JP2006251738A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent nitrogen oxides generated in a charging device from sticking to the surface of a photoreceptor drum with a simple constitution. <P>SOLUTION: A shutter member 31 is arranged so as to be moved between a shut-off position located between the surface of the photoreceptor drum 1 and the charging device 2 and a retreat position located between the surface of the photoreceptor drum 1 and a pre-exposure light source 30. The shutter member 31 includes a light-transmissive part which transmits the light emitted from the light source 30 and titanium dioxide as photocatalyst 31. Upon charging, the shutter member 31 located in the retreat position transmits the light emitted from the light source 30 so as to irradiate the surface of the photoreceptor drum 1 with the light, and also, light energy is supplied from the light source 30 to the photocatalyst. Upon not charging, the shutter member 31 located in the shut-off position prevents the nitrogen oxides generated in the charging device 2 from sticking to the surface of the photoreceptor drum 1, and also, scientifically decomposes the nitrogen oxides. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus provided with means for removing nitrogen oxides generated by a charger.

In image forming apparatuses such as printers, copiers, and facsimiles using a photoconductor, the surface of the photoconductor is charged by a charger. When a charger is used, nitrogen oxides (NOx) and ozone (O ₃ ) are generated by the discharge. In particular, when a corona charger (corona discharger) using corona discharge is used as the charger, the amount of nitrogen oxides or ozone generated is greater than when a charging roller or a charging blade is used.

  Nitrogen oxide or ozone reacts with moisture in the air to form nitric acid or a nitrate film on the photoreceptor. These nitric acid and nitrate films cause image deterioration such as image flow.

  Patent Document 1 describes means for removing ozone generated during corona discharge. This is provided with a shutter member that can close the opening of the corona discharger facing the photosensitive member, and a suction means for sucking air in the corona discharger, and when the shutter member closes the opening, the suction means is operated. Then, ozone stagnating in the corona discharger is sucked. Note that nitrogen oxide is also generated in addition to ozone during corona discharge, but this nitrogen oxide can also be sucked by using the shutter member as described above.

JP-A-5-297689

  However, according to the above-mentioned Patent Document 1, since ozone and nitrogen oxides generated during corona discharge are merely mechanically sucked together with air from the vicinity of the corona discharger, before the sucked air is discharged outside the apparatus. In addition, a configuration for reliably removing ozone and nitrogen oxides from the air is essential, and the configuration for that is complicated.

  Accordingly, an object of the present invention is to provide an image forming apparatus capable of decomposing ozone and nitrogen oxide generated during charging with a simple configuration.

  The present invention provides an image forming apparatus in which a toner image is formed on a movable image carrier surface by charging, exposure, and development, and the toner image is transferred to a transfer member to form an image. A charging means for charging the image carrier, a pre-exposure means for neutralizing the surface of the image carrier after the transfer and before the charging by light irradiation, and a blocking position for shutting off the surface of the image carrier and the charging means. A shutter member that opens between the surface of the image carrier and the charging unit and takes a retreat position between the surface of the image carrier and the pre-exposure unit, and the shutter member includes: A light transmitting portion that allows light emitted from the pre-exposure means to pass through and illuminate the surface of the image carrier when disposed at the retracted position; and when disposed at the retracted position, The light emitted from the pre-exposure means is irradiated. Has a photocatalyst activated, the Te, and wherein the.

  According to the present invention, the shutter member has the light transmission part and the photocatalyst, and can take the blocking position and the retracted position. The shutter member disposed at the blocking position blocks between the surface of the image carrier and the charging unit, so that nitrogen oxides and ozone generated by the charging unit move to the image carrier side and adhere to the image carrier. Can be mechanically (physically) prevented, and nitrogen oxides and ozone can be chemically decomposed by the photocatalyst. On the other hand, the shutter member disposed at the retracted position allows the light transmitted from the pre-exposure means to pass through the light transmitting portion and irradiate the image carrier to eliminate static electricity. Similarly, light energy is supplied to the photocatalyst by the light generated from the pre-exposure means in the shutter member disposed at the retracted position.

