JP2010014908A - Image forming apparatus and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of suitably suppressing deterioration of a charger. <P>SOLUTION: The image forming apparatus 1 includes an image forming part 17 and a shielding means 71. The image forming part 17 has a photoreceptor 27, and the charger 29 including an opening part 29c through which air flows in and an charging wire 29a, and charging the photoreceptor 27 by discharge from the charging wire 29a, and forms an image on a medium to be recorded 3 by using a developer image carried on the charged photoreceptor 27. The shielding means 71 shuts the opening part 29c of the charger 29 at least for a predetermined time from start-up of the charger 29. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to protection of a charger in an image forming apparatus, particularly an electrophotographic image forming apparatus.

Generally, if the charging wire of the charger becomes dirty, the discharge efficiency etc. will decrease. Therefore, an opening is provided in the case that houses the charger, and the charging wire is cleaned by accessing from the opening, or ozone generated during charging is opened. For example, Patent Literature 1 discloses a technique for discharging from a portion.
JP 2006-053233 A

However, when there is a user who cleans the inside of the image forming apparatus with a spray-type cleaning tool, if an abnormal discharge occurs in the charger while the spray gas remains, the charging wire may be burnt depending on the spray gas used. As a result, there is a risk of shortening the life of the charger.
An object of the present invention is to provide an image forming apparatus and a process cartridge that favorably suppress deterioration of a charger.

  As means for achieving the above object, an image forming apparatus according to a first aspect of the present invention is a charger including a photosensitive member, an opening through which air can flow, and a charging wire. An image forming unit that forms an image on a recording medium using a developer image carried on the charged photoreceptor, and at least when the charger is activated And a shielding means for closing the opening of the charger for a predetermined time.

  According to this configuration, when the charger is started, the possibility that the combustible spray gas sprayed for cleaning remains in or around the apparatus body is higher than when charging is started during use. It can be said. Therefore, by closing the charger opening for a predetermined time from the start-up of the charger, even if an abnormal discharge of the charger occurs within the predetermined time, contact between the abnormal discharge and the flammable gas Inconvenience caused by the above, for example, charring of the charging wire can be suppressed. Therefore, deterioration of the charger can be suitably suppressed.

  Here, “closing the opening” does not mean that gas is completely blocked from flowing into the charger through the opening. For this reason, even if the gas slightly flows into the charger through the opening, it is included in “closing the opening”.

  According to a second aspect of the present invention, in the image forming apparatus of the first aspect, the image forming apparatus includes an apparatus main body, the image forming unit is detachable from the apparatus main body, and the shielding means includes the When the image forming unit is attached to the apparatus main body, the opening of the charger is closed.

  Normally, when the image forming unit is mounted on the apparatus main body, there is a high possibility that flammable spray gas is blown into the apparatus for cleaning the inside of the apparatus. Therefore, according to this configuration, the inflow of the remaining combustible gas into the charger can be suppressed by closing the opening of the charger when the image forming unit is attached to the apparatus main body. As a result, inconvenience caused by contact between the abnormal discharge and the combustible gas is suitably suppressed even when the charger is abnormally discharged at the time of starting the charger.

  According to a third aspect, in the image forming apparatus according to the second aspect, the shielding means includes a first interlocking member that closes the opening in conjunction with the attachment / detachment of the image forming part with respect to the apparatus main body.

  According to this configuration, the opening can be automatically closed in conjunction with the attachment / detachment of the image forming unit with respect to the apparatus main body without requiring power, which is convenient. Further, since the opening of the charger is closed when the image forming unit is attached to or detached from the apparatus main body, the invasion of combustible gas or dust into the charger is preferably suppressed.

  According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the image forming apparatus further includes a detecting unit that detects an abnormal discharge of the charger, and the shielding unit includes the charging unit within the predetermined time. If the abnormal discharge of the charger is detected, the opening of the charger is kept closed thereafter, and if the abnormal discharge of the charger is not detected within the predetermined time, the opening of the charger Release the closure of the part.

  According to this configuration, when an abnormal discharge of the charger is detected, the opening of the charger is closed or kept closed, which is caused by the contact between the abnormal discharge of the charger and the combustible gas. It is possible to reduce inconvenience.

