Patent Publication Number: US-11385560-B1

Title: Image forming apparatus having ozone removal

Description:
FIELD 
     Embodiments described herein relate generally to image forming apparatuses and methods of processing ozone. 
     BACKGROUND 
     In the related art, an electrophotographic image forming apparatus includes a charger that charges a photoconductor drum. Some chargers charge the photoconductor drums by a scorotron method or a corotron method. The scorotron type or corotron type charger generates ozone when charging the photoconductor drum. In an image forming apparatus in the related art, a gas containing the ozone generated in the charger is discharged to the outside through a filter that adsorbs the ozone. On the other hand, the ozone is known to have a sterilizing effect. The image forming apparatus in the related art has a problem that, since the ozone is removed with the filter, the ozone having the sterilizing effect is not effectively utilized. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating a configuration example of an image forming apparatus according to an embodiment; 
         FIG. 2  is a diagram illustrating a ventilation mechanism of a first configuration example; 
         FIG. 3  is a diagram illustrating a state where the ventilation mechanism closes a shutter; 
         FIG. 4  is a diagram illustrating a state where the ventilation mechanism opens the shutter; 
         FIG. 5  is a diagram illustrating a ventilation mechanism of a second configuration example; 
         FIG. 6  is a diagram illustrating a state where the ventilation mechanism closes a first gas-discharge port with a shutter; 
         FIG. 7  is a diagram illustrating a state where the ventilation mechanism closes a second gas-discharge port with the shutter; 
         FIG. 8  is a flowchart illustrating an operation example of an ozone discharge mode; 
         FIG. 9  is a diagram schematically illustrating a state where a photoconductor drum with which an intermediate transfer belt abuts rotates in a forward direction; and 
         FIG. 10  is a diagram schematically illustrating a state where a photoconductor drum from which an intermediate transfer belt is separated is allowed to rotate in a reverse direction. 
     
    
    
     DETAILED DESCRIPTION 
     In general, according to one embodiment, an image forming apparatus includes a photoconductor, a charger, a ventilation mechanism, an exposure device, a developing device, a transfer device, and a controller. The charger charges the photoconductor. The ventilation mechanism guides ozone generated in the charger to an ozone discharge port. The exposure device forms an electrostatic latent image on the photoconductor charged by the charger. The developing device supplies a developer for developing the electrostatic latent image on the photoconductor. The transfer device transfers a toner image on the photoconductor developed by the developer supplied from the developing device to a medium. In an operation mode in which the ozone is discharged, the controller allows the ventilation mechanism to discharge the ozone generated in the charger from the ozone discharge port after stopping supply of the developer from the developing device to the photoconductor. According to another embodiment, an method of processing ozone in an image forming apparatus involves charging a photoconductor thereby generating ozone; guiding ozone generated to an ozone discharge port through a ventilation mechanism; forming an electrostatic latent image on the photoconductor charged; supplying a developer comprising toner for developing the electrostatic latent image on the photoconductor; transferring a toner image from the photoconductor to a medium; and allowing the ventilation mechanism to discharge the ozone generated from the ozone discharge port after stopping supply of the developer to the photoconductor in an operation mode. 
     Hereinafter, an image forming apparatus of an embodiment will be described with reference to the drawings. 
       FIG. 1  is a diagram illustrating a configuration example of an image forming apparatus  1  according to the embodiment. 
     As illustrated in  FIG. 1 , the image forming apparatus  1  is an electrophotographic image forming apparatus. The image forming apparatus  1  includes a controller  10 , a paper feeding mechanism  11 , a conveying mechanism  12 , a registration roller  13 , an intermediate transfer belt (intermediate transfer body)  14 , an image forming station  15  ( 151  to  154 ), a primary transfer roller (transfer device)  16  ( 161  to  164 ), a secondary transfer roller  17 , a fixing device  18 , a ventilation mechanism  19 , a motion sensor  21 , an optical sensor  22 , a temperature humidity sensor  23 , and the like. 
     The controller  10  controls operations of each component in the image forming apparatus  1 . The controller  10  includes a processor, various memories, and various interfaces. The controller  10  executes various processes by allowing the processor to execute a program. 
     The paper feeding mechanism  11  supplies sheets. The paper feeding mechanism  11  has a cassette for storing a plurality of the sheets. The paper feeding mechanism  11  supplies the sheets stored in the cassette to the conveying mechanism  12  one by one. The conveying mechanism  12  conveys the sheet. The conveying mechanism  12  conveys the sheet supplied from the paper feeding mechanism  11  to a discharge port. 
     The registration roller  13  stops the sheet conveyed by the conveying mechanism  12 . The registration roller  13  is provided at a front position (secondary transfer position) of the image transferred to the sheet. The secondary transfer position is a position facing the secondary transfer roller  17  and a sheet conveyance path via the intermediate transfer belt  14 . The registration roller  13  supplies the paper to the secondary transfer position at a timing when the image on the intermediate transfer belt  14  moves to the secondary transfer position. 
     The intermediate transfer belt  14  is a medium to which toner images formed by image forming stations  151  to  154  are transferred. The intermediate transfer belt  14  is an endless belt supported by a plurality of rollers. The intermediate transfer belt  14  is provided at a position corresponding to an arrangement of photoconductor drums  31  of the image forming stations  151  to  154 . In the configuration example illustrated in  FIG. 1 , the photoconductor drums  31  of the image forming stations  151  to  154  are arranged side by side in a horizontal direction. The intermediate transfer belt  14  is arranged above each of the photoconductor drums  31  arranged in the horizontal direction. 
     The intermediate transfer belt  14  is stretched on a driving roller  141 , a driven roller  142 , a tension roller  143 , and a position switching roller  144 . The driving roller  141  and the tension roller  143  are provided at positions separated from each other in the horizontal direction. The driven roller  142  is provided below the driving roller  141 . The position switching roller  144  is provided below the tension roller  143 . 
     The driving roller  141  drives the intermediate transfer belt  14  in a direction of an arrow a. The driven roller  142  supports the intermediate transfer belt  14  at a predetermined position. The driven roller  142  is driven by the intermediate transfer belt  14  rotated by the driving roller  141 . The tension roller  143  applies tension to the intermediate transfer belt  14  by an elastic force of an elastic body such as a spring. The tension roller  143  presses the intermediate transfer belt  14  outward. 
     The position of the position switching roller  144  is displaced according to an operation mode. In a color printing mode, the position switching roller  144  moves to a position (first position) for color printing. In a monochrome printing mode of printing an image in a single color of black, the position switching roller  144  moves to a position (second position) for monochrome printing. In addition, in an ozone discharge mode, the position switching roller  144  moves to a position (second position) for ozone discharge. 
