JP6417904B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus having a fixing device such as a printer, a copier, and a printer multifunction device, and more particularly to a technique for collecting ultra fine particles generated during driving of the fixing device.

  In an image forming apparatus such as a printer or a copying machine, a toner image formed on a recording sheet is thermally fixed by a fixing device to perform image forming processing on the recording sheet. Due to the heat generated when the fixing device is driven, ultra fine particles (ultra fine particles, hereinafter abbreviated as “UFP”) such as low-molecular siloxane particles having a particle diameter of 100 nm or less are formed from the substances constituting the fixing device. It is known to occur.

This UFP does not affect the human body or the environment in particular, but it is desirable to prevent the UFP from being discharged as much as possible given the recent rapid increase in people's awareness of environmental protection. .
As a technique for reducing the amount of UFP discharged, for example, Patent Document 1 discloses a technique for collecting UFP by introducing air containing UFP generated during driving of the fixing device to a filter.

  As a result, most of the UFP generated during driving of the fixing device is collected by the filter, so that the amount of UFP discharged can be reduced.

JP 2014-44238 A

However, in the above prior art, since all UFP generated during the driving of the fixing device is guided to the filter, when the frequency of use of the fixing device is high and the amount of UFP generated is large, the filter reaches the end of its life, It is necessary to change the filter frequently.
In this way, when the frequency of filter replacement increases, the number of times that the user asks the service person to replace the filter increases, and the service person must frequently travel to the user's place to perform the filter replacement work. There is a problem that the burden on both becomes large.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of reducing the amount of UFP guided to a filter during driving of a fixing device. To do.

In order to achieve the above object, an image forming apparatus according to an aspect of the present invention includes an ultrafine particle having moisture adsorbability generated in a housing of a fixing device that thermally fixes a toner image formed on a recording sheet, and moisture. An image forming apparatus that exhausts the contained gas to the outside of the apparatus in a state where the ultrafine particles are collected through a filter, and moves the gas in the middle of a gas flow path from the housing of the fixing device to the filter with a blowing means for, and a merging portion that merges with the conveyance path of the recording sheet after thermal fixing.

Here, the gas flow path leading to the merging portion from said housing, connects the upstream opening to the opening of the wall of the housing, a first duct to face the downstream opening in the conveying path, wherein the 1 the duct, as the blowing means takes in air through the upstream opening of the housing, a fan which blows the gas into the transportation path through the downstream opening may be provided.

Configuration the downstream of the merging portion, which includes a branch passage gas flow path is branched from the conveyance path at a position spaced a predetermined distance in the sheet conveyance direction than the merging portion, and discharges the gas to the outside through the branch passage It may be as. Further, the branch path may be constituted by a second duct , and the filter may be provided in the second duct.

The image forming apparatus may further include a cooling unit that cools the gas that passes through the gas flow path from the housing to the merging unit, and the recording sheet surface after heat fixing is provided from the merging unit . In addition, a sheet cooling means for cooling on the upstream side in the sheet conveying direction may be further provided .

The recording sheet outlet of the housing is bulged outward to ensure a long recording sheet moving length from the heat fixing position to the recording sheet outlet, and moisture evaporated from the recording sheet after heat fixing is discharged into the housing. It may be possible to lengthen the period.
The image forming apparatus includes an acquisition unit that acquires the type of the recording sheet may further comprise a blower speed control means for controlling the blowing speed of the blowing means in accordance with the type of recording sheet obtained.

The image forming apparatus may further include a moisture applying unit that applies moisture to the gas in a gas flow path between the junction and the branch path, and a gas flow from the housing to the junction You may further provide the moisture provision means to provide a water | moisture content to the said gas in a path | route . The image forming apparatus estimates an amount of moisture contained in a recording sheet to be subjected to a heat fixing operation, and the amount of moisture applied from the moisture applying unit increases as the estimated amount of moisture decreases. Further, a moisture application control means for controlling the amount of moisture to be applied may be further provided .

The image forming apparatus may further include a convection portion that convects the gas in a gas flow path from the housing to the merging portion. The image forming apparatus may further include a control unit that causes the blowing unit to blow out the convected gas to the joining unit only while the recording sheet passes through the joining unit .

The image forming apparatus is provided at a position facing each other across the conveying path and the downstream opening, further provided with a suction fan to pass in a thickness direction of the recording sheet by sucking a gas blown from the downstream opening May be .
The image forming apparatus includes a first charging means for charging the gas before said gas reaches the merging portion, and a second charging unit makes charging the recording sheet after thermal fixing the charging polarity opposite of said gas May be further provided .

The downstream opening and the fan may be arranged at a position where the gas can be blown out toward a surface opposite to the surface of the recording sheet that has been heat-fixed immediately before.

  By providing the above-described configuration, heat fixing is performed in the middle of the gas flow path from the fixing device housing to the filter, where the gas containing moisture adsorbing ultra fine particles generated in the fixing device housing reaches the filter. Since the recording sheet is merged with the conveyance path of the subsequent recording sheet, when the recording sheet after heat fixing reaches the joining portion, the ultrafine particles adsorbed to the water and the recording sheet come into contact with each other, It can be trapped on the recording sheet, and the amount of ultrafine particles collected on the filter can be reduced by the amount trapped.