  According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect, the shielding means opens the opening of the charger when the abnormal discharge of the charger is detected after the opening of the opening is released. Close again.

  According to this configuration, even when an abnormal discharge of the charger is detected again during printing after a lapse of a predetermined time from the start of the charger, the opening of the charger is closed again. Inconvenience due to contact between the abnormal discharge and the combustible gas can be reduced.

According to a sixth invention, in the image forming apparatus according to any one of the first to fifth inventions, the shielding means closes and opens the opening in conjunction with a drive motor for driving the image forming unit. Including a first interlocking member.
According to this configuration, since the opening can be mechanically closed and opened, the control is simplified. Further, the shielding means can be controlled in association with the printing operation of the image forming unit.

  According to a seventh invention, in the image forming apparatus according to any one of the first to sixth inventions, an openable / closable cover that allows the image forming hand to be accessed from the outside, and the opening of the cover in conjunction with the opening. And control means for closing the opening of the charger by shielding means.

  In order to clean the image forming unit, the cover accessible to the image forming unit may be opened, and flammable spray gas may be sprayed onto the image forming unit. According to this configuration, even in such a case, the opening of the charger is closed in conjunction with the opening of the cover. Therefore, it is preferable that the combustible gas flows into the inside from the opening of the charger. It is suppressed.

  A process cartridge according to an eighth aspect of the present invention is a process cartridge that is detachably attached to the image forming apparatus, and a photosensitive member that transfers a carried developer image onto a recording medium and air can flow in. A charger that has an opening and a charging wire and charges the photosensitive member by discharging from the charging wire, and the process cartridge is mounted on the image forming apparatus. Accordingly, the shielding means for closing and opening the opening of the charger is provided, and the shielding means closes the opening of the charger at least when the process cartridge is attached to and detached from the image forming apparatus.

  According to this configuration, the shielding unit can be appropriately controlled in association with the printing operation of the process cartridge in accordance with an operation from the image forming apparatus. For example, in order to suppress inconvenience due to contact between abnormal discharge and flammable gas, the charger opening is closed at least for a predetermined time from the start of the charger, and abnormal discharge occurs within the predetermined time. Depending on whether or not it has been done, it is possible to control whether to continue closing the opening or to open the opening.

  In general, when the process cartridge is attached to the image forming apparatus, there is a possibility that a combustible spray gas is sprayed inside the apparatus for cleaning the inside of the apparatus. Therefore, by closing the opening of the charger at least when the process cartridge is mounted on the image forming apparatus, the possibility of residual flammable gas entering the charger is reduced, and the charger is started. Even when abnormal discharge occurs, it is possible to suppress inconvenience due to contact between the abnormal discharge and the combustible gas. In addition, since the opening of the charger is closed even when the process cartridge is removed from the image forming apparatus, intrusion of flammable gas or dust into the charger is preferably suppressed. Therefore, deterioration of the charger can be suitably suppressed.

According to a ninth aspect of the present invention, in the process cartridge according to the eighth aspect, the shielding means is a drive motor of the image forming apparatus that drives the process cartridge in a state where the process cartridge is mounted on the image forming apparatus. In conjunction with this, an interlocking member for closing and opening the opening is provided.
According to this configuration, the opening of the charger can be mechanically closed and opened using the drive motor that is an existing configuration, so that the control is simplified.

  According to the image forming apparatus and the process cartridge of the present invention, it is possible to suitably suppress the deterioration of the charger.

<Embodiment>
An embodiment of the present invention will be described with reference to FIGS.
1. Overall Configuration of Image Forming Apparatus FIG. 1 is a side sectional view of an essential part showing an embodiment of a laser printer as an image forming apparatus of the present invention. In FIG. 1, a laser printer 1 includes a feeder unit 4 for feeding paper 3 (corresponding to “recording medium” of the present invention) into a main body frame (corresponding to “device main body” of the present invention) 2. And an image forming unit 5 for forming an image on the fed paper 3. Note that the image forming apparatus is not limited to a laser printer, and may be, for example, an LED printer or a so-called multifunction machine having a copy function and a facsimile function. Further, the printer is not limited to a monochrome printer, and may be a color printer.

