, in this image forming apparatus, a conveyance path for double-sided printing is provided so as to form an image on the back side of the paper, and the double-sided sensor 5 detects the paper for double-sided printing.

  1 illustrates an indirect transfer type tandem color image forming apparatus, a direct transfer type tandem color image forming apparatus, a drum type color image forming apparatus, or a monochrome image forming apparatus may be used. .

  FIG. 2 is a diagram illustrating an example of the configuration of the fixing device 20. The fixing device 20 basically includes a sheet, a fixing roller 201 that heats the toner image on the sheet, and a pressure roller 202 that is positioned in pressure contact with the fixing roller 201 and fixes the toner image on the sheet. Has been. In this fixing device 20, the fixing roller 201 and a heating roller 204 having a heater 203 inside are hung by a fixing belt 205 made of a material having good thermal conductivity, and are heated by the heating roller 204. The toner image is thermally fixed on the sheet by pressing the fixing belt 205 against the pressure roller 202. The outer periphery of the fixing roller 201 and the heating roller 204 is covered with a heat insulating cover 206. Temperature detecting thermistors 207 and 208 are provided in the vicinity of the pressure roller 202 and the heating roller 204, respectively, and a temperature adjusting thermostat 209 is provided in the vicinity of the heating roller 204. Reference numeral 210 denotes a separation plate for peeling the paper from the fixing roller 201, and 211 denotes a separation plate for peeling the paper from the pressure roller 202. In the fixing device 20, the heat generated by the heater 203 is transmitted to the paper and the toner on the paper via the fixing belt 205.

  FIG. 3 is a diagram showing another configuration of the fixing device 20. In this example, a heater 252 is provided inside the fixing roller 251. A metal core 254 is provided between the roller surface 253 of the fixing roller 251 and the heater 252. In this example, the heat generated by the heater 252 is transmitted from the cored bar 254 to the sheet and the toner on the sheet via the roller surface 253.

  FIG. 4 is a flowchart for explaining cooling by the fan in the first embodiment of the present invention, and also shows both the rotation direction of the cooling fan and the flow of wind. In the following embodiment, it is assumed that the fixing device of FIG. 3 is used, and although not shown, the cooling fan 101 can be reversed, and the direction of wind flow is reversed by the reverse rotation. It is assumed that it is attached to the main body in the vicinity of the fixing device 20.

  Although not shown, in this embodiment, each unit of the fixing device and the image forming apparatus is controlled by the CPU of the control circuit. The CPU expands a program code stored in a ROM (not shown) in a RAM, and executes control defined by the program code while using the RAM as a work area.

  In this control, when the power is turned on as shown in the flowchart of FIG. 4A to start the operation of the cooling fan 101 (step S401), the cooling fan 101 is turned on as shown in FIG. The blades 102 rotate in the direction of the arrow 103 where the wind flows from the inside of the machine to the outside of the machine, and the wind flows in the direction of the arrow 104 in FIG. At the same time, the temperature of the fixing roller 251 is measured by the thermistor 207, and it is checked whether or not the temperature is equal to or higher than a specified value (step S402). When the value is less than the specified value, the check is performed again. When the value is more than the specified value, the cooling fan 101 is rotated in the reverse direction, and the cooling fan 101 is rotated in the reverse direction (step S403). As a result, as shown in FIG. 4D, the blades 102 rotate in the direction of the arrow 105 where the wind flows from the outside to the inside of the machine, and the wind flows in the direction of the arrow 106 as shown in FIG.

  With this control, it is possible to suppress the temperature rise of the fixing roller 251 and the roller surface 253 after the power supply to the heater 252 is stopped. In addition, if the specified value (temperature) that serves as the determination criterion in step S402 is set lower than the abnormal temperature at which the fixing device 20 actually smokes, smoke generation can be reliably prevented. Further, if the power supply to the heater 252 is also stopped during the reverse rotation of the cooling fan 101, it is possible to obtain a smoke prevention effect at the time of abnormality.