  As a result, the life of the filter can be extended and the frequency of filter replacement can be reduced correspondingly, thereby reducing the burden on the user and service personnel required for filter replacement work.

1 is a diagram illustrating a configuration of a printer. 4 is a schematic cross-sectional view showing a trap configuration for trapping UFP generated in a housing 43 of the fixing device during driving of the fixing device 40. FIG. The relationship between the structure of the control part 50 and the component used as the control object by the control part 50 is shown. It is a table | surface which shows the experimental result which compared the amount of filter passing UFP at the time of using the trap structure of this Embodiment with a comparative example. The structure of a comparative example is shown. It is a schematic sectional drawing which shows the trap structure of a modification (1). It is a table | surface which shows the experimental result which compared the filter passing UFP amount at the time of using the trap structure of a modification (1) with a comparative example. It is a schematic sectional drawing which shows the trap structure of a modification (2). It is a flowchart which shows the operation | movement of the exhaust control process of the atmospheric gas to a recording sheet performed using the trap structure of a modification (2). It is a table | surface which shows the experimental result which compared the amount of filter passing UFP at the time of using the trap structure of a modification (2) with a comparative example. It is a schematic sectional drawing which shows the trap structure of a modification (3). It is a table | surface which shows the experimental result which compared the amount of filter passing UFP at the time of using the trap structure of a modification (3) with a comparative example. It is a schematic sectional drawing which shows the trap structure of a modification (4). It is a table | surface which shows the experimental result which compared the amount of filter passing UFP at the time of using the trap structure of a modification (4) with a comparative example.

(Embodiment)
Hereinafter, an embodiment of an image forming apparatus according to the present invention will be described using a tandem color digital printer (hereinafter simply referred to as “printer”) as an example.
[1] Configuration of Printer First, the configuration of the printer 1 according to the present embodiment will be described. FIG. 1 is a diagram illustrating a configuration of a printer 1 according to the present embodiment. As shown in FIG. 1, the printer 1 forms an image by an electrophotographic method, and includes an image process unit 10, a paper feeding unit 30, a fixing device 40, and a control unit 50.

  When the printer 1 is connected to a network (for example, a LAN) and receives a print instruction from an external terminal device (not shown) or an operation panel, the printer 1 forms toner images of yellow, magenta, cyan, and black based on the instruction. Then, these are multiplexed and transferred onto the recording sheet to form a full-color image, thereby executing a printing process on the recording sheet. Hereinafter, the reproduction colors of yellow, magenta, cyan, and black are expressed as Y, M, C, and K, and Y, M, C, and K are added as subscripts to the numbers of the components related to the reproduction colors.

The image processing unit 10 includes image forming units 10Y, 10M, 10C, and 10K, an intermediate transfer belt 21, a secondary transfer roller 23, and the like. Since the image forming units 10Y, 10M, 10C, and 10K have the same configuration, the configuration of the image forming unit 10Y will be mainly described below.
The image forming unit 10Y includes a photosensitive drum 11, a charger 12, an exposure unit 13, a developing unit 14, a cleaner 15 for cleaning the photosensitive drum 11, and the like disposed around the photosensitive drum 11. A Y-color toner image is formed on the body drum 11. The charger 12 charges the peripheral surface of the photosensitive drum 11 that rotates in the direction indicated by the arrow A.

The exposure unit 13 includes a light emitting element such as a laser diode, emits a laser beam L for forming a Y-color image by a drive signal from the control unit 50, and exposes the charged photosensitive drum 11 with the laser beam L. Thus, an electrostatic latent image is formed on the photosensitive drum 11.
The developing device 14 is disposed so as to face the photosensitive drum 11, and conveys charged toner to the photosensitive drum 11. The intermediate transfer belt 21 is an endless belt, is stretched around a driving roller 24 and a driven roller 25 and is driven to rotate in the direction of arrow B. The electrostatic latent image formed on each photoconductor drum is developed by the developing devices of the image forming units 10Y, 10M, 10C, and 10K, and the corresponding color toner image (unfixed image) on each photoconductor drum. Is formed.

  The formed toner image is assigned to each primary transfer roller corresponding to the image forming units 10Y, 10M, 10C, and 10K (in FIG. 1, only the primary transfer roller corresponding to the image forming unit 10Y is denoted by reference numeral 22, and the other primary transfer rollers). The reference numerals of the rollers are omitted.), So that the rollers are sequentially primary-transferred on the intermediate transfer belt 21 at different timings so as to be overlapped at the same position on the intermediate transfer belt 21, and then the secondary transfer roller. The toner image on the intermediate transfer belt 21 is secondarily transferred onto the recording sheet all at once by the action of the electrostatic force 23.