(1) Feeder unit The feeder unit 4 includes a paper feed tray 6 that is detachably attached to the bottom of the main body frame 2, a paper pressing plate 7 provided in the paper feed tray 6, and a paper feed tray 6. A feed roller 8 provided above one end side (hereinafter, one end side (right side of the paper in FIG. 1) is the front side and the opposite side (left side of the paper in FIG. 1) is the rear side); On the other hand, a registration roller 12 is provided on the downstream side in the conveyance direction of the sheet 3.
The uppermost sheet 3 on the sheet pressing plate 7 is fed one by one by the rotation of the sheet feeding roller 8. The fed paper 3 is sent to the registration roller 12. The registration roller 12 is composed of a pair of rollers, and after registering the paper 3, sends the paper 3 to the transfer position of the toner image on the photosensitive drum 27.

(2) Image Forming Unit The image forming unit 5 includes a scanner unit 16, a process cartridge (corresponding to an “image forming unit” in the present invention) 17, and a fixing unit 18.
(A) Scanner Unit The scanner unit 16 is provided in the upper part of the main body frame 2 and includes a laser light emitting unit (not shown), a polygon mirror 19 that is rotationally driven, a plurality of lenses, a plurality of reflecting mirrors, and the like. Yes. The laser beam based on the image data emitted from the laser emitting unit is high-speed on the surface of the photosensitive drum 27 of the process cartridge 17 via the polygon mirror 19, the plurality of lenses, and the plurality of reflecting mirrors as indicated by a chain line. Irradiated by scanning.

(B) Process Cartridge The process cartridge 17 is provided below the scanner unit 16. The process cartridge 17 includes a drum cartridge 26 that is detachably attached to the main body frame 2, a developing cartridge 28 that is accommodated in the drum cartridge 26, and a shielding unit that closes the opening 29 c of the charger 29. 70 (refer to FIG. 2).

  The developing cartridge 28 is detachably housed in the drum cartridge 26 and includes a developing roller 31, a supply roller 33, and a toner hopper 34. The toner hopper 34 is filled with, for example, positively charged toner as a developer.

Then, the toner in the toner hopper 34 is discharged from a toner supply port 37 opened in the rear side portion of the toner hopper 34. A supply roller 33 is rotatably provided behind the toner supply port 37, and a developing roller 31 is rotatably provided facing the supply roller 33. The toner discharged from the toner supply port 37 is supplied to the developing roller 31 by the rotation of the supplying roller 33, and at this time, the toner is positively frictionally charged between the supplying roller 33 and the developing roller 31.
The drum cartridge 26 includes a photosensitive drum 27 (corresponding to the “photosensitive member” of the present invention), a charger 29, and a transfer roller 30.

  The photosensitive drum 27 is disposed behind the developing roller 31 so as to face the developing roller 31 and is supported by the drum cartridge 26 so as to be rotatable in the arrow direction (clockwise). The photosensitive drum 27 includes a drum main body, and a metal drum shaft 27a that supports the drum main body and is provided at the shaft center of the drum main body. Here, a positively chargeable photosensitive layer is formed on the surface of the drum body.

  The charger 29 is disposed above the photosensitive drum 27 so as to face the photosensitive drum 27 at a predetermined interval and is supported by the drum cartridge 26. The charger 29 is a scorotron charger having a charging wire 29a and a grid 29b, and generates a corona discharge from the charging wire 29a to uniformly charge the surface of the photosensitive drum 27 to a positive polarity here. A predetermined charging voltage is applied to the charging wire 29a.

  The surface of the photosensitive drum 27 is first uniformly charged positively by the charger 29 as the photosensitive drum 27 rotates, and then exposed by high-speed scanning of the laser beam from the scanner unit 16. An electrostatic latent image is formed.

  Next, when the developing roller 31 rotates, the toner carried on the surface of the developing roller 31 and charged positively is formed on the surface of the photosensitive drum 27 when it comes into contact with the photosensitive drum 27. It is supplied to the electrostatic latent image and selectively carried thereon to be visualized and developed.

  The transfer roller 30 is disposed below the photosensitive drum 27 so as to face the photosensitive drum 27 and is supported by the drum cartridge 26 so as to be rotatable in the direction of the arrow (counterclockwise). During the transfer operation, the transfer roller 30 is applied with a predetermined transfer bias voltage, and the developed electrostatic latent image is transferred onto the paper 3.

