JP2017015802A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can suppress the number of generation of UFPs.SOLUTION: An image forming apparatus 10 comprises: an exhaust passage 381 that guides an air exhausted from a fixing device 37 to the outside, the fixing device heating a toner transferred to a sheet to fix the toner to the sheet; a charging part 383 that is provided in the exhaust passage 381 and charges ultra fine particles in the air to have a first polarity; a collection part 384 that is provided on the downstream side of the charging part 383 in an air-blowing direction of the exhaust passage 381 and is charged to have a second polarity that is a reverse polarity to the first polarity; and a control part 5 that makes an absolute value of a charging voltage of at least one of the charging part 383 and collection part 384 in a preset first period from the start of operation of the fixing device 37, larger than that in a preset second period after the passage of the first period.SELECTED DRAWING: Figure 2

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. On the other hand, a configuration is known in which UFP generated in the fixing device is removed by electrostatic adsorption (see, for example, Patent Document 1). For example, after UFP is charged to either positive polarity or negative polarity, a configuration in which the UFP is collected using a negative electrode or a positive electrode having a reverse polarity is conceivable.

JP 2010-2803 A

  However, the amount of UFP generated is extremely large at the start of the image forming process, and thereafter tends to gradually decrease. Therefore, when the voltage applied to the negative electrode or the positive electrode is constant, only one of the UFP collection effect when the UFP generation amount is large and the power saving effect when the UFP generation amount is small. Priority will be given.

  An object of the present invention is to provide an image forming apparatus capable of suppressing the number of UFP discharges while saving power.

  An image forming apparatus according to one aspect of the present invention includes an exhaust path, a charging unit, a collection unit, and a control unit. The exhaust path guides air discharged from a fixing device that heats and fixes the toner transferred to the sheet to the outside. The charging unit is provided in the exhaust path and charges the ultrafine particles in the air to the first polarity. The collection unit is provided on the downstream side of the charging unit in the blowing direction of the exhaust path, and is charged with a second polarity opposite to the first polarity. The controller sets the absolute value of the charging voltage of at least one of the charging unit and the collecting unit in a first period set in advance from the start of operation of the fixing device in advance after the elapse of the first period. Make it larger than the second period.

  According to the present invention, it is possible to suppress the number of UFPs discharged from the image forming apparatus while saving power.

FIG. 1 is a diagram showing a configuration of an image forming apparatus according to an 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 embodiment of the present invention. FIG. 3 is a diagram showing a result of suppressing the emission rate of UFP and VOC in the image forming apparatus according to the embodiment of the present invention. FIG. 4 is a flowchart showing an example of the charging air blowing control process executed by the image forming apparatus according to the embodiment of the present invention.

  Embodiments of the present invention will be described below 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.

[Schematic Configuration of Image Forming Apparatus 10]
First, a schematic configuration of the image forming apparatus 10 according to the 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 control unit 5 is a control device including a CPU, a RAM, a ROM, an EEPROM (registered trademark), and the like, and executes various processes by the CPU according to a control program stored in the ROM or the EEPROM. The image forming apparatus 10 is controlled.

  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.

  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 casing of the fixing device 37. The fixing device 37 includes a heating unit 373 such as a halogen heater disposed inside the heating roller 371. The pressure roller 372 is indirectly heated by the heating unit 373 through 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. Further, the fixing device 37 includes a temperature detection unit 374 including a thermistor for detecting the temperature of the fixing device 37, and the temperature detected by the temperature detection unit 374 is input to the control unit 5.

  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. As a result, the fixing device 37 heats the toner transferred to the sheet and fixes it to 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. On the other hand, a configuration is conceivable in which the UFP generated in the fixing device 37 is charged positively or negatively, and collected using an electrode having a polarity opposite to that. However, in the configuration in which the positive polarity or the negative polarity is charged, UFP that is hardly charged to the polarity cannot be collected. On the other hand, in the image forming apparatus 10, the number of UFPs generated is suppressed by the following configuration.

[Exhaust mechanism 38]
Next, the exhaust mechanism 38 will be described with reference to FIG. FIG. 2 is a schematic diagram of a main part showing the configuration of the exhaust mechanism 38 of the image forming apparatus 10.

