JP2016031450A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can suppress the number of discharge of UFPs.SOLUTION: An image forming apparatus includes: a fixing device 37 that has a heating part 373 and heats a toner transferred to a sheet to fix the toner to the sheet; a first path 381 and a second path 382 that guide the air exhausted from the fixing device 37 to the outside of the apparatus; a shutter 384 that opens/closes an exhaust port 38B of the first path 381 and the second path 382; and a control part 5 that closes the exhaust port 38B with the shutter 384 when a continuous heating time by the heating part 373 reaches a predetermined threshold or more.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an electrophotographic image forming apparatus.

  An electrophotographic image forming apparatus is equipped with a fixing device that fixes toner transferred to a sheet. The fixing device includes a heating roller that is heated to a predetermined fixing temperature, and a pressure roller that can rotate while being pressed against the heating roller. The toner transferred to the sheet is melted and fixed on the sheet when passing through the nip region of the heating roller and the pressure roller.

  By the way, in recent years, it is desired to suppress the number of UFP (Ultra Fine Particle) emission as well as VOC (Volatile Organic Compounds) in the fixing device. For example, it has been found that this UFP is generated by heating a silicon-based material used for a heating roller and a pressure roller of a fixing device. In addition, a configuration is known in which a shutter capable of opening and closing an exhaust port is provided in order to prevent thermal diffusion generated in a fixing device in a low temperature environment (see, for example, Patent Document 1).

JP-A-7-64422

  However, in general, when an image is formed at a high temperature in the fixing device, an exhaust port for air exhausted from the fixing device is opened. Therefore, it is possible to suppress the number of UFPs discharged to the outside, which increases in a high temperature environment. Can not.

  An object of the present invention is to provide an image forming apparatus capable of suppressing the number of UFP discharged.

  An image forming apparatus according to an aspect of the present invention includes a fixing device, a path, an opening / closing unit, and a control unit. The fixing device has a heat source, and heats the toner transferred to the sheet to fix it on the sheet. The path guides the air discharged from the fixing device to the outside of the apparatus. The opening / closing part can open and close the path. The control unit closes the path by the opening / closing unit when the continuous heating time by the heat source reaches a predetermined first threshold value or more.

  According to the present invention, the number of UFP discharged from the image forming apparatus can be suppressed.

FIG. 1 is a diagram showing a configuration of an image forming apparatus according to the first embodiment of the present invention. FIG. 2 is a diagram showing the configuration of the exhaust mechanism of the image forming apparatus according to the first embodiment of the present invention. FIG. 3 is a block diagram showing a schematic configuration of the control unit of the image forming apparatus according to the first embodiment of the present invention. FIG. 4 is a flowchart illustrating an example of a first exhaust control process executed by the control unit of the image forming apparatus according to the first embodiment of the present invention. FIG. 5 is a diagram illustrating a suppression result of the emission rate of UFP and VOC in the image forming apparatus according to the first embodiment of the present invention. FIG. 6 is a graph showing a suppression result of the emission rate of UFP and VOC in the image forming apparatus according to the first embodiment of the present invention. FIG. 7 is a flowchart illustrating an example of a second exhaust control process executed by the control unit of the image forming apparatus according to the second embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention. In addition, the following embodiment is an example which actualized this invention, Comprising: The thing of the character which limits the technical scope of this invention is not.

[First Embodiment]
[Schematic Configuration of Image Forming Apparatus 10]
First, a schematic configuration of the image forming apparatus 10 according to the first embodiment of the present invention will be described.

  In FIG. 1, the image forming apparatus 10 is a printer including an image forming unit 3, a paper feeding unit 4, and a control unit 5. Note that facsimile machines, copiers, and multifunction machines are also examples of the image forming apparatus according to the present invention.