     While moving in the direction of the arrow a, the intermediate transfer belt  14  transfers the toner images formed by the image forming stations  151  to  154 . The intermediate transfer belt  14  retains the toner images transferred from the image forming stations  151  to  154 . The intermediate transfer belt  14  carries the toner images transferred from the image forming stations  151  to  154  to the secondary transfer position where the secondary transfer roller  17  and the sheet to be conveyed in the conveyance path face each other. 
     The image forming stations  151  to  154  include the photoconductor drum (photoconductor)  31 , a developing device  32 , an exposure device  33 , a charger  34 , and a cleaner  35 , respectively. The image forming stations  151  to  154  form an image with toner contained in the developing device  32 . Hereinafter, the image forming station  151  is assumed to form a yellow image with toner of yellow contained in the developing device  32 . The image forming station  152  is assumed to form an image of magenta with toner of magenta contained in the developing device  32 . The image forming station  153  is assumed to form an image of cyan with toner of cyan contained in the developing device  32 . The image forming station  154  is assumed to form an image of black with toner of black contained in the developing device  32 . 
     An image is formed on an outer circumference surface of the photoconductor drum  31 . The outer circumference surface of the photoconductor drum  31  is an image carrier. The outer circumference surface of the photoconductor drum  31  moves as the photoconductor drum rotates. The photoconductor drum  31  rotates in a forward direction or a reverse direction under the control of the controller  10 . The photoconductor drum  31  rotates in the forward direction when forming the image on the outer circumference surface (when executing an image printing operation). In the configuration example illustrated in  FIG. 1 , the forward direction is a direction of an arrow b illustrated in  FIG. 1 . By rotating the photoconductor drum  31  in the forward direction, the outer circumference surface of the photoconductor drum  31  moves along the moving direction (direction of the arrow a) of the intermediate transfer belt  14 . 
     The charger  34  charges the outer circumference surface of the photoconductor drum  31  so as to have a negative polarity. The charger  34  employs a charging method in which the ozone is generated using a wire or a needle such as a scorotron or a corotron. The on and off of the charger  34  are controlled by the controller  10 . In the ozone discharge mode, the charger  34  becomes an ozone generator that generates the ozone under the control of the controller  10 . 
     The ventilation mechanism  19  is a mechanism for discharging a gas containing the ozone generated in the charger  34  to an outside of a housing. The ventilation mechanism  19  illustrated in  FIG. 1  is a first configuration example. The ventilation mechanism  19  includes fans  41 , a duct  42 , ventilation paths  43  and  44 , a fan  45 , a first gas-discharge port (ozone discharge port)  46 , a shutter  47 , a second gas-discharge port (filter discharge port)  48 , a filter  49 , and the like. 
     The fans  41  are provided corresponding to the chargers  34  of the image forming stations  151  to  154 . Each of the fans  41  sends each gas containing the ozone generated in the chargers  34  of the corresponding image forming stations  151  to  154  to the duct  42 . The gas sent to the duct  42  is discharged from the first gas-discharge port  46  or the second gas-discharge port  48  to the outside of the housing of the image forming apparatus  1  through the ventilation path  43  or the ventilation path  44 . It is noted that the ventilation mechanism  19  will be described in detail later. 
     The exposure device  33  exposes the photoconductor drum  31  charged so as to have a negative polarity with a laser. The exposure device  33  exposes the outer circumference surfaces of the photoconductor drums  31  based on image information of the corresponding colors of the image forming stations  151  to  154 . An electrostatic latent image is formed on the outer circumference surface of the photoconductor drum  31  exposed with the laser from the exposure device  33 . The photoconductor drum  31  retains the electrostatic latent image formed by the exposure device  33 . The photoconductor drum  31  rotates in the forward direction to move the electrostatic latent image formed on the outer circumference surface by the exposure device  33  to the developing position which the developing device  32  faces. 
     The developing device  32  develops the electrostatic latent image on the outer circumference surface of the photoconductor drum  31  with toner. The photoconductor drum  31  retains the toner image visualized by the toner supplied from the developing device  32 . The developing device  32  contains a developer of the image formed by each of the image forming stations  151  to  154 . 
     For example, the image forming station  151  forms an image of yellow, which is one of a plurality of colors constituting a color image. The developing device  32  of the image forming station  151  contains toner of yellow and carriers as a developer. The image forming station  151  develops the electrostatic latent image of the photoconductor drum  31  with the toner of yellow contained in the developing device  32 . The image forming station  151  carries the toner image of yellow developed on the photoconductor drum  31  rotating in the forward direction to the primary transfer position where the photoconductor drum  31  and a primary transfer roller  161  face each other. The toner image of yellow on the photoconductor drum  31  of the image forming station  151  is transferred to the intermediate transfer belt  14  by the primary transfer roller  161  at the primary transfer position. 
     The image forming station  152  forms an image of magenta, which is one of the plurality of colors constituting the color image. The developing device  32  of the image forming station  152  contains the toner of magenta and carriers as a developer. The image forming station  152  develops the electrostatic latent image of the photoconductor drum  31  with the toner of magenta contained in the developing device  32 . The image forming station  152  carries the toner image of magenta developed on the photoconductor drum  31  rotating in the forward direction to the primary transfer position where the photoconductor drum  31  and a primary transfer roller  162  face each other. The toner image of magenta on the photoconductor drum  31  of the image forming station  152  is transferred to the intermediate transfer belt  14  by the primary transfer roller  162  at the primary transfer position. 
     The image forming station  153  forms an image of cyan, which is one of the plurality of colors constituting the color image. The developing device  32  of the image forming station  153  contains the toner of cyan and carriers as a developer. The image forming station  153  develops the electrostatic latent image of the photoconductor drum  31  with the toner of cyan contained in the developing device  32 . The image forming station  153  carries the toner image of cyan developed on the photoconductor drum  31  rotating in the forward direction to the primary transfer position where the photoconductor drum  31  and the primary transfer roller  163  face each other. The toner image of cyan on the photoconductor drum  31  of the image forming station  153  is transferred to the intermediate transfer belt  14  by the primary transfer roller  163  at the primary transfer position. 
     The image forming station  154  forms an image of black. The developing device  32  of the image forming station  154  contains the toner of black and carriers as a developer. The image forming station  154  develops the electrostatic latent image of the photoconductor drum  31  with the toner of black contained in the developing device  32 . The image forming station  154  carries the toner image of black developed on the photoconductor drum  31  rotating in the forward direction to the primary transfer position where the photoconductor drum  31  and the primary transfer roller  164  face each other. The toner image of black on the photoconductor drum  31  of the image forming station  154  is transferred to the intermediate transfer belt  14  by the primary transfer roller  162  at the primary transfer position. 
