JP2010128152A - Image forming device and method of controlling the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device extending life of a discharge member performing corona discharge. <P>SOLUTION: A laser printer 1 includes: a photosensitive drum 61; a charger 62 having a charging wire 62A performing corona discharge and charging the photosensitive drum 61; an exposing unit 4 exposing the charged photosensitive drum 61 to light and forming an electrostatic latent image on the photosensitive drum; a developing cartridge 7 having a developing roller 71 that carries thereon developer, and developing the electrostatic latent image formed on the photosensitive drum 61; a transfer roller 63 acting on the photosensitive drum 61; and a controller 10 controlling voltage to be applied to the charging wire 62A and the transfer roller 63. The controller 10 can carry out a mode in which first voltage is applied to the charging wire 62A, and a mode in which second voltage having the same polarity as the first voltage and having an absolute value greater than surface potential of the developing roller 71 is applied to the transfer roller 63 without applying voltage to the charging wire 62A. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that charges a surface of a photoconductor, exposes it to form an electrostatic latent image, supplies a developer to the electrostatic latent image, and develops the image forming apparatus, and a control method thereof.

  In general, in an image forming apparatus such as a laser printer, the surface of a photosensitive drum is charged and then exposed to form an electrostatic latent image, and toner is supplied to the electrostatic latent image for development, thereby transferring the image onto a sheet. An image (toner image) is formed. As such an image forming apparatus, there is known an image forming apparatus that includes a charger that charges the surface of a photosensitive drum with a discharge member such as a charging wire that performs corona discharge (see, for example, Patent Document 1).

JP 2006-39139 A

  By the way, since the surface potential of the uncharged photosensitive drum has an absolute value smaller than the surface potential of the developing roller carrying the charged toner, the photosensitive drum is charged during, for example, a warm-up operation or a cleaning operation. When rotated without being applied, toner adheres to the surface and the photosensitive drum is soiled with toner. In order to suppress such a phenomenon, normally, when rotating the photosensitive drum, the photosensitive drum is charged by applying a voltage to a charger (discharge member), and the surface potential is made higher than the surface potential of the developing roller. The absolute value is increased.

  In the conventional image forming apparatus, when charging the photosensitive drum, the same voltage as that applied during the developing operation is applied to the discharge member. Since the voltage applied during the developing operation has a relatively large absolute value, when such a voltage (current) is always applied when the photosensitive drum is rotated, foreign matter (silica or the like) on the discharge member depends on the energization time. ) Is promoted. If a certain amount or more of foreign matter adheres to the discharge member, corona discharge cannot be performed normally, and the life of the discharge member is shortened.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of extending the life of a discharge member that performs corona discharge and a control method thereof.

  In order to achieve the above-described object, an image forming apparatus of the present invention includes a photosensitive member and a discharge member that performs corona discharge. The charger that charges the photosensitive member and the charged photosensitive member are exposed and statically exposed. An exposure device that forms an electrostatic latent image; a developer carrier that carries a developer; a developing device that develops an electrostatic latent image formed on the photoconductor; and a first means that acts on the photoconductor And a control device for controlling a voltage applied to the discharge member and the first means, wherein the control device applies a first voltage to the discharge member; A mode in which a second voltage having the same polarity as the first voltage and having a larger absolute value than the surface potential of the developer carrier is applied to the first means without applying a voltage. And are configured to be executable.

  Further, the present invention that achieves the above-described object has a photosensitive member and a discharge member that performs corona discharge, and a charger for charging the photosensitive member, and exposing the charged photosensitive member to form an electrostatic latent image. An exposure device for forming, a developer carrying member for carrying a developer, a developing device for developing an electrostatic latent image formed on the photoconductor, and a first means acting on the photoconductor. A method for controlling an image forming apparatus, comprising: applying a first voltage to the discharge member; and applying the first voltage to the first means without applying a voltage to the discharge member. And applying a second voltage having the same polarity as the voltage of the developer and having an absolute value larger than the surface potential of the developer carrying member.

  According to the present invention, the second voltage is applied to the mode in which the first voltage is applied to the discharge member and the first means that acts on the photosensitive member without applying the voltage to the discharge member. By executing the mode in which the voltage is applied, the energization time of the discharge member can be shortened compared to the conventional case. As a result, adhesion of foreign matter to the discharge member can be suppressed, so that the life of the discharge member can be extended.