  The image forming unit 3 is an electrophotographic image forming unit that forms an image on a sheet based on image data input from an information processing apparatus such as a personal computer. Specifically, the image forming unit 3 includes a photosensitive drum 31, a charging device 32, an optical scanning device (LSU) 33, a developing device 34, a transfer roller 35, a cleaning device 36, a fixing device 37, an exhaust mechanism 38, and an exhaust mechanism 38. A paper tray 39 is provided. The sheet is a sheet material such as paper, coated paper, postcard, envelope, and OHP sheet.

  Here, as shown in FIG. 1, the fixing device 37 includes a pair of heating rollers 371 and a pressure roller 372 that are rotatably supported by a housing of the fixing device 37. The fixing device 37 includes a heating unit 373 (an example of a heat source of the present invention) such as a halogen heater disposed inside the heating roller 371. The heating unit 373 may be an IH heater that is disposed outside the heating roller 371 and induction-heats the heating roller 371. The heating roller 371 is heated to a predetermined fixing temperature by the heating unit 373. The fixing temperature is, for example, 200 ° C. to 220 ° C.

  The outer surface of the heating roller 371 is covered with a fluorine-based paint such as PFA or PTFE. As a result, the toner on the sheet is fixed to the sheet without adhering to the heating roller 371. In addition, the heating roller 371 is black coated with a metal oxide on the inner peripheral surface with a modified silicon adhesive. Thereby, the heat of the heating unit 373 is efficiently absorbed by the heating roller 371.

  The material of the pressure roller 372 includes elastic members such as elastic silicon rubber. The pressure roller 372 is urged toward the pressure roller 372 by an urging mechanism (not shown), and can be rotated while being in pressure contact with the heating roller 371. As a result, a nip region is formed between the heating roller 371 and the pressure roller 372. In the fixing device 37, when the heating roller 371 is rotationally driven by a driving force of a motor (not shown), the pressure roller 372 pressed against the heating roller 371 is driven to rotate. The toner transferred to the sheet is heated and fixed on the sheet when the sheet passes through the nip region between the heating roller 371 and the pressure roller 372.

  By the way, the modified silicon used for the black coating of the inner peripheral surface of the heating roller 371 may volatilize a siloxane component that becomes UFP when heated by the heating unit 373 and reaches a predetermined temperature or higher. . In addition, the silicon rubber used as the material of the pressure roller 372 may be heated to volatilize the siloxane component that becomes UFP when the temperature exceeds a predetermined temperature. When the temperature reaches a predetermined temperature or higher, the air around the fixing device 37 is discharged to the outside in order to cool the fixing device 37. At that time, UFP generated in the fixing device 37 may be discharged to the outside. On the other hand, in the image forming apparatus 10, the number of UFP discharged is suppressed by the following configuration.

[Exhaust mechanism 38]
Next, the exhaust mechanism 38 will be described with reference to FIG.

  The exhaust mechanism 38 can exhaust air from the fixing device 37 to the outside of the image forming apparatus 10. Specifically, the exhaust mechanism 38 includes a first path 381, a second path 382, a blower fan 383, a shutter 384, and a filter member 390. In the exhaust mechanism 38, an exhaust duct for guiding the air discharged from the fixing device 37 to the outside of the apparatus is formed by the first path 381 and the second path 382.

  The first path 381 has an air inlet 38 A provided in the vicinity of the fixing device 37. The air inlet 38A is provided in the vicinity of one end of the fixing device 37 in the main scanning direction (depth direction in FIG. 2). The second path 382 has an exhaust port 38 </ b> B that discharges air to the outside of the image forming apparatus 10.

  The blower fan 383 is provided between the first path 381 and the second path 382. The blower fan 383 has a plurality of wings and is rotationally driven by a driving force supplied from a driving motor 383A (see FIG. 3). The blower fan 383 generates an air flow in a direction from the first path 381 toward the second path 382. That is, the blower fan 383 blows air sucked from the intake port 38A of the first path 381 toward the exhaust port 38B. Air sucked from the intake port 38A of the first path 381 is discharged out of the image forming apparatus 10 from the exhaust port 38B of the second path 382. The blowing power of the blower fan 383 can be controlled by the control unit 5. Details of the control of the blower fan 383 by the controller 5 will be described later.