     The cleaner  35  cleans the toner remaining on the photoconductor drum  31  without being transferred to the intermediate transfer belt  14 . The cleaner  35  recovers the toner on the surface of the rotating photoconductor drum  31  with a cleaning blade. By rotating the photoconductor drum  31  in the forward direction, the outer circumference surface cleaned by the cleaner  35  moves to a charging position of the charger  34  again. 
     The primary transfer rollers  161  to  164  correspond to the image forming stations  151  to  154 , respectively. Each of the primary transfer rollers  161  to  164  transfers the toner images on the photoconductor drums  31  of the corresponding image forming stations  151  to  154  to the intermediate transfer belt  14 . 
     The primary transfer roller  161  faces the photoconductor drum  31  of the image forming station  151  with the intermediate transfer belt  14  interposed therebetween. The primary transfer roller  162  faces the photoconductor drum  31  of the image forming station  152  with the intermediate transfer belt  14  interposed therebetween. The primary transfer roller  163  faces the photoconductor drum  31  of the image forming station  153  with the intermediate transfer belt  14  interposed therebetween. The primary transfer roller  164  faces the photoconductor drum  31  of the image forming station  154  with the intermediate transfer belt  14  interposed therebetween. 
     When printing an image in color (in the color printing mode), the primary transfer rollers  161  to  164  overlappingly transfer the toner images formed by the image forming stations  151  to  154  to the intermediate transfer belt  14 . The primary transfer roller  161  transfers the toner image of yellow formed by the image forming station  151  to the intermediate transfer belt  14 . The primary transfer roller  162  overlappingly transfers the toner image of magenta formed by the image forming station  152  to the toner image of yellow on the intermediate transfer belt  14 . The primary transfer roller  163  overlappingly transfers the toner image of cyan formed by the image forming station  153  to the toner images of yellow and magenta on the intermediate transfer belt  14 . The primary transfer roller  164  overlappingly transfers the toner image of black formed by the image forming station  154  to the toner images of yellow, magenta, and cyan on the intermediate transfer belt  14 . 
     When printing an image in a single color of black (in the monochrome printing mode), the primary transfer roller  164  transfers the toner image formed by the image forming station  154  to the intermediate transfer belt  14 . 
     The image forming apparatus  1  includes a separation mechanism for separating the intermediate transfer belt  14  and the photoconductor drum  31  according to the operation mode. For example, in the monochrome printing mode, the controller  10  separates the intermediate transfer belt  14  from the photoconductor drums  31  of the image forming stations  151  to  153 . When executing ozone discharge (in the ozone discharge mode), the controller  10  separates the intermediate transfer belt  14  from the photoconductor drums  31  of the image forming stations  151  to  154 . 
     In the configuration example illustrated in  FIG. 1 , the image forming apparatus  1  includes a color separation mechanism  60  and a monochrome separation mechanism  70  as the separation mechanisms. The color separation mechanism  60  separates the intermediate transfer belt  14  from the photoconductor drums  31  of the image forming stations  151  to  153 . The monochrome separation mechanism  70  separates the intermediate transfer belt  14  from the photoconductor drum  31  of the image forming station  154 . 
     The color separation mechanism  60  includes an arm  61 , an arm  62 , an arm  63 , an operation arm  65 , and a slider  66 . 
     The arms  61 ,  62 , and  63  have an L-shape. For the arms  61 ,  62 , and  63 , one-side ends of the L-shapes are fixed to the primary transfer rollers  161 ,  162 , and  163 , and the other-side ends are fixed to the slider  66 . The arms  61 ,  62 , and  63  are fixed at respective predetermined positions with the L-shaped bent portions as axes. The arm  62  rotates about the axis of the bent portion. 
     One end of the operation arm  65  is engaged with the slider  66 , and the other end can be allowed to press the position switching roller  144 . The position switching roller  144  can switch between the first position and the second position. The position switching roller  144  is at the first position in a state of being pressed by the operation arm  65 . The position switching roller  144  at the first position is pushed by the operation arm  65  and presses the intermediate transfer belt  14  against each photoconductor drum  31 . The position switching roller  144  is at the second position in a state where the pressing from the operation arm  65  is released. The position switching roller  144  is displaced to the second position by the tension of the intermediate transfer belt  14  when the pressing from the operation arm  65  is released. 
     The slider  66  includes a moving mechanism that moves under the control of the controller  10 . The slider  66  moves to the left from the position illustrated in  FIG. 1  by the moving mechanism. In addition, the slider  66  can also move to the left and, after that, return to the position illustrated in  FIG. 1 . 
     The arms  61  to  63  and the operation arm  65  cooperate with the movement of the slider  66 . When the slider  66  moves to the left from the position illustrated in  FIG. 1 , the arms  61 ,  62 , and  63  rotate clockwise about the axis of the bent portion. If the arms  61 ,  62 , and  63  rotate clockwise, the primary transfer rollers  161 ,  162 , and  163  are displaced in a direction to be separated from the photoconductor drum  31 . 
     The operation arm  65  presses the position switching roller  144  in a state where the slider  66  is in the position illustrated in  FIG. 1 . The position switching roller  144  pushed by the operation arm  65  is at the first position for pressing the intermediate transfer belt  14 . 
     If the slider  66  moves to the left from the position illustrated in  FIG. 1 , the end portion of the operation arm  65  is disengaged from the position where the position switching roller  144  is pressed. If the end portion of the operation arm  65  is disengaged from the position switching roller  144 , the pressing from the operation arm  65  is released. If the pressing from the operation arm  65  is released, the position switching roller  144  is displaced in the direction approaching the slider  66  by the tension of the intermediate transfer belt  14 . That is, if the slider  66  moves to the left from the position illustrated in  FIG. 1 , the position switching roller  144  is displaced from the first position to the second position. 
     If the slider  66  moves to the left, the primary transfer rollers  161 ,  162 , and  163  are separated from the photoconductor drums  31 , and the position switching roller  144  is displaced to the second position. The intermediate transfer belt  14  is separated from the photoconductor drums  31  of the image forming stations  151  to  153  by the displacement of the primary transfer rollers  161 ,  162 , and  163  and the position switching roller  144 . The controller  10  executes the monochrome printing in a state where the intermediate transfer belt  14  is separated from the photoconductor drums  31  of the image forming stations  151  to  153 . 
     The monochrome separation mechanism  70  includes an arm  71 , an operation arm  72 , a position switching roller  73 , and a slider  74 . 
     The arm  71  has an L-shape. For the arm  71 , one-side end of the L-shape is fixed to the primary transfer roller  164 , and the other-side end is fixed to the slider  74 . The arm  71  is fixed at a predetermined position with the L-shaped bent portion as an axis. The arm  71  rotates about the axis of the bent portion. 