The paper feeding unit 30 includes a paper feeding cassette 31 that stores recording sheets (here, a paper indicated by a symbol S), a feeding roller 32 that feeds the paper S of the paper feeding cassette 31 one by one onto the sheet conveyance path 39, and Conveying rollers 33 and 34 for conveying the fed paper S are provided.
The fixing device 40 includes a fixing roller 41 (here, for example, a heating type fixing roller using a halogen heater is used) and a pressure roller 42 that presses the fixing roller 41. The recording sheet that has been secondarily transferred is heated and pressurized to thermally fix the toner image on the recording sheet. The pressure roller 42 is driven to rotate by a pressure roller driving motor (not shown), so that the fixing roller 41 is driven to rotate. A temperature sensor (not shown) is disposed in the vicinity of the fixing roller 41, and the control unit 50 monitors the surface temperature of the fixing roller 41 via the temperature sensor, and the surface temperature is set to a target temperature (for example, for example). The heating amount of the halogen heater is controlled so as to be maintained at 180 ° C.

FIG. 2 is a schematic cross-sectional view showing a trap configuration for trapping UFP generated in the housing 43 of the fixing device while the fixing device 40 is driven. Hereinafter, the trap configuration will be described with reference to FIG. 2. As shown in FIG. 2, the fixing device 40 is accommodated in a housing 43. An opening is provided in the wall surface of the housing 43 on the side where the fixing roller 41 is accommodated, and the opening is connected to the intake port 401 of the duct 400 (the opening on the upstream side of the duct in the gas flow path). doing.

  Further, slits (gap) 431 and 432 for allowing the recording sheet to pass through the sheet conveyance path 39 are formed on both sides of the housing 43 in the conveyance direction. Further, the housing 43 has a bulging portion 430 that bulges the slit 432 on the outlet side outward. In this manner, by expanding the slit 432 outward, the recording sheet moving length from the heat fixing position (fixing nip) to the slit 432 on the exit side is secured longer than in the case where the slit 432 is not expanded, and thermal fixing is performed. It is possible to lengthen the period during which water evaporated from the subsequent recording sheet is discharged into the housing. As a result, the contact frequency between UFP and moisture in the atmospheric gas can be increased, and the adsorption of water molecules and UFP can be promoted accordingly.

  An outlet 402 (opening on the downstream side in the gas flow path direction) of the duct 400 is a position facing the sheet conveyance path 39 on the downstream side in the sheet conveyance direction from the housing 43 and upstream in the sheet conveyance direction from the external exhaust duct 600 (housing). Is provided at a position facing the sheet conveyance path 39 of the recording sheet discharged from (after heat fixing). Exhaust fans 403 and 404 are arranged on the intake port 401 side and the outlet 402 side in the duct 400, respectively.

As described above, the gas flow path formed by the duct 400 is configured to merge with the sheet conveyance path 39 of the recording sheet after heat fixing.
On the downstream side in the sheet conveyance direction from the junction where the gas flow path of the duct 400 and the sheet conveyance path 39 merge, the gas flow path branches off from the sheet conveyance path 39 at a position away from the junction in the sheet conveyance direction by a predetermined distance. The gas is discharged to the outside through the branch path.

The branch path is configured by an external exhaust duct 600, and an exhaust fan 603 is disposed on the intake port 601 side in the external exhaust duct 600. Further, a UFP collecting filter 604 is disposed on the gas flow path from the intake port 601 to the outlet 602 of the external exhaust duct 600.
The filter 604 may be a filter that can collect UFP. For example, a HEPA filter (High Efficiency Particulate Air Filter) or a ULPA filter (Ultra Low Penetration Air Filter) can be used. An electrostatic filter may be used.

The outlet 402 of the duct 400 and the intake port 601 of the outside-exhaust duct 600 are configured to communicate with each other by a sheet conveyance path 63 (part indicated by a dotted rectangle) formed by the conveyance guide members 61 and 62. Has been.
Low molecular siloxane, which is a major component of UFP, is water-adsorbing, and hydrogen bonds are formed between oxygen atoms, which are constituent elements of low molecular siloxane, and hydrogen atoms, which are constituent elements of water molecules. As a result, water molecules and low molecular weight siloxane are adsorbed. Thereby, low molecular siloxane (UFP) having low affinity with the recording sheet can be adsorbed to the fibers of the recording sheet (here, paper) having high affinity with moisture as follows.

  The heat generated from the fixing device 40 in the housing 43 at the time of heat fixing, UFP, and gas containing moisture evaporated from the recording sheet (hereinafter referred to as “atmosphere gas”) are discharged from the housing 43 into the duct 400 by the exhaust fan 403. It is taken into the duct 400 through the intake port 401. At least a part of the UFP contained in the atmospheric gas comes into contact with water molecules and adsorbs to the water molecules while passing through the duct 400. Then, the atmospheric gas containing the UFP and the adsorbed moisture is blown out from the outlet 402 of the duct 400 toward the area of the sheet conveyance path where the outlet 402 faces by the exhaust fan 404 disposed on the downstream side of the duct 400. When the heat-fixed recording sheet passes through the region, moisture adsorbed on the surface of the recording sheet and adsorbed by UFP is trapped on the recording sheet.

The blown-out atmospheric gas is then guided to the passage 63 by the exhaust fan 603 disposed in the outside-exhaust exhaust duct 600, proceeds along the passage 63 along the sheet conveyance direction, and passes through the passage 63. The UFP contained in the atmospheric gas and the adsorbed moisture are trapped in the recording sheet in contact with the recording sheet passing through the passage 63.
After passing through the passage 63, the atmospheric gas is taken into the duct 600 by the exhaust fan 603 from the intake port 601 of the external exhaust duct 600 that communicates with the outlet 402 of the duct 400, and the external exhaust duct. After passing through a UFP collection filter 604 disposed in 600, the UFP is collected to the filter and exhausted to the outside of the apparatus.