  As shown in FIG. 1, a front cover 2a that can be opened and closed with the lower end side as a central axis is provided on the front surface of the main body frame 2, and the process cartridge 17 includes the front cover (the “cover” in the present invention). 2a) is opened and accommodated in the main body frame 2 in a detachable manner. A cover opening / closing sensor 2b for detecting opening / closing of the front cover 2a is provided in the main body frame 2 in the vicinity of the front cover 2a.

(C) Fixing Unit As shown in FIG. 1, the fixing unit 18 is provided on the rear downstream side of the process cartridge 17, the heating roller 41, the pressing roller 42 that presses the heating roller 41, and the heating roller 41 and the pressing unit. A pair of transport rollers 43 provided on the downstream side of the roller 42 is provided.

  In the fixing unit 18, the toner transferred onto the paper 3 in the process cartridge 17 is heat-fixed while the paper 3 passes between the heating roller 41 and the pressing roller 42, and then the paper 3 is transferred to the transport roller 43. Is conveyed to the paper discharge path 44. The paper 3 sent to the paper discharge path 44 is sent to the paper discharge roller 45 and is discharged onto the paper discharge tray 46 by the paper discharge roller 45.

2. Configuration of Shielding Unit Next, a shielding unit 70 provided in the process cartridge 17 will be described with reference to FIGS. FIG. 2 is an explanatory view showing a state of the shielding unit 70 immediately after the process cartridge 17 is mounted on the main body frame 2, and FIG. 3 shows a state in which the shielding unit 70 is driven by the drive gear 51 of the printer 1. It is explanatory drawing shown. FIG. 4 is an explanatory view showing a state of the shielding unit 70 immediately after the process cartridge 17 is taken out from the main body frame 2.

  As shown in FIG. 2, for example, the shielding unit 70 includes a shutter 71, a gear 72, an inner gear 72 a, a movable gear 73, a movable gear support shaft 73 a, an intermediate joint 74, a spring 75, and a regulating member 76. The shutter 71 is bent in an L shape, and is supported by the support portion 71 a so as to be rotatable with respect to the process cartridge 17. The gear 72 and the inner gear 72a rotate integrally. The movable gear 73 is coupled to the inner gear 72a by a movable gear support shaft 73a. Further, the movable gear 73 meshes with the inner gear 72 a and rotates as the gear 72 rotates. The intermediate joint 74 is provided between the shutter 71 and the movable gear 73. The regulating member 76 regulates the opening degree of the shutter 71 when the shutter 71 comes into contact therewith.

  The gear 72 is rotatably provided when the process cartridge 17 is taken out from the main body frame 2. The gear 72 is disposed at a position that engages with a driving gear 51 provided in a laser printer (hereinafter simply referred to as “printer”) 1 when the process cartridge 17 is mounted on the main body frame 2. The drive gear 51 is driven by the main motor M via, for example, a predetermined power transmission mechanism (not shown). The main motor M is for driving various components of the image forming unit 5 for printing, for example, the photoreceptor 27 and the like. If the main motor M is also used for opening and closing the shutter 71 and is controlled to perform warm-up and printing operations of the configuration related to printing after charging is turned on, the shutter 71 can be opened in conjunction with the printing operation.

  In such a configuration of the shielding unit 70, when the process cartridge 17 is mounted on the main body frame 2, as shown in FIG. 2, the shutter 71 closes the opening 29 c of the charger 29 by the spring 75. As described above, the reason why the opening 29c of the charger 29 is closed when the process cartridge 17 is mounted is as follows.

  That is, when the process cartridge 17 is attached to the main body frame 2, there is a possibility that combustible spray gas is blown into the printer 1 for cleaning the inside of the printer 1. Therefore, when the process cartridge 17 is mounted on the main body frame 2, the opening 29 c of the charger 29 is closed to reduce the possibility of the residual flammable gas entering the charger 29, thereby charging the charger 29. This is because inconvenience caused by contact between the abnormal discharge and the flammable gas can be suppressed even when an abnormal discharge occurs at the time of starting.