     One end of the operation arm  72  is engaged with the slider  74 , and the other end can be allowed to press the position switching roller  73 . The position switching roller  73  can switch between the first position and the second position. The position switching roller  73  is at the first position in a state of being pressed by the operation arm  72 . The position switching roller  73  at the first position is pushed by the operation arm  72  to press the intermediate transfer belt  14  against the photoconductor drum  31 . The position switching roller  73  allows the intermediate transfer belt  14  to abut with the photoconductor drum  31  of the image forming station  154  at the first position in which the position switching roller  73  is pressed by the operation arm  72 . For example, the position switching roller  73  allows the intermediate transfer belt  14  to abut with the photoconductor drum  31  for black even in a state where the photoconductor drum  31  for color and the intermediate transfer belt  14  are separated from each other. 
     The position switching roller  73  is at the second position in a state where the pressing from the operation arm  72  is released. The position switching roller  73  is displaced to the second position by the tension of the intermediate transfer belt  14  if the pressing from the operation arm  72  is released. The position switching roller  73  separates the intermediate transfer belt  14  and the photoconductor drum  31  of the image forming station  154  at the second position. 
     The slider  74  includes a moving mechanism that moves under the control of the controller  10 . The slider  74  moves to the left from the position illustrated in  FIG. 1  by the moving mechanism. In addition, the slider  74  can also move to the left and, after that, return to the position illustrated in  FIG. 1 . 
     The arm  71  and the operation arm  72  cooperate with the movement of the slider  74 . If the slider  74  moves to the left from the position illustrated in  FIG. 1 , the arm  71  rotates clockwise about the axis of the bent portion. The primary transfer roller  164  is displaced in a direction in which the arm  71  rotates clockwise to be separated from the photoconductor drum  31 . 
     If the slider  74  moves to the left from the position illustrated in  FIG. 1 , the end portion of the operation arm  72  that presses the position switching roller  73  is disengaged from the position switching roller  73 . The position switching roller  73  from which the operation arm  72  is disengaged is displaced in the direction approaching the slider  74  by the tension of the intermediate transfer belt  14 . If the slider  74  moves to the left from the position illustrated in  FIG. 1 , the position switching roller  73  is displaced from the first position to the second position. 
     If the slider  74  moves to the left, the primary transfer roller  164  and the position switching roller  73  are displaced in the direction to be separated from the photoconductor drum  31 . The intermediate transfer belt  14  is separated from the photoconductor drum  31  of the image forming station  154  by the displacement of the primary transfer rollers  164  and the position switching rollers  73  as the slider  74  moves to the left. The controller  10  executes the ozone discharge mode described later in a state where the intermediate transfer belt  14  and each photoconductor drum  31  are separated by the color separation mechanism  60  and the monochrome separation mechanism  70 . 
     It is noted that the controller  10  may discharge the ozone by separating the intermediate transfer belt  14  and the photoconductor drums  31  of the image forming stations  151  to  153  by the color separation mechanism  60 . For example, the controller  10  separates the intermediate transfer belt  14  from the photoconductor drums  31  of the image forming stations  151  to  153  by the color separation mechanism  60 . The controller  10  may allow the ozone generated by the chargers  34  of the image forming stations  151  to  153  in which the photoconductor drum  31  is separated from the intermediate transfer belt  14  to be discharged. 
     The secondary transfer roller  17  transfers the toner image formed on the intermediate transfer belt  14  to the sheet. The secondary transfer roller  17  faces the sheet supplied from the registration roller  13  with the intermediate transfer belt  14  interposed therebetween at the secondary transfer position. The registration roller  13  supplies the sheet to the secondary transfer position at the timing when the toner image on the intermediate transfer belt  14  moves to the secondary transfer position. The secondary transfer roller  17  transfers the toner image on the intermediate transfer belt  14  to the sheet at the secondary transfer position. 
     The fixing device  18  fixes the toner image transferred from the intermediate transfer belt  14  to the sheet by the secondary transfer roller to the sheet. The fixing device  18  heats and pressurizes the sheet to which the toner image is transferred. The toner on the sheet is fixed to the sheet by the heat and pressure applied to the sheet from the fixing device  18 . The fixing device  18  discharges the fixing-processed sheets from the discharge port. 
     The motion sensor  21  senses a person. The motion sensor  21  uses a periphery of the image forming apparatus  1  as a detection range. The motion sensor  21  may be any sensor that detects a person being present in the periphery of the image forming apparatus  1  and is not limited to a sensor of a specific detection method. The motion sensor  21  supplies a detection signal indicating the presence or absence of a person to the controller  10 . The controller  10  determines whether or not a person is present in the periphery of the image forming apparatus  1  based on the detection signal from the motion sensor  21 . 
     The optical sensor  22  detects brightness. The optical sensor  22  uses the periphery of the image forming apparatus  1  as a detection range. The optical sensor  22  detects the brightness and supplies a detection signal indicating the brightness to the controller  10 . The controller  10  specifies the brightness of the periphery of the image forming apparatus  1  based on the detection signal indicating the brightness detected by the optical sensor  22 . 
     The temperature humidity sensor  23  detects temperature and humidity. The temperature humidity sensor  23  detects the temperature and the humidity inside the housing of the image forming apparatus  1 . The temperature humidity sensor  23  supplies a detection signal indicating the temperature and the humidity to the controller  10 . The controller  10  specifies the temperature and the humidity in the housing of the image forming apparatus  1  based on the detection signal indicating the temperature and the humidity detected by the temperature humidity sensor  23 . 
     Next, the configuration of the ventilation mechanism for discharging the gas containing the ozone generated in the charger  34  to the outside of the housing in the image forming apparatus  1  according to the embodiment will be described. 
       FIG. 2  is a diagram illustrating the ventilation mechanism  19  of the first configuration example in the image forming apparatus  1  according to the embodiment. 
     It is noted that  FIG. 1  is a diagram schematically illustrating a configuration example in which the inside of the image forming apparatus  1  including the ventilation mechanism  19  of the first configuration example is viewed from the front side.  FIG. 2  is a diagram schematically illustrating the configuration example in which the inside of the image forming apparatus  1  having the configuration illustrated in  FIG. 1  is viewed from the side (back side) opposite to that of  FIG. 1 . 
     As illustrated in  FIGS. 1 and 2 , the ventilation mechanism  19  includes fans  41 , a duct  42 , a first ventilation path  43 , a second ventilation path  44 , a fan  45 , a first gas-discharge port  46 , a shutter  47 , and a second gas-discharge port  48 , and a filter  49 . 