  That is, the shutter member arranged at the blocking position physically and chemically prevents the attachment of nitrogen oxides and ozone to the image carrier, and the shutter member arranged at the retracted position hinders pre-exposure. In addition, light energy is supplied to the photocatalyst. In this way, even when the retracting position of the shutter member is set between the surface of the image carrier and the pre-exposure means, and the space is used efficiently, the shutter member does not interfere with the pre-exposure, By using the pre-exposure means as a light source for applying light energy to the photocatalyst, the configuration can be simplified.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, what attached | subjected the same code | symbol in the same drawing or a different drawing performs the same structure or the same effect | action, The duplication description is abbreviate | omitted suitably about these.

<Embodiment 1>
FIG. 1 shows an image forming apparatus to which the present invention can be applied. The image forming apparatus shown in FIG. 1 is an electrophotographic image forming apparatus. FIG. 1 shows a vertical section of the image forming apparatus as viewed from the front side, that is, from the side where a user or service person is located when operating the image forming apparatus. It is a schematic diagram equivalent to a surface view. Examples of the image forming apparatus to which the present invention can be applied include a printer, a copying machine, a facsimile machine, and a complex machine of these.

  The image forming apparatus shown in FIG. 1 includes a drum-shaped electrophotographic photosensitive member (hereinafter referred to as “photosensitive drum”) 1 as an image carrier inside a main body frame (image forming apparatus main body). Around the photosensitive drum 1, a charger 2, an exposure device 3, a developing device 4, a transfer member 5, and a cleaning device 6 as a charging unit are arranged almost sequentially from the upstream side along the rotation direction (arrow R 1 direction). It is installed. The photosensitive drum 1, the charger 2, the developing device 4, the transfer member 5, and the cleaning device 6 are all formed long in a direction along the axis of the photosensitive drum 1 (hereinafter referred to as “longitudinal direction” as appropriate). Hereinafter, the photosensitive drum 1 to the cleaning device 6 will be described in this order.

  As the photosensitive drum 1, for example, a surface in which an organic photo semiconductor (OPC) is provided as the photosensitive layer 8 on the surface of a conductive drum base 7 such as aluminum can be used. The photosensitive drum 1 is rotationally driven at a predetermined process speed (circumferential speed) in the direction of arrow R1 by a driving means (not shown).

As the charger 2, a corona charger is used in the present embodiment. The charger 2 has a metal shield 10 and a metal discharge wire 11 which is also the same. Of these, the shield 10 is formed by the back plate 10a and the two side plates 10b so that the cross-sectional shape shown in the figure is a "U" shape, with the opening 10c facing the surface of the photosensitive drum 1. It is arranged. A large number of through holes h are formed in the back plate 10 a of the shield 10. These through-holes h are used for smoothly guiding the gas to be processed such as nitrogen oxide (NOx) and ozone (O ₃ ) generated by the charger 2 during charging into the duct 20 described later. A high-voltage charging bias is applied to the charger 2 by a charging bias application power source (not shown). Thereby, the surface of the photosensitive drum 1 is uniformly charged to a predetermined polarity and potential.

  As the exposure apparatus 3, a laser exposure apparatus can be used. The exposure device 3 performs on / off control of the laser beam La based on the image information, and scans and exposes the surface of the photosensitive drum 1 after charging with the laser beam La. As a result, the charge in the exposed portion is removed, and an electrostatic latent image based on the image information is formed on the photosensitive drum 1.

  The developing device 4 develops the electrostatic latent image. The developing device 4 includes a developing container 12 that stores a developer mainly composed of a carrier and toner, and a developing sleeve 13 that rotates in the direction of arrow R13. The developing sleeve 13 carries the developer on its surface and rotates in the direction of arrow R13 to convey the developer to the developing portion D facing the surface of the photosensitive drum 1. Further, a developing bias is applied to the developing sleeve 13 by a developing bias applying power source (not shown). As a result, the toner in the developer adheres to the electrostatic latent image on the photosensitive drum 1, and the electrostatic latent image is developed as a toner image.