  Further, when the drive gear 51 is driven, for example, as shown in FIG. 3, the gear 72 rotates counterclockwise in accordance with the clockwise rotation of the drive gear 51. Then, according to the rotation of the gear 72, the movable gear 73 moves counterclockwise while meshing with the inner gear 72a. Accordingly, the intermediate joint 74 moves in a direction in which the shutter 71 is brought into contact with the regulating member 76, whereby the shutter 71 rotates about the support portion 71a against the contraction force of the spring 75, and the opening portion. 29c is opened. If the drive gear 51 continues to rotate even after the shutter 71 contacts the regulating member 76, the movable gear 73 rotates clockwise according to the rotation of the gear 72 as shown in FIG. And the energy from the drive gear 51 is released. When the rotation of the drive gear 51 is reversed, the shutter 71 closes the opening 29c by moving the intermediate joint 74 in the reverse direction in accordance with the reverse movement of the movable gear 73.

  With such a configuration, the shielding unit 70 can be appropriately controlled in association with the printing operation of the process cartridge 17 in accordance with an operation from the printer 1. For example, in order to suppress inconvenience due to contact between the abnormal discharge of the charger 29 and the flammable gas, the opening 29c of the charger is closed for a predetermined time from the start of the charger 29, and within the predetermined time. Depending on whether or not abnormal discharge has occurred, it is possible to control whether to continue closing the opening or to open the opening. Further, since the main motor M which is the configuration of the existing printer 1 can be used to mechanically close and open the opening 29c of the charger, the control is simplified.

Further, immediately after the process cartridge 17 is taken out from the main body frame 2, even if the opening 29 c of the charger 29 is in an open state, as shown in FIG. The opening 29c of the charger 29 is closed by the contraction force. Therefore, invasion of combustible gas or dust into the charger 29 is suitably suppressed.
The shutter 71, the gear 72, the inner gear 72a, the movable gear 73, the movable gear support shaft 73a, the intermediate joint 74, and the spring 75 are the “interlocking member”, “first interlocking member”, and “second” in the present invention. Corresponds to “linkage member”.

3. Electrical Configuration Next, the electrical configuration according to the present invention of the printer 1 will be described with reference to FIG. FIG. 5 is a schematic block diagram of the electric circuit 60 mounted on the circuit board 52. The electric circuit 60 includes a CPU (an example of a control unit in the present invention) 61, and a ROM 62, a RAM 63, a timer 64, a motor driving unit 65, a charging voltage application unit 66, and a charging current detection circuit 67 connected to the CPU 61.

  The CPU 61 controls the entire printer 1 and is connected to the cover opening / closing sensor 2 b, the image forming unit 5, and the display device 21. When the opening of the front cover 2a is detected by the cover opening / closing sensor 2b, the CPU 61 drives the motor driving unit 65 and closes the opening 29c of the charger 29 by the shielding unit 70 in conjunction with the opening of the front cover 2a. . Therefore, even when the front cover 2a is opened and the combustible spray gas is sprayed onto the image forming unit 5 for cleaning the inside of the printer 1, for example, the image forming unit 5, the opening of the charger 29 It is suppressed suitably that combustible gas flows in into the inside from 29c. If the opening 29c is already closed by the shielding unit 70 when the front cover 2a is opened, the CPU 61 detects, for example, the closing of the opening 29c by a predetermined sensor and does not drive the motor driving unit 65. .

  The ROM 62 stores an operation program and the like for the entire apparatus, and the RAM 63 stores image data and the like used for print processing. The timer 64 counts a predetermined time related to the control of the printer 1, for example, a standby time.

  In addition, the motor driving unit 65 generates a driving signal for driving a motor such as the main motor M. The charging voltage application unit 66 generates a charging voltage to be applied to the charger 29, and the charging current detection circuit 67 detects the charging current that flows when the charging voltage is applied.

4). Control when Abnormal Discharge Occurs Next, control when abnormal discharge occurs when charging the photosensitive drum 27 by the charger 29 will be described with reference to FIG. FIG. 6 is a flowchart showing a process when an abnormal discharge occurs during the printing process of the printer 1. The process is executed by the CPU 61 according to a predetermined program. At the start of this process, the opening 29 c of the charger 29 is closed by the shutter 71 of the process cartridge 17.