     The fans  41  ( 411 ,  412 ,  413 , and  414 ) are provided corresponding to the chargers  34  of the image forming stations  151  to  154 , respectively. The fan  411  sends a gas containing the ozone generated in the charger  34  of the image forming station  151  to the duct  42 . The fan  412  sends a gas containing the ozone generated in the charger  34  of the image forming station  152  to the duct  42 . The fan  413  sends a gas containing the ozone generated in the charger  34  of the image forming station  153  to the duct  42 . The fan  414  sends a gas containing the ozone generated in the charger  34  of the image forming station  154  to the duct  42 . 
     The duct  42  takes the gases containing the ozone generated in the chargers  34  of the image forming stations  151  to  154  via the fans  411  to  414 . The duct  42  is branched into the first ventilation path  43  and the second ventilation path  44 . 
     The first ventilation path  43  includes a ventilation path extending upward from a branch portion with the second ventilation path  44 . The first gas-discharge port  46  is connected to the tip of the ventilation path extending upward from the first ventilation path  43 . The first gas-discharge port  46  is a discharge port for discharging the gas passing through the first ventilation path  43  to the outside of the housing of the image forming apparatus  1 . The first gas-discharge port  46  is an ozone discharge port that discharges the gas containing the ozone if the ozone is generated in the charger  34 . The ventilation mechanism  19  can widely diffuse the ozone, which has a heavier specific gravity than air, by discharging the gas containing the ozone generated by the charger  34  from the first gas-discharge port  46  provided above the image forming apparatus  1 . The ozone is known to have a virus sterilizing effect. By diffusing the ozone from the first gas-discharge port  46 , it is possible to sterilize the periphery of the image forming apparatus  1 . 
     The fan  45  is provided in front of the first gas-discharge port  46  from the first ventilation path  43 . The fan  45  sends the gas in the first ventilation path  43  to the first gas-discharge port  46 . The fan  45  may be arranged in the ventilation path  43  or may be installed in the first gas-discharge port  46 . The fan  45  can allow the gas containing the ozone taken from the charger  34  to be likely to be discharged from the first gas-discharge port  46  provided above. In addition, as the air volume of the fan  45  is increased, the ozone discharged from the first gas-discharge port  46  is likely to be diffused outside the housing of the image forming apparatus  1 . 
     The shutter  47  is provided to the first gas-discharge port  46 . The shutter  47  opens or closes the first gas-discharge port  46 . 
     If the shutter  47  is opened, the first gas-discharge port  46  can discharge the gas passing through the first ventilation path  43  to the outside of the housing of the image forming apparatus  1 . If the ozone discharge condition is satisfied, the controller  10  allows the gas containing the ozone to be discharged from the first gas-discharge port  46  by opening the shutter  47 . 
     If the shutter  47  is closed, the first gas-discharge port cannot discharge the gas passing through the first ventilation path  43  to the outside of the housing of the image forming apparatus  1 . If the shutter  47  is closed, the first gas-discharge port  46  is shut off, so that the gas taken from the charger  34  is discharged from the second gas-discharge port  48 . If the ozone discharge condition is not satisfied, the controller  10  allows the gas containing the ozone to be discharged from the second gas-discharge port  48  without discharging the gas containing the ozone from the first gas-discharge port  46  by closing the shutter  47 . 
     The shutter  47  also operates as a louver that changes the direction of the flow of the gas discharged from the first gas-discharge port  46 . 
       FIG. 3  illustrates a state where the shutter  47  in the ventilation mechanism  19  of the first configuration example is closed.  FIG. 4  illustrates a state where the shutter  47  in the ventilation mechanism  19  of the first configuration example is opened. 
     As illustrated in  FIG. 3 , if the shutter  47  is closed, the first gas-discharge port  46  does not discharge the gas in the first ventilation path  43 . If the shutter  47  is opened, the gas discharged from the first gas-discharge port  46  flows along the direction of the shutter  47 . As illustrated in  FIG. 4 , if the upper portion of the shutter  47  is opened in a state where the lower portion of the shutter  47  is aligned with the first gas-discharge port  46 , the gas discharged from the first gas-discharge port  46  is discharged upward. The shutter  47  allows the gas discharged from the first gas-discharge port  46  to be likely to be diffused outside the housing of the image forming apparatus  1  by discharging the gas discharged from the first gas-discharge port  46  upward. 
     It is noted that the shutter  47  may change the direction not only into the vertical direction but also into the horizontal direction. By changing the direction not only into the vertical direction but also into the horizontal direction, the shutter  46  can diffuse the flow of gas discharged from the first gas-discharge port  46  not only in the vertical direction but also in the horizontal direction. 
     The second ventilation path  44  includes a ventilation path extending downward from the branch portion with the first ventilation path  43 . The second gas-discharge port  48  is provided in a lower portion of the image forming apparatus  1 . The second gas-discharge port  48  is connected to the tip of the ventilation path extending downward from the second ventilation path  44 . The second gas-discharge port  48  is a discharge port for discharging the gas passing through the second ventilation path  44  to the outside of the housing of the image forming apparatus  1 . The filter  49  that adsorbs the ozone is provided to the second gas-discharge port  48 . The filter  49  removes the ozone from the gas sent from the second ventilation path  44  to the second gas-discharge port  48 . 
     The second gas-discharge port  48  is a filter discharge port that discharges the gas from which the ozone is removed by the filter  49  to the outside of the housing of the image forming apparatus  1 . As mentioned above, the ozone is known to have a virus sterilizing effect. However, even if the ozone discharged from the image forming apparatus  1  has a concentration that does not affect a human body, the odor or the like may be unpleasant to the human body. Unless the ozone discharge condition such as the absence of a person is satisfied, the controller  10  performs controlling so that the gas containing the ozone is discharged from the second gas-discharge port  48  through the filter  49 . 
     It is noted that a gate G may be provided to the branch portion between the first ventilation path  43  and the second ventilation path  44 . The gate G blocks the flow of gas from the duct  42  to the first ventilation path  43  or the flow of gas from the duct  42  to the second ventilation path  44 . For example, if the ozone is discharged from the first gas-discharge port  46 , the gate G blocks the movement of gas from the duct  42  to the second ventilation path  44 . If the ozone is not discharged, the gate G blocks the ventilation from the duct  42  to the first ventilation path  43 . 
     Next, a second configuration example of the ventilation mechanism in the image forming apparatus according to the embodiment will be described. 
       FIG. 5  is a diagram illustrating a ventilation mechanism  50  of the second configuration example in the image forming apparatus  1  according to the embodiment. 
       FIG. 5  is a diagram schematically illustrating a configuration example in which the inside of the image forming apparatus  1  including the ventilation mechanism  50  of the second configuration example is viewed from the back side. 