  Since the second voltage has the same polarity as the first voltage and has an absolute value larger than the surface potential of the developer carrying member, the second voltage is photosensitive by the action of the first means to which the second voltage is applied. The surface of the body can be charged so that the absolute value is larger than the surface potential of the developer carrying member. As a result, it is possible to prevent the developer from adhering to the photoreceptor and causing the photoreceptor to become dirty with the developer.

  According to the present invention, the mode for applying the first voltage to the discharge member and the mode for applying the second voltage to the first means without applying the voltage to the discharge member are executed. By doing so, the energization time of the discharge member can be shortened, so that the adhesion of foreign matter to the discharge member can be suppressed, and the life of the discharge member can be extended.

<Configuration of laser printer>
Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. In the drawings to be referred to, FIG. 1 is a cross-sectional view showing an overall configuration of a laser printer as an example of an image forming apparatus.

  Here, in the following description, the direction will be described with reference to the user who uses the laser printer. That is, in FIG. 1, the right side toward the paper surface is the “front” side, the left side toward the paper surface is the “rear” side, the back side toward the paper surface is the “right” side, and the front side toward the paper surface is “left”. ”Side. In addition, the vertical direction toward the page is the “vertical” direction.

  As shown in FIG. 1, the laser printer 1 includes a main body housing 2 in which a paper sheet 3 as an example of a recording sheet is fed, an exposure device 4, and a toner image (developer) on the paper P. Image forming), a fixing device 8 for thermally fixing the toner image on the paper P, a main motor 9, and a control device 10 for controlling the operation of the laser printer 1 are mainly provided.

  The paper feed unit 3 is disposed in the lower part of the main body housing 2 and is detachably attached to the main body housing 2, and a swingable paper provided in the paper feed tray 31. It mainly includes a pressing plate 32, a paper feed roller 33, a paper feed pad 34, paper dust removing rollers 35 and 36, and a registration roller 37 provided above the front side of the paper feed tray 31.

  In the paper feed unit 3, the paper P in the paper feed tray 31 is brought close to the paper feed roller 33 by the paper pressing plate 32, sent out by the paper feed roller 33 and the paper feed pad 34, and the paper dust removing rollers 35, 36. Then, after passing through the registration roller 37, each sheet is conveyed to the process cartridge 5 one by one.

  The exposure apparatus 4 is arranged at the upper part in the main body housing 2 and mainly includes a laser light emitting unit (not shown), a polygon mirror 41 that is rotationally driven, lenses 42 and 43, and reflecting mirrors 44, 45, and 46. In preparation. In the exposure apparatus 4, the laser light (see the chain line) based on the image data emitted from the laser light emitting part is reflected or passed through the polygon mirror 41, the lens 42, the reflecting mirrors 44 and 45, the lens 43 and the reflecting mirror 46 in this order. The surface of the photosensitive drum 61 is scanned at high speed.

  The process cartridge 5 is disposed below the exposure device 4 and is detachably mounted on the main body housing 2 through an opening formed when the front cover 21 provided on the front side of the main body housing 2 is opened. It has become. The process cartridge 5 includes a drum cartridge 6 and a developing cartridge 7 as an example of a developing device.

  The drum cartridge 6 includes a photosensitive drum 61 as an example of a photosensitive member, a charger 62, and a transfer roller 63 (transfer member) as an example of a first unit in a hollow drum case 60 that forms an outer frame. A cleaning brush 64 as an example of a cleaning member is mainly provided.

  The photosensitive drum 61 is rotatably supported by the drum case 60. In the photosensitive drum 61, a cylindrical drum body having conductivity is grounded, and a chargeable photosensitive layer is formed on the surface portion (outer peripheral surface) of the drum body.

  The charger 62 is disposed above the photosensitive drum 61 so as to face the photosensitive drum 61 at a predetermined interval so as not to contact the photosensitive drum 61. The charger 62 is stretched along the axial direction of the photosensitive drum 61, and generates a corona discharge by applying a charging bias (voltage) to uniformly charge the surface of the photosensitive drum 61. As an example, the charging wire 62A is mainly provided. In addition, the presence or absence of a grid electrode is arbitrary.