  The transfer member 5 transfers the toner image on the photosensitive drum 1 to a recording material (for example, paper, transparent film) P as a recording medium. The recording material P is conveyed in the direction of the arrow Kp by a sheet feeding / conveying means having a sheet feeding cassette, a sheet feeding roller, a conveying roller, a registration roller, etc. (all not shown), and the recording material P is moved between the photosensitive drum 1 and the transfer member 5. Supplied to the transfer portion T. At this time, a transfer bias is applied to the transfer member 5 by a transfer bias application power source (not shown). As a result, the toner image on the photosensitive drum 1 is transferred onto the recording material P.

  The cleaning device 6 cleans the surface of the photosensitive drum 1. The cleaning device 6 includes a cleaning blade 14 in contact with the surface of the photosensitive drum 1 and a cleaning container 15. During the transfer described above, the toner (transfer residual toner) that is not transferred onto the recording material P and remains on the surface of the photosensitive drum 1 is wiped off by the cleaning blade 14 and collected in the cleaning container 15. The photosensitive drum 1 from which the transfer residual toner on the surface has been removed is used for the next image formation starting from the above-described charging.

  On the other hand, the recording material P after the toner image is transferred is conveyed to a fixing device (not shown). The fixing device includes a fixing roller (not shown) and a pressure roller (not shown) pressed against the fixing roller, and a fixing nip portion (not shown) is formed between the two rollers. . The recording material P after transfer of the toner image is heated and pressurized by a fixing device when passing through the fixing nip portion. As a result, the toner image is fixed on the recording material P.

  A series of image forming processes described above, that is, charging by the charger 2, exposure by the exposure device 3, development by the developing device 4, transfer by the transfer member 5, cleaning by the cleaning device 6, and fixing by the fixing device, The image formation on the recording material P is completed.

  In the above-described image forming apparatus, when the surface of the photosensitive drum 1 is charged by the charger 2, if a high-voltage charging bias is applied to the charger 2 by the charging bias application power source, the space between the charger 2 and the photosensitive drum 1 surface is applied. Corona discharge occurs. At this time, nitrogen oxides and ozone are generated.

  In the present invention, the effect of the photosensitive drum 1 due to these nitrogen oxides and ozone is reduced by the shutter member having a photocatalyst. The configuration and operation will be described in detail below.

  As shown in FIG. 1, an image forming apparatus to which the present invention can be applied includes a charger 2 as a charging unit, a light source 30 as a pre-exposure unit, and a shutter member 31.

  As the charger 2, a corona charger is used as described above. The charger 2 is disposed above the photosensitive drum 1 and faces the surface of the photosensitive drum 1 with the opening 10c of the shield 10 facing downward. Nitrogen oxides and ozone generated in the vicinity of the charger 2 during charging are heavier than air, and therefore the opening 10c descends toward the surface of the photosensitive drum 1.

Air in the vicinity of the charger 2 is guided along a flow path 26 formed inside the duct 20. The duct 20 has a flow path 26 for guiding air from the vicinity of the charger 2 to the outside of the image forming apparatus main body (not shown). A plurality of arrows a in the flow path 26 indicate the direction of air flow in the flow path 26. In the following description, the upstream side and the downstream side along the air flow are simply referred to as “upstream side” and “downstream side”, respectively. The duct 20 has a hood 23 in a portion corresponding to the air inlet on the most upstream side. The hood 23 is configured to cover the back surface side and the side surface side of the charger 2, that is, to cover substantially the entire charger 2 except for the portion corresponding to the opening 10 c of the shield 10 of the charger 2. . Nitrogen oxides (described as “NOx” in FIG. 1) and ozone (described as “O ₃ ” in FIG. 1) generated in the vicinity of the charger 2 when the photosensitive drum 1 is charged are transferred to other regions by the hood 23. In addition, the hood 23 and the through hole h of the back plate 10a of the shield 10 are efficiently guided to the flow path 26. An exhaust port 25 through which air in the duct 20 is discharged is formed on the most downstream side of the duct 20.

  The fan 21 is disposed in the vicinity of the exhaust port 25 on the most downstream side in the duct 20. The fan 21 generates an air flow in the flow path 26 of the duct 20 by its rotation. The flow of air in the flow path 26 is formed as a flow that flows substantially in the direction of the arrow a from the vicinity of the hood 23 on the most upstream side of the duct 20 to the vicinity of the exhaust port 25 on the most downstream side.