  The filter member 390 is provided closer to the fixing device 37 than a position where the second path 382 can be opened and closed by the shutter 384. Specifically, the filter member 390 is provided on the upstream side of the exhaust port 38 </ b> B in the blowing direction of the blowing fan 383 in the second path 382. Thereby, the filter member 390 collects UFP in the air at a position downstream of the exhaust mechanism 38 in the blowing direction. Note that the filter member 390 may be positively charged by a DC voltage supplied from a power source (not shown) or negatively charged by a DC voltage supplied from a power source (not shown). It is done.

  The shutter 384 is provided outside the filter member 390 at the exhaust port 38B. Specifically, the shutter 384 is provided on the downstream side of the filter member 390 in the blowing direction of the second fan 383 in the second path 382. The shutter 384 is a partition member that can open and close the exhaust port 38B, and opens and closes by a driving force supplied from a driving motor 384A (see FIG. 3). The amount of air exhausted from the second path 382 is controlled by opening and closing the shutter 384. Before the image formation by the image forming apparatus 10 is started, the exhaust port 38B is opened by the shutter 384.

  Further, it is conceivable that the exhaust mechanism 38 further includes a collection unit that collects UFP by another method instead of the filter member 390 or in addition to the filter member 390. For example, a configuration in which the image forming apparatus 10 includes a cyclone type dust collecting device that separates air and dust by applying a centrifugal force generated by swirling to the air of the second path 382 may be considered. .

[Control unit 5]
The control unit 5 is a microcomputer including a CPU, a ROM, a RAM, a DRIVER, and the like, and controls the operation of the image forming apparatus 10. The ROM stores a control program for executing image forming processing. The CPU is a processor that controls each element connected to the control unit 5 by executing a control program stored in the ROM. The RAM is used as a work area (primary storage area) for various processes executed by the CPU. The DRIVER is a circuit that drives a drive motor 383A that rotates the blower fan 383 and a drive motor 384A that opens and closes the shutter 384 in accordance with a control instruction from the CPU. The control unit 5 may be configured by an electronic circuit such as an integrated circuit (ASIC, DSP).

  The control unit 5 functions as a heating control unit 51, a heating time determination unit 52, a shutter control unit 53, and a fan control unit 54 by executing the control program using the CPU.

  The heating control unit 51 controls the presence or absence of heating of the heating unit 373 and the heating amount. The heating roller 371 is heated by the heating unit 373.

  The heating time determination unit 52 determines whether or not the continuous heating time by the heating unit 373 is equal to or greater than a predetermined first threshold value. Specifically, the first threshold value is a predetermined time based on a measurement result of UFP generated from the fixing device 37 when the heating time by the heating unit 373 continues, and is about 10 seconds, for example. .

  The shutter control unit 53 drives the drive motor 384A and controls the opening / closing of the exhaust port 38B by the shutter 384. The shutter control unit 53 closes the exhaust port 38B by the shutter 384 when the continuous heating time by the heating time determination unit 52 is determined to be equal to or greater than the first threshold value.

  The fan controller 54 controls the rotation of the blower fan 383 by driving the drive motor 383A. The fan controller 54 rotates the blower fan 383 in response to the heating controller 51 starting heating. In addition, the fan control unit 54 increases the rotation speed of the blower fan 383 when the exhaust port 38B is closed by the shutter 384 compared to when the exhaust port 38B is opened by the shutter 384. Slow down. Accordingly, the exhaust force of the blower fan 383 becomes a second exhaust force weaker than the first exhaust force when the exhaust port 38B is opened by the shutter 384. For example, when the shutter 384 is closed, the inside of the second path 382 can be suppressed from becoming a positive pressure, and an increase in the burden on the blower fan 383 can be suppressed. In addition, air containing a large amount of UFP is prevented from leaking from the gap between the shutters 384, so that the air stays in the second path 382, and UFP in the air easily aggregates due to Brownian motion.