  When a predetermined print instruction is input while the printer 1 is in a print standby state, this processing is started. Then, in step S110, the CPU 61 turns on the operation of the charging voltage application unit 66 to start charging the charger 29. That is, the charger 29 is activated.

  Next, in step S <b> 120, the CPU 61 waits for a predetermined time from the activation of the charger 29, for example, for 300 msec to 500 msec. In step S130, it is determined whether an abnormal discharge has occurred during standby. Note that whether or not abnormal discharge has occurred is normally determined based on the charging current detected by the charging current detection circuit 67, for example, because the charging current increases when abnormal discharge occurs.

  If it is determined in step S130 that an abnormal discharge has occurred during standby, the process proceeds to step S210. On the other hand, if it is determined in step S130 that no abnormal discharge has occurred during standby, in step S140, the CPU 61 starts driving the main motor M to open the opening 29c of the charger 29. To do. When the drive of the main motor M is started, the drive gear 51 rotates in a direction to open the closing of the opening 29c by the shutter 71, and the shutter 71 opens against the force of the spring 75. Next, in step S150, in order to perform the printing operation, the image forming unit 5 is warmed up and the printing operation is started. In step S160, it is determined whether or not an abnormal discharge has occurred during the printing operation. If it is determined in step S160 that an abnormal discharge has occurred during the printing operation, the process proceeds to step S210. That is, here, the main motor M is also used to open and close the shutter 71, and the shutter 71 is opened in conjunction with warm-up and printing operations after charging is turned on.

  In step S210, the CPU 61 stops the printing operation because an abnormal discharge has occurred. In step S220, it is determined whether the shutter 71 is currently open. If the shutter 71 is closed, that is, if an abnormal discharge occurs during the standby in step S120, the process proceeds to step S240. On the other hand, if it is determined in step S220 that the shutter 71 is currently open, in step S230, the main motor M is reversed for a predetermined time and the shutter 71 is closed. Then, the process proceeds to step S240.

  In step S240, the CPU 61 notifies the user of the occurrence of abnormal discharge, and causes the display device 21 to display a discharge error in order to prompt appropriate measures. In step S250, it is determined whether there is an error cancellation instruction. If there is an error cancel instruction, the process returns to step S110 to restart the printing process. When there is no error cancel instruction, the controller waits for an error cancel instruction.

  On the other hand, if it is determined in step S160 that an abnormal discharge has not occurred during the printing operation, the printing operation is continued, and it is determined in step S170 whether the printing operation has ended. If the printing operation has not been completed, the process returns to step S160. If the printing operation has been completed, the printing operation is stopped in step S180, and the print standby state is entered. In step S190, it is determined whether there is a next printing operation instruction. If there is a next print operation instruction, the process returns to step S110. If there is no next print operation instruction, the process waits until the next print operation instruction is issued.

5). Effects of the embodiment At the time of starting the charger 29, there is a possibility that the combustible spray gas sprayed for cleaning remains inside or around the main body frame 2 as compared with the charging operation after the starting. It can be said that it is expensive. Therefore, by closing the opening 29c of the charger 29 for a predetermined time from the start of the charger 29 (for example, 300 msec to 500 msec), there is a possibility that the combustible gas may enter the charger 29 or enter the charger 29. The amount can be reduced. As a result, even when an abnormal discharge of the charger 29 occurs within a predetermined time from the start of the charger 29, inconvenience caused by the contact between the abnormal discharge and the combustible gas, for example, the charging wire 29a is burnt. And the like, and the deterioration of the charger 29 can be suitably suppressed.

  If abnormal discharge is detected when the charger 29 is activated, the opening 29c of the charger 29 is kept closed, and the charger 29 is abnormal during printing after a predetermined time has elapsed since the activation. When discharge is detected, the opening 29c opened during printing is closed again. Therefore, inconvenience due to contact between the abnormal discharge of the charger 29 and the combustible gas can be reduced.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.

(1) Although the example in which the image forming unit is the process cartridge 17 that can be attached to and detached from the main body frame 2 has been shown, the image forming unit may be fixed to the main body frame 2.
(2) Although the example in which the shielding unit (shielding means) 70 is provided in the process cartridge (image forming unit) 17 has been shown, the present invention is not limited to this. The shielding unit 70 may be provided inside the main body frame 2, for example, in the scanner unit 16 or the like.