  The filter 22 is disposed upstream of the fan 21 in the vicinity of the most downstream side of the duct 20. The filter 22 is disposed so as to cross the flow path 26 of the duct 20, that is, to block the entire flow path 26 in a direction orthogonal to the air flow. Air flowing through the flow path 26 inside the duct 20 passes through the filter 22 from the upstream side to the downstream side. At this time, nitrogen oxides and ozone in the air are collected by the filter 22 and removed from the air.

  The light source 30 is disposed on the downstream side of the cleaning device 6 along the rotational direction of the photosensitive drum 1 and on the upstream side of the charger 2 so as to face the surface of the photosensitive drum 1. The light source 30 has both a light wavelength suitable for static elimination (electrostatic cleaning) of the surface of the photosensitive drum 1 after cleaning and a light wavelength suitable for wavelength characteristics of a photocatalyst 31a described later carried on the shutter member 31. Have a bandwidth of.

  The shutter member 31 is a plate-like member having an arc shape in cross section as shown in FIG. 1 and is formed long along the longitudinal direction of the photosensitive drum 1. The shutter member 31 is configured to be movable in the direction of the arrow between a blocking position indicated by a broken line and a retracted position indicated by a solid line, and is moved by a driving means (not shown). The operation of this drive means is controlled by a CPU 32 (control means, see FIG. 2) described later. Here, the blocking position of the shutter member 31 is a position where the surface of the photosensitive drum 1 and the charger 2 are blocked, and is a position where the opening of the hood 23 of the duct 20 is closed. On the other hand, the retracted position is a position where the surface of the photosensitive drum 1 and the charger 2 are opened to be inserted between the surface of the photosensitive drum 1 and the light source 30.

  The shutter member 31 is formed of a transparent acrylic material or transparent glass. That is, the whole is a light transmission part. For this reason, when the shutter member 31 is disposed at the retracted position, the light emitted from the light source 30 can pass through the shutter member 31 and irradiate the surface of the photosensitive drum 1. In the above description, the case where the entire shutter member 31 is made of a light-transmitting material has been described. Instead, only a portion that needs to transmit light is provided with a light-transmitting portion in a window shape, Other portions may be made of a material that does not transmit light.

Further, the shutter member 31 carries the photocatalyst 31 a over the surface thereof, that is, the almost front surface of the surface facing the light source 30. In the present invention, titanium dioxide (TiO ₂ ) is used as the photocatalyst 31a. Titanium dioxide is known to have an effect of decomposing nitrogen oxides when irradiated with light. Nitrogen oxide can be decomposed into nitrogen and water by the photocatalytic action of titanium dioxide. Some titanium dioxides also react to wavelengths in the visible light range, but those that react to blue or ultraviolet light are common, and titanium dioxides of the type that react to light wavelengths λ ≦ 550 nm such as blue or ultraviolet light are more common. It is known that nitrogen oxides can be decomposed more efficiently. Therefore, in the present embodiment, a light source including a large band (second light wavelength region) of this light wavelength λ ≦ 550 nm is used as the light source 30 described above. Specifically, the first light wavelength region (wavelength band) suitable for the photosensitivity characteristics of the photosensitive drum 1 to neutralize the surface of the photosensitive drum 1 with one LED such as a white LED, and the first suitable for the photocatalyst 3. It has two optical wavelength regions of two optical wavelength regions (for example, λ ≦ 550 nm) at the same time. Here, the second light wavelength region is a wavelength region in which the light wavelength is shorter than that of the first light wavelength region.

  Further, when titanium dioxide is used as the photocatalyst 31a coated on the shutter member 31 as described above, the titanium dioxide has hydrophilicity. For this reason, the water generated when the nitrogen oxides are decomposed is uniformly held without forming water droplets on the surface of the shutter member 31, so that the light transmitting portion of the shutter member 31 is not fogged. . Therefore, the light generated by the light source 30 during the pre-exposure can be pre-exposed on the surface of the photosensitive drum 1 with a sufficient amount of light without being reduced when passing through the light transmission portion.