[First exhaust control process]
Hereinafter, the procedure of the first exhaust control process executed by the control unit 5 will be described with reference to FIG. In the flowchart of FIG. 4, steps S1, S2,... Represent processing procedure (step) numbers. The first exhaust control process by the control unit 5 is executed when the image forming apparatus 10 executes the image forming process. Here, the first exhaust control process is executed by the shutter control unit 53 and the fan control unit 54. In the following processing, it is assumed that an image formation instruction is input to the image forming apparatus 10.

<Step S1>
In step S1, the control unit 5 drives the drive motor 383A to start rotation of the blower fan 383. As a result, the atmosphere around the fixing device 37 is exhausted to the outside, and the temperature is prevented from rising suddenly even when the heating roller 371 starts to be heated.

<Step S2>
In step S2, the control unit 5 determines whether or not the continuous heating time of the heating unit 373 is equal to or greater than a predetermined first threshold value. The first threshold value is set in advance based on simulation or experiment as the time for the number of UFPs generated from the heating roller 371 of the fixing device 37 to reach a predetermined amount or more. The controller 5 starts counting the continuous heating time from when the heating by the heating unit 373 is started. And the said control part 5 will transfer a process to step S3, if the said continuous heating time becomes more than the said 1st threshold value (YES side of S2). In addition, the said control part 5 makes a process wait in step S2 until the said continuous heating time becomes more than the said 1st threshold value (NO side of S2).

<Step S3>
In step S3, the control unit 5 weakens the driving force of the driving motor 383A and changes the rotation of the blower fan 383 to a low speed. In other words, the control unit 5 changes the exhaust force of the blower fan 383 to the second exhaust force that is weaker than the first exhaust force when the exhaust port 38B is open. Thus, when the exhaust port 38B is closed by the shutter 384, air is prevented from being exhausted to the outside through the gap of the shutter 384, and air heated by heat generated by the fixing device 37 is prevented. Are moved to the first path 381 and the second path 382.

<Step S4>
In step S <b> 4, the control unit 5 drives the drive motor 384 </ b> A and closes the exhaust port 38 </ b> B by the shutter 384. As a result, air containing UFP remains in the first path 381 and the second path 382.

  Thereby, UFPs contained in the air collide with each other due to Brownian motion or the like, and the number of UFPs decreases. Further, the agglomerated UFP becomes easy to be collected by the filter member 390 because the particle diameter becomes large. As described above, in the image forming apparatus 10, the number of UFP discharged during the operation of the image forming apparatus 10 is suppressed by the opening / closing control of the shutter 384.

<Step S5>
In step S <b> 5, the control unit 5 determines whether or not the stop time after the heating of the heating unit 373 has stopped is equal to or greater than a predetermined second threshold value. Here, the control unit 5 starts counting the stop time from when the heating by the heating unit 373 is stopped. And the said control part 5 will shift a process to step S6, if the said stop time becomes more than the said 2nd threshold value (YES side of S5). On the other hand, the control unit 5 causes the process to wait in step S5 until the stop time becomes equal to or greater than the second threshold (NO side of S5). The second threshold is a time required for UFP in the first path 381 and the second path 382 to be equal to or less than a predetermined number by aggregation after the heating of the heating unit 373 is finished. is there. The second threshold value may be a predetermined time based on the measurement result.

  Note that it is conceivable that the image forming process is input again after the image forming process is once completed. In this case, the control unit 5 executes the step S5. The control unit 5 determines whether or not the stop time when the heating of the heating unit 373 is stopped due to the end of the image forming process is equal to or longer than the second threshold value. In this way, the control unit 5 performs the same process as when the image forming process has been continued once the image forming process has been completed.