  The transfer roller 63 is rotatably supported by the drum case 60 and is disposed below the photosensitive drum 61 so as to contact the photosensitive drum 61. The transfer roller 63 is configured to transfer a toner image formed on the photosensitive drum 61 onto the paper P by applying a transfer bias VT (see FIG. 3) during transfer.

  The cleaning brush 64 is arranged behind the photosensitive drum 61 so that the tip thereof is in contact with the photosensitive drum 61. The cleaning brush 64 collects toner adhered to the photosensitive drum 61 (toner remaining without being transferred), paper dust, and the like by applying a cleaning bias during a cleaning operation or development. It is configured.

  The developing cartridge 7 is configured to be detachably attached to the drum cartridge 6 (drum case 60). The developing cartridge 7 mainly includes a developing roller 71 as an example of a developer carrier, a supply roller 72, and a layer thickness regulating blade 73 in a developing case 70, and has a toner containing portion 74. .

The developing roller 71 is disposed in contact with the photosensitive drum 61 in front of the photosensitive drum 61, and supplies toner as an example of a developer to the electrostatic latent image formed on the surface of the photosensitive drum 61. It is configured. A developing bias VD (see FIG. 3) is applied to the developing roller 71 during development.
The supply roller 72 is a member that supplies toner to the developing roller 71, and is disposed in contact with the developing roller 71 in front of the developing roller 71.

The layer thickness regulating blade 73 is a member that regulates the thickness of the toner carried on the developing roller 71 in sliding contact with the developing roller 71.
The toner storage portion 74 is a portion that stores toner, and is formed in front of the supply roller 72. The toner storage unit 74 is provided with an agitator 74A that rotates and agitates the toner in the toner storage unit 74 and supplies the toner to the supply roller 72.

  In the process cartridge 5 configured as described above, the surface of the photosensitive drum 61 is uniformly charged by the charger 62 (charging wire 62A) to which the charging bias V1 (first voltage) (see FIG. 3) is applied. Then, exposure is performed by high-speed scanning of laser light from the exposure device 4. Thereby, the potential of the exposed part is lowered, and an electrostatic latent image based on the image data is formed.

  At this time, the toner in the toner container 74 is supplied onto the supply roller 72 and is supplied onto the developing roller 71 by the sliding contact between the supply roller 72 and the developing roller 71. The toner supplied onto the developing roller 71 enters between the developing roller 71 and the layer thickness regulating blade 73 by the rotation of the developing roller 71 and is carried on the developing roller 71 as a thin layer having a constant thickness.

  The toner carried on the developing roller 71 is supplied to the electrostatic latent image on the photosensitive drum 61 when the developing roller 71 and the photosensitive drum 61 come into contact with each other. As a result, the electrostatic latent image is visualized (developed), and a toner image is formed on the photosensitive drum 61. Then, the sheet P is conveyed between the photosensitive drum 61 and the transfer roller 63 so that the toner image on the photosensitive drum 61 is transferred onto the sheet P.

  The fixing device 8 is disposed behind the process cartridge 5 (on the downstream side in the conveyance direction of the paper P), and is disposed so as to face the heating roller 81 and sandwich the paper P between the heating roller 81 and the heating roller 81. The apparatus mainly includes a pressure roller 82 and a conveyance roller 83 that conveys the paper P after fixing.

  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 on which the toner image has been thermally fixed is discharged onto a paper discharge tray 23 provided on the upper surface of the main body housing 2 by a transport roller 83 and a pair of paper discharge rollers 22.

  The main motor 9 supplies a driving force to each part of the laser printer 1 via a power transmission mechanism (not shown) such as the paper feed roller 33, the photosensitive drum 61, the transfer roller 63, the developing roller 71, the agitator 74A, and the heating roller 81. It is a known motor that is provided, and is disposed at an appropriate position in the main body housing 2.

  The control device 10 includes a CPU, a RAM, a ROM, an input / output circuit (not shown), and the like, and is arranged at an appropriate position in the main body housing 2. The control device 10 detects the charging wire 62A and the transfer roller based on the input image data and various instructions, the program and data stored in the ROM, the output of a sensor (not shown) provided in the main body housing 2, and the like. The overall operation of the laser printer 1 is controlled by controlling the voltage applied to 63 and the like, the drive of the main motor 9 and the like.

