JP2012022015A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of smoothly exhausting ozone and discharge products in an electrifying device and preventing the ozone and discharge products from flowing back in the electrifying device, thereby preventing the generation of an output image such as a void.SOLUTION: In the image forming apparatus including an exhaust system 31 for discharging the ozone and discharge products generated in the electrifying device to the outside of the image forming apparatus, a path 32 is provided in the exhaust system 31, an exhaust fan 301 is disposed in the path 32, and further, an opening and closing shutter 305 which can be opened and closed in conjunction with the operation state of the exhaust fan 301 is disposed between the electrifying device and the exhaust fan 301.

Description

  The present invention relates to an image forming apparatus provided with an exhaust device that discharges ozone and discharge products generated in a charging device to the outside of the image forming apparatus.

  In an electrophotographic image forming apparatus such as a copying machine or a printer, a charging device applies a charge to the surface of a photoreceptor on which a photosensitive layer containing a photoconductive material is formed to uniformly charge the surface. Thereafter, an electrostatic latent image corresponding to the image data is formed, and the electrostatic latent image is developed into a visible image by a developer containing toner supplied from the developing device. After transfer to the recording material, the recording material is fixed by heating and pressurizing with a fixing roller, and an output image is formed on the recording material.

  As the charging device, a roller charging device, a brush charging device, or the like may be used. However, since the charging device is in direct contact with the photoconductor or the intermediate transfer belt, the photoconductor or the intermediate transfer belt is worn out. For this reason, a corona charging device such as a scorotron charger system is employed in an image forming apparatus having a relatively high printing speed.

The corona charging device is suitable for an image forming apparatus having a relatively high printing speed, but has a drawback that discharge products such as ozone (O ₃ ) and nitrogen oxide (NO _x ) are generated. Specifically, nitrogen molecules (N ₂ ) present in the atmosphere are dissociated into nitrogen atoms (N) due to the energy associated with the discharge of electrons emitted from the corona charging device, which are oxygen molecules (O ₂ ). Nitrogen oxide (nitrogen dioxide: NO ₂ ) is generated by combining with N. On the other hand, oxygen molecules (O ₂ ) are also dissociated into oxygen atoms (O), which are combined with oxygen molecules (O ₂ ) to generate ozone (O ₃ ).

  When the ozone generated in this manner is accumulated in the image forming apparatus, the photoconductor deteriorates due to the strong oxidizing power of ozone, and white spots or the like are generated in the output image. In the case of nitrogen oxides, the accumulated nitrogen oxides adhere to the surface of the photoconductor, and the charge on the photoconductor is diffused, resulting in white spots in the output image.

  In order to solve such problems, the image forming apparatus is usually provided with an exhaust device that forcibly releases ozone and discharge products together with air to the outside of the image forming apparatus.

  For example, in Japanese Patent Application Laid-Open No. 62-283357 (Patent Document 1), as shown in FIG. 13, an opening / closing shutter 18 is provided in the discharge port 17 provided in the charger 4 arranged above the photosensitive drum 3. It has also been proposed to close the open / close shutter 18 during image formation and open the open / close shutter 18 after completion of the image formation process to prevent the ozone and discharge products from staying in the charger 4.

JP-A-62-283357

  However, the occurrence of white spots in the output image is not only due to the effects of ozone and discharge product stagnation in the charging device, but also the exhaust fan disposed to release them outside the image forming apparatus stops. After that, it was found that there is an influence that these flow backward from the passage of the exhaust device toward the charging device.

  In the exhaust device disclosed in Patent Document 1, an exhaust fan is simply disposed on the exterior of the main body of the image forming apparatus even when trying to prevent an output image such as white spots from being generated. The air that circulates inside the main body can only be discharged to the outside of the main body, and in order to positively discharge the ozone and discharge products in the charging device, the exhaust fan continues to operate for a long time even after printing is finished. There was a need. Alternatively, even if an exhaust device having a high exhaust capability is used, it is necessary to continue operating the exhaust fan until ozone and discharge products in the charging device are completely discharged. In this case, a large amount of electric power may be consumed, but it is indispensable to prevent the ozone and discharge products in the charging device from flowing backward from the exhaust device toward the charging device.

  The present application has been made in view of the above problems, and prevents output images such as white spots from being generated by preventing backflow of ozone and discharge products into the charging device. An object of the present invention is to provide an image forming apparatus that does not spend much time.

  The present invention is an image forming apparatus including a photoconductor and a charging device that uniformly charges the surface of the photoconductor, and releases ozone and discharge products generated by the charging device to the outside of the image forming device. In the image forming apparatus including the exhaust device, the exhaust device includes a passage, an exhaust fan is disposed in the passage, and an open / close shutter is disposed between the charging device and the exhaust fan. It is characterized by being.

  In the present invention, it is preferable that the opening / closing shutter is opened / closed in conjunction with an operating state of the exhaust fan. In the present invention, it is preferable that an air flow rate detection member for detecting the amount of airflow generated in the passage is disposed in the passage, and the opening / closing shutter opens and closes according to the amount of airflow.

