JP2006039168A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent ozone and TVOC generated within an image forming apparatus from being discharged out of the apparatus, by steadily decomposing and removing them within the apparatus for a long time. <P>SOLUTION: The image forming apparatus incorporates: a photocatalyst sheet 14 having a photocatalyst; a light source 13 for irradiating the photocatalyst sheet 14 with light including a wavelength in a ultraviolet ray area; and an exhaust purification unit 1 having an air intake fan 12. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile, and more particularly to an image forming apparatus that removes ozone generated in the apparatus.

  In an image forming apparatus using an electrostatic copying process, a charging unit that uniformly charges a photoconductor, a transfer unit that transfers a toner image on the photoconductor to a transfer sheet, and a toner neutralization unit that neutralizes residual toner on the photoconductor Is widely used, and ozone is generated by this corona discharge. If ozone is discharged outside the apparatus, it may adversely affect the human body, and the odor may cause discomfort to surrounding people.

Thus, for example, Patent Document 1 proposes a technique for providing a filter to adsorb ozone and preventing ozone from being discharged outside the apparatus. Patent Document 2 proposes a technique in which a photocatalyst layer is provided on a casing of a charging unit that performs corona discharge, and the generated ozone is decomposed and removed by the photocatalyst layer.
Japanese Patent Laid-Open No. 10-307525 (Claims (0013) to (0017)) JP-A-11-282318 (Claims (0052) to (0060))

  However, the adsorption removal of ozone by the filter has a problem that the adsorption performance of the filter drops in a short period of time due to the adsorption of ozone, and the user or serviceman must frequently replace the filter. In addition, in the method in which the photocatalyst layer is provided on the casing of the charging unit and ozone is decomposed and removed, most of the generated ozone is released to the outside of the casing before being decomposed by the photocatalyst layer, and the desired effect cannot be obtained. There was a problem.

  In addition, volatile organic components (“TVOC”) are generated from a PCB (Polychlorobiphenyl) substrate disposed in the apparatus and toner when heat-fixed. If this TVOC is discharged out of the apparatus, it may adversely affect the human body and the like, as well as ozone, and the odor may cause discomfort to the person. However, the awareness of TVOC problems has not been high so far, and only measures have been taken to remove TVOC at the same time using a filter for removing ozone. As described above, the adsorption removal method using a filter has an essential problem that the adsorption performance of the filter is reduced in a short period of time.

  Accordingly, the present invention has been made in view of such conventional problems, and an object of the present invention is to provide an image forming apparatus capable of stably removing ozone and TVOC generated in the apparatus over a long period of time. It is in.

  As a result of intensive studies to achieve the above object, the present inventor has found out that radical ions generated when ozone is decomposed using a photocatalyst is useful for decomposing TVOC, and have made the present invention. . That is, the image forming apparatus of the present invention includes an exhaust purification unit having a photocatalyst holding member provided with a photocatalyst, a light source that irradiates the photocatalyst holding member with light including a wavelength in the ultraviolet region, and an intake fan and / or an exhaust fan. The exhaust purification unit decomposes ozone and TVOC generated in the apparatus.

  Here, from the viewpoint of more reliably decomposing and removing ozone and TVOC, it is preferable to further provide a duct for guiding the air containing ozone and / or TVOC from the ozone and / or TVOC generation site to the exhaust purification unit.

  As the photocatalyst holding member, a filter in which a photocatalyst layer is formed on the substrate surface or a filter in which a photocatalyst is supported on a fiber is recommended.

  In the image forming apparatus of the present invention, air containing ozone and TVOC is sucked into the exhaust purification unit by the intake fan and / or the exhaust fan, and the photocatalyst is irradiated with ultraviolet rays by the light source built in the unit, and redox is performed on the surface of the photocatalyst. A reaction is caused to decompose ozone and TVOC. At this time, since radical ions generated by the decomposition of ozone decompose TVOC, ozone and TVOC can be decomposed quickly and reliably at the same time.

  If a duct for guiding the air containing ozone and / or TVOC from the ozone and / or TVOC generation point to the exhaust purification unit is further provided, the generated ozone and TVOC can be reliably drawn into the exhaust purification unit. Ozone and TVOC can be more completely eliminated from the apparatus.

  Further, when a photocatalyst holding member having a photocatalyst layer formed on the substrate surface or a filter having a photocatalyst supported on a fiber is used, the processing capacity per unit volume is increased and the unit can be downsized.

  The image forming apparatus of the present invention will be described below with reference to the drawings. The present invention is not limited to these embodiments.