  Note that a period during which the recording sheet does not pass through the area (a period from when the preceding recording sheet passes through the area until the subsequent recording sheet passes through the area) is exhausted from the outlet 402 of the duct 400. The atmospheric gas passes through the passage 63 by the exhaust fan 603 and is taken in from the intake port 601, and UFP contained in the atmospheric gas is collected by the filter 604 and then exhausted outside the apparatus.

Returning to the description of FIG. 1, the control unit 50 is a so-called computer including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and performs printing processing on a recording sheet. Control overall operation.
FIG. 3 shows the relationship between the configuration of the control unit 50 and the components to be controlled by the control unit 50. The control unit 50 includes a CPU 501, a communication interface (I / F) unit 502, a ROM (Read Only Memory) 503, a RAM (Random Access Memory) 504, an image data storage unit 505, and the like.

The communication I / F unit 502 is an interface for connecting to a LAN such as a LAN card or a LAN board. The ROM 503 stores a program for controlling the image processing unit 10, the paper feeding unit 30, the fixing device 40, the operation panel 8, the exhaust fans 403, 404, and 603.
The RAM 504 is used as a work area when the CPU 501 executes a program.
The image data storage unit 505 stores image data for printing input via the communication I / F unit 502.

The CPU 501 controls the image processing unit 10, the sheet feeding unit 30, the fixing device 40, the operation panel 8, the exhaust fans 403, 404, and 603 by executing various programs stored in the ROM 503.
The operation panel 8 includes a liquid crystal display, a touch panel stacked on the liquid crystal display, operation buttons for inputting various instructions, and the like, and receives input of various instructions from the user through operations of the touch panel, the operation buttons, and the like. The exhaust fans 403, 404, and 603 are controlled to be turned on / off and the exhaust speed (blower speed) by the controller 50.

FIG. 4 is a table showing experimental results comparing the amount of UFP guided to the filter when the trap configuration of the present embodiment is used (hereinafter referred to as “filtered UFP amount”) with a comparative example.
FIG. 5 shows a configuration of a comparative example. In the figure, the same components as those in the trap configuration of the present embodiment in FIG. 2 are assigned the same reference numerals and the description thereof is omitted, and differences will be described below. As shown in FIG. 5, in the configuration of the comparative example, the atmospheric gas is taken in from the intake port 401 of the duct 400D by the exhaust fan 403, and then directly guided to the filter 604 and passes through the filter to the UFP. Is collected and exhausted to the outside of the aircraft. The housing 43D of the comparative example does not have the bulging portion 430.

  In the above experiment, a predetermined number (here, 50 sheets) of recording sheets (here, A4 size plain paper recording sheets) are thermally fixed using the trap configuration of the present embodiment and the configuration of the comparative example, respectively. When the operation is executed, the amount of UFP in the housings 43 and 43D (hereinafter referred to as “initial UFP amount”) and the amount of UFP guided to the filter 604 are respectively determined using a UFP particle counter (P-Trak Model 8525). It was performed by measuring at the time interval (here, 1 second interval).

As the filter 604, an electrostatic filter (HEPA filter) is used. The surface wind speed of the atmospheric gas exhausted by the exhaust fan 404 from the outlet 402 of the duct 400 in the trap configuration of the present embodiment is 0.3 m / s, and the filter 604 is used. The surface wind speed of the atmospheric gas passing through the chamber was 0.2 m / s, and the length of the transport guide 61 (passage 63) was 10 cm.
The initial UFP amount (U0) and filter-passed UFP amount (U) in the table of FIG. 4 indicate average values of measured values (measured values of the UFP particle counter) measured at a predetermined time interval, and “estimated trap rate” “(T)” indicates the percentage of UFP estimated to be trapped in the recording sheet in UFP (U0) contained in the atmospheric gas. T is calculated by the following calculation formula (1).

T = (U0-U) / U0 × 100 (1)
As shown in the experimental results of FIG. 4, when the trap configuration of the present embodiment is used, the amount of UFP passing through the filter is reduced by 10% compared to the configuration of the comparative example. That is, as shown by the estimated trap rate of the trap configuration of the present embodiment, 10% of the initial UFP amount is trapped on the recording sheet before being guided to the filter 604, and the amount of UFP passed through the filter is compared accordingly. It is estimated that it is reduced by 10% compared to the case of the example configuration.

As described above, in the trap configuration of the present embodiment, a part of UFP generated from the fixing device 40 in the housing 43 during the heat fixing operation can be trapped on the recording sheet after the heat fixing. The amount of UFP passing through the filter can be reduced, and the life of the filter can be extended.
As a result, the frequency of filter replacement can be reduced, and the burden on users and service personnel required for filter replacement work can be reduced.
(Modification)
As described above, the present invention has been described based on the above embodiment, but it is needless to say that the present invention is not limited to the above embodiment, and the following modifications can be implemented.