  In the present invention, it is preferable that an airflow direction detection member for detecting a direction of an airflow generated in the passage is disposed in the passage, and the opening / closing shutter is opened / closed according to the direction of the airflow.

  Further, the present invention is characterized in that the open / close shutter has a backflow prevention mechanism for preventing the ozone and the discharge product from flowing back to the charging device.

  Furthermore, in the present invention, it is preferable that the backflow prevention mechanism is a check valve.

According to the present invention, an exhaust device that discharges ozone and discharge products generated in the charging device to the outside of the image forming apparatus includes a passage, and an exhaust fan is disposed in the passage, and further, a passage that leads to the charging device side. Since the opening / closing shutter is disposed between the charging device side and the exhaust fan, the opening / closing shutter can be opened / closed in conjunction with the operating state of the exhaust fan.

  Further, according to the present invention, since the air flow rate detection member is also disposed in the passage, the opening / closing shutter can be closed when the amount of airflow is small, and the opening / closing shutter can be opened when the amount of airflow is large.

  Further, according to the present invention, since the airflow direction detecting member is also disposed in the passage, the opening / closing shutter is closed when the airflow direction is from the image forming apparatus side to the charging apparatus side, and the airflow direction is from the charging apparatus side. The open / close shutter can be opened when the image forming apparatus is on the side.

  In addition, according to the present invention, the open / close shutter can be appropriately opened / closed not only according to the operating status of the exhaust fan but also according to the amount and direction of the airflow. Power is not consumed.

  Further, according to the present invention, the open / close shutter has a backflow prevention mechanism that prevents backflow of ozone and discharge products to the charging device, so that the ozone and discharge products in the charging device can be smoothly exhausted, These can be prevented from flowing back into the charging device with high accuracy, and output images such as white spots are not generated.

  Furthermore, according to the present invention, since the backflow prevention mechanism is a simple check valve, ozone and discharge products can be prevented from backflowing into the charging device without requiring complicated control and sensors. .

1 is a schematic cross-sectional view illustrating a configuration of an image forming apparatus including an exhaust device according to an embodiment of the present invention. FIG. 2 is a schematic top view illustrating a configuration of a photoreceptor, a charging unit, and their periphery according to an embodiment of the present invention. It is the schematic which shows a mode that the ozone and discharge product which were produced with the charging unit which is embodiment of this invention pass an exhaust duct, and are discharged | emitted. 1 is a schematic block diagram illustrating an electrical configuration of an image forming apparatus according to an embodiment of the present invention. It is the schematic which shows the structure of the exhaust apparatus used as the 1st Example of embodiment of this invention. (A) It is the schematic which shows the mode of the exhaust apparatus when the opening-and-closing shutter is closed. (B) It is the schematic which shows the mode of the exhaust apparatus when the opening-and-closing shutter is open. 6 is a timing chart showing control for operating the open / close shutter according to an image forming operation according to the first example of the embodiment of the present invention; It is the schematic which shows the structure of the exhaust apparatus used as the comparative example of embodiment of this invention. (A) It is the schematic which shows the mode of an exhaust apparatus when an exhaust fan is rotating. (B) It is the schematic which shows the mode of an exhaust apparatus when an exhaust fan has stopped. (C) It is the schematic front view which looked at the exhaust fan when the exhaust fan has stopped from the front. It is a graph which shows the result of having measured the ozone density | concentration in the charging unit after the printing used as the 1st Example of embodiment of this invention. It is a graph which shows the result of having measured the ozone concentration in the charging unit used as the comparative example of embodiment of this invention. (A) It is a graph which shows the result of having measured the ozone concentration in the charging unit during printing and after printing. (B) It is a graph which shows the result of having measured the ozone concentration in the charging unit after printing. It is the schematic which shows the structure of the exhaust apparatus used as the 2nd Example of embodiment of this invention. (A) It is the schematic which shows the mode of the exhaust apparatus when the opening-and-closing shutter is closed. (B) It is the schematic which shows the mode of the exhaust apparatus when the opening-and-closing shutter is open. 10 is a timing chart showing control related to the operation of the open / close shutter 305 controlled in accordance with the detection of the airflow sensor 306 in the course of the image forming operation according to the second example of the embodiment of the present invention; It is the schematic which shows the structure of the exhaust apparatus used as the 3rd Example of embodiment of this invention. (A) It is the schematic which shows the mode of the exhaust apparatus when a non-return valve is closed. (B) It is the schematic which shows the mode of the exhaust apparatus when the non-return valve is open. It is the schematic which shows the charging device used as the prior art example of embodiment of this invention, and a periphery structure.

  FIG. 1 is an example of a schematic cross-sectional view illustrating a configuration of an image forming apparatus 100 including an exhaust device 31 according to an embodiment of the present invention.

  Here, as the image forming apparatus 100, a laser printer that forms a multicolor or single color output image on a recording material such as paper based on image data input from the outside or image data obtained by reading a document is taken as an example. Explained.