Further, the control device 10 applies a voltage to the charging wire 62A and the transfer roller 63.
A drum development mode in which a charging bias V1 (first voltage) is applied to the charging wire 62A, and a transfer bias V2 (second) described later with respect to the transfer roller 63 without applying a voltage to the charging wire 62A. The drum charging mode is applied.

<Control of laser printer by control device>
Next, control of the laser printer 1 by the control device 10 will be described. In this embodiment, the case of using a positively chargeable toner that moves from the high potential side to the low potential side will be described, but the same control is performed even when a negatively chargeable toner is used. Can do.

[Control action during image formation]
First, the control of the laser printer 1 by the control device 10 at the time of image formation from when image data is received until development or transfer is executed and the main motor stops driving will be described. FIG. 2 is a flowchart showing the control of the laser printer by the control device at the time of image formation, and FIG. 3 is a time chart showing the voltage application state to the developing roller, the charging wire and the transfer roller and the output state of the main motor. FIG. 4 is a schematic view showing the main part of the laser printer. Note that the time chart shown in FIG. 3 shows the timing of voltage application and main motor driving, and does not show the exact time of voltage application or main motor driving.

  As shown in FIGS. 2 and 3, when image data is transmitted from a personal computer (not shown) that instructs image formation to the laser printer 1, the control device 10 receives the image data (step S101). . When receiving the image data, the control device 10 applies a transfer bias V2 (second voltage) to the transfer roller 63 (first means) (step S102). At this time, no voltage is applied to the charging wire 62A. That is, when receiving the image data, the control device 10 starts the drum charging mode.

  The transfer bias V2 has the same polarity as the charging bias V1 (first voltage) applied to the charging wire 62A during development (in this embodiment, “positive”), and development that carries positively charged toner. A voltage higher than the surface potential of the roller 71 is set.

  Next, the control device 10 starts driving the main motor 9 (step S103). As a result, the photosensitive drum 61 rotates, but the surface of the photosensitive drum 61 is charged to a potential higher than the surface potential of the developing roller 71 by the action of the transfer roller 63 to which the transfer bias V2 is applied. Therefore, electrical adhesion of toner to the photosensitive drum 61 is suppressed. As a result, it is possible to prevent the photosensitive drum 61 from being stained with toner during the warm-up operation before development.

  Note that the transfer bias V2 (second voltage) is desirably set to a voltage (V2> VD) higher than the development bias VD. According to this, since the transfer bias V2 is surely higher than the surface potential of the developing roller 71 to which the developing bias VD is not applied, the electrical adhesion of the toner to the photosensitive drum 61 is reliably suppressed, and the photosensitive drum It is possible to more reliably suppress the body drum 61 from being contaminated with toner.

  Next, the control device 10 performs a warm-up operation before development, for example, stirring of the toner in the toner container 74 by the agitator 74A, supplying the toner to the supply roller 72, energizing the heat source of the heating roller 81, etc. for a predetermined time. Execute (Step S104). Then, the control device 10 connects the main motor 9 and the paper feed roller 33 (paper feed unit 3) via a power transmission mechanism (gear, etc.) (not shown) so that power can be transmitted, and increases the output of the main motor 9. Then, the paper feed roller 33 is rotated. As a result, the conveyance (feed) of the paper P in the paper feed tray 31 is started (step S105).

  Thereafter, the control device 10 applies the charging bias V1 to the charging wire 62A and starts the drum developing mode (step S106). Specifically, as shown in FIG. 3, the control device 10 determines the charging wire 62 </ b> A at a timing (timing before time T <b> 2) before the moving time T from time T <b> 4 when the developing bias VD is applied to the developing roller 71. Application of the charging bias V1 is started. Specifically, in the present embodiment, the application of the charging bias V1 is started at time T1, which is a time before the photosensitive drum 61 rotates once from time T4.

  Here, as shown in FIG. 4, the moving time T corresponds to the charging position C charged by the charging wire 62 </ b> A on the surface of the rotating photosensitive drum 61, and the developing position D where the toner is supplied from the developing roller 71. This is the time it takes to move to.

