JP2014197114A - Image forming apparatus - Google Patents

Abstract

An object of the present invention is to provide an image forming apparatus in which variation in surface potential of a photosensitive drum is suppressed. A laser printer according to the present invention charges a photosensitive drum, a housing that rotatably supports the photosensitive drum, a motor configured to drive the photosensitive drum, and the photosensitive drum. And a control device 100 configured to control the motor 200 and the charger 62. The control device 100 is configured to turn off the charger 62 after turning off the motor 200. [Selection] Figure 1

Description

  The present invention relates to an image forming apparatus including a photosensitive drum and a charger for charging the photosensitive drum.

  2. Description of the Related Art Conventionally, there is known an image forming apparatus including a photosensitive drum that is rotationally driven by a driving source and a charger for charging the photosensitive drum (see Patent Document 1). In this image forming apparatus, the charger is turned off at the same time as the drive source is turned off.

JP 2005-208147 A

  By the way, even if the drive source is turned OFF, the photosensitive drum does not stop immediately but rotates for a while due to inertia of the drive source. For this reason, in the configuration of Patent Document 1, after the charger is turned off, the photosensitive drum rotates by inertia, and a portion that is not charged by the charger is formed on the surface of the photosensitive drum. This portion is in an unstable state, causing a problem that the surface potential of the photosensitive drum varies.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that suppresses variations in surface potential of a photosensitive drum.

In order to achieve the above-described object, an image forming apparatus of the present invention includes a photosensitive drum, a casing that rotatably supports the photosensitive drum, a driving source configured to drive the photosensitive drum, and a charging of the photosensitive drum. And a controller configured to control the drive source and the charger.
The control device is configured to turn off the charger after turning off the drive source.

  When the surface potential of the photosensitive drum varies, a potential difference is likely to occur in each part of the surface, and thus the developer easily moves from the developing roller to the photosensitive drum. For this reason, the surface of the photosensitive drum is soiled by a developer or the like, and the soiled portion passes through the contact position with the transfer roller, so that the transfer roller is soiled, and consequently, the back of the paper is easily stained during printing.

  However, according to the above-described configuration, since the charger is turned off after the drive source is turned off, even if the photosensitive drum rotates due to the inertia of the drive source, the rotated portion is easily charged. Therefore, as compared with the configuration in which the driving source and the charger are turned off simultaneously, the surface potential variation of the photosensitive drum can be suppressed, and the backside contamination of the paper during printing can be reduced.

  In the above-described configuration, the control device can be configured to control the charger to be turned off after the operation of the drive source is stopped.

  According to such a configuration, since the charger is turned off after the operation of the drive source is stopped and the rotation of the photosensitive drum is stopped, variations in the surface potential of the photosensitive drum can be further suppressed.

  Further, in the configuration in which the control device turns off the charger after the operation of the drive source is stopped, the control device is based on an electric signal obtained from the drive source after stopping the supply of power to the drive source. It may be controlled to turn off the charger.

  The above-described image forming apparatus can be configured to include a transfer roller configured to rotate following the photosensitive drum.

  In the configuration in which the transfer roller is driven to rotate by the photosensitive drum, it is necessary to increase the contact pressure between the photosensitive drum and the transfer roller because the transfer roller rotates due to the frictional force generated between the transfer roller and the photosensitive drum. When the contact pressure between the photosensitive drum and the transfer roller is increased, when the surface potential of the photosensitive drum varies and the surface of the photosensitive drum becomes dirty, the dirt is likely to adhere to the transfer roller. However, with the configuration described above, variations in the surface potential of the photosensitive drum can be suppressed, so that even if the contact pressure is increased, the backside of the paper during printing is less likely to occur.

  In the above-described configuration, the housing can be detachably attached to the main body of the image forming apparatus, and the transfer roller can be provided in the housing and have a diameter smaller than that of the photosensitive drum.

  As the diameter of the transfer roller decreases, the contact pressure of the transfer roller to the photosensitive drum increases. For this reason, when the surface potential of the photosensitive drum varies due to variations in the surface potential of the photosensitive drum, the contamination easily adheres to the transfer roller. However, with the above-described configuration, variations in the surface potential of the photosensitive drum can be suppressed, so that even if the contact pressure increases, the problem of paper back contamination during printing is less likely to occur.

  In the above configuration, the charger can be configured not to contact the photosensitive drum.