  As shown in FIG. 1, the image forming apparatus 100 includes an exposure unit E, four sets of image forming units pa, pb, pc, pd, an intermediate transfer belt 11, a secondary transfer unit 14, a fixing unit 15, and an internal paper feeding unit. 16, a manual paper feed unit 170, a paper discharge unit 180, and a housing 20 for housing these members.

  The image forming apparatus 100 applies black (K) and four hues of cyan (C), magenta (M), and yellow (Y), which are three subtractive primary colors obtained by color separation of a color image. Image formation is performed in the image forming units pa, pb, pc, and pd using the corresponding image data. The image forming portions pa, pb, pc, pd are arranged in a line in the moving direction of the intermediate transfer belt 11.

  The image forming portion pa includes a photoreceptor 101a, a charging unit 103a, a developing unit 102a, a cleaning unit 104a, and a primary transfer unit 13a. The photosensitive member 101a is an electrostatic latent image carrier, and a charging unit 103a, a developing unit 102a, and a cleaning unit 104a are disposed around the photosensitive member 101a. The primary transfer unit 13a is disposed in pressure contact with the photoreceptor 101a via the intermediate transfer belt 11. The other three sets of image forming units pb, pc, and pd have the same configuration as the image forming unit pa, and each set of developing units 102a, 102b, 102c, and 102d includes toners for each color of black, cyan, magenta, and yellow. Is housed.

  The photoconductors 101a, 101b, 101c, and 101d have a cylindrical shape and rotate when a driving force is transmitted from a driving source (not shown). Each of the photoconductors 101a, 101b, 101c, and 101d includes a cylindrical conductive substrate and a photosensitive layer provided on the surface of the conductive substrate.

  The charging units 103a, 103b, 103c, and 103d are disposed along the axial direction of the photosensitive members 101a, 101b, 101c, and 101d so as to face the surfaces of the photosensitive members 101a, 101b, 101c, and 101d. The charging units 103a, 103b, 103c, and 103d are non-contact charging devices, and uniformly charge the surfaces of the photoreceptors 101a, 101b, 101c, and 101d to a predetermined potential.

  The exposure unit E includes a semiconductor laser (not shown), a polygon mirror 6, a first fθ lens 7, a second fθ lens 8, and the like, and each laser beam modulated by image data of each hue of black, cyan, magenta, and yellow. Is irradiated on each of the surfaces of the photoconductors 101a, 101b, 101c, and 101d. On each of the photoreceptors 101a, 101b, 101c, and 101d, an electrostatic latent image is formed by image data of each hue of black, cyan, magenta, and yellow.

  The developing unit 102a contains a black developer. The developer includes a toner and an external additive. The external additive improves the fluidity of the toner. The developing unit 102a supplies black developer to the surface of the photoreceptor 101a on which the electrostatic latent image is formed, and visualizes the electrostatic latent image into a toner image.

  As the toner, a toner generally used in an electrophotographic image forming apparatus is used. That is, the toner contains a binder resin, a colorant, a charge control agent, a release agent, and the like. A fluidity improver is used as the external additive. Specifically, silica, titanium oxide, silicon carbide, aluminum oxide, or the like is used as the fluidity improver. The fluidity improver may have a surface hydrophobized with, for example, a polyorganosiloxane having a trimethylsilyl group. The hydrophobizing treatment is preferably performed on silica, for example. As the fluidity improver, one kind of substance may be used alone, or two or more kinds of substances may be used in combination. The amount of the external additive used for the toner is not particularly limited, but is preferably 0.1 to 3.0 parts by weight with respect to 100 parts by weight of the toner.

  The intermediate transfer belt 11 is stretched between the driving roller 11a and the driven roller 11b to form a loop-shaped moving path. The outer peripheral surface of the intermediate transfer belt 11 faces the photoconductor 101d, the photoconductor 101c, the photoconductor 101b, and the photoconductor 101a in this order. Primary transfer units 13a, 13b, 13c, and 13d are disposed at positions facing the respective photoreceptors 101a, 101b, 101c, and 101d with the intermediate transfer belt 11 interposed therebetween. The respective positions at which the intermediate transfer belt 11 faces the photoconductors 101a, 101b, 101c, and 101d are the primary transfer positions.

  In the primary transfer units 13a, 13b, 13c, and 13d, in order to transfer the toner images carried on the surfaces of the photoconductors 101a, 101b, 101c, and 101d onto the intermediate transfer belt 11, a polarity opposite to that of the toner is charged. A primary transfer bias is applied by constant voltage control. As a result, the toner images of the respective colors formed on the photoconductors 101a, 101b, 101c, and 101d are sequentially transferred onto the outer peripheral surface of the intermediate transfer belt 11, and a full-color toner image is formed on the outer peripheral surface of the intermediate transfer belt 11. Is done. The toner remaining on the surfaces of the photoconductors 101a, 101b, 101c, and 101d after being transferred is collected by the cleaning units 104a, 104b, 104c, and 104d, respectively.