  FIG. 5 is a flow chart for explaining cooling by the fan in the second embodiment of the present invention, and shows both the rotation direction of the cooling fan and the flow of wind. In the second embodiment, the cooling fan 101 is not driven until the temperature of the fixing roller 251 reaches a preset temperature (step S501). This temperature monitoring is performed by the thermistor 207.

  That is, as shown in FIG. 5 (a), it is checked whether or not the temperature detected by the thermistor 207 is equal to or higher than a preset specified value (step S501). (Step S502), as shown in FIG. 5 (b), it is rotated in the direction of arrow 103 where the wind flows from the inside of the machine to the outside of the machine, and the wind is flowed in the direction of arrow 104 as shown in FIG. 5 (c).

  In this way, by not rotating the cooling fan 101 until the temperature of the fixing roller 251 exceeds a certain temperature (= no airflow is generated in the apparatus), temperature variations in the portion where the fixing roller 251 contacts the paper can be reduced. Can do. Further, the time until the fixing roller 251 is heated to a predetermined temperature can be shortened.

  FIG. 6 is a flowchart for explaining cooling by the fan in the third embodiment of the present invention, and also shows both the rotation direction of the cooling fan and the flow of wind. In the third embodiment, the drive control of the cooling fan 101 is performed by determining the temperature gradient value as well as the temperature value.

  That is, when the power is turned on as shown in FIG. 6A and the operation of the cooling fan 101 is started (step S601), as shown in FIG. 6B, the blades 102 of the cooling fan 101 are in-machine. Rotate in the direction of arrow 103 where the wind flows out of the machine, and the wind flows in the direction of arrow 104 as shown in FIG. At the same time, the temperature of the fixing roller 251 is measured by the thermistor 207, and it is checked whether or not the temperature is equal to or higher than a specified value (step S602). If it becomes equal to or higher than the specified value, it is checked whether or not the temperature gradient is equal to or higher than the specified value (step S603). The temperature gradient may be measured, for example, how many times the temperature rises per second.

For example, when the judgment temperature = 200 ° C., the temperature at which smoke actually occurs = 230 ° C., and the time for continuing to raise the temperature = 10 seconds,
If the temperature gradient is 2 ° C / second, the expected temperature reached = 220 ° C <230 ° C
If the temperature gradient is 4 ° C / sec, the expected temperature reached = 240 ° C> 230 ° C
As a result, when the temperature gradient is 2 ° C./second, the temperature does not reach 230 ° C. even if the temperature is continuously raised for 10 seconds, so that the reverse rotation control of the cooling fan 101 is not performed. On the other hand, when the temperature gradient is 4 ° C./second, if the temperature is continuously raised for 10 seconds, the temperature will exceed 230 ° C., so that the reverse rotation control of the cooling fan 101 is performed (step S604). As a result, the blade 102 of the cooling fan 101 rotates in the direction of the arrow 105 where the wind flows from the outside of the machine into the machine as shown in FIG. 6D, and in the direction of the arrow 106 as shown in FIG. 6E. The wind flows and the fixing roller 251 can be cooled.

  In this way, by determining the temperature gradient value in addition to the temperature value, how many times the temperature of the fixing roller 251 and the fixing roller surface 253 actually increase after the power supply to the heater 252 is stopped. Therefore, it is possible to prevent an erroneous determination such that the cooling fan 101 is reversely rotated with respect to a case where the temperature does not actually rise to an abnormal temperature.

  FIG. 7 is a flowchart for explaining cooling by the fan in the fourth embodiment of the present invention, and also shows both the rotation direction of the cooling fan and the flow of wind. In the fourth embodiment, heat is applied from the fixing roller 251 to the paper and the toner on the paper, so that the amount of heat at the portion of the fixing roller 251 in contact with the paper is reduced. This improves the accuracy of preventing misjudgment.