     As illustrated in  FIG. 5 , the ventilation mechanism  50  includes a fan  51 , a duct  52 , a ventilation path  53 , a first gas-discharge port (ozone discharge port)  56 , a shutter  57 , a second gas-discharge port (filter discharge port)  58 , and a filter  59 . 
     The fans  51  ( 511 ,  512 ,  513 , and  514 ) are provided corresponding to the chargers  34  of the image forming stations  151  to  154 , respectively. The fan  511  sends the gas containing the ozone generated in the charger  34  of the image forming station  151  to the duct  52 . The fan  512  sends the gas containing the ozone generated in the charger  34  of the image forming station  152  to the duct  52 . The fan  513  sends the gas containing the ozone generated in the charger  34  of the image forming station  153  to the duct  52 . The fan  514  sends the gas containing the ozone generated in the charger  34  of the image forming station  154  to the duct  52 . 
     The duct  52  takes the gas containing the ozone generated in the chargers  34  of the image forming stations  151  to  154  via the fans  511  to  514 . The duct  52  is connected to the ventilation path  53  extending upward. 
     The first gas-discharge port  56  and the second gas-discharge port  58  are connected to the tip of the ventilation path  53  extending upward from the connection portion with the duct  52 . The first gas-discharge port  56  and the second gas-discharge port  58  are discharge ports for discharging the gas passing through the ventilation path  53  to the outside of the housing of the image forming apparatus  1 . The first gas-discharge port  56  and the second gas-discharge port  58  are arranged side by side. 
     The filter  59  that adsorbs the ozone is provided to the second gas-discharge port  58 . The filter  59  removes the ozone from the gas discharged from the second gas-discharge port  58 . Since the first gas-discharge port  56  is not provided with a filter or the like, the gas containing the ozone flowing from the charger  34  through the ventilation path  53  is discharged. 
     The shutter  57  slides so as to shut off any one of the first gas-discharge port  56  and the second gas-discharge port  58 . 
       FIG. 6  illustrates a state where the shutter  57  closes the first gas-discharge port  56  in the ventilation mechanism  50  of the second configuration example.  FIG. 7  illustrates a state where the shutter  57  closes the second gas-discharge port  58  in the ventilation mechanism  50  of the second configuration example. 
     As illustrated in  FIG. 6 , if the shutter  57  closes the first gas-discharge port  56 , the second gas-discharge port  58  is opened. If the first gas-discharge port  56  is closed and the second gas-discharge port  58  is opened, the gas in the ventilation path  53  is discharged from the second gas-discharge port  58 . If the shutter  57  closes the first gas-discharge port  56 , the gas containing the ozone generated by the charger  34  is discharged from the second gas-discharge port  58  after the ozone is removed by the filter  59 . 
     As illustrated in  FIG. 7 , if the shutter  57  closes the second gas-discharge port  58 , the first gas-discharge port  56  is opened. If the first gas-discharge port  56  is opened and the second gas-discharge port  58  is closed, the gas in the ventilation path  53  is discharged from the first gas-discharge port  56 . If the shutter  57  closes the second gas-discharge port  58 , the gas containing the ozone generated in the charger  34  is discharged from the first gas-discharge port  56  without removing the ozone. 
     Next, the operations of the image forming apparatus  1  according to the embodiment will be described. 
       FIG. 8  is a flowchart illustrating an operation example of the ozone discharge mode in the image forming apparatus  1  according to the embodiment. It is noted that the ozone discharge mode illustrated in  FIG. 8  is an operation example of discharging the ozone in a state where the printing process (image formation) is not executed. 
     The controller  10  determines whether or not to execute the operation (ozone discharge mode) of discharging the ozone generated by the charger  34  to the outside of the housing (ACT 11 ). If the preset condition is satisfied, the controller  10  determines that the operation of discharging the ozone in the ozone discharge mode is executed. For example, the controller  10  may execute the operation of discharging the ozone in a preset time zone. In addition, the controller  10  may execute the operation of discharging the ozone according to a user&#39;s instruction. 
     If the ozone discharging is executed (YES in ACT 11 ), the controller  10  confirms that the person is absent (ACT 12 ). The controller  10  confirms that a person is absent in the periphery of the image forming apparatus  1  based on the detection result of the person by the motion sensor  21 . In addition, the controller  10  confirms that a person is absent because the brightness detected by the optical sensor  22  is lower than the threshold value. In addition, if the person is not detected by the motion sensor  21  and the brightness detected by the optical sensor  22  is lower than the threshold value, the controller  10  may determine that a person is absent. 
     If it is determined that a person is present (NO in ACT 12 ), the controller  10  does not perform the operation in the ozone discharge mode of discharging the ozone. 
     If it is confirmed that a person is absent (YES in ACT 12 ), the controller  10  determines that the operation of discharging the ozone generated in the charger  34  is executed. When executing the operation of discharging the ozone, the controller  10  performs pre-processes before discharging the ozone (ACT 13  to ACT 15 ). 
     As a pre-process of discharging the ozone, the controller  10  separates the intermediate transfer belt  14  from each photoconductor drum  31  by the separation mechanism (ACT 13 ). The controller  10  separates the intermediate transfer belt  14  from the photoconductor drums  31  of the image forming stations  151  to  154  by the color separation mechanism  60  and the monochrome separation mechanism  70 . By separating the intermediate transfer belt  14  and the photoconductor drum  31 , deterioration of the intermediate transfer belt  14  and the photoconductor drum  31  due to the operation of discharging the ozone can be reduced. 
     In addition, the controller  10  stops supplying the developer from the developing device  32  to the photoconductor drum  31  as a pre-process of discharging the ozone (ACT 14 ). The controller  10  stops the supply of the toner to the photoconductor drum  31  by rotating a developing roller that supplies the toner in the developing device  32  to the photoconductor drum  31  in the reverse direction. 
       FIG. 9  is a diagram schematically illustrating a state where the photoconductor drum  31  with which the intermediate transfer belt  14  abuts rotates in the forward direction.  FIG. 10  is a diagram schematically illustrating a state where the photoconductor drum  31  from which the intermediate transfer belt  14  is separated is allowed to rotate in the reverse direction. 
     As illustrated in  FIG. 9 , the developing device  32  includes a developing roller  321  and stirring rollers  322  and  323 . If the photoconductor drum  31  rotates in the forward direction, the developing device  32  supplies the toner stirred by the stirring roller  322  to the photoconductor drum  31  by the developing roller  321 . 