  (1) In the trap configuration of the above embodiment, the housing 43 is provided with the bulging portion 430, and the period during which the moisture evaporated from the recording sheet after heat fixing by the fixing device 40 is discharged into the housing is lengthened. The UFP contained in the atmospheric gas is adsorbed with moisture by using the evaporated moisture from the sheet, but instead of providing the bulging portion 430, a moisture spraying device comprising a water storage tank, pump, spray nozzle, etc. It is good also as controlling the drive of a water | moisture-content spraying apparatus by the control part 50, spraying mist-like water | moisture content, and adsorb | sucking UFP contained in atmospheric gas to a water | moisture content using the sprayed water | moisture content.

  FIG. 6 shows the configuration of this modification. In the figure, the same components as those of the configuration of FIG. 2 of the above embodiment are given the same numbers and the description thereof is omitted, and differences will be described below. As shown in the figure, in the configuration of this modification, the housing 43A does not have the bulging portion 430 like the housing of the comparative example, and the atmospheric gas downstream of the fixing device 40 is transferred to the sheet conveyance path 39. The downstream side in the sheet conveyance direction of the outlet 402 of the duct 400C to be exhausted (between the junction where the gas flow path of the duct 400 and the sheet conveyance path 39 merge and the branch where the gas flow path branches from the sheet conveyance path 39). A water spraying device 63 is disposed on the surface.

The water spray device 63 has a water storage tank 63A and a spray nozzle 63B, and has a pump (not shown) built therein. By controlling the driving of the pump by the control unit 50, the spraying of mist-like water from the water spraying device 63 is controlled.
FIG. 7 is a table showing experimental results comparing the filter-passed UFP amount with the comparative example when the trap configuration of this modification is used.

  The experimental conditions are the same as in FIG. As shown in the experimental results of FIG. 7, when the trap configuration of this modification is used, the amount of filter-passed UFP is reduced by 5% compared to the configuration of the comparative example. That is, as shown by the estimated trap rate of the trap configuration of this modification example, 5% of the initial UFP amount is trapped on the recording sheet before being guided to the filter 604, and the filter-passed UFP amount correspondingly is compared with the comparative example. It is estimated that it is reduced by 5% compared to the case of the configuration.

The water spray device 63 may be arranged in the duct 400C of FIG.
In this modification, the amount of water sprayed from the water spray device 63 may be adjusted according to the amount of water contained in the recording sheet to be heat-fixed.
Specifically, a table indicating the correspondence between the type (paper type), basis weight, size, and moisture content of the recording sheet to be heat-fixed is stored in advance in the ROM 503, and a communication interface ( Based on information on the type, basis weight, and size of the recording sheet to be thermally fixed, which is input from the I / F) unit 502 and the operation panel 8, the corresponding moisture content is specified from the table, and the recording sheet It is good also as controlling so that the moisture content sprayed from the moisture spraying device 63 may increase, so that the estimated moisture content is small.

  The amount of water to be sprayed can be controlled by changing the pressure of the pump by the control unit 50, for example. Specifically, a table indicating the correspondence relationship between the pump pressure and the moisture content of the recording sheet is stored in the ROM 503 in advance, and the control unit 50 uses the table to calculate the estimated moisture content of the recording sheet. The amount of water to be sprayed can be controlled by determining the pressure of the corresponding pump and driving the water spray device 63 at the determined pressure.

The water content of the recording sheet may be estimated by measuring using a moisture sensor.
(2) The trap configuration of the above embodiment may be modified as shown in FIG. In the figure, the same components as those of the configuration of FIG. 2 of the above embodiment are given the same numbers and the description thereof is omitted, and differences will be described below. In the modified example shown in the figure, a moisture spray device 405 having the same configuration as that of the modified example (1) and a convection chamber 407 for convection of the captured atmospheric gas are provided in a duct 400A in which the atmospheric gas in the housing 43 is captured. Newly provided.

In the convection chamber 407, stirring screws 4071, 4072, and 4073 are disposed, and the driving of these stirring screws is controlled by the control unit 50.
Furthermore, a shutter 408 is provided at the outlet 4074 of the convection chamber 407, and the opening and closing of the shutter 408 is controlled by the control unit 50. In addition, on the upstream side of the slit 431 of the housing 43 in the sheet conveyance direction and the upstream side of the outlet 402 of the duct 400A in the sheet conveyance direction, paper passing sensors 71 and 72 for detecting that the leading edge of the recording sheet has passed are respectively arranged. ing.

The arrangement position of the sheet passing sensor 72 is the time from when the leading edge of the recording sheet is detected until the leading edge reaches the position on the sheet conveying path 39 facing the upstream edge of the outlet 402 in the sheet conveying direction. After the shutter 408 is opened, it is determined in advance so as to coincide with the time that the atmospheric gas in the convection chamber 407 is guided to the outlet 402 by the exhaust fan 404.
FIG. 9 is a flowchart showing the operation of the exhaust control process of the atmospheric gas to the recording sheet, which is executed using the trap configuration of this modification.