<Step S6>
In step S <b> 6, the control unit 5 drives the drive motor 384 </ b> A to open the exhaust port 38 </ b> B by the shutter 384. As a result, air with a reduced number of UFPs is exhausted from the exhaust port 38B.

<Step S7>
In step S7, the controller 5 increases the driving force of the driving motor 383A to change the rotation of the blower fan 383 to a normal speed. In other words, the control unit 5 changes the exhaust force of the blower fan 383 to the first exhaust force. At this time, since the shutter 384 is opened, the burden on the blower fan 383 does not increase. Then, the amount of exhaust from the exhaust port 38B increases, and ventilation in the image forming apparatus 10 is promoted.

<Step S8>
In step S <b> 8, the control unit 5 determines whether or not the driving time after the blower fan 383 starts rotating is equal to or greater than a predetermined third threshold value. In other words, the control unit 5 determines whether or not the opening time after opening the exhaust port 38B has reached or exceeded the third threshold value. In addition, the said control part 5 starts the count of drive time, when the ventilation by the said ventilation fan 383 is started by the said step S7. Then, when the driving time becomes equal to or longer than the third threshold value (YES side of S8), the control unit 5 shifts the process to step S9. The controller 5 causes the process to wait in step S8 until the drive time becomes equal to or greater than the third threshold (NO side of S8). Here, the third threshold value is a time required for the cooling of the fixing device 37 to end after the blower fan 383 starts driving. It can be considered that the third threshold is a predetermined time based on the measurement result. The opening time refers to the time that the open state continues after the exhaust port 38B is opened by the shutter 384.

<Step S9>
In step S <b> 9, the control unit 5 stops the drive motor 383 </ b> A and stops the rotation of the blower fan 383. The control unit 5 returns the process to the start. Next, when an image formation instruction is input, the control unit 5 repeats the processing from step S1 again.

[Example]
Hereinafter, a measurement result of the number of UFP generated in the image forming apparatus 10 will be described.

More specifically, as a measurement condition, the image forming apparatus 10 configured by mounting the exhaust mechanism 38 on a printer “LS-4020N” manufactured by Kyocera Document Solutions Inc. is placed in a stainless steel casing of about 5 m ^3. Deploy. The air inside the housing is ventilated at 15 m ³ / h by a blower or the like. Then, continuous printing for 10 minutes was performed after ventilation for 2 hours, and the number of UFPs generated during the 10 minutes was measured by the FMPS. This measurement was performed in accordance with the new certification standard RAL-UZ171 of the environmental label system “Blue Angel” established by the German Federal Environmental Agency. Further, as a comparative example, measurement was also performed for a state where the exhaust mechanism 38 was not attached to the image forming apparatus 10.

  For the measurement of the number of UFPs, FMPS (Fast Response Mobility Particle Sizer Model 3091) manufactured by TSI Incorporated was used. In the FMPS, the particles in the input air are charged, and the generation of UFP based on the value of the current that flows when the particles adhere to an electrode disposed at a predetermined movement distance corresponding to the UFP. The number is measured. Note that, as a method for measuring the number of UFPs, a method is used in which the number of particles having a predetermined size or less is counted based on the result of photographing the air discharged from the image forming apparatus 10 with an imaging device. Is also possible.

  In addition to the measurement of the number of UFPs, VOC generated in the image forming apparatus 10 was sampled at 100 ml / min with an adsorption tube containing an activated carbon-based adsorbent. Further, VOC was continuously sampled for 50 minutes after the image forming apparatus 10 was stopped. Then, the sampled adsorption tube was desorbed with a heat desorption apparatus, and the amount of VOC generated was measured with a gas chromatograph mass spectrometer (GCMS). The VOC amount was calculated according to the emission rate calculation formula of the “Blue Angel” environmental label system established by the German Federal Environmental Agency.

  FIG. 5 is a diagram showing the emission rates of UFP and VOC discharged from the image forming apparatus 10. In the embodiment, the exhaust mechanism 38 is mounted, and the comparative example is the exhaust. A case where the mechanism 38 is not mounted is shown.