  However, when image data is input to only a part of the hues of yellow, magenta, cyan, and black, it corresponds to the hue of the input image data among the four photoconductors 101a, 101b, 101c, and 101d. The electrostatic latent image and the toner image are formed only on a part of the image. That is, at the time of monochrome image formation, the electrostatic latent image and the toner image are formed only on the photoreceptor 101a corresponding to the black hue, and only the black toner image is transferred to the outer peripheral surface of the intermediate transfer belt 11. Is done.

  Each primary transfer unit 13a, 13b, 13c, 13d has a conductive surface such as conductive ethylene / propylene / diene copolymer rubber or conductive foamed urethane on the surface of a shaft made of a metal such as stainless steel having a diameter of 8 to 10 mm. The elastic material is applied so that a high voltage is uniformly applied to the intermediate transfer belt 11 by the elastic material. At each primary transfer position, the toner image transferred to the outer peripheral surface of the intermediate transfer belt 11 is conveyed to a secondary transfer position that is a position facing the secondary transfer unit 14 by the rotation of the intermediate transfer belt 11. The secondary transfer unit 14 is in pressure contact with the outer peripheral surface of the intermediate transfer belt 11 whose inner peripheral surface is in contact with the peripheral surface of the drive roller 11a during image formation at a predetermined nip pressure.

  When a recording material such as paper fed from the internal paper feed unit 16 or the manual paper feed unit 170 passes between the secondary transfer unit 14 and the intermediate transfer belt 11, the secondary transfer unit 14 receives toner. A high voltage having a polarity opposite to the charging polarity is applied. As a result, the toner image is transferred from the outer peripheral surface of the intermediate transfer belt 11 to the paper surface.

  Of the toner adhering to the intermediate transfer belt 11 from a part or all of the photoconductors 101a, 101b, 101c, and 101d, the toner remaining on the intermediate transfer belt 11 without being transferred onto paper is mixed in the next step. In order to prevent it, it is collected by the waste toner unit 12.

  The fixing unit 15 includes a fixing roller 15a and a pressure roller 15b. The paper on which the toner image is transferred is guided to the fixing unit 15 and is heated and pressed by passing between the fixing roller 15a and the pressure roller 15b. As a result, the toner image is firmly fixed on the paper surface. The paper on which the toner image is fixed is discharged onto the paper discharge unit 180 by the paper discharge roller 180a.

  In the image forming apparatus 100, a substantially vertical direction for feeding the paper stored in the internal paper feeding unit 16 to the paper discharge unit 180 between the secondary transfer unit 14 and the intermediate transfer belt 11 and via the fixing unit 15. Paper transport path P1 is provided.

  In the paper transport path P1, the pickup roller 16a that feeds the paper in the internal paper feeding unit 16 one by one into the paper transport path P1, and the rotation speed that transports the fed paper along the paper transport path P1 are changed. A free conveying roller R6 is arranged. Further, in the paper transport path P1, a registration roller 19 that guides the transported paper between the secondary transfer unit 14 and the intermediate transfer belt 11 at a predetermined timing, and a paper discharge roller that discharges the paper to the paper discharge unit 180. 180a is arranged.

  In the image forming apparatus 100, a sheet conveyance path P <b> 2 is formed between the manual sheet feeding unit 170 and the registration roller 19. In the paper transport path P2, as in the configuration of the paper transport path P1, a pickup roller 170a that feeds the papers placed on the manual paper feed unit 170 one by one into the paper transport path P2, and transport rollers R1, R2 , R3 are arranged.

  Further, a sheet conveyance path P3 is formed between the paper discharge roller 180a and the upstream side of the registration roller 19 in the sheet conveyance path P1. The paper discharge roller 180a is rotatable in both forward and reverse directions. When forming a single-sided image for forming an output image on one side of the paper and for forming a second-side image in forming a double-sided image for forming an output image on both sides of the paper, Driven in the forward direction, the paper is discharged to the paper discharge unit 180.

  On the other hand, when the first side image is formed in the double-sided image formation, the paper discharge roller 180a is driven in the normal rotation direction until the rear end of the paper passes through the fixing unit 15, and then the rear end of the paper is sandwiched. Is driven in the reverse direction to guide the paper into the paper transport path P3. Conveying rollers R4 and R5 are arranged in the sheet conveying path P3. As a result, the paper on which the output image is formed on only one side at the time of double-sided image formation is guided to the paper transport path P1 with the front and back sides and the front and rear ends reversed.

  The registration roller 19 synchronizes the sheet fed from the internal sheet feeding unit 16 or the manual sheet feeding unit 170 or the sheet conveyed via the sheet conveying path P3 with a timing synchronized with the rotation of the intermediate transfer belt 11. Then, it is guided between the secondary transfer unit 14 and the intermediate transfer belt 11. Therefore, the registration roller 19 stops rotating when the operation of the photosensitive member 101a and the intermediate transfer belt 11 is started, and the paper fed or conveyed prior to the rotation of the intermediate transfer belt 11 has its front end at the registration roller 19 The movement in the sheet conveyance path P1 is stopped in a state where the sheet 19 is in contact with the sheet 19. Thereafter, the registration roller 19 rotates at the position where the secondary transfer unit 14 and the intermediate transfer belt 11 are in pressure contact with each other at the timing when the front end of the paper and the front end of the toner image formed on the intermediate transfer belt 11 face each other. Start.