  FIG. 1 is a vertical sectional view showing an embodiment of the image forming apparatus of the present invention. The image forming apparatus in this figure is a so-called in-body discharge type image forming apparatus. A paper discharge space 3 having an opening on the front side is formed at a substantially central portion in the vertical direction of the apparatus main body 2. On the bottom surface of the paper discharge space 3, a tray 87 for placing paper to be discharged is integrally formed with the casing. On the other hand, a reading mechanism 91 for reading a document is built in the upper side of the paper discharge space 3, and an image forming mechanism is built in the lower side of the paper discharge space 3.

  The image forming mechanism will be described. The surface of the photosensitive drum 70 is uniformly charged positively or negatively by a charging device 71. On the other hand, a document (not shown) is placed on the document placing table 90, and the image data is read by the reading device 91. The read image data is written on the surface of the photosensitive drum 70 by a laser scanner (exposure device) 72, and an electrostatic latent image is formed on the surface of the photosensitive drum 70. Specifically, in the case of the reverse development method, the charge corresponding to the image is removed, and in the case of the regular development method, the charge corresponding to the background is removed to form an electrostatic latent image. Next, the electrostatic latent image on the photosensitive drum 70 is visualized with toner by the developing device 73. At this time, the charging polarity of the toner is the same as the charging polarity of the photosensitive drum 70 in the case of the reversal development method, and is opposite to the charging polarity of the photosensitive drum 70 in the case of regular development.

  On the other hand, the paper P stored in the paper feed cassette 81 is pulled out by the pickup roller 82, sandwiched between the paper feed roller 83 and the separating roller 84, and sent to the conveyance path. Then, the registration roller pair 11 feeds the paper P to the transfer unit at the timing when the toner image on the photosensitive drum 70 reaches the transfer unit. In the transfer portion, the sheet P is sandwiched between the photosensitive drum 70 and the transfer roller 74, and a charge having a polarity opposite to the toner charging polarity is applied to the transfer roller 74. Toner image moves onto the paper P. The toner remaining on the photosensitive drum 70 without moving onto the paper P is removed and collected by the cleaning roller 75. On the other hand, the paper P on which the toner image is placed is conveyed to the fixing roller pair 85. Here, the toner image is heated and pressurized by the fixing roller pair 85 and fixed on the paper P. Then, the paper P is sent to the discharge roller pair 86 and discharged to the tray 87. The paper P placed on the manual feed tray 88 is fed to the registration roller pair 11 by the paper feed roller 89, and thereafter passes through the same path as the above-described transport path.

  Above the discharge roller pair 86 is provided an exhaust purification unit (hereinafter sometimes simply referred to as “unit”) 1 where ozone generated by corona discharge or the like, and a PCB substrate disposed in the apparatus, The TVOC generated from the heated toner is decomposed and removed. A specific configuration of the unit 1 is shown in FIG.

The unit 1 in FIG. 2 includes a rectangular parallelepiped case 11, an intake fan 12 provided on the bottom surface of the case 11, and a fluorescent lamp that is attached in the longitudinal direction of the case 11 and emits light including a wavelength in the ultraviolet region. Light source) 13, a photocatalyst sheet (photocatalyst holding member) 14 installed at a predetermined inclination so that light from the fluorescent lamp 13 is irradiated substantially vertically on the lower right side surface of the case 11, And an exhaust port 15 formed on the upper right side. The photocatalyst sheet 14 is obtained by forming a photocatalyst layer 14b containing TiO ₂ as a photocatalyst on the surface of a plate-like substrate 14a.

When the photocatalyst sheet 14 is irradiated with ultraviolet light from the fluorescent lamp 13, the photocatalyst is excited, and ozone contacting the photocatalyst sheet 14 is decomposed by the following chemical reaction formula (1). At this time, moisture in the air in contact with the photocatalyst sheet 14 is also decomposed by the following chemical reaction formula (2).
2O ₃ + H ₂ O → OH + 2O ₂ + HO ₂ .--- (1)
_{H 2 O → · OH + H} · ---------- (2)

  And “.OH” (hereinafter referred to as “OH radical”) generated by the decomposition of ozone and moisture has a strong oxidizing action, and reacts with TVOC to decompose it. In particular, the OH radical causes a reaction to open the benzene ring.

  The air taken into the unit 1 by the intake fan 12 is discharged from the exhaust port 15 to the outside of the unit 1 after ozone and TVOC are decomposed, removed and purified by the chemical reaction.

Examples of the photocatalyst used in the present invention include TiO ₂ , WO ₃ , ZnO, and CdS, and these can be used alone or in combination of two or more. Among these, the use of anatase TiO ₂ is recommended from the viewpoints of reaction efficiency, safety, irradiation light wavelength, and the like. Further, when a metal such as Pt, Pd, Rh, or Nb is mixed, the photocatalytic action can be further promoted.

  In order to form the photocatalyst layer 14b on the substrate 14a, a conventionally known method such as a chemical vapor deposition method, neutralization or hydrolysis of an inorganic metal salt, hydrolysis of a metal alkoxide, or a sol-gel method can be used.