  FIG. 6 is a graph showing the emission rates of UFP and VOC discharged from the image forming apparatus 10, where a curve 61 shows the measurement result of the example and a curve 62 shows the measurement result of the comparative example. . In FIG. 6, a timing T <b> 1 indicates a timing at which image formation by the image forming apparatus 10 is started, and a timing T <b> 2 indicates a timing at which image formation by the image forming apparatus 10 ends. The timing T2 is a time 10 minutes after the timing T1.

  Referring to FIGS. 5 and 6, the UFP emission rate in the image forming apparatus 10 of the embodiment including the exhaust mechanism 38 is higher than that of the image forming apparatus 10 of the comparative example not including the exhaust mechanism 38. It turns out that it is suppressed. Further, as shown in FIG. 5, the VOC emission rate in the image forming apparatus 10 of the embodiment including the exhaust mechanism 38 is also similar to that of the image forming apparatus 10 of the comparative example not including the exhaust mechanism 38. It is suppressed in comparison.

[Second Embodiment]
In the above description of the first embodiment, the case where the exhaust port 38B is closed by the shutter 384 in the image forming apparatus 10 until the end of image formation has been described, but the present invention is not limited to this. is not. For example, the control unit 5 may open the exhaust port 38B with the shutter 384 after a predetermined time has elapsed since the exhaust port 38B was closed with the shutter 384. Further, after the continuous heating time reaches the first threshold or more, the control unit 5 uses the shutter 384 to perform the exhaust port 38B at a predetermined cycle while the heating by the heating unit 373 continues. It is also possible to open and close the door. Such a configuration is useful when the calorific value of the fixing device 37 is large or when the amount of water evaporated from the sheet is large. Specifically, it is conceivable that the control unit 5 executes a second exhaust control process (see FIG. 7) described later, instead of the first embodiment described above. In addition, description about the structure etc. which are common in 1st Embodiment mentioned above is abbreviate | omitted.

[Second exhaust control process]
Hereinafter, the procedure of the second exhaust control process executed by the control unit 5 will be described with reference to FIG. In the flowchart of FIG. 7, steps S1, S21, S22,... Represent processing procedure (step) numbers. The second exhaust control process by the control unit 5 is executed when the image forming apparatus 10 executes the image forming process. Moreover, the said control part 5 will transfer a process to step S21, if the said continuous heating time becomes more than the said 1st threshold value in the said step S2 of a said 2nd exhaust control process (YES side of S2).

<Step S21>
In step S21, the control unit 5 determines whether or not the stop time after the heating of the heating unit 373 is stopped is equal to or more than a predetermined second threshold value, as in step S5. Here, the control unit 5 starts counting the stop time from when the heating by the heating unit 373 is stopped. And the said control part 5 will transfer a process to step S29, if the said stop time becomes more than the said 2nd threshold value (YES side of S21). On the other hand, when it is determined that the stop time is not equal to or longer than the second threshold, the control unit 5 shifts the process to step S22 (NO side of S21). In other words, in step S21, the control unit 5 determines whether or not the heating by the heating unit 373 is continued according to whether or not the stop time is equal to or greater than the second threshold value. When the stop time is not equal to or longer than the second threshold, it is determined that the heating by the heating unit 373 is continued.

  Note that it is conceivable that the image forming process is input again after the image forming process is once completed. In this case, the control unit 5 executes step S21. The control unit 5 determines whether or not the stop time when the heating of the heating unit 373 is stopped due to the end of the image forming process is equal to or longer than the second threshold value. In this way, the control unit 5 performs the same process as when the image forming process has been continued once the image forming process has been completed.

<Step S22>
In step S22, the control unit 5 weakens the driving force of the driving motor 383A and changes the rotation of the blower fan 383 to a low speed. In other words, the control unit 5 changes the exhaust force of the blower fan 383 to the second exhaust force.