  The exhaust mechanism 38 can exhaust the air in the vicinity of the fixing device 37 to the outside of the image forming apparatus 10. Specifically, the exhaust mechanism 38 includes an exhaust path 381, a blower fan 382, a first charging unit 383, a first collecting unit 384, a second charging unit 385, a second collecting unit 386, A power source 387, a power source 388, and a filter member 389 are provided.

  The exhaust path 381 is an exhaust duct used to guide the air discharged from the fixing device 8 to the outside of the image forming apparatus 10 and has, for example, a rectangular cross section or a circular cross section. The exhaust path 381 has an intake port 38A provided in the vicinity of the fixing device 37 and an exhaust port 38B for discharging air to the outside of the image forming apparatus 10. For example, 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 blower fan 382 is a blower that blows air sucked from the intake port 38 </ b> A of the exhaust path 381 toward the exhaust port 38 </ b> B and discharges the air outside the image forming apparatus 10. Hereinafter, the direction of the air blow by the blower fan 382 is referred to as a blow direction D1.

  The first charging unit 383, the first collecting unit 384, the second charging unit 385, and the second collecting unit 386 are provided in the exhaust path 381, and for example, a wire is formed in a filter shape (a mesh shape or a mesh shape). This is a filter member having a filter surface formed in a lattice shape. The first charging unit 383, the first collection unit 384, the second charging unit 385, and the second collection unit 386 are configured so that the filter surface is perpendicular to the blowing direction D 1 in the exhaust path 381. In this state, it is arranged in the exhaust path 381. The filter surface is, for example, rectangular or circular like the shape of the exhaust path 381. The first charging unit 383, the first collecting unit 384, the second charging unit 385, and the second collecting unit 386 each have a plurality of filter surfaces in the air blowing direction D1 of the exhaust path 381. It may be.

  The first charging unit 383 is connected to the power source 387 and is discharged when a positive DC voltage is applied from the power source 387, and the UFP in the air of the exhaust path 381 is positive ( An example of the first polarity) is charged. The positive DC voltage applied from the power source 387 to the first charging unit 383 is, for example, +2 kV or +4 kV.

  The first collection unit 384 is connected to the power source 388 and is charged to a negative polarity when a negative DC voltage (an example of the second polarity) is applied from the power source 388. The negative DC voltage applied from the power source 388 to the first collector 384 is, for example, −100V or −200V.

  On the other hand, the second charging unit 385 is provided on the downstream side of the first collecting unit 384 in the blowing direction D1. The second charging unit 385 is connected to the power source 388, and discharges when a negative DC voltage is applied from the power source 388, and the UFP in the air of the exhaust path 381 is negative (second) Charge to one example of polarity). The negative DC voltage applied from the power source 388 to the second charging unit 385 is, for example, −2 kV or −4 kV. That is, the power supply 388 is a power supply device capable of outputting at least four systems of −100 V, −200 V, −2 kV, and −4 kV. The power supply 388 may be a power supply device that can output an arbitrary voltage in the range of −100 V to −4 kV, for example.

  The power source 387 and the power source 388 are controlled by the control unit 5, for example, when an image forming process is executed in the image forming apparatus 10, the first charging unit 383, the first collecting unit 384, A voltage is applied to the second charging unit 385 and the second collection unit 386. A voltage such as −2 kV or −4 kV may be applied from the power source 388 to the first collection unit 384 and the second charging unit 385. Further, the first charging unit 383 and the second charging unit 385 are not limited to the filter member having the filter surface as long as the UFP can be charged, and may be a discharge wire or a needle electrode. .

  Further, the second collection unit 386 is provided on the downstream side of the second charging unit 385 in the blowing direction D1. The second collection unit 386 is connected to the power source 387 and is charged positively when a positive DC voltage (an example of the first polarity) is applied from the power source 387. The positive DC voltage applied from the power source 387 to the second collector 386 is, for example, + 100V or + 200V. That is, the power supply 387 is a power supply device capable of outputting at least four systems of +100 V, +200 V, +2 kV, and +4 kV. The power supply 387 may be a power supply device that can output an arbitrary voltage in the range of +100 V to +4 kV, for example. A voltage such as +2 kV or +4 kV may be applied from the power source 388 to the first charging unit 383 and the second collection unit 386, respectively.