  When the contact-type charger is provided, the surface of the photosensitive drum is electrically grounded through the charger, so that variations in surface potential can be suppressed. On the other hand, if the configuration includes a non-contact type charger, since the charger and the photosensitive drum are separated from each other, variation in the surface potential of the photosensitive drum is effectively suppressed as in the case of the contact type charger. I can't. However, with the above-described configuration, variations in the surface potential of the photosensitive drum can be suppressed, so that even with a configuration including a non-contact type charger, the problem of paper back contamination during printing is less likely to occur.

  When the image forming apparatus described above has a developing roller that is pressed against the photosensitive drum and further includes a developing cartridge that is detachable from the housing, the developing roller is pressed against the photosensitive drum from below the photosensitive drum. It can be set as a structure.

  In a configuration in which the developing roller is pressed against the photosensitive drum from below the photosensitive drum, when the developing cartridge is pressed against the housing, the force by which the developing roller presses the photosensitive drum from below is partially offset by the weight of the developing roller. . For this reason, when the supply of power to the drive source is stopped, the photosensitive drum easily rotates excessively due to the inertia of the drive source. However, with the above-described configuration, variations in the surface potential of the photosensitive drum can be suppressed, so that even if the photosensitive drum rotates excessively, the problem of the back side of the paper during printing is less likely to occur.

  According to the present invention, variations in the surface potential of the photosensitive drum can be suppressed.

1 is a cross-sectional view of a laser printer according to an embodiment of the present invention. It is sectional drawing which shows a process cartridge. It is a flowchart which shows operation | movement of a control apparatus. It is the time chart (a) which concerns on operation | movement of each parameter which concerns on embodiment of this invention, and the time chart (b) which concerns on operation | movement of the charger which concerns on a conventional structure. FIG. 7A shows a state where the power supply to the motor is stopped around the photosensitive drum of the conventional configuration, FIG. 9B shows a state where the motor operation stops, and the motor operates again so that the non-charged area becomes the developing roller. (C) when passing through the contact position, and (d) when passing through the contact position with the transfer roller. FIG. 4A is a diagram when power supply to the motor is stopped around the photosensitive drum, and FIG. 4B is a diagram when the motor operation is stopped. It is a flowchart which shows operation | movement of the control apparatus which concerns on a modification.

  Next, an embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In the following description, first, the overall configuration of the laser printer 1 as an example of the image forming apparatus according to the embodiment of the present invention will be described, and then the characteristic part of the present invention will be described in detail.

  In the following description, the direction will be described with reference to the user when using the laser printer 1. That is, in FIG. 1, the left side toward the paper surface is “front side”, the right side toward the paper surface is “rear side”, the rear side toward the paper surface is “left side”, and the front side toward the paper surface is “right side”. To do. In addition, the vertical direction toward the page is defined as the “vertical direction”.

<Schematic configuration of laser printer>
As shown in FIG. 1, the laser printer 1 includes an apparatus main body 2 as an example of a main body, a feeder unit 3 for feeding paper P, a scanner unit 4, and a process for transferring a toner image onto the paper P. The apparatus mainly includes a cartridge 5, a fixing device 8 that thermally fixes a toner image on the paper P, a control device 100, and a motor 200 as an example of a drive source that drives a photosensitive drum 61 and the like described later. The control device 100 will be described later.

  The apparatus main body 2 includes a top cover 22 and a front cover 23. Further, the apparatus main body 2 has an opening 21A for attaching / detaching a process cartridge 5 (described later) at the upper part thereof, and an insertion port 21B for inserting the paper P at the front part thereof.

  The front cover 23 is provided with a rotating shaft 23A of the front cover 23 at a lower portion on the front side of the apparatus main body 2, and rotates forward about the rotating shaft 23A. In FIG. 1, the front cover 23 indicated by a two-dot chain line is in a state where the front side of the apparatus main body 2 is closed, and the front cover 23 indicated by a solid line is in a state where the front side of the apparatus main body 2 is opened.

The feeder unit 3 is located in the lower part of the apparatus main body 2 and includes a paper feed tray 31 on which the paper P is placed and a paper feed mechanism 32 that feeds the paper P on the paper feed tray 31.
The paper feed tray 31 includes a mounting table 31 </ b> A disposed at the lower part of the apparatus main body 2 and the above-described front cover 23.