<Step S23>
In step S23, the control unit 5 drives the drive motor 384A and closes the exhaust port 38B by the shutter 384. As a result, air containing UFP remains in the first path 381 and the second path 382.

<Step S24>
In step S24, the control unit 5 resets the time of the open / close timer to zero. The opening / closing timer is a timer function built in the control unit 5 and is used to time the timing at which the exhaust port 38B is periodically opened and closed by the shutter 384.

<Step S25>
In step S25, the control unit 5 determines whether or not the time of the timer has reached or exceeded a predetermined fourth threshold value. In other words, the control unit 5 determines whether or not the closing time after the exhaust port 38B is closed by the shutter 384 has reached the fourth threshold value or more. The controller 5 starts counting the time of the open / close timer from when the shutter 384 is closed and from when the shutter 384 is opened. When the time of the timer becomes equal to or longer than the fourth threshold value (YES side of S25), the control unit 5 shifts the process to step S26. On the other hand, the control unit 5 waits in step S25 until the time of the timer becomes equal to or greater than the fourth threshold value (NO side of S25). Here, the fourth threshold value is defined as the air that is heated by the fixing device 37 and contains moisture in the first path 381 and the second path 382 after the exhaust port 38B is closed and closed by the shutter 384. This is a time within a range where no adverse effect occurs on the sheet on which the image is formed even if held in the above. It can be considered that the fourth threshold is a predetermined time based on the measurement result. The closing time refers to a time during which the closed state continues after the exhaust port 38B is closed by the shutter 384.

<Step S26>
In step S <b> 26, the control unit 5 drives the drive motor 384 </ b> A to open the exhaust port 38 </ b> B by the shutter 384. As a result, air containing a small amount of UFP and containing moisture is exhausted from the exhaust port 38B.

<Step S27>
In step S27, the control unit 5 increases the driving force of the driving motor 383A to change the rotation of the blower fan 383 to a normal speed. In other words, the control unit 5 changes the exhaust force of the blower fan 383 to the first exhaust force. Accordingly, the air around the fixing device 37 is exhausted to the outside, and the room temperature air is moved around the fixing device 37.

<Step S28>
In step S28, the control unit 5 determines whether or not the time of the timer has become equal to or greater than a predetermined fifth threshold value. The control unit 5 causes the process to wait in step S28 until the time of the timer becomes equal to or greater than the fifth threshold value (NO side of S28). On the other hand, when the time of the timer becomes equal to or greater than the fifth threshold value (YES side of S28), the control unit 5 returns the process to step S21. When the control unit 5 determines in step S21 that the stop time is not greater than or equal to the second threshold, the process proceeds to step S22 and step S23. The fifth threshold value is necessary for the air held in the first path 381 and the second path 382 to be exhausted from the exhaust port 38B after the exhaust port 38B is opened by the shutter 384. It ’s a great time. The fifth threshold value may be a predetermined time based on the measurement result. The fifth threshold value may be the same value as the fourth threshold value. The fourth threshold value and the fifth threshold value are examples of the period of the present invention.

  As described above, the control unit 5 repeatedly executes steps S21 to S28 until an interrupt process is completed after image formation is completed. In other words, while the heating by the heating unit 373 continues, the control unit 5 repeatedly executes the process of opening and closing the exhaust port 38B by the shutter 384 at a predetermined cycle. Further, the control unit 5 increases or decreases the exhaust force of the blower fan 383 in the cycle according to the opening and closing of the exhaust port 38 </ b> B by the shutter 384. As a result, the image forming apparatus 10 exhausts heated air containing moisture and suppresses the number of UFP discharged. This is useful when the installation environment of the image forming apparatus 10 is hot and humid.