     If the charger  34  is turned on, the outer circumference surface of the photoconductor drum  31  is charged at a position facing the charger  34 . The charger  34  charges the photoconductor drum  31  and generates the ozone. Even in the ozone discharge mode in which the image formation is not performed, the controller  10  rotates the photoconductor drum  31  if the charger  34  is turned on. In a case where the developing device  32  does not move if the photoconductor drum  31  rotates in the forward direction, there is a possibility that the outer circumference surface of the photoconductor drum  31  may be scraped by the developer. In addition, if the developing device  32  is continuously moved without performing the image formation, the developing device  32  continues to circulate the toner that is not consumed. Therefore, if the ozone is discharged without performing the image formation, the controller  10  executes a control (supply stopping control for the developer) for stopping the supply of the developer from the developing device  32  to the photoconductor drum  31 . 
     As illustrated in  FIG. 10 , the controller  10  stops the supply of the toner from the developing device  32  to the photoconductor drum  31  by rotating the developing roller  321  in the reverse direction. The controller  10  can prevent the developer from being interposed between the photoconductor drum  31  and the developing device  32  by rotating the developing roller  321  in the reverse direction. 
     It is noted that the image forming apparatus may stop the supply of the toner to the photoconductor drum  31  by a control other than the reverse rotation of the developing roller  321  as a supply stopping control for the developer. For example, the image forming apparatus  1  may stop the supply of the toner to the photoconductor drum  31  by physically separating the developing device  32  and the photoconductor drum  31 . 
     If the supply of the toner to the photoconductor drum  31  is stopped, the controller  10  turns off the developing device (ACT 15 ). If the toner is not interposed between the photoconductor drum  31  and the developing device  32 , the outer circumference surface of the photoconductor drum  31  is not scraped by the toner, and thus, it is not necessary to operate the developing device  32 . If the developing device  32  is stopped, the developing device  32  can suppress deterioration without unnecessarily stirring the toner. 
     After turning off the developing device  32 , the controller  10  rotates the photoconductor drum  31  in the forward direction (ACT 16 ). If the photoconductor drum  31  rotates in the forward direction, the controller  10  turns on the charger  34  (ACT 17 ). The charger  34  generates the ozone by turning on the charging under the control of the controller  10 . 
     If the generation of the ozone is started, the controller  10  opens the first gas-discharge port  46  (or  56 ), which is an ozone discharge port (ACT 18 ). The controller  10  opens the first gas-discharge port  46  (or  56 ) by moving the shutter  47  (or  57 ). If the first gas-discharge port  46  (or  56 ) is opened, the image forming apparatus  1  is in a state where the gas containing the ozone generated by the charger  34  can be discharged to the outside of the housing. 
     If the first gas-discharge port  46  (or  56 ) is opened, the controller  10  drives (rotates) the fans  41  and  45  (or  51 ) (ACT 19 ). By driving the fans  41  and  45  (or  51 ), the gas containing the ozone generated in the charger  34  is sent from the charger  34  to the first gas-discharge port  46  (or  56 ). 
     In the case of the ventilation mechanism  19  of the first configuration example illustrated in  FIGS. 1 and 2 , the controller  10  opens the first gas-discharge port  46  by opening the shutter  47 . As illustrated in  FIG. 4 , the controller  10  diffuses the gas discharged from the first gas-discharge port  46  upward by opening the upper portion of the shutter  47 . In addition, the controller  10  may diffuse the gas discharged from the first gas-discharge port  46  over a wide range by periodically changing the direction of the shutter  47 . 
     If the first gas-discharge port  46  is opened, the controller  10  drives the fans  41  and  45  in the ventilation mechanism  19  of the first configuration example. The fans  41  take the gas containing the ozone generated by the charger  34  into the duct  42  by driving under the control of the controller  10 . The gas containing the ozone taken into the duct  42  is sent to the first gas-discharge port  46  through the ventilation path  43  by the fans  41  and the fan  45  and is discharged from the first gas-discharge port  46 . 
     In addition, in the case of the ventilation mechanism  50  of the second configuration example illustrated in  FIG. 5 , the controller  10  opens the first gas-discharge port  56  and closes the second gas-discharge port  58  by using the shutter  57 . For example, as illustrated in  FIG. 7 , the controller  10  moves the shutter  57  to a position where the second gas-discharge port  58  is closed by the shutter  57 . It is noted that the ventilation mechanism  50  may include a louver that controls the wind direction of the gas discharged from the first gas-discharge port  56 . The controller  10  may diffuse the gas discharged from the first gas-discharge port  56  over a wide range by controlling the direction of the louver. 
     If the first gas-discharge port  56  is opened, the controller  10  drives the fan  51 . The fan  51  takes the gas containing the ozone generated by the charger  34  into the duct  52  by driving under the control of the controller  10 . The gas containing the ozone taken into the duct  52  is discharged from the first gas-discharge port  56  through the ventilation path  53  by the fan  51 . It is noted that the ventilation mechanism  50  may be provided with a fan for sending the gas containing the ozone taken into the duct  52  to the first gas-discharge port  56  in the periphery of the ventilation path  53  or the first gas-discharge port  56 . 
     The controller  10  determines whether or not the ozone discharge mode is terminated while continuing to discharge the ozone by the operations of ACT 16  to ACT 19  (ACT 20 ). For example, if the time zone for discharging the ozone is set, the controller  10  terminates the ozone discharge mode if the time zone ends. 
     In addition, the controller  10  may terminate the ozone discharge mode based on the detection result detected by each sensor during the operation in the ozone discharge mode. For example, the controller  10  may continuously detect a person by the motion sensor  21  during the operation in the ozone discharge mode. The controller  10  terminates the ozone discharge mode if the motion sensor  21  detects a person. In addition, the controller  10  may continuously detect the brightness by the optical sensor  22  during the operation in the ozone discharge mode. The controller  10  terminates the ozone discharge mode if the brightness detected by the optical sensor  22  becomes higher than a predetermined threshold value. 
     If the ozone discharge mode is continued (NO in ACT 20 ), the controller  10  determines whether or not the supply of the developer to the photoconductor drum  31  is needed (ACT 21 ). During the execution in the ozone discharge mode, the controller  10  periodically executes the operation of cleaning the toner supplied to the photoconductor drum  31  with the cleaner  35 . If it is determined that the supply of the toner is not needed (NO in ACT 21 ), the controller  10  returns to ACT 20  and continues the operation of discharging the ozone until it is determined that the ozone discharge mode is terminated. 
     The image forming stations  151  to  154  include the cleaner  35  for removing the toner adhering (remaining) to the outer circumference surface of the photoconductor drum  31 . If the cleaner  35  continues to clean the outer circumference surface of the photoconductor drum  31  to which the toner does not adhere for a long time, there is a possibility that deterioration may progress. That is, the deterioration can be suppressed by periodically performing an operation in which the cleaner  35  actually removes the toner adhering to the photoconductor drum  31 . 