  At the time of full color image formation in which image formation is performed in all of the image forming portions pa, pb, pc, and pd, the primary transfer units 13a, 13b, 13c, and 13d are transferred to all the photosensitive members 101a, 101b, 101c, and 101d. The intermediate transfer belt 11 is brought into pressure contact. On the other hand, at the time of monochrome image formation in which image formation is performed only on the image forming portion pa, only the primary transfer unit 13a presses the intermediate transfer belt 11 against the photosensitive member 101a.

  In the image forming apparatus 100 according to the embodiment of the present invention, a scorotron charger type corona charging device is employed as the charging unit 103a. As a result, ozone and discharge products are generated around the four sets of image forming portions pa, pb, pc, and pd. Therefore, the exhaust device 31 that discharges the ozone and discharge products to the outside of the image forming apparatus 100, that is, in the direction of the arrows. It is provided in an opening provided on the side portion of the housing 20 of the forming apparatus 100.

  FIG. 2 is a schematic top view showing the configuration of the photoconductor 101a, the charging unit 103a, and the periphery thereof. As shown in FIG. 2, the charging unit 103a has a sawtooth-shaped charge generating portion Q for generating charges, and a mesh grid electrode (not shown) in the gap between the charge generating portion Q and the photosensitive member 101a. Yes. An air flow is generated in the direction of the arrow, and ozone and discharge products generated in the charge generation unit Q in the charging unit 103a are discharged. The direction of the arrow is connected to the exhaust duct 32 shown in FIG.

  FIG. 3 is a schematic view of the charging unit 103a and the other three sets of charging units as seen from the top surface of the image forming apparatus 100 shown in FIG. 1, and the ozone and discharge products generated by these charging units are shown. It is a figure which shows a mode that it discharges through the exhaust duct 32 which has a cylindrical shape, and is a figure which shows the periphery of the charging unit 103a shown in FIG.

  When the exhaust fan 301 is operated, an air flow is generated in the direction of the arrow in the charging unit 103a as shown in FIG. 2, and ozone and discharge products generated by corona discharge of the charging unit 103a are moved in the direction of the arrow shown in FIG. Then, it passes through the exhaust duct 32 and is discharged outside the image forming apparatus 100 shown in FIG.

  As illustrated in FIG. 4, the image forming apparatus 100 includes an apparatus control unit 21, a storage unit 22, and a calculation unit 23. The apparatus control unit 21 comprehensively controls the image forming operation in the image forming apparatus 100.

  In the storage unit 22, print commands input via an operation panel (not shown) having a display unit 24 and an input unit 25 arranged on the upper surface of the image forming apparatus 100, and illustrations arranged at various locations inside the image forming apparatus 100. Detection results from various sensors and the like, image data input from an external device via the USB (registered trademark) / LAN 26, various setting values and a data table for controlling the operation of each unit in the image forming apparatus 100, Programs for executing various controls can be stored. As the storage means 22, those commonly used in this field can be used, and examples thereof include a read only memory (ROM), a random access memory (RAM), and a hard disk drive (HDD). Examples of the external device include an electric / electronic device that can form or acquire image data and can be electrically connected to the image forming apparatus 100, such as a computer or a digital camera.

  The calculation unit 23 extracts various data such as a print command, detection result, image data, and the like stored in the storage unit 22 and a program for executing various controls, and performs various detections and / or determinations.

  The apparatus control unit 21 performs operation control by sending a control signal to each unit in the image forming apparatus 100 according to various determination results, calculation results, and the like in the calculation unit 23. The device control means 21 and the calculation means 23 are processing circuits realized by, for example, a microcomputer, a microprocessor or the like provided with a central processing unit (CPU) (not shown).

  Further, the image forming apparatus 100 is, for example, a multifunction machine including a scanner, a printer, and peripheral devices. The reading unit 27 that reads a document image, converts the read document image into an appropriate electrical signal, and generates image data. The image processing unit 28 visualizes the generated image data with toner and forms an output image on paper, and the periphery of the above-described image forming units pa, pb, pc, pd, finishers and sorters that are post-processing devices A peripheral device control unit 29 for controlling the device is provided.