<Step S29>
In step S29, the controller 5 stops the drive motor 383A and stops the rotation of the blower fan 383. The control unit 5 returns the process to the start. After opening the shutter 384 in step S26, the control unit 5 determines in step S28 whether or not the opening time has reached the fifth threshold value or more. Further, after determining that the control unit 5 has reached the fifth threshold value or more, the controller 5 determines whether or not the stop time is the second threshold value or more in the step S21 and has reached the second threshold value or more. In step S29, the blower fan 383 is stopped. Therefore, when the control unit 5 stops the blower fan 383 in step S29, the opening and closing of the exhaust port 38B by the shutter 384 is ended without closing the exhaust port 38B by the shutter 384. Next, when an image formation instruction is input, the control unit 5 repeats the processing from step S1 again.

  As described above, according to the image forming apparatus 10, when the number of UFP generated in the fixing device 37 increases, the exhaust port 38 </ b> B is closed by the shutter 384, and UFPs aggregate due to Brownian motion or the like. Is done. As a result, the image forming apparatus 10 can suppress the number of UFPs discharged outside the apparatus.

3: Image forming unit 4: Paper feeding unit 5: Control unit 10: Image forming device 37: Fixing device 38: Exhaust mechanism 38A: Intake port 38B: Exhaust port 51: Heating control unit 52: Heating time determination unit 53: Shutter control Unit 54: fan control unit 371: heating roller 372: pressure roller 373: heating unit 381: first path 382: second path 383: blower fan 384: shutter 390: filter member

Claims (13)

A fixing device having a heat source and heating the toner transferred to the sheet to fix it on the sheet;
A path for guiding the air discharged from the fixing device to the outside of the apparatus;
An opening / closing part capable of opening and closing the path;
A control unit that closes the path by the opening and closing unit when a continuous heating time by the heat source reaches a predetermined first threshold value or more;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, further comprising a filter member provided closer to the fixing device than a position where the path can be opened and closed by the opening and closing unit. Further comprising a blower that generates an air flow exhausted from the fixing device to the outside of the apparatus through the path;
The said control part changes the exhaust force of the said ventilation part to the 2nd exhaust force weaker than the 1st exhaust force when the said path | route is open, when the said path | route is closed. The image forming apparatus described in 1.   The image forming apparatus according to claim 3, wherein the control unit changes the exhaust force of the air blowing unit to the second exhaust force when the continuous heating time reaches the first threshold value or more.   When the control unit has stopped the heating by the heat source and the stop time has reached a predetermined second threshold or more, the control unit opens the path and the exhaust force of the air blowing unit is increased. The image forming apparatus according to claim 3, wherein the image forming apparatus is changed to one exhaust force.   The said control part stops the said ventilation part, when the opening time of the said path | route reaches more than the predetermined 3rd threshold value after the said stop time reaches | attains more than the said 2nd threshold value. Image forming apparatus.   The image forming apparatus according to claim 3, wherein the control unit stops the air blowing unit after a predetermined second threshold value has elapsed after stopping the heating by the heat source.   When the closing time of the route reaches a predetermined fourth threshold or more, the control unit opens the route by the opening / closing unit and changes the exhaust force of the blower unit to the first exhaust force. Item 8. The image forming apparatus according to Item 7.   The control unit opens and closes the path by the opening and closing unit at a predetermined cycle while the heating by the heat source continues after the continuous heating time reaches the first threshold or more. The image forming apparatus described in 1.   When the control unit opens the path by the opening and closing unit when the closing time reaches the fourth threshold or more, and when the opening time of the path reaches a predetermined fifth threshold or more, The image forming apparatus according to claim 9, wherein the process of closing the path by the opening / closing unit is repeatedly executed.   When the opening time of the path reaches the fifth threshold or more and the heating by the heat source is not continued, the control unit opens and closes the path without closing the path by the opening and closing unit. The image forming apparatus according to claim 10, wherein the opening and closing of the path by the unit is finished and the blower unit is stopped. The fixing device includes a pair of rollers arranged in pressure contact with each other,
The image forming apparatus according to claim 1, wherein the heat source heats one or both of the rollers.   The image forming apparatus according to claim 12, wherein the roller includes silicon rubber.

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