  First, as shown in FIG. 7A, when the power is turned on to start the operation of the cooling fan 101 (step S601), the blades 102 of the cooling fan 101 are in-flight as shown in FIG. 7B. Rotate in the direction of arrow 103 where the wind flows out of the machine, and the wind flows in the direction of arrow 104 as shown in FIG. At the same time, measurement of the temperature of the fixing roller 251 is also started by the thermistor 207. Next, it is checked whether or not there is a print command (step S702). If not, it is checked whether or not the temperature of the fixing roller 251 is equal to or higher than a specified value (= A + α ° C.) (step S703). Here, α is the temperature drop of the fixing roller 251. If it is equal to or less than the specified value, the process returns to step S702 to check again for the presence of a print command. On the other hand, if it is equal to or greater than the specified value, the cooling fan 101 is reversely rotated (step S704). As a result, as shown in FIG. 7D, the blade 102 rotates in the direction of the arrow 105 in which the wind blows into the machine from the outside of the machine, and the wind flows in the direction of the arrow 106 as shown in FIG. 7E.

  On the other hand, if there is a print command in step S702, it is checked whether or not the temperature of the fixing roller 251 is equal to or higher than a specified value (= A ° C.) (step S705). If it is equal to or less than the specified value, the process returns to step S702 to check again whether there is a print command. If it is equal to or greater than the specified value, the process proceeds to step S704, and the cooling fan 101 is rotated in the reverse direction.

  By applying heat to the sheet and toner on the sheet from the fixing roller 251, the amount of heat at the portion of the fixing roller 251 in contact with the sheet decreases, and the heater generates heat to compensate for it. The temperature drop of the fixing roller 251 caused by applying heat to the paper and the toner on the paper from the fixing roller 251 is reflected in the determination temperature for the rotation change of the cooling fan 101, so that the temperature actually rises to an abnormal temperature. It is possible to improve the accuracy of preventing misjudgment that causes the fan to reversely rotate for a case that is not performed. Furthermore, by combining with the third embodiment described above, it is possible to further improve the accuracy of preventing erroneous determination that causes the fan to reversely rotate in a case where the temperature does not actually rise to an abnormal temperature.

  The control based on the temperature detection result by the thermistor 207 of the fixing roller 251 includes a storage device that stores each specified value in advance, a current temperature detection result by the thermistor 207, and information such as a specified value stored in the storage device. The comparison may be performed by a control device including a CPU that controls on / off and forward / reverse rotation of the cooling fan 101 based on the result. These storage devices and control devices may be shared with the system of the image forming apparatus.

Thus, according to this embodiment,
(1) By arbitrarily changing the rotation direction of the fan, the airflow can be changed, and control can be performed to switch between a flow path that blows directly against the heat source and a flow path that discharges the atmosphere. This makes it possible to achieve both rapid cooling at the time of abnormality and exhaust heat for temperature adjustment.
(2) By rotating the fan in the direction of sucking air until a certain condition is satisfied, it can function as a fan for exhaust heat necessary for image formation.
(3) By rotating the fan in the direction of blowing wind under certain conditions, it can function as a fan necessary when the fixing device is rapidly cooled.
(4) The fan stops when a certain condition is met, whereby the airflow is stabilized (eliminated) and the temperature distribution uniformity of the fixing device can be improved. It also contributes to shortening the temperature rise time. Furthermore, energy consumption can be reduced by stopping the fan.
(5) While the temperature threshold value is not exceeded, the control for rotating the fan in the direction of sucking the wind is performed, and when the temperature threshold value is exceeded, whether the temperature rise gradient threshold value is exceeded is added to the criterion. When the fixing device does not actually become abnormal, it is possible to reduce the risk of performing control to reverse the fan by erroneous determination.
(6) Since the control is performed to reverse the fan at a temperature lower than the temperature at which the fixing device actually becomes abnormal and the rapid cooling is started, it is possible to reduce the risk of not being able to prevent smoke generation even if the rapid cooling is performed.
(7) Since it is possible to perform control to reverse the fan only when it is predicted that smoke will actually occur, there is a risk of performing control to reverse the fan due to an erroneous determination, and a risk that it will not be in time for smoke prevention even if it is rapidly cooled Both can be reduced simultaneously.
(8) By controlling the start of rotation of the fan by setting the temperature at which the in-machine cooling by the fan is required as a threshold, the temperature inside the image forming apparatus immediately after the power is turned on is not high, and the fan is not required Can be stopped, the airflow is stabilized (eliminated), and the temperature distribution uniformity of the fixing device can be improved. Moreover, energy consumption can be reduced by stopping the fan, and the rotational speed of the fan can be reduced. Further, during the fan stop period, the temperature rise gradient of the fixing device is increased by the amount of exhaust heat due to the airflow, so the time required for the fixing device to reach a printable temperature can be shortened.
(9) By taking into consideration that the fixing temperature is lowered due to the paper taking the heat of the fixing device by passing the paper, it is possible to reduce the risk of performing control to reverse the fan due to an erroneous determination.
There are effects such as.