  Of course, the photocatalyst holding member is not limited to the one in which the photocatalyst layer 14b is formed on the substrate 14a, and may be a filter in which the photocatalyst is supported on a fiber. By using a filter, the processing capacity per unit volume is increased and the unit can be downsized.

  In the unit 1 of FIG. 2, air containing ozone and TVOC is taken into the unit 1 by the intake fan 12 and purified, and then exhausted from the exhaust port 15. For example, an intake port and an exhaust fan are provided, The air may be sucked into the unit from the air inlet by discharging the air outside with an exhaust fan. Of course, an intake fan and an exhaust fan may be provided in the unit. However, in this case, it is necessary to adjust the exhaust amount of the exhaust fan to be larger than the intake amount of the intake fan so that the unit always has a negative pressure.

  In the image forming apparatus of FIG. 1, the unit 1 is disposed above the charging device 71 and the transfer roller 74 that generate ozone, and above the pair of fixing rollers 85 that generate TVOC by fixing and heating the toner. Yes. As a result, air containing a large amount of ozone and TVOC is heated and rises, and is efficiently taken into the unit 1. However, depending on the type of the image forming apparatus, the charging device, the transfer device, and the fixing roller pair may be arranged horizontally. In the case of such an image forming apparatus, it is difficult to efficiently take in air containing a lot of ozone or TVOC into the unit 1 regardless of the installation position of the unit 1. Therefore, in such a case, it is recommended to install a duct in order to actively take in air containing a lot of ozone and TVOC into the unit 1. FIG. 3 shows an example embodiment in which a duct is provided.

  FIG. 3 is a schematic configuration diagram of an image forming apparatus in which a charging device 71, a transfer device 74, and a fixing roller pair 85 are horizontally arranged. The sheets fed one by one from the sheet feeding cassette 81 by the pickup roller 82 are transported to the photosensitive drum 70 at a predetermined timing through a transport path, with the leading edge thereof being adjusted by the registration roller pair 11 and waiting.

  On the other hand, after the surface of the photosensitive drum 70 is uniformly charged by the charging device 71, an electrostatic latent image is formed on the photosensitive drum 70 by the exposure device 72. The electrostatic latent image is visualized as a toner image by the toner supplied from the developing device 73, and is transferred onto the fed paper by the transfer roller 74. The sheet on which the toner image is placed is conveyed to the fixing roller pair 85, and is heated and pressed by the heating roller and the pressure roller to fix the toner image on the sheet. The sheet on which the toner image is fixed is discharged onto a discharge tray 87 by a discharge roller pair 86.

  In the image forming apparatus having such a configuration, the duct 4 is disposed so that the air inlets 43a and 43b are positioned in the vicinity of the photosensitive drum 70 and the fixing roller pair 85, and the rear surface 21 of the apparatus (shown in FIG. 4). The ozone and TVOC generated by the charging device 71 and the fixing roller pair 85 are fed to the unit 1 ′ provided outside the unit. FIG. 4 shows a cutaway perspective view showing a state in which the duct 4 and the unit 1 ′ are attached.

  In FIG. 4, a unit 1 ′ is provided outside the back wall 21 of the image forming apparatus by attachment means (not shown), and one end of the duct 4 is connected to the air inlet of the unit 1 ′. The duct 4 extending from the unit 1 ′ passes through the back wall 21, and then advances straight to the vicinity of the fixing roller pair 85 (shown in FIG. 3), and the photosensitive drum 70 ( Branches to a duct 42 that travels in the vicinity of (shown in FIG. 3). The duct 41 goes straight and extends in the vicinity of the fixing roller pair 85 to a position substantially the same as the front end of the fixing roller pair 85. An air inlet 43a elongated in the axial direction is formed on the surface of the duct 41 facing the fixing roller. The other duct 42 advances to the vicinity of the photosensitive drum 70 along the back wall 21, then bends toward the front of the apparatus, and extends to the same position as the front end of the photosensitive drum 70. An air inlet 43b elongated in the axial direction is also formed on the surface of the duct 42 on the photosensitive drum side.

  The internal structure of the unit 1 ′ is the same as that of FIG. 2 except that the mounting position of the intake fan is the connection part of the duct 4. When an unillustrated intake fan is driven, ozone generated by the charging device 71 and the transfer device 74 (shown in FIG. 3) and TVOC generated by the fixing roller pair 85 are sucked from the openings 43a and 43b, and the duct 41, 42 and sent to unit 1 ′. In the unit 1 ′, ozone and TVOC are decomposed as described above, and the purified air is discharged from the exhaust port 15.

  In the apparatus of this embodiment, the duct 4 is arranged in the vicinity of the photosensitive drum 70 and the fixing roller pair 85, but the arrangement position of the duct 4 is not limited to this, and other ozone and TVOC are used. What is necessary is just to arrange | position suitably in the part which generate | occur | produces.