     If a predetermined toner supply condition is satisfied during the execution of the ozone discharge mode, the controller  10  supplies the toner to the photoconductor drum  31 . The cleaner  35  removes the toner adhering to the photoconductor drum  31 . The toner supply condition is stored in the memory in the controller  10 . For example, the toner supply condition is an interval at which the cleaner  35  cleans the toner supplied to the photoconductor drum  31  during the execution of the ozone discharge mode. 
     The toner supply condition may be set according to the environment such as temperature and humidity. As a toner supply condition, as the temperature and humidity become higher, the time interval for supplying the toner to the photoconductor drum  31  is set to be shorter. That is, as the temperature and humidity become higher, the actual toner cleaning is performed more frequently, so that deterioration can be suppressed in a high temperature and high humidity environment. 
     If it is determined that the supply of the toner to the photoconductor drum  31  is needed (YES in ACT 21 ), the controller  10  drives the developing device  32  (ACT 22 ). The developing device  32  drives the developing rollers  321  and the stirring rollers  322  and  323  according to the control of the controller  10 . If the developing device  32  is driven, the toner is supplied from the developing device  32  to the photoconductor drum  31  that rotates in the forward direction. The outer circumference surface of the photoconductor drum  31  to which the toner is supplied from the developing device  32  is cleaned by the cleaner  35 . 
     The controller  10  executes the supply of the toner from the developing device  32  to the photoconductor drum  31  until a predetermined time elapses from the start of the supply of the toner (NO in ACT 23 ). The controller  10  determines that the supply of the toner is terminated if a predetermined time is elapsed from the start of the supply of the toner (YES in ACT 23 ). If it is determined that the supply of the toner is stopped, the controller  10  proceeds to ACT 14  and executes a supply stopping control for the toner. After stopping the supply of the toner, the controller  10  executes the operations subsequent to ACT 14  again. 
     If the controller  10  determines that the ozone discharge mode is terminated (YES in ACT 20 ), the controller  10  stops the operation of discharging the ozone. For example, if the ozone discharge mode is terminated, the controller  10  stops the operations of each component, and the first gas-discharge port  46  or  56  is closed by the shutter  47  or  57 . 
     According to the above-described operation example, the image forming apparatus has the ozone discharge mode as an operation mode of discharging the ozone without performing the image formation. If the ozone is discharged without performing the image formation, the image forming apparatus rotates the developing roller of the developing device in the direction opposite to the forward direction for developing the electrostatic latent image on the photoconductor drum. The image forming apparatus peels off the developer by rotating the developing roller in the reverse direction and, after that, rotates the photoconductor drum in the forward direction to turn on the charger. The image forming apparatus discharges the ozone generated by the charger from the discharge port by a ventilation mechanism. 
     If the ozone is discharged without performing the image formation, the image forming apparatus can rotate the photoconductor drum in a state where the developer does not abut with the outer circumference surface of the photoconductor drum. As a result, if the operation of discharging the ozone is performed without performing the image formation, the image forming apparatus can suppress the deterioration of the photoconductor drum. In addition, since the developing device does not need to be operated if the ozone is discharged without performing the image formation, the image forming apparatus can suppress the deterioration of the developer. 
     In addition, if the ozone is discharged without performing the image formation, the image forming apparatus rotates the photoconductor drum after separating the intermediate transfer belt and the photoconductor drum. Accordingly, if the operation of discharging the ozone is executed without performing the image formation, the image forming apparatus can suppress deterioration of the photoconductor drum and the intermediate transfer belt. 
     It is noted that, in the above-described operation example, the ozone discharge mode of discharging the ozone if the image forming apparatus  1  is in a state where the image formation is not performed is described. However, the image forming apparatus  1  may allow the ozone to be discharged during the execution of the image formation if a person is absent in the periphery. During the execution of the image formation, the charger  34  generates the ozone in order to charge the photoconductor drum  31 . Therefore, if the fans  41  and  45  (or  51 ) is driven by opening the first gas-discharge port  46  (or  56 ) during the execution of the image formation, the ozone generated by the charger  34  is discharged from the first gas-discharge port  46  (or  56 ). 
     For example, the controller  10  confirms that a person is absent in the periphery based on the detection signal of the motion sensor  21  or the detection signal of the optical sensor  22  during the execution of the image formation. When the controller  10  confirms that a person is absent in the periphery during the execution of the image formation, the controller  10  opens the shutter  47  to open the first gas-discharge port  46  and drives the fans  41  and  45 . Accordingly, when a person is absent in the periphery during the execution of the image formation, the image forming apparatus  1  provided with the ventilation mechanism  19  can discharge the ozone generated by the charger  34  from the first gas-discharge port  46 . 
     In addition, when the controller  10  confirms that a person is absent in the periphery during the execution of the image formation, the controller  10  moves the shutter  57  to a position where the first gas-discharge port  56  is opened and drives the fan  51 . Accordingly, when a person is absent in the periphery during the execution of the image formation, the image forming apparatus  1  provided with the ventilation mechanism  50  can discharge the ozone generated by the charger  34  from the first gas-discharge port  46 . 
     In addition, the image forming apparatus  1  may diffuse the discharged ozone by cooperating with an air conditioning equipment. For example, the image forming apparatus  1  is provided with a communication interface for communicating with the controller of the air conditioning equipment. The communication interface may be a wireless communication (Bluetooth (registered trademark), WiFi (registered trademark), or the like) interface or may be a wired communication (wired LAN) interface. The controller  10  of the image forming apparatus  1  communicates with the controller of the air conditioning equipment via the communication interface. 
     The controller  10  of the image forming apparatus  1  controls the direction of the wind from the air conditioning equipment so as to be set to the direction of diffusing the ozone discharged from the first gas-discharge port  46  (or  56 ) in accordance with the timing of discharging the ozone. For example, the controller  10  of the image forming apparatus  1  instructs the air conditioning equipment of the direction of the wind based on the position of the wind out-blowing port of the air conditioning equipment and the installation position of the image forming apparatus  1 . Accordingly, the image forming apparatus can allow the ozone discharged from the first gas-discharge port as the ozone discharge port to be diffused over a wide range. 
     In addition, the server capable of communicating with the image forming apparatus  1  may control the air conditioning equipment according to the execution situation of the ozone discharge mode in the image forming apparatus  1 . For example, the server controls the direction of wind by the air conditioning equipment based on the position of the image forming apparatus  1  that executes the ozone discharge mode and the position of the wind out-blowing port of the air conditioning equipment. Accordingly, the server can allow the ozone discharged from the first gas-discharge port of the image forming apparatus to be diffused over a wide range. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel apparatus and methods described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the apparatus and methods described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.