  The filter member 389 is provided in the exhaust port 38B of the exhaust path 381. The filter member 389 collects dust, UFP, VOC, and the like in the air exhausted through the exhaust path 381.

  In the exhaust mechanism 38 configured as described above, the UFP contained in the air discharged through the exhaust path 381 is effectively absorbed by the first collection unit 384 and the second collection unit 386. To be collected.

  Specifically, in the exhaust path 381, UFP is charged to the positive polarity by the first charging unit 383. As a result, the positively charged UFP is collected on the downstream side of the first charging unit 383 by the first collection unit 384 that is negatively charged.

  Further, UFP is charged to the negative polarity by the second charging unit 385 on the downstream side of the first collection unit 384 in the exhaust path 381. As a result, the negatively charged UFP is collected on the downstream side of the second charging unit 385 by the second collecting unit 386 that is positively charged.

  Accordingly, in the exhaust path 381, UFP is effectively collected by the first collection unit 384 and the second collection unit 386 and discharged from the exhaust path 381 to the outside of the image forming apparatus 10. The number of UFPs is suppressed.

  In the present embodiment, the first charging unit 383 and the second collecting unit 386 are charged with positive polarity, and the first collecting unit 384 and the second charging unit 385 are charged with negative polarity. Explained the case. On the other hand, the first charging unit 383 and the second collection unit 386 are negatively charged, and the first collection unit 384 and the second charging unit 385 are positively charged. Is considered.

  By the way, a plurality of collection units each including the first charging unit 383, the first collection unit 384, the second charging unit 385, and the second collection unit 386 are provided in the exhaust path 381. It is also conceivable as another embodiment. Thereby, the number of UFPs discharged from the exhaust mechanism 38 can be further suppressed.

  In particular, when a plurality of collection units are provided, the absolute values of the charging voltages of the first charging unit 383 and the second charging unit 385 are located upstream of the blowing direction D1 in the exhaust path 381. It is possible that the said collection part located in the downstream rather than a collection part is larger. Specifically, the positive charging voltage of the first charging unit 383 of the collection unit on the downstream side in the blowing direction D1 in the exhaust path 381 is the first charging unit 383 of the collection unit on the upstream side. Higher than the positive charging voltage. In addition, the negative charging voltage of the second charging unit 385 of the downstream collecting unit is lower than the negative charging voltage of the second charging unit 385 of the upstream collecting unit. Thereby, the charging performance of UFP in the said collection part of a downstream becomes higher than the said collection part of an upstream.

  Similarly, when a plurality of sets of the collection units are provided, the absolute values of the charging voltages of the first collection unit 383 and the second collection unit 385 are positioned on the upstream side in the blowing direction D1 in the exhaust path 381. It is conceivable that the collecting unit located downstream is larger than the collecting unit. Specifically, the negative charging voltage of the first collecting portion 384 of the collecting portion on the downstream side in the air blowing direction D1 in the exhaust path 381 is the first collecting value of the collecting portion on the upstream side. It is lower than the negative charging voltage of the portion 384. Further, the positive charging voltage of the second collecting unit 386 of the downstream collecting unit is higher than the positive charging voltage of the second collecting unit 386 of the upstream collecting unit. Thereby, the collection force of UFP in the said collection part of a downstream becomes higher than the said collection part of an upstream.

  According to these configurations, there is an increased possibility that the UFP that has not been collected by the upstream collection unit will be collected by the downstream collection unit, and the UFP discharged from the image forming apparatus 10 The number is further suppressed.

  Further, when a plurality of sets of the collection units are provided, the width of the blowing direction in the blowing direction D1 of the first charging unit 383 and the second charging unit 385 is the width of the blowing direction D1 in the exhaust path 381. It is conceivable that the collecting part located on the downstream side is larger than the collecting part located on the upstream side. Specifically, the number of filter surfaces in the blowing direction D1 of the first charging unit 383 of the collecting unit on the downstream side in the blowing direction D1 in the exhaust path 381 is the same as that of the collecting unit on the upstream side. More than the first charging unit 383. In addition, the number of filter surfaces in the blowing direction D1 of the first collection unit 384 of the downstream collection unit is greater than that of the first collection unit 384 of the upstream collection unit. Thereby, the charging performance of UFP in the said collection part of a downstream becomes higher than the said collection part of an upstream.