  The exhaust device 31 includes the exhaust duct 32 shown in FIG. 3, an exhaust fan 301 as exhaust means disposed in the exhaust duct 32, a drive means 302 and an exhaust control means 303. The driving unit 302 is a motor that rotates the exhaust fan 301 and the opening / closing shutter 305, and the exhaust control unit 303 controls the rotation of these motors.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples.
Example 1
FIG. 5 is a schematic diagram showing the configuration of the exhaust device 31 according to the first example of the embodiment of the present invention. The exhaust device 31 includes an exhaust duct 32 having a cylindrical shape communicating the inside and the outside of the image forming apparatus 100 shown in FIG. 1, an exhaust fan 301 having a blade shape as exhaust means disposed in the exhaust duct 32, A driving unit 302, an exhaust control unit 303, and an ozone filter 304 shown in FIG. 4 are provided, and an open / close shutter 305 having a disk shape is provided between the inside of the image forming apparatus 100 and the exhaust fan 301. The driving unit 302 is a motor that rotates the exhaust fan 301 and the opening / closing shutter 305, and the exhaust control unit 303 controls the rotation of these motors.

  The ozone filter 304 is disposed in the passage of the exhaust duct 32 that forcibly releases the ozone generated in the image forming apparatus 100 together with the air, whereby the ozone is decomposed and the image forming apparatus 100 is decomposed. The concentration of ozone exhausted outside can be reduced.

  FIG. 5A is a schematic diagram showing the state of the exhaust device 31 when the open / close shutter 305 is closed, and FIG. 5B shows the state of the exhaust device 31 when the open / close shutter 305 is open. FIG. FIG. 5C is a schematic plan view of the exhaust fan 301 as viewed from the front.

  As shown in FIG. 5A, the open / close shutter 305 is a rotary type that rotates in the direction of the arrow. When the open / close shutter 305 is closed, the exhaust duct 32 is shown in FIG. 5A. Stop at a position that blocks the inside passage. As a result, the airflow in the direction of the arrow flowing from the inside of the image forming apparatus 100 to the outside can be prevented from passing, and at the same time, the airflow that flows backward in the exhaust duct 32 toward the inside of the image forming apparatus can be prevented.

  On the other hand, when the open / close shutter 305 is open, the open / close shutter 305 rotates 90 ° from the position closing the passage, and as shown in FIG. 5B, the air in the exhaust duct 32 can pass in the direction of the arrow. To stop.

  Further, as shown in FIG. 5C, by having a blade shape with almost no gap between the blades, if the exhaust fan 301 stops, the air in the image forming apparatus 100 can be exhausted to the outside until then. However, the exhaust fan 301 becomes a wall, and air collides with the exhaust fan 301 and flows back into the image forming apparatus 100.

  FIG. 6 is a timing chart showing control for operating the open / close shutter in accordance with the image forming operation according to the first example of the embodiment of the invention. In this embodiment, the image forming operation is started, and before the charging unit 103a shown in FIG. 1 uniformly charges the surface of the photoconductor 101a to a predetermined potential, first, the exhaust fan 301 is rotated simultaneously with the rotation. As shown in FIG. 5B, the open / close shutter 305 is opened so that ozone and discharge products generated from the inside of the image forming apparatus 100 shown in FIG. 1 can be released. Thereafter, the surface of the photoreceptor 101a is uniformly charged to a predetermined potential by the charging unit 103a.

  When this image forming operation, that is, the operation of uniformly charging the surface of the photosensitive member 101a to a predetermined potential by the charging unit 103a is finished, the exhaust fan 301 is stopped, but it rotates with inertia for a while.

  Thereafter, the exhaust fan 301 is completely stopped, that is, at the timing of the broken line shown in FIG. 6, the open / close shutter 305 is closed to prevent backflow of ozone and discharge products.

In this way, ozone and discharge products can be prevented from flowing back into the charging unit 103a, so that an output image such as white spots does not occur.
(Comparative example)
FIG. 7 is a schematic diagram showing a configuration of an exhaust device 31c as a comparative example of the embodiment of the present invention. The difference from the first embodiment is that there is no open / close shutter 305.

  FIG. 7A is a schematic diagram showing the state of the exhaust device 31c when the exhaust fan 301 rotates in the direction of the arrow, and FIG. 7B shows the exhaust when the exhaust fan 301 is stopped. 3 is a schematic view showing a state of the device 31. FIG. When the exhaust fan 301 is rotating, an air flow flowing in the direction of the arrow shown in FIG. 7A, that is, from the inside of the image forming apparatus 100 to the outside is generated, and the air in the image forming apparatus 100 is exhausted to the outside. . The driving unit 302 drives the exhaust fan 301.

  On the other hand, when the exhaust fan 301 is stopped, the airflow flowing in the direction of the arrow shown in FIG. 7B, that is, from the inside of the image forming apparatus 100 to the outside collides with the exhaust fan 301, so The air cannot be exhausted to the outside and flows back into the image forming apparatus 100.

  In the comparative example shown in FIG. 7, even if the air in the image forming apparatus 100 shown in FIG. 1 is exhausted to the outside, if the exhaust fan 301 is stopped, the air collides with the exhaust fan 301, and the image forming apparatus 100. Therefore, as long as the power of the image forming apparatus 100 is turned on, the exhaust fan 301 must be continuously operated even after the image forming operation is finished.