1 is a configuration diagram showing an outline of an example of an image forming apparatus to which the present invention is applied. It is a figure which shows an example of a structure of a fixing device. 5 is a box showing another example of the configuration of the fixing device. It is a figure which shows the flowchart for demonstrating the cooling by the fan in 1st Example of this invention with the rotation direction of a cooling fan, and the flow of a wind. It is a figure which shows the flowchart for demonstrating the cooling by the fan in 2nd Example of this invention with the rotation direction of a cooling fan, and the flow of a wind. It is a figure which shows the flowchart for demonstrating the cooling by the fan in 3rd Example of this invention with the rotation direction of a cooling fan, and the flow of a wind. It is a figure which shows the flowchart for demonstrating the cooling by the fan in 4th Example of this invention with the rotation direction of a cooling fan, and the flow of a wind. It is a figure which shows the flowchart for demonstrating the cooling by the conventional fan with the rotation direction of a cooling fan, and the flow of a wind.

Explanation of symbols

1y, 1m, 1c, 1k Photoconductor 8 Transfer belt 20 Fixing device 101 Cooling fan 102 Blade 201, 251 Fixing roller 202 Pressure roller 203, 252 Heating heater 205 Fixing belt 207 Thermistor

Claims (10)

In an image forming apparatus that includes an in-machine air cooling fan, transfers an image formed on an image carrier to a recording medium, and fixes the image by a fixing unit.
An image forming apparatus comprising control means for taking outside air into the apparatus by changing the rotation direction or exhausting the air inside the apparatus. The image forming apparatus according to claim 1.
The image forming apparatus, wherein the control unit rotates the internal cooling fan in a direction to exhaust air from the inside of the apparatus until a predetermined condition is satisfied. The image forming apparatus according to claim 1.
The image forming apparatus according to claim 1, wherein the control unit sucks outside air and rotates the in-machine cooling fan in a direction to blow air into the apparatus when a predetermined condition is satisfied. The image forming apparatus according to claim 1.
The image forming apparatus according to claim 1, wherein the control unit does not rotate the internal cooling fan in any direction when a predetermined condition is satisfied. The image forming apparatus according to claim 2 or 3,
The image forming apparatus according to claim 1, wherein the predetermined condition is that a fixing temperature exceeds a preset value. The image forming apparatus according to claim 2 or 3,
The image forming apparatus according to claim 1, wherein the predetermined condition is that the fixing temperature exceeds a preset value and exceeds a preset temperature rise gradient. The image forming apparatus according to claim 5.
The image forming apparatus according to claim 1, wherein the preset value is a temperature lower than a temperature at which smoke is emitted from the fixing unit. The image forming apparatus according to claim 6.
The preset value is a temperature lower than the temperature at which smoke is emitted from the fixing unit, and the difference between the set value of the low temperature and the temperature at which the fixing unit emits smoke is divided by a preset temperature increase gradient value. The image forming apparatus is characterized in that the measured value is shorter than the time for the temperature to rise due to inertia even after the power supply to the fixing unit is cut off. The image forming apparatus according to claim 7 or 8,
The image is characterized in that the temperature lower than the temperature at which the fusing unit emits smoke is set lower when there is no sheet passing command than when the fixing unit has a command to pass a recording medium. Forming equipment. The image forming apparatus according to claim 4.
The image forming apparatus according to claim 1, wherein the predetermined condition is that a fixing temperature does not exceed a preset value.

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