  Similarly, when a plurality of sets of the collection units are provided, the width of the blowing direction in the blowing direction D1 of the first collecting unit 384 and the second collecting unit 386 is the blowing direction in the exhaust path 381. It is conceivable that the collecting unit located on the downstream side is larger than the collecting unit located on the upstream side of D1. Specifically, the number of filter surfaces in the blowing direction D1 of the first collecting portion 384 of the collecting portion on the downstream side in the blowing direction D1 in the exhaust path 381 is the number of filter surfaces in the upstream on the collecting portion. More than the first collection part 384. In addition, the number of filter surfaces in the blowing direction D1 of the second collection unit 386 of the downstream collection unit is greater than that of the second collection unit 386 of the upstream collection unit. Thereby, the collection force of UFP in the said collection part of a downstream becomes higher than the said collection part of an upstream.

  According to these configurations, there is an increased possibility that the UFP that has not been collected by the upstream collection unit will be collected by the downstream collection unit, and the UFP discharged from the image forming apparatus 10 The number is further suppressed.

  Note that the second charging unit 385 may have a larger absolute value of the charging voltage or a larger width in the blowing direction than the first charging unit 383. Similarly, it is conceivable that the absolute value of the charging voltage is larger or the width in the blowing direction is larger in the second collecting portion 386 than in the first collecting portion 384.

  By the way, the amount of UFP generated is extremely large at the start of the image forming process, and thereafter tends to gradually decrease. Therefore, when the voltage applied to the negative electrode or the positive electrode is constant, only one of the UFP collection effect when the UFP generation amount is large and the power saving effect when the UFP generation amount is small. Priority will be given. On the other hand, in the image forming apparatus 10, the control unit 5 executes a charging air blowing control process (see FIG. 4) described later, thereby saving power and discharging UFP from the image forming apparatus 10. The number decreases.

[Charging ventilation control processing]
Hereinafter, an example of the procedure of the charged air blowing control process executed by the control unit 5 will be described with reference to FIG.

<Step S1>
In step S1, the controller 5 determines whether or not the operation of the fixing device 37 has been started. For example, in the image forming apparatus 10, the control unit 5 starts the operation of the fixing device 37 when the image forming apparatus 10 is turned on or returned from the power saving mode. Therefore, in step S1, the control unit 5 may determine that the operation of the fixing device 37 is started when the image forming apparatus 10 is turned on or returned from the power saving mode. .

  If it is determined that the operation of the fixing device 37 has started (S1: Yes), the process proceeds to step S2, and if it is determined that the operation of the fixing device 37 has not started (S1: No), the process waits in step S1.

  By the way, it is known that the amount of UFP generated becomes extremely large when the temperature of the fixing device 37 increases from a low state. Therefore, only when the temperature of the fixing device 37 detected by the temperature detection unit is equal to or lower than a preset lower limit value, the control unit 5 shifts the process to step S <b> 2 and the temperature of the fixing device 37. Is higher than the lower limit, the process proceeds to step S5. Thus, when the temperature of the fixing device 37 is higher than the lower limit value, charging and blowing are performed not only in the second period but also in the first period, according to the second charging condition and the second blowing condition described later. It will be. That is, the absolute value of the charging voltage in the first period is larger than that in the second period only when the temperature of the fixing device 37 is equal to or lower than the lower limit value.

<Step S2>
In step S2, the control unit 5 controls the power supply device 387 and the power supply 388 under a preset first charging condition, and the first charging unit 383, the first collecting unit 384, and the second charging unit. The unit 385 and the second collection unit 386 are charged. The first charging condition is set in advance as a charging condition corresponding to a first period set in advance from the start of operation of the fixing device 37. For example, under the first charging condition, the value of the positive charging voltage applied to the first charging unit 383 and the second charging unit 385 is +4 kV, and the first collecting unit 384 and the second collecting unit. The value of the negative charging voltage applied to 386 is set to -200V. Note that the absolute value of the charging voltage under the first charging condition is larger than the charging voltage corresponding to the second period described later.