When the power is turned on, the control unit 50 drives the exhaust fans 403 and 404 and controls the shutter 408 to be in an open state (step S901), starts warming up the fixing device 40, and fixes the fixing roller. When the surface temperature of 41 reaches the target temperature, the warm-up is finished and the image forming operation is started (step S902).
Then, after the sheet passing sensor 71 detects that the leading end of the recording sheet has passed, a predetermined time required for the leading end to reach the nip portion between the fixing roller 41 and the pressure roller 42 has elapsed, and the recording When the heat fixing operation on the sheet is started (step S903: YES), the control unit 50 drives the moisture spraying device 405 and the agitation screws 4071, 4072, and 4073 so that the shutter 408 is closed. Then, the atmospheric gas is guided to the convection chamber 407 and convected while giving moisture to the atmospheric gas taken into the duct 400A by the exhaust fan 403 (step S904).

Thereby, the contact frequency of UFP and moisture contained in the atmospheric gas can be increased, and adsorption of water molecules and UFP can be promoted.
Thereafter, when the sheet passing sensor 72 detects that the leading edge of the recording sheet has passed (step S905: YES), the control unit 50 controls the shutter 408 to be in an open state (step S906), and the recording is performed. For a predetermined time required for the sheet to finish passing through the region of the sheet conveyance path 39 where the outlet 402 of the duct 400A faces (the rear end of the recording sheet has finished passing through the end of the region in the sheet conveyance direction), the atmospheric gas is The air is exhausted toward the region (step S907: NO).

After the predetermined time has elapsed (step S907: YES), the control unit 50 stops the moisture spray device 405 and the stirring screws 4071, 4072, and 4073 (step S908).
The control unit 50 repeats the operations from step S903 to step S908 until the heat fixing operation ends (step S909: YES).

In addition, in the trap structure of this modification, it is good also as a structure which does not provide the water spray apparatus 405 but provides only the convection chamber 407. In this case as well, as in the case of the present modification, the contact frequency between UFP and moisture contained in the atmospheric gas can be increased, and the adsorption of water molecules and UFP can be promoted.
FIG. 10 is a table showing experimental results comparing the filter-passed UFP amount with the comparative example when the trap configuration of this modification is used.

  The experimental conditions are the same as in FIG. As shown in the experimental results of FIG. 10, when the trap configuration of this modification is used, the amount of filter-passed UFP is reduced by 15% compared to the configuration of the comparative example. That is, as shown in the estimated trap rate of the trap configuration of this modification, 15% of the initial UFP amount is trapped on the recording sheet before being guided to the filter 604, and the filter-passed UFP amount correspondingly is compared with the comparative example. It is estimated that it is reduced by 15% compared to the case of the configuration.

  (3) The trap configuration of the above embodiment may be modified as shown in FIG. In the figure, the same components as those of the configuration of FIG. 2 of the above embodiment are given the same numbers and the description thereof is omitted, and differences will be described below. In the modification shown in the figure, a duct 600 </ b> A having an intake port 601 is provided at a position opposite to the outlet 402 of the duct 400 </ b> B from which the atmospheric gas containing moisture adsorbing UFP is exhausted across the sheet conveyance path 39. Yes.

  The atmospheric gas exhausted from the outlet 402 of the duct 400B passes through the mesh-shaped air-permeable conveyance guide member 62A, and is disposed on the downstream side in the gas flow path direction of the intake port 601 of the duct 600A. Thus, the air is sucked into the duct 600A from the intake port 601 and taken in, passes through the filter 604 disposed in the duct 600A, and is exhausted outside the apparatus in a state where UFP is collected in the filter. Has been.

In the above configuration, the exhaust speed of the exhaust fan 603 is set in advance to an exhaust speed at which the atmospheric gas can be taken in from the intake port 601 without hindering the conveyance of the recording sheet.
With the configuration of this modification, the recording sheet after heat fixing is exhausted from the outlet 402 of the duct 400B when passing through the region of the sheet conveyance path where the outlet 402 of the duct 400B and the intake port 601 of the duct 600A face each other. Since the atmospheric gas can be passed in the thickness direction of the recording sheet, UFP and adsorbed moisture can be adsorbed not only on the surface of the recording sheet but also on the inside.

FIG. 12 is a table showing experimental results comparing the filter-passed UFP amount with the comparative example in the case of using the trap configuration of the modified example.
The experimental conditions are the same as in FIG. 4 except that the exhaust fan 404 and the passage 63 are not provided. As shown in the experimental results of FIG. 12, when the trap configuration of this modification is used, the filter-passed UFP amount is reduced by 30% compared to the configuration of the comparative example. That is, as shown by the estimated trap rate of the trap configuration of this modification, 30% of the initial UFP amount is trapped on the recording sheet before being led to the filter 604, and the filter-passed UFP amount correspondingly is compared with the comparative example. It is estimated that it is reduced by 30% compared to the case of the configuration.

  (4) The trap configuration of the above embodiment may be modified as shown in FIG. In the figure, the same components as those of the configuration of FIG. 2 of the above embodiment are given the same numbers and the description thereof is omitted, and differences will be described below. In the modification shown in the figure, a charger 81 for charging atmospheric gas is provided in the duct 400, and the recording sheet is placed downstream of the housing 43 in the sheet conveyance direction and upstream of the outlet 400 of the duct 400 in the sheet conveyance direction. A charger 82 is provided for charging the gas with a polarity opposite to that of the atmospheric gas. As the chargers 81 and 82, for example, a corona charger can be used.