  (3) The example in which the shielding unit (shielding means) 70 is configured by an interlocking member (shutter 71, gear 72, movable gear 73, intermediate joint 74, spring 75, etc.) operating in conjunction with the main motor M is shown. However, the present invention is not limited to this. The shielding means may be any configuration as long as it can close the opening 29c of the charger at least for a predetermined time from the start of the charger. For example, the opening 29c may be opened and closed by electromagnetic shielding means controlled by the CPU 61.

1 is a schematic side sectional view showing an internal configuration of a laser printer according to Embodiment 1 of the present invention. Illustration of the shielding unit when the process cartridge is installed Explanatory drawing of shielding unit when driving gear is driven Illustration of the shielding unit immediately after removal of the process cartridge Schematic block diagram of the printer electrical circuit Flow chart showing processing when abnormal discharge occurs

Explanation of symbols

1. Laser printer (image forming device)
2a ... Front cover (cover)
3 ... paper (recording medium)
17 ... Process cartridge (image forming section)
27 ... Photosensitive drum (photoconductor)
29 ... Scorotron charger (charger)
29c ... Opening 61 of the charger 61 ... CPU (control means)
70 ... Shielding unit (shielding means)
71 ... Shutter (shielding means, interlocking member)
72 ... Gear (shielding means, interlocking member)
72a ... inner gear (shielding means, interlocking member)
73 ... Movable gear (shielding means, interlocking member)
73a ... movable gear support shaft (shielding means, interlocking member)
74 ... Intermediate joint (shielding means, interlocking member)
75 ... Spring (shielding means, interlocking member)
M ... Main motor (drive motor)

Claims (9)

A charging device including a photosensitive member and an opening through which air can flow and a charging wire, the charging device charging the photosensitive member by discharging from the charging wire, and being carried by the charged photosensitive member An image forming unit that forms an image on a recording medium using the developed developer image;
An image forming apparatus comprising: a shielding unit that closes the opening of the charger at least for a predetermined time from the start of the charger. The image forming apparatus according to claim 1.
The image forming apparatus includes an apparatus main body,
The image forming unit includes the shielding unit and is detachable from the apparatus main body.
The shielding means closes the opening of the charger when the image formation is mounted on the apparatus main body. The image forming apparatus according to claim 2.
The shielding means includes a first interlocking member that closes the opening in conjunction with attachment / detachment of the image forming unit to / from the apparatus main body. The image forming apparatus according to any one of claims 1 to 3,
Further comprising detection means for detecting abnormal discharge of the charger,
The shielding means includes
If the abnormal discharge of the charger is detected within the predetermined time, the opening of the charger is kept closed thereafter,
When the abnormal discharge of the charger is not detected within the predetermined time, the opening of the charger is released. The image forming apparatus according to claim 4.
The shielding means includes
If the abnormal discharge of the charger is detected after the opening of the opening is released, the opening of the charger is closed again. In the image forming apparatus according to any one of claims 1 to 5,
A drive motor for driving the image forming unit;
The shielding means includes a second interlocking member for closing and opening the opening in conjunction with the drive motor. In the image forming apparatus according to any one of claims 1 to 6,
An openable / closable cover that allows the image forming unit to be accessed from the outside;
Control means for closing the opening of the charger by the shielding means in conjunction with opening of the cover;
Is further provided. A process cartridge that is detachably attached to an image forming apparatus,
A photoreceptor for transferring the carried developer image to a recording medium;
A charger having an opening through which air can flow and a charging wire, and charging the photosensitive member by discharging from the charging wire;
The shielding means for closing and opening the opening of the charger according to an operation from the image forming apparatus in a state where the process cartridge is mounted on the image forming apparatus;
The shielding unit closes the opening of the charger at least when the process cartridge is attached to and detached from the image forming apparatus. The process cartridge according to claim 8, wherein
The shielding means is interlocked to close and open the opening in conjunction with a drive motor of the image forming apparatus that drives the process cartridge in a state where the process cartridge is mounted on the image forming apparatus. It has a member.

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