<Step S3>
In step S <b> 3, the control unit 5 controls the blower fan 382 under a preset first blowing condition, and starts blowing by the blower fan 382. The first blowing condition is set in advance as a blowing condition corresponding to the first period. For example, under the first air blowing condition, the rotational speed of the air blowing fan 382 is set to 3000 rpm. In addition, the rotation speed of the said ventilation fan 382 in a said 1st ventilation condition is smaller than the rotation speed corresponding to the below-mentioned 2nd period, and the ventilation volume by the said ventilation fan 382 is small. As a result, the speed of the air passing through the air blowing path 381 in the first period is reduced, so that the charging efficiency of UFP by the first charging unit 383 and the second charging unit 385 is increased and the first collection is performed. The UFP collection effect by the part 384 and the second collection unit 385 is enhanced.

<Step S4>
In step S4, the control unit 5 determines whether or not a change condition for determining a change timing of the first charging condition and the first air blowing condition is satisfied. Specifically, when the first period after the start of the operation of the fixing device 36 is determined in time, the change condition is that a time corresponding to the first period elapses. When the first period is determined as a period until the temperature of the fixing device 36 detected by the temperature detecting unit 374 reaches a preset temperature, the change condition is determined by the fixing device. The temperature of 36 reaches the set temperature.

  If it is determined that the change condition is satisfied (S4: Yes), the process proceeds to step S5. If it is determined that the change condition is not satisfied (S4: No), the process is performed as described above. Wait in step S4.

<Step S5>
In step S5, the control unit 5 controls the power supply device 387 and the power supply 388, and the first charging unit 383, the first collection unit 384, the second charging unit 385, and the second collection unit. The charging condition of the unit 386 is changed from the first charging condition to a preset second charging condition. The second charging condition is preset as a charging condition corresponding to a preset second period after the first period has elapsed. For example, under the second charging condition, the absolute value of the positive charging voltage applied to the first charging unit 383 and the second charging unit 385 is smaller than the charging voltage (+4 kV) corresponding to the first period. It is set to +2 kV. In the second charging condition, the absolute value of the negative charging voltage applied to the first collecting unit 384 and the second collecting unit 386 is a charging voltage (-200 V) corresponding to the first period. Is set to −100V, which is smaller than that. That is, the collection effect of the first charging unit 383, the first collection unit 384, the second charging unit 385, and the second collection unit 386 in the first period is higher than that in the second period.

  In the present embodiment, the absolute values of all the charging voltages of the first charging unit 383, the first collection unit 384, the second charging unit 385, and the second collection unit 386 in the first charging condition are used. A case where the value is larger than the second charging condition will be described. On the other hand, as another embodiment, at least one charge of the first charging unit 383, the first collection unit 384, the second charging unit 385, and the second collection unit 386 in the first charging condition. It is only necessary that the absolute value of the voltage is larger than the second charging condition. The charging voltage is applied to at least one of the first charging unit 383, the first collection unit 384, the second charging unit 385, and the second collection unit 386 only during the first period. In other words, it may be not performed in the second period.

<Step S6>
In step S <b> 6, the control unit 5 controls the blower fan 382 and changes the blower condition of the blower fan 382 from the first blower condition to a preset second blower condition. The second blowing condition is set in advance as a blowing condition corresponding to the second period. For example, in the second air blowing condition, the rotational speed of the blower fan 382 is set to 1500 rpm, which is smaller than the rotational speed (3000 rpm) corresponding to the first period. That is, the amount of air blown by the blower fan 382 in the first period is smaller than that in the second period.

<Step S7>
In step S <b> 7, the control unit 5 determines whether an end condition for determining the end timing of the application of the charging voltage by the power supply device 387 and the power supply 388 and the end of blowing by the blower fan 382 is satisfied. . Specifically, the end condition is that a preset time has elapsed since the end of the image forming process executed by the image forming apparatus 10. Further, the termination condition may be that the temperature of the fixing device 36 detected by the temperature detection unit 374 has decreased to a predetermined temperature or less.