As a result, the UFP contained in the atmospheric gas and the recording sheet that adsorbs the UFP are charged with different polarities, so that the UFP can be easily adsorbed by the recording sheet by electrostatic force.
FIG. 14 is a table showing experimental results comparing the filter-passed UFP amount with the comparative example when the trap configuration of this modification is used.

The experimental conditions are the same as in FIG. 4, and the voltage applied to the charger 81 is −500 V, and the voltage applied to the charger 82 is +500 V.
As shown in the experimental results of FIG. 14, when the trap configuration of this modification is used, the amount of filter-passed UFP is reduced by 20% compared to the configuration of the comparative example. That is, as shown by the estimated trap rate of the trap configuration of this modification example, 20% of the initial UFP amount is trapped on the recording sheet before being led to the filter 604, and the filter-passed UFP amount correspondingly is compared with the comparative example. It is estimated that it is reduced by 20% compared to the case of the configuration.

(5) Although the cooling mechanism for cooling the atmospheric gas taken into the duct 400 is not provided in the above embodiment, the cooling mechanism may be provided. It is desirable that the cooling be performed at 50 ° C. or more with respect to the temperature of the atmospheric gas in the housing 43 of the fixing device 40 before the atmospheric gas reaches the outlet 402 of the duct 400.
As a result, the condensation of the UFP and the adsorbed water can be promoted, and as a result, the water easily penetrates into the inside of the recording sheet due to the capillary phenomenon, and the UFP not only on the surface of the recording sheet but also on the internal fibers. Adsorption is facilitated, and the trap efficiency of UFP on the recording sheet can be increased.

  The cooling mechanism may be configured to cool the atmospheric gas passing through the duct 400 by providing heat radiation fins on the outer periphery of the duct 400 to increase the heat radiation area (for example, Japanese Patent Application Laid-Open No. 2007-114265). (Refer to paragraphs 0077 to 0080 of the publication and the configuration of the duct 62 described in FIG. 4), and the duct 400 may be submerged in a cooling water tank to cool the atmospheric gas passing through the duct 400 (for example, (See the configuration of the cooling mechanism 60 ″ described in paragraph 0098 of FIG. 5 and FIG. 5B). The duct 400 may be formed of a member having high thermal conductivity.

  Further, instead of cooling the duct 400, or in addition to cooling the duct 400, the recording sheet after heat fixing is located downstream of the housing 43 in the sheet conveyance direction and from the outlet 602 of the duct 600 in the sheet conveyance direction. A cooling mechanism for cooling the surface may be provided. As the cooling mechanism, for example, a cooling fan may be used, the conveyance guide member may be formed of a member having high thermal conductivity, or a heat radiation fin may be provided on the conveyance guide member.

This modification can be similarly applied to the trap configurations of Modifications (1) to (4).
(6) Further, the exhaust direction of the atmospheric gas from the outlet 402 of the duct 400 to the recording sheet may be any direction as long as the exhausted atmospheric gas can contact the surface of the recording sheet. . This modification can be similarly applied to the modifications (1) to (5).

(7) Also, the recording sheet has different thicknesses, surface fiber roughnesses, and the like depending on the type (paper type), and the water absorption and the fiber surface density differ depending on the type. Accordingly, there is a difference in the amount of moisture adsorbed on the recording sheet when the atmospheric gas is exhausted from the duct to the recording sheet at the same exhaust speed.
For example, in the case of a recording sheet in which the fiber is coated with a coating agent, such as coated paper, and both the water absorption rate and the fiber surface density are low, the exhaust speed of the atmospheric gas exhausted from the duct is the same as that of plain paper. In this case, the amount of moisture adsorbed on the recording sheet is smaller than that of plain paper.

  For this reason, it is good also as controlling exhaust speed according to the kind of recording sheet so that the difference of the moisture adsorption amount between the types of recording sheet may become small. Specifically, for each type of recording sheet that should trap UFP adsorbed in advance, the exhaust speed (blowing speed) of the exhaust fan 404 at the time of trapping is determined by performing an experiment or the like. A table showing the correspondence relationship between the type of the exhaust speed and the determined exhaust speed is stored in the ROM 503 or the like, and the control unit 50 refers to the table at the time of executing the print job, and starts the communication interface (I / F) unit 502, The type of recording sheet input from the operation panel 8 is acquired, the exhaust speed corresponding to the acquired type of recording sheet is specified, and the exhaust fan 404 is controlled so that the atmospheric gas is exhausted at the specified exhaust speed. It is good as well.

  As a result, even in the case of a recording sheet having a low water absorption rate and low fiber surface density, such as coated paper, the exhaust speed is faster than the default exhaust speed (for example, the exhaust speed set for plain paper). By setting it so that the contact frequency between the atmospheric gas and the recording sheet can be increased, the amount of adsorption of UFP and adsorbed moisture to the recording sheet can be increased accordingly (in the case of plain paper). The difference from the adsorption amount can be reduced).