  On the other hand, in the case of the embodiment shown in FIG. 5, if the opening / closing shutter 305 is closed, the airflow flowing backward into the image forming apparatus 100 cannot pass through the opening / closing shutter 305, and the image forming operation is completed. The exhaust fan 301 can be stopped immediately. As a result, a great amount of power is not consumed.

  FIG. 8 is a graph showing the results of measuring the ozone concentration in the charging unit after printing when the exhaust device 31 of the present invention is used. The vertical axis represents ozone concentration, the horizontal axis represents time, and the vertical broken line in the graph represents the printing end point. The ozone concentration that has decreased after the end of printing does not increase again.

  On the other hand, FIG. 9 is a graph showing the result of measuring the ozone concentration in the charging unit after printing when the exhaust device 31c of the comparative example is used. FIG. 9A is a graph showing the results of measuring the ozone concentration in the charging unit 103a during printing and after printing. FIG. 9B shows the ozone concentration in the charging unit 103a after printing. It is an enlarged view of a result.

  When measuring the ozone concentration, a Teflon (registered trademark) tube having an outer diameter of 3 mm is installed in the center in the longitudinal direction of the charging unit 103a shown in FIG. Measured using a model number EG2001F).

  As shown in FIG. 9A, during the period of the arrow, that is, during printing, the amount of ozone generated by the charging unit 103a and the amount of ozone discharged by the rotation of the exhaust fan 301 are in an equilibrium state. The ozone concentration is stable at a constant concentration. As indicated by the vertical broken line, after the printing is completed, ozone is no longer generated from the charging unit 103a, and the ozone concentration in the charging unit 103a is rapidly decreased while the exhaust fan 301 is rotating. Thereafter, when the exhaust fan 301 stops, the ozone concentration increases again as shown in FIG. This is because, while the exhaust fan 301 is rotating, ozone that has been exhausted to the outside also flows back into the charging unit 103a because the exhaust fan 301 becomes a wall when the exhaust fan 301 stops and the ozone rebounds. .

In the present invention, the timing at which the exhaust fan 301 is completely stopped and the opening / closing shutter 305 is closed varies depending on the output of the exhaust fan 301, the immediately preceding operating rotational speed, the width of the passage in the exhaust duct 32, and the like. Judging from the time in which the ozone concentration in (b) flows backward, it is approximately 10 seconds after the exhaust fan 301 is completely stopped.
(Example 2)
FIG. 10 is a schematic diagram showing a configuration of an exhaust device 31a which is a second example of the embodiment of the present invention. The exhaust device 31a is different from the first embodiment in that an open / close shutter 305a having a door shape is used as an open / close shutter, and between the open / close shutter 305a and the exhaust fan 301 and on the inner wall of the exhaust duct 32. The difference is that there is an airflow sensor 306.

  FIG. 10A is a schematic diagram showing the state of the exhaust device 31a when the open / close shutter 305a is closed, and FIG. 10B shows the state of the exhaust device 31a when the open / close shutter 305a is open. FIG. The difference from FIG. 5 which is the first example of the embodiment of the present invention is that the opening / closing shutter 305a is not a rotary type but a door state, and further, between the opening / closing shutter 305a and the exhaust fan 301, That is, an airflow sensor 306 is provided.

  As shown in FIG. 10A, when the open / close shutter 305a is closed, the door closes in the direction of the broken line arrow, closes the passage in the exhaust duct 32, and flows from the inside of the image forming apparatus 100 to the outside. Do not allow airflow in the direction.

  On the other hand, as shown in FIG. 10B, when the open / close shutter 305a is open, the door is opened in the direction of the broken arrow, and the air in the exhaust duct 32 can pass in the direction of the arrow. The airflow sensor 306 may be either an airflow detection member that detects the amount of airflow or an airflow direction detection member that detects the direction of the airflow.

  FIG. 11 is a timing chart showing control related to the operation of the open / close shutter 305 controlled in accordance with the detection of the airflow sensor 306 in the image forming operation process according to the second example of the embodiment of the present invention.

  In this embodiment, the image forming operation is started, and before the charging unit 103a uniformly charges the surface of the photoconductor 101a to a predetermined potential, the exhaust fan 301 rotates to detect the amount of airflow. As soon as the airflow sensor 306 as a member detects the wind speed, the opening / closing shutter 305a is opened. This is because ozone and discharge products generated from the inside of the image forming apparatus 100 can be released.

  Thereafter, the surface of the photoreceptor 101a is uniformly charged to a predetermined potential by the charging unit 103a.

  When this image forming operation, that is, the operation of uniformly charging the surface of the photosensitive member 101a to a predetermined potential by the charging unit 103a is finished, the exhaust fan 301 is stopped, but it rotates with inertia for a while.

  Thereafter, the exhaust fan 301 is completely stopped, and the wind speed detected by the airflow sensor 306 becomes zero, but the opening / closing shutter 305a is closed immediately before that, that is, at the timing of the broken line shown in FIG. Prevent backflow.