<Step S8>
In step S8, the control unit 5 ends the application of the charging voltage by the power supply device 387 and the power source 388 and the blowing by the blower fan 382, and returns the process to step S1.

  As described above, in the image forming apparatus 10, the charging air blowing control process is executed, so that the first period immediately after the start of the operation of the fixing device 37 is more charged than the second period thereafter. The absolute value of the voltage increases. Further, the amount of air blown by the blower fan 382 is less in the first period immediately after the start of the operation of the fixing device 37 than in the second period thereafter. Therefore, the UFP collection efficiency by the exhaust mechanism 381 in the first period with a large amount of UFP generation is high. On the other hand, in the image forming apparatus 10, by executing the charging air blowing control process, the absolute value of the charging voltage is smaller in the second period than in the first period, and power saving is realized. . In the second period, the amount of air blown by the blower fan 382 is larger than that in the first period, and the temperature in the image forming apparatus 10 can be lowered.

  Hereinafter, a measurement result of the number of UFP generated in the image forming apparatus 10 will be described. FIG. 3 is a diagram showing the emission rates of UFP and VOC discharged from the image forming apparatus 10. In FIG. 3, when the exhaust mechanism 38 is attached and the charged air blowing control process is executed in the first embodiment, the charged air blow control process is executed in the comparative example 1 although the exhaust mechanism 38 is attached. Otherwise, Comparative Example 2 shows the measurement results when the exhaust mechanism 38 is not mounted.

More specifically, as the measurement condition, the image forming apparatus 10 configured by mounting the exhaust mechanism 38 on a printer “TASKalfa 7550ci” manufactured by Kyocera Document Solutions Inc. is disposed in a stainless steel casing of about 5 m ^3. . In addition, ventilation is performed at a flow rate of 15 m ³ / h by a blower or the like with respect to the internal air of the housing. 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 FMPS (Fast Response Mobility Particle Sizer Model 3091) manufactured by TSI Incorporated. 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.

  In the FMPS, the particles in the air that are input are charged, and the UFP is based on the value of the current that flows as a result of the particles adhering to an electrode disposed at a predetermined movement distance corresponding to the UFP. The number of occurrences 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.

[Example 1]
In the first exemplary embodiment, the charging and blowing control process is executed in the image forming apparatus 10, so that charging and blowing are performed in the first period under the first charging condition and the first blowing condition, and the second period. During the period, charging and blowing are performed under the second charging condition and the second blowing condition. That is, in the first period, the charging voltage of the first charging unit 383 is +4 kV, the second charging unit 385 is −4 kV, the second collecting unit 386 is +200 V, and the first collecting unit 384 is −200 V. Is applied. On the other hand, in the second period, the charging voltage of the first charging unit 383 is +2 kV, the second charging unit 385 is −2 kV, the second collection unit 386 is +100 V, and the first collection unit 384 is −100 V. Is applied. Further, the rotational speed of the blower fan 382 in the first period is 3000 rpm, and the rotational speed of the blower fan 382 in the second period is 1500 rpm. When the rotational speed of the blower fan 382 is 1500 rpm, for example, the intake flow rate to the exhaust path 381 is 10 L / min. In the first embodiment, the first period is 10 minutes, and charging and blowing are always performed under the first charging condition and the first blowing condition during the execution of the measurement.

  In the first embodiment, the charging voltage of the first charging unit 383, the second charging unit 385, the first collecting unit 384, and the second collecting unit 386 is compared with the charging voltage of the first comparative example. It has doubled and the collection efficiency of UFP is high. Accordingly, as shown in FIG. 3, the UFP emission rate in the image forming apparatus 10 of the first embodiment is not limited to the comparative example 2 in which the exhaust mechanism 38 is not mounted, but also the comparative example. The image forming apparatus 10 is significantly lower than the image forming apparatus 10.