  2 is a control block diagram of the charger 2, the fan 21, the shutter member (shutter) 31, and the light source (pre-exposure) 30 in the image forming apparatus shown in FIG. FIG. 3 is a time chart showing an example of operation timing of the charger 2, the fan 21, the shutter member 31, and the light source 30. In FIG. 3, “shutter open” means that the shutter member 31 in FIG. 1 is disposed at the retracted position indicated by the solid line, and “shutter closed” means that the shutter member 31 in FIG. Means that it is arranged at a blocking position indicated by a broken line. This also applies to FIGS. 7 and 9 described later.

  As shown in FIG. 2, the CPU 32 performs ON / OFF control of the charger 2, ON / OFF control of the fan 21, opening / closing control of the shutter member 31, and ON / OFF control of the light source 30. The CPU 32 first turns on the fan 21 earlier by the time Tfp than the start of the charging operation of the charger 2. This is to prevent nitrogen oxides falling on the surface of the photosensitive drum 1 by sucking the nitrogen oxides falling and adhering to the shutter 31 along the flow path 26 of the duct 20 by the fan 21. . Next, the shutter 31 is turned on with a delay of time Tfs from the start of the operation of the fan 21, and then the charger 2 and the pre-exposure device 30 are turned on with a delay of time Tsp. While the charger 2 is on, the fan 21 and the pre-exposure device 30 are kept on, and the shutter 31 is also kept open. During this time, the light emitted from the light source 30 passes through the light transmitting portion of the shutter member 31 and irradiates the surface of the photosensitive drum 1 to eliminate the charge, and simultaneously irradiates the photocatalyst 31a coated on the surface of the shutter member 31. Thus, light energy is supplied to the photocatalyst 31a. The CPU 32 turns off the charger 2 to end charging, and turns off the light source 30 at the same time.

  Next, the shutter member 31 is closed with a delay of time Ts from the end of charging, and the fan 21 is turned off with a delay of time Tsf after the shutter member 31 is closed. This is because if the fan 21 is turned off before the shutter 31 is securely closed, the nitrogen oxide in the duct 20 may fall onto the surface of the photosensitive drum 1.

  Nitrogen oxide flowing in the direction of arrow a in the flow path 26 in the duct 20 by the rotation of the fan 21 is recovered by the filter 22. During charging, ozone is also generated in addition to the nitrogen oxides, and this ozone is also collected by the filter 22.

  The filter 22 becomes dirty as the image formation is used. Therefore, for example, cleaning or replacement may be performed when the integrated value of the charging time reaches a predetermined time.

  According to the present embodiment, as described above, the shutter member 31 includes the light transmission part and the photocatalyst 31a, and can take a blocking position and a retracted position. The shutter member 31 disposed at the blocking position when not charged blocks between the surface of the photosensitive drum 1 and the charger 2, so that nitrogen oxides and ozone generated by the charger 2 move to the photosensitive drum 1 side. Adhering to the surface of the photosensitive drum 1 can be prevented mechanically (physically), and nitrogen oxides and ozone can be chemically decomposed by the photocatalyst. On the other hand, the shutter member 31 disposed at the retracted position at the time of charging allows the light generated from the light source 30 to pass through the light transmitting portion and irradiate the surface of the photosensitive drum 1 by the light transmitting portion. . Similarly, the shutter member 31 disposed at the retracted position is supplied with light energy to the photocatalyst by the light generated from the light source 30.

  On the other hand, the shutter member 31 disposed at the blocking position physically and chemically prevents the attachment of nitrogen oxides and ozone to the photosensitive drum 1, and the shutter member 31 disposed at the retracted position prevents pre-exposure. In addition, light energy is supplied to the photocatalyst. As described above, even when the retracting position of the shutter member 31 is set between the surface of the photosensitive drum 1 and the light source 30 and the space is efficiently used, the shutter member 31 does not interfere with the pre-exposure. The configuration can be simplified by diverting the pre-exposure means as the light source 30 for applying light energy to the photocatalyst 31a.

<Embodiment 2>
FIG. 4 shows a circuit diagram for driving the pre-exposure device 30. FIG. 5 shows a light source 30 driven by this circuit. FIG. 6 is a control block diagram of the charger 2, the fan 21, the shutter 31, the first light source 30a, and the second light source 30b. FIG. 5 is a view of the light source 30 as viewed from the surface side of the photosensitive drum 1, and the horizontal direction in the figure corresponds to the longitudinal direction of the photosensitive drum 1. That is, the entire light source 30 is formed long along the axis (bus line) of the photosensitive drum 1.