  As described above, by starting application of the charging bias V1 to the charging wire 62A at a timing before time T2, the surface of the photosensitive drum 61 is uniformly charged by the charging wire 62A (charging bias V1). Since only the portion can be subjected to development, the image quality can be kept good and constant. Since charging by the transfer roller 63 is contact charging, it is difficult to uniformly charge the surface of the photosensitive drum 61 (uniform enough to maintain image quality), and the portion charged by the transfer roller 63 is used for development. If it is done, the image quality may be degraded.

  After starting the application of the charging bias V1 (drum development mode), the control device 10 changes the transfer bias applied to the transfer roller 63 from V2 to VT (step S107). Specifically, as shown in FIG. 3, the control device 10 is after applying the charging bias V1 to the charging wire 62A and before applying the developing bias VD (between time T1 and time T4). In addition, the transfer bias applied to the transfer roller 63 is changed from V2 to VT. Specifically, in the present embodiment, the transfer bias applied to the transfer roller 63 is changed from V2 to VT at time T3 between time T1 and time T4.

  Thus, by changing the transfer bias applied to the transfer roller 63 from V2 to VT between time T1 and time T4, the surface of the photosensitive drum 61 is charged with the transfer roller 63 (transfer bias V2) and the charging. At least one of the wires 62A (charging bias V1) can be always charged. As a result, the surface of the photosensitive drum 61 can be continuously charged to a potential higher than the surface potential of the developing roller 71, so that electrical adhesion of toner to the photosensitive drum 61 is suppressed, and the photosensitive drum is reduced. It is possible to reliably suppress 61 from being stained with toner.

  In addition, by changing the transfer bias applied to the transfer roller 63 from V2 to VT before the development bias VD is applied (before time T4), a time for stabilizing the voltage (transfer bias VT) of the transfer roller 63 is obtained. Can be secured. As a result, transfer can be performed without being affected by an unstable voltage inevitably generated at the moment when the transfer bias is changed, so that the image quality can be kept good and constant.

  After a predetermined time has elapsed since the transfer bias was changed from V2 to VT, the control device 10 applies the developing bias VD to the developing roller 71 (step S108, time T4). As a result, development is performed and a toner image is formed on the photosensitive drum 61 and transferred to the fed paper P.

  Then, the control device 10 stops the application of the developing bias VD after the end of development (supply of toner to the electrostatic latent image) (step S109, time T5), and stops the application of the transfer bias VT after the end of transfer (step S109). S110, time T6). Thereafter, the control device 10 performs a known operation such as cleaning of the photosensitive drum 61, and finally stops driving the main motor 9 and applying the charging bias V1 (step S111, time T7).

[Control operations other than during image formation]
Next, a laser printer by the control device 10 during operations other than image formation, for example, during warm-up operations such as after power-on or after replacement of the process cartridge 5 or during cleaning operations (when the cleaning operation is performed alone). The control 1 will be briefly described. FIG. 5 is a flowchart showing the control of the laser printer by the control device during the warm-up operation or the cleaning operation.

  As shown in FIG. 5, when the laser printer 1 is turned on, a new process cartridge 5 is installed and the front cover 21 is closed, or an instruction to start cleaning is input, the control device 10 Information is received (step S201). When receiving the information, the control device 10 applies a transfer bias V2 (second voltage) to the transfer roller 63 (step S202). At this time, no voltage is applied to the charging wire 62A. That is, the control device 10 starts the drum charging mode.

  Next, the control device 10 starts driving the main motor 9 (step S203). As a result, the photosensitive drum 61 rotates, but the surface of the photosensitive drum 61 is charged to a potential higher than the surface potential of the developing roller 71 by the action of the transfer roller 63 to which the transfer bias V2 is applied. Therefore, it is possible to suppress the photosensitive drum 61 from being stained with toner.

  Then, the control device 10 performs a warming-up operation (for example, stirring of the toner in the toner storage unit 74 by the agitator 74A, supply of the toner to the supply roller 72, etc.), a cleaning operation by the cleaning brush 64, and the like (step S204). . The control device 10 performs a warming-up operation, a cleaning operation, and the like for a predetermined time, and then stops driving the main motor 9 and applying the transfer bias V2 (step S211).