  In this way, ozone and discharge products can be prevented from flowing back into the charging unit 103a, so that an output image such as white spots does not occur.

  In addition, as in the first embodiment, when the image forming operation is completed, the exhaust fan 301 can be stopped immediately, so that a large amount of power consumption is not consumed.

Further, in the case of the first embodiment shown in FIG. 5, even if the open / close shutter 305 is provided, it depends on the output of the exhaust fan 301, the immediately preceding operating rotational speed, the width of the passage in the exhaust duct 32, and the like. Although the timing of backflow into the image forming apparatus 100 could not be determined, an airflow sensor 306 serving as an airflow detecting member for detecting the amount of airflow or an airflow direction detecting member for detecting the direction of the airflow is also provided. Thus, since the amount or direction of the airflow can be detected immediately, it is possible to prevent the backflow into the image forming apparatus 100 with high accuracy.
(Example 3)
FIG. 12 is a schematic diagram showing a configuration of an exhaust device 31b according to a third example of the embodiment of the present invention. This embodiment differs from the first embodiment in that a check valve 307 as a backflow prevention mechanism having a spring 308 is used as an open / close shutter.

  FIG. 12A is a schematic view showing the state of the exhaust device 31b when the check valve 307 is closed, and FIG. 12B shows the state of the exhaust device 31 when the check valve 307 is open. FIG. A significant difference from the first embodiment shown in FIG. 5 is that a check valve 307 is disposed between the inside of the image forming apparatus 100 and the exhaust fan 301.

  As shown in FIG. 12A, the check valve 307 is pressed by the spring 308 in the direction of the arrow in the normal state, so that the airflow flows back from the outside to the inside of the image forming apparatus 100. It is not possible.

  On the other hand, as shown in FIG. 12B, if an air flow is generated from the inside of the image forming apparatus 100 to the outside, the spring pressure of the spring 308 is lost in the direction of the broken arrow, and the air flow is in the direction of the arrow. You can pass.

  In this way, by providing the check valve 307 as a backflow prevention mechanism, the ozone and discharge products in the charging unit 103a can be smoothly exhausted, and the backflow into the charging unit 103a can be accurately performed. Therefore, an output image such as white spots does not occur.

  Furthermore, since a simple check valve 307 is used as the backflow prevention mechanism, it is possible to prevent ozone and discharge products from flowing back into the charging unit 103a without requiring complicated control and airflow sensors.

  Note that the structure of the backflow prevention mechanism is not limited to this as long as airflow from the inside to the outside of the image forming apparatus 100 can pass through and can be prevented from flowing back from the outside to the inside.

E Exposure unit P1 Paper transport path (P2, P3)
Q Charge generator R1 Conveying roller (R2, R3, R4, R5, R6)
pa Image forming unit (pb, pc, pd)
6 Polygon mirror 7 First fθ lens 8 Second fθ lens 11 Intermediate transfer belt 11a Drive roller 11b Driven roller 12 Waste toner unit 13a Primary transfer unit (13b, 13c, 13d)
14 Secondary transfer unit 15 Fixing unit 15a Fixing roller 15b Pressure roller 16 Internal paper feeding unit 16a Pickup roller 19 Registration roller 20 Housing 21 Device control means 22 Storage means 23 Calculation means 24 Display part 25 Input part 27 Reading part 28 Image Processing unit 29 Peripheral device control unit 31 Exhaust device 32 Exhaust duct 100 Image forming apparatus 101a Photosensitive member (101b, 101c, 101d)
102a Development unit (102b, 102c, 102d)
103a Charging unit (103b, 103c, 103d)
104a Cleaning unit (104b, 104c, 104d)
170 Manual feed unit 170a Pickup roller 180 Paper discharge unit 180a Paper discharge roller 301 Exhaust fan 302 Drive means 303 Exhaust control means 304 Ozone filter 305 Open / close shutter 306 Airflow sensor 307 Check valve 308 Spring

Claims (6)

  An image forming apparatus comprising: a photoconductor; and a charging device that uniformly charges the surface of the photoconductor; and an exhaust device that discharges ozone and discharge products generated by the charging device to the outside of the image forming device. The exhaust device includes a passage, an exhaust fan is disposed in the passage, and an open / close shutter is disposed between the charging device and the exhaust fan. .   The image forming apparatus according to claim 1, wherein the opening / closing shutter opens and closes in conjunction with an operating state of the exhaust fan.   The image forming apparatus according to claim 2, wherein an air flow rate detection member that detects an amount of airflow generated in the passage is disposed in the passage, and the opening / closing shutter opens and closes according to the amount of airflow. apparatus.   The airflow direction detection member for detecting the direction of the airflow generated in the passage is disposed in the passage, and the opening / closing shutter opens and closes according to the direction of the airflow. Image forming apparatus.   The image forming apparatus according to claim 1, wherein the open / close shutter includes a backflow prevention mechanism that prevents the ozone and the discharge product from flowing back to the charging device. The image forming apparatus according to claim 5, wherein the backflow prevention mechanism is a check valve.