  As shown in FIG. 5, the entire light source 30 is configured by arranging 24 LEDs aligned in the longitudinal direction. Among these LEDs, a total of 12 LEDs L1 to L12 have a wavelength region (first light wavelength region) suitable for the photosensitive characteristics of the photosensitive drum 1 in order to neutralize the surface of the photosensitive drum 1. A light source (first LED array unit) 30a is configured. On the other hand, a total of 12 LEDs L21 to L32 have a second light source (second wavelength) having a wavelength region (band of light wavelength λ ≦ 550 nm) suitable for the wavelength characteristics of titanium dioxide as the photocatalyst 31a of the shutter member 31. LED array part) 30b. The first light sources 30a are arranged at equal intervals over almost the entire area from the vicinity of one end of the light source 30 to the vicinity of the other end. Similarly, the second light sources 30b are arranged at equal intervals over substantially the entire area from the vicinity of one end of the light source 30 to the vicinity of the other end.

  Moreover, each LED which comprises the 1st light source 30a and each LED which comprises the 2nd light source 30b are arrange | positioned alternately. That is, as shown in FIG. 5, L1, L21, L2, L22,... Further, as shown in FIG. 4, the first light source 30a is divided into three blocks L1 to L4, L5 to L8, and L9 to L12. Each block has resistors R1 to R3, respectively, and is connected in parallel. The same applies to the second light source 30b. That is, as shown in FIG. 4, the second light source 30b is divided into three blocks L21 to L24, L25 to L28, and L29 to L32. Each block has resistors R4 to R6, and is connected in parallel. The first light source 30a is ON / OFF controlled by the CPU 32 via the transistor Tr1. The second light source 30b is ON / OFF controlled by the CPU 32 via the transistor Tr2. The first light source 30a and the second light source 30b are controlled ON / OFF independently by the CPU 32, respectively. When the first light source 30a is turned on, the surface of the photosensitive drum 1 can be irradiated with light almost evenly in the direction of the bus bar, and uneven discharge due to uneven light irradiation can be prevented. Further, when the second light source 30b is turned on, titanium dioxide as the photocatalyst 31a supported on the surface of the shutter member 31 can be irradiated with light almost evenly, and the photocatalyst is uniformly distributed over the entire surface of the shutter member 31. It has become possible to demonstrate the effect.

  FIG. 7 shows operation timings of the charger 2, the fan 21, the shutter member (shutter) 31, the first light source 30a (pre-exposure: L1 to L12), and the second light source 30b (pre-exposure: L21 to L32). It is a time chart. Since the operation of the charger 2, the fan 21, the shutter member 31, and the first light source 30a in FIG. 7 is the same as that in FIG. 3, the description thereof will be omitted, and only the second light source 30b will be described here.

  The second light source 30b emits light for a time Tl after the operation of the charger 2 and the first light source 30b is completed. During this time, the fan 21 continues to operate, and the shutter 31 is in the retracted position (open state). The retracted position of the shutter member 31 is as described above. In this state, it is inserted between the surface of the photosensitive drum 1 and the light source 30. In this state, the second light source 30b irradiates the shutter member 31 with light having a light wavelength λ ≦ 550 nm, and supplies light energy to titanium dioxide (photocatalyst) coated on the surface of the shutter member 31. After turning off the second light source 30b, the shutter member 31 is closed (disposed at the blocking position) with a delay of time Tls, and then the fan 21 is stopped with a delay of time Tsf.

  By such control of the second light source 30b, light energy is accumulated in the titanium dioxide of the shutter member 31 by light having the light wavelength λ ≦ 550 nm of the second light source 30b. Thereafter, when the shutter member 31 is moved from the retracted position to the blocking position, the nitrogen oxides falling on the shutter member 31 can be decomposed by the light energy accumulated in the titanium dioxide.

  According to the present embodiment, the light source 30 includes the first light source 30a effective for neutralizing the photosensitive drum 1, and the second light source 30b effective for activating titanium dioxide as the photocatalyst 31a. By properly using the first and second light sources 30a and 30b, the light emitted from the light source 30 can be used effectively and the life of the light source 30 can be extended.