With reference to the BAM standard "Test method for determining emissions from hardcopy devices within the framework of granting eco-labels to office devices according to RAL-UZ62, RAL-UZ85 and YY ¹ " (April 2003 edition) The TVOC and ozone emissions outside the apparatus were measured between the image forming apparatus equipped with the unit and the image forming apparatus not equipped with the unit. The specific experimental method is as follows.

(Measurement of TVOC)
FIG. 5 shows a schematic configuration diagram of the measuring apparatus. The image forming apparatus shown in FIG. 1 or FIG. 2 is carried into a 6.5 m ³ chamber, and is divided into “standby mode”, “image forming mode” + “rear running mode”, and the following measurement conditions Thus, the amount of TVOC discharged in each mode was measured by sampling the air in the chamber. The results are shown in Table 1. In the table, the image forming apparatus illustrated in FIG. 1 is referred to as “image forming apparatus A”, and the image forming apparatus illustrated in FIG. 3 is referred to as “image forming apparatus B”.

(Measurement condition)
In the “standby mode” in which image formation was not performed, the “standby mode” was continued for 60 minutes, and sampling was performed at 100 mL / min for the last 20 minutes. In the case of “image forming mode” + “back running mode”, the image forming mode and the back running mode were continuously performed for 120 minutes, and sampling was continuously performed at 100 mL / min. The “image forming mode” was 13 minutes for the image forming apparatus A and 10 minutes for the image forming apparatus B out of 120 minutes.

(Collection method)
Collection agent: TENAX-TA
Thermal desorption equipment (ATD: Perkin Elmer Turbo Matrix)
OVEN TEMP: 280 ° C (15 minutes)
TRAP TEMP: -10 ° C → 330 ° C (25.5 minutes)

(Gas chromatography mass spectrometer)
(GL: Shimadzu Corporation GC-17A, MS: Shimadzu Corporation QP-5050A)
Separation column: DB-5 (30 mm × 0.32 mm)
Method: 40 ° C (4 minutes) → 10 ° C / minute → 300 ° C (5 minutes)

(Measurement substance)
TVOC: n-hexane to n-hexadecane
: Calculate the total value of all values quantified at 2 μg / m ³ or more in terms of toluene.
Determination of benzene and styrene

(Measurement of ozone concentration)
The measurement method of ozone is as follows. Using a UV photometric continuous automatic ozone concentration meter (Nippon Thermo Electron: MODEL49C), the air discharged from the discharge port of the chamber was sucked with a Teflon tube, and the ozone concentration was continuously monitored. The measurement ranges were 0 to 100 ppb and 0 to 500 ppb, and data was recorded every 15 seconds. The results are shown in Table 1.

(Ozone concentration meter)
Nippon Thermo Electron UV Light O ₃ Automatic Analyzer “MODEL49C”
Detection limit: 1.0 ppb
Response time: 20 seconds Sample flow rate: 1-3 L / min
Range: 0-0.05 to 200 ppm (0-0.1 to 400 mg / m ³ )

  As is apparent from Table 1, with respect to TVOC, both the image forming apparatus A and the image forming apparatus B did not differ greatly depending on the presence or absence of the unit in the “standby mode”, but “image forming mode + back-running mode”. Then, the amount of emissions was much lower than those without units. In addition, ozone emissions were significantly lower than those with no unit.

1 is a vertical sectional view showing an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a partially cutaway perspective view of a unit mounted on the image forming apparatus of FIG. 1. It is a vertical sectional view showing another embodiment of the image forming apparatus according to the present invention. It is a perspective view which shows the part of the duct and unit of FIG. It is a schematic block diagram of a measuring apparatus.

Explanation of symbols

1,1 'unit 4 duct 11 case 12 intake fan 13 fluorescent lamp (light source)
14 Photocatalyst sheet (photocatalyst holding member)
14a base material 14b photocatalyst layer 15 exhaust port 41, 42 duct 43a, 43b opening

Claims (4)

  A photocatalyst holding member provided with a photocatalyst, a light source that irradiates the photocatalyst holding member with light including a wavelength in the ultraviolet region, and an exhaust purification unit having an intake fan and / or an exhaust fan are provided in the apparatus by the exhaust purification unit. An image forming apparatus that decomposes generated ozone and volatile organic components.   The image forming apparatus according to claim 1, further comprising a duct that guides air containing ozone and / or volatile organic components from a location where ozone and / or volatile organic components are generated to the exhaust purification unit.   The image forming apparatus according to claim 1, wherein the photocatalyst holding member has a photocatalyst layer formed on a surface of a substrate.   The image forming apparatus according to claim 1, wherein the photocatalyst holding member is a filter having a photocatalyst supported on a fiber.

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