  The paper feed mechanism 32 mainly includes a paper feed roller 32A, a separation roller 32B, and a separation pad 32C. The paper feed roller 32A is arranged on the upstream side of the separation roller 32B in the transport direction of the paper P and on the rear end of the placement table 31A. The separation roller 32B is disposed to face the separation pad 32C.

  In the feeder unit 3, after the front cover 23 is tilted forward to form the paper feed tray 31, the paper P is placed on the paper feed tray 31. Then, when the paper feed roller 32A comes into contact with the paper P placed on the paper feed tray 31 and rotates, the paper P placed on the paper feed tray 31 is sent to the separation roller 32B and sent out. The sheets P are separated one by one between the separation roller 32 </ b> B and the separation pad 32 </ b> C and conveyed toward the process cartridge 5.

  The scanner unit 4 is provided on the front side in the apparatus main body 2 and includes a laser light emitting unit, a polygon mirror, a lens, a reflecting mirror, and the like (not shown). In this scanner unit 4, a laser beam is irradiated on the surface of a photosensitive drum 61 described later by high-speed scanning.

  The process cartridge 5 is located near the center of the rear side of the apparatus main body 2 and is provided above the paper feed mechanism 32. The process cartridge 5 includes a drum cartridge 6 and a developing cartridge 7.

  The drum cartridge 6 is configured to be detachable from the apparatus main body 2 through the opening 21 </ b> A toward the upper front side. As illustrated in FIG. 2, the drum cartridge 6 and a photosensitive drum 61 provided in the casing 69 are provided. A charger 62 and a transfer roller 63 are provided. The drum cartridge 6 will be described later.

  The developing cartridge 7 includes a developing frame 79, a developing roller 71, a supply roller 72, and a layer thickness regulating blade 73, and is detachable from the housing 69 of the drum cartridge 6.

The developing roller 71 is a member configured to carry toner on the peripheral surface, and is rotatably provided on the developing frame 79. The developing roller 71 is disposed so as to be pressed against the photosensitive drum 61 from an obliquely lower front side of the photosensitive drum 61.
The supply roller 72 is a member configured to supply the toner adhered to the peripheral surface thereof to the developing roller 71, and is disposed obliquely below the developing roller 71.

  The layer thickness regulating blade 73 is a member configured to regulate the layer thickness of the toner on the developing roller 71, and is formed of metal. The base end of the layer thickness regulating blade 73 is fixed above the developing roller 71, and the front end protruding substantially downward from the base end is in contact with the front peripheral surface of the developing roller 71.

  In the developing cartridge 7, the toner accommodated in the toner accommodating chamber 74 formed in the developing frame 79 is stirred by the agitator 75 and then supplied to the developing roller 71 by the supply roller 72. At this time, the toner is positively frictionally charged between the supply roller 72 and the developing roller 71. The toner supplied onto the developing roller 71 enters between the layer thickness regulating blade 73 and the developing roller 71 as the developing roller 71 rotates, and is further developed as a thin layer having a constant thickness while being frictionally charged. It is carried on a roller 71.

  In the drum cartridge 6, the surface of the rotating photosensitive drum 61 is uniformly charged by the charger 62 and then exposed by high-speed scanning of the laser beam from the scanner unit 4. As a result, the potential of the exposed portion is lowered, and an electrostatic latent image based on the image data is formed on the surface of the photosensitive drum 61.

  Next, toner from the developing cartridge 7 is supplied to the electrostatic latent image, and a toner image is formed on the surface of the photosensitive drum 61. Thereafter, the paper P is conveyed between the photosensitive drum 61 and the transfer roller 63, whereby the toner image carried on the surface of the photosensitive drum 61 is transferred onto the paper P.

  Returning to FIG. 1, the fixing device 8 is located at the upper rear of the apparatus main body 2 and is disposed above the process cartridge 5. The fixing device 8 mainly includes a heating roller 81 and a pressure roller 82.

The heating roller 81 is a member that heats the paper P, and a heat source (not shown) such as a halogen lamp is provided therein.
The pressure roller 82 is a member that sandwiches and transports the paper P with the heating roller 81, and is provided obliquely above the heating roller 81.

  In the fixing device 8 configured as described above, the toner transferred onto the paper P is thermally fixed while the paper P passes between the heating roller 81 and the pressure roller 82. The paper P thermally fixed by the fixing device 8 is conveyed to a discharge roller 9 disposed on the downstream side of the fixing device 8, and is discharged from the discharge roller 9 onto a discharge tray 24.