<Embodiment 3>
This embodiment is an example in which a humidity sensor 33 is provided as shown in FIG. 8 and the operation timing of each member described later is changed. 8 is obtained by adding a humidity sensor 33 to the image forming apparatus shown in FIG. 1, and the other configuration is the same as that shown in FIG.

  FIG. 9 shows the configuration of the image forming apparatus shown in FIG. 8, based on the output of the humidity sensor 33, the fan 21, the shutter member (shutter) 31, and the second light source (pre-exposure: corresponding to the above-described members). L21 to L32), and a time chart showing the operation timing of the photosensitive drum 1 changed.

  The operation timing when the humidity is low is the same as that shown in FIG. That is, the operation timings of the charger 2, the fan 21, the shutter member 31, the first light source 30a, and the second light source 30b are the same as those shown in FIG. However, the time “Tfe” of the fan 21 and the time “Ts” of the shutter member 31 in FIG. 7 are described as a time “Tfed” and a time “Tsd”, respectively.

  Here, as shown in FIG. 9, the operation timing of the charger 2 and the first light source 30a is the same regardless of the change in humidity (regardless of whether the humidity is high or low). In contrast, the fan 21 extends the time Tfed when the humidity is low to the time Tfed when the humidity is high. The shutter member 31 extends the time Tsd when the humidity is low to the time Tsw when the humidity is high. The second light source 30b extends the light emission time Tl when the humidity is low by the time ΔTl when the humidity is high. Further, the photosensitive drum 1 continues to rotate until the end of the light emission of the second light source 30b even if the image formation is completed after the start of charging and the charging operation is completed. The reason for this is as follows. Since the light wavelength region of the second light source 30b is on the shorter wavelength side than the light sensitivity band of the photosensitive drum 1, the influence of the light from the second light source 30b is small but not unaffected. For this reason, by always irradiating one predetermined place of the photosensitive drum 1, the photosensitive characteristic of that part is deteriorated more than the others. Then, the deterioration of the photosensitive characteristic is a cause of uneven density of the image, and the life of the photosensitive drum 1 is shortened. Therefore, as described above, the photosensitive drum 1 is rotated even during the light emission time of the second light source 30b, so that the influence of light irradiation on the photosensitive drum 1 can be made uniform, so that local photosensitive deterioration occurs. Accordingly, it is possible to prevent the occurrence of density unevenness in the image and to extend the life of the photosensitive drum 1. Accordingly, as shown in FIG. 9, the photosensitive drum 1 is rotated for the same time ΔTl as the light emission time extension ΔTl of the second light source 30b when the humidity is high.

  Each timing when the charger 2, the fan 21, the first light source 30a, the second light source 30b, and the photosensitive drum 1 are turned from the ON state to the OFF state, and the shutter member 31 is changed from the open state to the closed state. The timing is the same regardless of the humidity level.

<Embodiment 4>
10, 11, and 12 show this embodiment. FIG. 10 is a control block diagram showing a configuration for changing the control of the first light source 30a and the second light source 30b in accordance with the output result of the humidity sensor 33, particularly with the humidity sensor 33. A light amount control signal is issued from the CPU 32 to control the light amount of the second light source 30b.

  FIG. 11 is a diagram showing a circuit configuration of the light source 30 for realizing the configuration of FIG. The control of the first light source 30a controls the light emission timing by an ON / OFF signal. In this case, the light quantity of the first light source 30a is constant without being changed. The second light source 30b has a constant current circuit configuration in addition to the ON / OFF control signal, and changes the current flowing to the second light source 30b of the constant current circuit by the light amount control signal from the CPU 32. Thus, the light amount of the second light source 30b is changed.