This modification can be applied in the same manner to Modifications (1) to (6).
(8) In the above embodiment, the atmospheric gas is blown out from the outlet 402 of the duct 400 and is brought into contact with the surface of the recording sheet that has been heat-fixed immediately before, but the atmospheric gas was heat-fixed immediately before. It is good also as making it contact with the surface on the opposite side to the surface of the recording sheet of the side.
For example, instead of the duct 400, a duct having a duct inlet on the pressure roller 42 side of the housing 43 and a duct outlet on the opposite side of the position of the outlet 402 and the conveyance path are provided instead of the duct 400. It is good also as comprising so that gas may contact the said surface of the other side.

As a result, the toner image that has been heat-fixed immediately before and the atmospheric gas can be prevented from contacting each other, and the atmospheric gas can be prevented from affecting the toner image after the thermal fixing.
The configuration of this modification can be similarly applied to the modifications (1), (2), and (4) to (7).
(9) In the above embodiment and the modified examples (1) to (8), the atmospheric gas is guided to the downstream side of the fixing device 40 through the duct and is brought into contact with the recording sheet surface. The medium that guides the recording medium is not limited to the duct, and another medium, for example, the housing may be extended in the sheet conveying direction to bring the atmospheric gas into contact with the recording sheet surface.

In the above embodiment and the modified examples (1) to (8), a roller type fixing device is used as the fixing device. However, the fixing device is not limited to the roller type, and is a belt type. It may be.
Further, the heating method of the fixing device is not limited to the fixing device of the heating method using a halogen heater, and other heating methods may be used. For example, an electromagnetic induction heating type fixing device or a heating type fixing device using a resistance heating element may be used.

  The present invention relates to an image forming apparatus having a fixing device such as a printer, a copying machine, or a printer multifunction device, and can be used particularly as a technique for collecting ultra fine particles generated during driving of the fixing device.

DESCRIPTION OF SYMBOLS 1 Printer 10 Image process part 30 Paper feed part 40 Fixing device 41 Fixing roller 42 Pressure roller 43 Frame 50 Control part 403, 404, 603 Exhaust fan 604 Filter

Claims (16)

A gas containing water-adsorbing ultrafine particles and moisture generated in the housing of the fixing device that thermally fixes the toner image formed on the recording sheet is exhausted outside the apparatus while the ultrafine particles are collected through a filter. An image forming apparatus that
The gas flow path from the housing of the fixing device to the filter has an air blowing means for moving the gas and a merging portion that merges with the conveyance path of the recording sheet after thermal fixing. Image forming apparatus.   The gas flow path from the housing to the joining portion is a first duct in which an upstream opening is connected to an opening of a wall surface of the housing and a downstream opening is exposed to the transport path, and the inside of the first duct 2. The fan according to claim 1, further comprising: a fan that takes in a gas from the housing through the upstream opening and blows the gas out of the housing through the downstream opening. The image forming apparatus described.   The downstream side of the merging part includes a branching path in which a gas flow path branches off from the conveying path at a position a predetermined distance away from the merging part in the sheet conveying direction, and the gas is discharged to the outside through the branching path. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   The image forming apparatus according to claim 3, wherein the branch path is configured by a second duct, and the filter is provided in the second duct.   The image forming apparatus according to claim 1, further comprising a cooling unit that cools a gas that passes through a gas flow path from the housing to the junction.   The image forming apparatus according to claim 1, further comprising a sheet cooling unit that cools the surface of the recording sheet after heat fixing on the upstream side in the sheet conveyance direction from the merging portion.   The recording sheet outlet of the housing is bulged outward to ensure a long recording sheet moving length from the heat fixing position to the recording sheet outlet, and moisture evaporated from the recording sheet after heat fixing is discharged into the housing. The image forming apparatus according to claim 1, wherein a period of time during which the recording is performed is long. Acquisition means for acquiring the type of recording sheet;
A blowing speed control means for controlling the blowing speed by the blowing means according to the type of the recording sheet obtained;
The image forming apparatus according to claim 1, further comprising:   The image forming apparatus according to claim 3, further comprising a moisture applying unit that applies moisture to the gas in a gas flow path between the junction and the branch path.   The image forming apparatus according to claim 1, further comprising a moisture applying unit that applies moisture to the gas in a gas flow path from the housing to the junction. An estimation means for estimating the amount of water contained in the recording sheet to be subjected to the thermal fixing operation;
Moisture application control means for controlling the amount of water to be applied, so that the estimated water content is smaller, the amount of water applied from the water application means is increased,
The image forming apparatus according to claim 9, further comprising:   The image forming apparatus according to claim 10, further comprising a convection portion that convects the gas in a gas flow path from the housing to the merging portion. The image forming apparatus according to claim 12, further comprising a control unit that causes the blowing unit to blow out the convected gas to the merge unit only while the recording sheet passes through the merge unit.   3. The suction fan according to claim 2, further comprising a suction fan that is provided at a position facing the downstream opening with the conveyance path interposed therebetween, and sucks the gas blown from the downstream opening to pass in the thickness direction of the recording sheet. Image forming apparatus. First charging means for charging the gas before the gas reaches the joining portion;
A second charging means for charging the recording sheet after heat fixing to a polarity opposite to the charging polarity of the gas;
The image forming apparatus according to claim 1, further comprising:   The downstream opening and the fan are arranged at positions where the gas can be blown out toward a surface opposite to the surface of the recording sheet on the side that has been heat-fixed immediately before. Item 3. The image forming apparatus according to Item 2.

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