<Drum cartridge configuration>
Next, the drum cartridge 6 will be described.
The photosensitive drum 61 is formed with a photosensitive layer on the surface of a cylindrical drum body having conductivity, and is rotatably supported by a housing 69.

  In this embodiment, the developing cartridge 7 is pressed against the drum cartridge 6 from below, that is, the photosensitive drum 61 is pressed against the developing roller 71 from below. Therefore, the force with which the developing roller 71 presses the photosensitive drum 61 from below is partially offset by the weight of the developing roller 71.

  The charger 62 is a member that uniformly charges the surface of the photosensitive drum 61, and is disposed to face the photosensitive drum 61 substantially above the photosensitive drum 61. Note that the charger 62 in the present embodiment has a non-contact configuration that does not contact the photosensitive drum 61.

  The transfer roller 63 is configured to come into contact with the rear surface of the photosensitive drum 61 and to rotate following the photosensitive drum 61. In this embodiment, the transfer roller 63 is pressed against the photosensitive drum 61 so that the transfer roller 63 is driven to rotate by the photosensitive drum 61.

  The transfer roller 63 has a smaller diameter than the photosensitive drum 61. With this configuration, the contact area between the photosensitive drum 61 and the transfer roller 63 is reduced, and the contact pressure between the photosensitive drum 61 and the transfer roller 63 is increased.

<Control device>
Next, the control device 100 will be described.
The control device 100 includes, for example, a CPU, a ROM, a RAM, and the like, and is configured to perform ON / OFF control of the charger 62 and the motor 200 according to a program prepared in advance. Note that the ON state of the charger 62 here refers to starting the application of the charging bias to the charger 62, and the OFF state of the charger 62 refers to stopping the application of the charging bias to the charger 62. Say. Moreover, ON of the motor 200 means supplying electric power to the motor 200, and OFF of the motor 200 means stopping supplying electric power to the motor 200.

  The control device 100 controls the motor 200 to be turned off, that is, the charger 62 is turned off after the supply of power to the motor 200 is stopped. More specifically, the control device 100 controls the charger 62 to be turned off after a predetermined time T0 has elapsed since the supply of power to the motor 200 is stopped. The predetermined time T0 is longer than the stop time T1 from when the supply of power to the motor 200 is stopped until the operation of the motor 200 is stopped, and can be set as appropriate through experiments, simulations, and the like.

The control device 100 configured as described above executes control according to the flowchart shown in FIG.
As shown in FIG. 3, the control device 100 determines whether or not there is a print command (S1). In step S1, if the control device 100 determines that there is no print command (S1: No), this control is terminated, and if it is determined that there is a print command (S1: Yes), the motor 200 is turned on. At the same time, the charger 62 is turned on (S3). Thereafter, the control device 100 executes print control (S4).

  After step S4, the control device 100 determines whether or not printing has been completed for all the printed sheets instructed by the print command (S5). If the printing is not completed (S5: No), the control device 100 repeats the process of step S4. If the printing is completed (S5: Yes), the power supply to the motor 200 is stopped (S6).

  After step S6, the control device 100 determines whether or not a predetermined time T0 has elapsed (S7). When the predetermined time T0 has not elapsed (S7: No), the control device 100 repeats the process of step S7, and when the predetermined time T0 has elapsed (S7: Yes), the charger 62 is turned off (S8). ), The print control is terminated.

The effects of the control device 100 configured as described above will be described.
As shown in FIG. 4A, the control device 100 turns on the motor 62 and turns on the charger 62 (time t1). Here, the rotation speed of the motor 200 becomes a predetermined rotation speed V after a predetermined short time has elapsed after the motor 200 is turned on (time t2).

  When the printing is completed, the control device 100 stops supplying power to the motor 200 (time t3), and turns off the charger 62 after a predetermined time T0 (time t5).

  The motor 200 rotates slightly due to inertia after the supply of power is stopped. Specifically, the motor 200 gradually decreases from the predetermined rotation speed V after the supply of power is stopped (time t3). When the stop time T1 elapses, the rotation speed of the motor 200 becomes zero and the operation of the motor 200 stops (time t4).