[Comparative Example 1]
As Comparative Example 1, the charging and blowing control process is not executed in the image forming apparatus 10, and charging and blowing are performed in the second charging condition and the second blowing condition in both the first period and the second period. Measurements were made when performed. That is, a charging voltage of +2 kV is applied to the first charging unit 383, −2 kV is applied to the second charging unit 385, + 100V is applied to the second collecting unit 386, and −100V is applied to the first collecting unit 384. The rotational speed of the blower fan 382 is 1500 rpm.

  In the comparative example 1, the charging voltage of the first charging unit 383, the second charging unit 385, the first collecting unit 384, and the second collecting unit 386 is compared with the charging voltage of the first embodiment. It is halved and the UFP collection efficiency is low. Therefore, as shown in FIG. 3, the UFP emission rate in the image forming apparatus 10 of the comparative example 1 is lower than that of the comparative example 2 in which the exhaust mechanism 38 is not mounted. 1 is higher than that of the image forming apparatus 10.

[Comparative Example 2]
As Comparative Example 2, measurement was also performed in a state where the exhaust mechanism 38 was not attached to the image forming apparatus 10. In Comparative Example 2, since the exhaust mechanism 38 is not mounted, UFP collection efficiency is low. Therefore, as shown in FIG. 3, the UFP emission rate in the image forming apparatus 10 of the comparative example 2 is higher than those of the first and comparative examples.

3: Image forming unit 4: Paper feeding unit 5: Control unit 10: Image forming device 37: Fixing device 371: Heating roller 372: Pressure roller 373: Heating unit 374: Temperature detecting unit 38: Exhaust mechanism 38A: Intake port 38B : Exhaust port 381: exhaust path 382: blower fan 383: first charging unit 384: first collecting unit 385: second charging unit 386: second collecting unit 387: power source 388: power source 389: filter member

Claims (8)

An exhaust path for guiding the air discharged from the fixing device that heats and fixes the toner transferred to the sheet to the outside;
A charging unit provided in the exhaust path for charging the ultrafine particles in the air to a first polarity;
A collecting unit provided on the downstream side of the charging unit in the blowing direction of the exhaust path and charged to a second polarity opposite to the first polarity;
The absolute value of the charging voltage of at least one of the charging unit and the collecting unit in a first period preset from the start of operation of the fixing device is set to be greater than a preset second period after the first period has elapsed. A control unit to enlarge,
An image forming apparatus comprising: An air blowing section for blowing air toward the exhaust port of the exhaust path;
An air blowing control unit that reduces the amount of air blown by the air blowing unit in the first period than the second period;
The image forming apparatus according to claim 1, further comprising: A temperature detection unit for detecting the temperature of the fixing device;
Only when the temperature detected by the temperature detection unit at the start of operation of the fixing device is equal to or lower than a preset lower limit value, the control unit detects the charging unit and the collection unit in the first period. The image forming apparatus according to claim 1, wherein an absolute value of at least one of the charging voltages is made larger than the second period. The charging unit is a first charging unit, the collection unit is a first collection unit,
A second charging unit provided on the downstream side of the first collection unit in the blowing direction of the exhaust path and charging the ultrafine particles in the air to the second polarity;
A second collection unit that is provided downstream of the second charging unit in the blowing direction of the exhaust path and is charged to the first polarity;
Further comprising
The control unit calculates an absolute value of at least one charging voltage of the first charging unit, the first collecting unit, the second charging unit, and the second collecting unit in the first period in the second period. The image forming apparatus according to claim 1, wherein the image forming apparatus is larger than the image forming apparatus.   The image forming apparatus according to claim 4, wherein the first collection unit and the second collection unit are filter members having a filter surface that is arranged perpendicular to a blowing direction of the exhaust path.   6. The image forming apparatus according to claim 4, wherein the first charging unit and the second charging unit are filter members having a filter surface that is arranged perpendicular to a blowing direction of the exhaust path.   The said exhaust path is provided with two or more sets of collection parts which make the said 1st charging part, the said 1st collection part, the said 2nd charging part, and the said 2nd collection part into 1 set. The image forming apparatus according to claim 6. The fixing device includes a pair of rollers arranged in pressure contact with each other, and a heating unit that heats one or both of the rollers,
The image forming apparatus according to claim 1, wherein the roller includes silicon rubber.

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