  FIG. 12 is a diagram showing the relationship between the humidity (horizontal axis) and the amount of light (vertical axis) of the second light source 30b. If the humidity is lower than a certain value (level 1 or lower in FIG. 12), the light amount of the second light source 30b is set to a predetermined minimum light amount (light amount min). Conversely, when the humidity is higher than a certain value (level 2 or higher in FIG. 12), the light amount of the second light source 30b is set to a predetermined maximum light amount (light amount max). The relationship between the humidity and the light amount between humidity level 1 and level 2 in FIG. 12 is a monotonically increasing linear relationship, and control is performed to increase the light amount as the humidity increases. When the humidity is high, nitrous acid is generated when NOx is combined with moisture on the photosensitive drum 1, thereby causing image degradation such as image flow. On the other hand, as in this embodiment, the photocatalytic action of titanium dioxide (photocatalyst 31a) coated on the surface of the shutter member 31 is more active by increasing the amount of light of the second light source 30b as the humidity increases. To increase the ability to decompose nitrogen oxides. Thereby, it is possible to prevent the generation of nitrous acid, which is the cause of image flow, even in a high humidity environment.

1 is a longitudinal sectional view schematically showing a schematic configuration of an image forming apparatus according to a first embodiment. 3 is a control block diagram in the first embodiment. FIG. 3 is a time chart in the first embodiment. FIG. 6 is a circuit configuration diagram in a second embodiment. 6 is a diagram illustrating a configuration of a light source in Embodiment 2. FIG. FIG. 10 is a control block diagram in the second embodiment. 10 is a time chart in the second embodiment. 5 is a longitudinal sectional view schematically showing a schematic configuration of an image forming apparatus according to Embodiment 3. FIG. 10 is a time chart in the third embodiment. FIG. 10 is a control block diagram in the fourth embodiment. FIG. 10 is a circuit configuration diagram in a fourth embodiment. In Embodiment 4, it is a figure explaining the relationship between humidity and a light quantity.

Explanation of symbols

1 Photosensitive drum (image carrier)
2 Charger (charging means)
3 Exposure device 4 Development device 5 Transfer member 6 Cleaning device 20 Duct 21 Fan 22 Filter 30 Light source (pre-exposure means)
30a 1st light source 30b 2nd light source 31 Shutter member 31a Photocatalyst 32 CPU (control means)
33 Humidity sensor

Claims (11)

In an image forming apparatus for forming a toner image on a surface of a movable image carrier by charging, exposure, and development, and transferring the toner image to a transfer target to form an image.
Charging means for charging the surface of the image carrier;
Pre-exposure means for neutralizing the surface of the image carrier after the transfer and before the charging by light irradiation;
A blocking position for blocking between the surface of the image carrier and the charging unit, and opening between the surface of the image carrier and the charging unit to retract between the surface of the image carrier and the pre-exposure unit. A shutter member that takes a retracted position to be
The shutter member is
A light transmission part that allows the light emitted from the pre-exposure means to pass through and illuminate the surface of the image carrier when disposed at the retracted position;
A photocatalyst that is activated by being irradiated with light emitted from the pre-exposure means when arranged at the retracted position;
An image forming apparatus. The shutter member is disposed at the retracted position when charged by the charging means, and is disposed at the blocking position when not charged.
The image forming apparatus according to claim 1. The photocatalyst is titanium dioxide;
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The pre-exposure means includes a first light source having a first light wavelength region for neutralizing the surface of the image carrier, and a light wavelength shorter than the first wavelength region for activating the photocatalyst. A second light source having a second wavelength region of the region,
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The pre-exposure means turns on the first light source and turns off the second light source during charging by the charging means.
The image forming apparatus according to claim 4. A duct that forms a flow path that guides air in the vicinity of the charging means, a fan that generates a flow of air inside the duct, and a filter that is disposed in the flow path inside the duct,
The duct covers the periphery of the charging means and has an opening in a portion facing the surface of the image carrier,
The shutter member closes the opening when disposed in the blocking position;
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. When the shutter is in the retracted position, the fan is kept on.
The image forming apparatus according to claim 6. A humidity sensor for detecting the humidity around the image carrier;
Control means for controlling the operation time of the fan and the opening and closing time of the shutter member based on the detection result of the humidity sensor,
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The control means controls a light emission time of the second light source based on a detection result of the humidity sensor.
The image forming apparatus according to claim 8. The control means controls a light amount of the second light source based on a detection result of the humidity sensor;
The image forming apparatus according to claim 8, wherein the image forming apparatus is an image forming apparatus. The control means rotates the image carrier during a light emission period of the second light source.
11. The image forming apparatus according to any one of 8 to 10, wherein:

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