  Incidentally, as shown in FIG. 4B, the control device in the conventional configuration is configured to turn off the charger 62 at the same time as the supply of power to the motor 200 is stopped. In this configuration, when the charger 62 is turned off (see FIG. 5A), the motor 200 rotates slightly due to inertia, and thus the photosensitive drum 61 rotates for a while (see FIG. 5B). At this time, since the charger 62 is OFF, the surface of the photosensitive drum 61 that has passed the position facing the charger 62 is not charged, and an uncharged region X is formed. In the uncharged region X, the surface of the photosensitive drum 61 is not charged and the potential becomes unstable, so that the surface potential varies.

  Thereafter, the motor 200 is turned on again, the photosensitive drum 61 is rotated, and the uncharged region X passes through the contact position A with the developing roller 71. At this time, since the surface potential of the photosensitive drum 61 varies in the uncharged region X, a potential difference is generated between the portions on the surface of the photosensitive drum 61. Therefore, the toner T easily moves from the developing roller 71 to the uncharged area X, and the toner T adheres to the uncharged area X (see FIG. 5C).

  When the uncharged region X passes through the contact position B with the transfer roller 63, the toner T in the uncharged region X adheres to the transfer roller 63 (see FIG. 5D). In particular, in this embodiment, since the contact pressure between the photosensitive drum 61 and the transfer roller 63 is high, the toner T in the uncharged region X is likely to adhere to the transfer roller 63. If the toner T adheres to the transfer roller 63 and the transfer roller 63 becomes dirty, when the paper P passes the contact position B during printing, the transfer roller 63 adheres to the paper P and stains on the back side occur. It becomes easy.

  However, in the present embodiment, since the charger 62 is turned off after the predetermined time T0 has elapsed even if the power supply to the motor 200 is stopped, the photosensitive drum 61 rotates even if it rotates due to the inertia of the motor 200. The portion is easily charged (see FIGS. 6A and 6B). Therefore, as compared with the conventional configuration, variations in the surface potential of the photosensitive drum 61 can be suppressed, and the back stain of the paper P during printing can be reduced.

  In this embodiment, since the operation of the motor 200 is stopped and the rotation of the photosensitive drum 61 is stopped, the charger 62 is turned off. Therefore, even if the photosensitive drum 61 is rotated due to inertia of the motor 200, an uncharged region remains. It is not formed on the surface of the photosensitive drum 61 (see FIG. 6B). That is, since the variation in the surface potential of the photosensitive drum 61 can be further suppressed, even if the photosensitive drum 61 is rotated again thereafter, the transfer roller 63 is not easily soiled, and as a result, the backside of the paper P during printing is stained. Further reduction can be achieved.

  In this embodiment, since the contact pressure between the photosensitive drum 61 and the transfer roller 63 is increased, when the surface potential of the photosensitive drum 61 varies and the surface of the photosensitive drum 61 becomes dirty, the dirt is transferred to the transfer roller. The structure is easy to adhere to 63. However, according to the present embodiment, variation in the surface potential of the photosensitive drum 61 can be suppressed, so that even if the contact pressure is high, the problem of the back stain of the paper P during printing can be made difficult to occur.

  Here, when the contact-type charger is provided, variation in the surface potential of the photosensitive drum 61 can be suppressed by electrically grounding the charger, but a non-contact-type charger 62 is provided. With this configuration, it is not possible to effectively suppress variations in the surface potential of the photosensitive drum 61 via the charger 62. However, in the present embodiment, since the variation in the surface potential of the photosensitive drum 61 can be suppressed, even with the configuration provided with the non-contact type charger 62, the problem of the back side of the paper P during printing occurs. Can be difficult.

  In this embodiment, the force with which the developing roller 71 presses the photosensitive drum 61 is partially offset by the weight of the developing roller 71, so that when the supply of power to the motor 200 is stopped, the photosensitive drum 61 is moved to the motor 200. Due to its inertia, it is easy to rotate. However, according to the present embodiment, variations in the surface potential of the photosensitive drum 61 can be suppressed, so that even if the photosensitive drum 61 rotates excessively, it is possible to make it difficult to cause a problem of the back side of the paper P during printing.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. About a concrete structure, it can change suitably in the range which does not deviate from the meaning of this invention. In the following description, components that are substantially the same as those in the above embodiment are given the same reference numerals and description thereof is omitted.

  In the embodiment, the control is performed to turn off the charger 62 after a predetermined time T0 has elapsed since the control device 100 stopped supplying power to the motor 200, but the present invention is not limited to this. For example, the controller 62 may be controlled to turn off the charger 62 based on an electrical signal obtained from the motor 200 after the supply of power to the motor 200 is stopped.

  Specifically, the control device 100 detects the counter electromotive force of the motor 200 and controls the charger 62 to be turned off when the counter electromotive force becomes smaller than a predetermined value I. The predetermined value I is a value of the back electromotive force when the operation of the motor 200 is substantially stopped, and can be set as appropriate by experiment, simulation, or the like. The back electromotive force of the motor 200 can be detected by connecting a resistor or the like to the motor 200 and detecting the current flowing through the resistor with an ammeter or the like.

The control device 100 configured as described above executes control according to the flowchart shown in FIG.
The process up to step S6 is the same as in FIG. 6, and the control device 100 determines whether or not the back electromotive force of the motor 200 is smaller than the predetermined value I (S9). When the back electromotive force of the motor 200 is greater than or equal to the predetermined value I (S9: No), the control device 100 repeats the process of step S9, and when the back electromotive force of the motor 200 is smaller than the predetermined value I (S9: Yes), The charger 62 is turned off (S8). Thereafter, the print control is terminated.

  In the embodiment, the control device 100 controls the charger 62 to be turned off after the operation of the motor 200 is stopped. However, if the power supply to the motor is stopped, the charger 100 is turned off. You may set the timing to do arbitrarily.

  In the above-described embodiment, the transfer roller 63 is configured to rotate following the photosensitive drum 61. However, the present invention is not limited to this, and the transfer roller may be configured to rotate by driving a motor or the like.

  In the embodiment, the transfer roller 63 has a smaller diameter than the photosensitive drum 61. However, the present invention is not limited to this, and for example, the transfer roller may have the same diameter as the photosensitive drum. .

  In the above-described embodiment, the transfer roller 63 is provided in the housing 69. However, the present invention is not limited to this. For example, the transfer roller may be provided in the apparatus main body.

  In the above-described embodiment, the developing cartridge 7 and the drum cartridge 6 are configured separately. However, the present invention is not limited to this, and the casing may be a casing that supports both the photosensitive drum and the developing roller. .

  In the embodiment, the developing roller 71 is disposed below the photosensitive drum 61. However, the present invention is not limited to this, and the developing roller 71 may not be disposed below the photosensitive drum.

  In each of the above-described embodiments, the laser printer is exemplified as the image forming apparatus. However, the present invention is not limited to this, and may be another image forming apparatus such as a color printer or a multifunction peripheral.

  In each of the embodiments, the motor 400 as an example of the drive source is illustrated, but the present invention is not limited to this. For example, a transmission gear that transmits power to the photosensitive drum may be used as the drive source. In this configuration, the transmission gear can be configured such that the driving force from the motor is transmitted via, for example, a gear mechanism that can switch between transmission and non-transmission of power. In this case, the control device may control to turn off the transmission gear by switching the gear mechanism from the power transmission state to the non-transmission state, and then turn off the charger. Even if it is such a structure, the effect similar to the said embodiment can be acquired.

DESCRIPTION OF SYMBOLS 1 Laser printer 6 Drum cartridge 7 Developing cartridge 61 Photosensitive drum 62 Charger 63 Transfer roller 69 Case 71 Developing roller 100 Control device 200 Motor

Claims (7)

A photosensitive drum;
A housing that rotatably supports the photosensitive drum;
A drive source configured to drive the photosensitive drum;
A charger configured to charge the photosensitive drum;
A controller configured to control the drive source and the charger;
The image forming apparatus, wherein the control device is configured to turn off the charger after turning off the drive source.   The image forming apparatus according to claim 1, wherein the control device controls the charger to be turned off after the operation of the drive source is stopped.   3. The control device according to claim 2, wherein the controller controls the charger to be turned off based on an electric signal obtained from the drive source after stopping the supply of power to the drive source. 4. Image forming apparatus.   The image forming apparatus according to claim 1, further comprising a transfer roller configured to rotate following the photosensitive drum. The housing is configured to be detachable from the main body of the image forming apparatus,
The image forming apparatus according to claim 4, wherein the transfer roller is provided in the housing and has a diameter smaller than that of the photosensitive drum.   The image forming apparatus according to claim 1, wherein the charger is not in contact with the photosensitive drum. A developing roller that is pressed against the photosensitive drum and further configured to be detachable from the housing;
The image forming apparatus according to claim 1, wherein the developing roller is pressed against the photosensitive drum from below the photosensitive drum.

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