  As described above, the laser printer 1 according to the present embodiment executes the drum development mode in which the charging bias V1 is applied to the charging wire 62A from time T1 to time T7 during image formation, and image data during image formation. A drum charging mode in which a transfer bias V2 is applied to the transfer roller 63 is executed from the time of reception to time T1, during a warm-up operation, and during a cleaning operation. As a result, no voltage is applied to the charging wire 62A from the time of image data reception at the time of image formation to the time T1, so that the energization time of the charging wire 62A can be made shorter than before. As a result, it is possible to suppress the adhesion of foreign matter to the charging wire 62A depending on the energization time, so that the life of the charging wire 62A can be extended.

  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 above embodiment, an example (see FIG. 3) in which the application of the charging bias V1 to the charging wire 62A is started at the time T1 that is a time before the photosensitive drum 61 makes one rotation from the time T4 is shown. The invention is not limited to this. For example, the application of the charging bias V1 to the charging wire 62A may be started at a timing before the movement time T from time T4, that is, at time T2. According to this, since the time (energization time) for supplying the charging bias V1 to the charging wire 62A can be shortened, it is possible to further suppress the adhesion of foreign matter to the charging wire 62A depending on the energization time. Thus, the service life of the charging wire 62A can be further extended.

  In the above-described embodiment, as shown in FIG. 3, the drum developing mode is executed from time T1 to time T7, and the drum charging mode is executed from time T1 to time T1. However, the present invention is not limited to this. For example, charging is performed from the timing (time T2) before the movement time T from the time T4 when the developing bias VD is applied in FIG. 3 to the time (time T6) when the transfer bias VT needs to be applied to the transfer roller 63. The drum development mode in which the charging bias V1 is applied to the wire 62A is executed, and the drum charging mode in which the voltage is not applied to the charging wire 62A and the transfer bias V2 is applied to the transfer roller 63 otherwise. You may make it perform. According to this, since the energization time of the charging wire 62A can be further reduced, it is possible to further suppress the adhesion of foreign matter to the charging wire 62A, and to further extend the life of the charging wire 62A. Become.

  In the embodiment, the transfer bias V2 is simultaneously applied to the transfer roller 63 during the drum developing mode in which the charge bias V1 is applied to the charging wire 62A (between times T1 and T3 in FIG. 3). However, the present invention is not limited to this. For example, when application of the charging bias V1 (first voltage) to the charging wire 62A (discharge member) is started at time T1 in FIG. 3, the transfer bias V2 (second voltage) to the transfer roller 63 (first means) is started at the same time. ) May be stopped or changed.

  In the above-described embodiment, the charger 62 having the charging wire 62A stretched as an example of the discharge member is employed. However, the present invention is not limited to this. For example, the needle electrodes are arranged in a row and the needle electrodes are arranged. Alternatively, a charger (so-called sawtooth charger) that performs corona discharge at the tip of the tip may be used.

  In the embodiment, the transfer roller 63 is employed as an example of the first means. However, the present invention is not limited to this, and for example, a cleaning brush 64 (cleaning member) may be employed. Specifically, as shown in FIG. 6, when image data is received, a cleaning bias V2 (second voltage) is applied to the cleaning brush 64, and cleaning is performed at time T3 (between time T1 and time T4). The bias may be changed from V2 to VC (voltage applied during the cleaning operation). When using positively charged toner, the cleaning bias V2 has the same polarity (positive) as the charging bias V1 (first voltage) and is set to a voltage higher than the surface potential of the developing roller 71. .

  Since the surface of the photosensitive member is charged by the cleaning member to which the second voltage is applied so that the absolute value is larger than the surface potential of the developer carrying member, the second voltage is a cleaning operation in the conventional configuration. The absolute value is sometimes set to be larger than the voltage applied to the cleaning member (for example, about 1 to 2 kV). Supplementally, the voltage applied to the cleaning member during the cleaning operation in the conventional configuration is insufficient to charge the surface of the photoconductor so that the absolute value is larger than the surface potential of the developer carrier. It was not possible to obtain an effect of suppressing the contamination of the body with the developer on the developer carrying member.

  In the embodiment, the transfer roller 63 (transfer member) and the cleaning brush 64 (cleaning member) that act on the photosensitive drum 61 (photoreceptor) at the time of development are exemplified as the first means, but the present invention is not limited to this. It is not something. Specifically, a dedicated member (for example, a roller) that does not act on the photoconductor during development but acts on the photoconductor other than during development (charges the photoconductor) may be employed as the first means. . Since such a first means does not act on the photoconductor during development, the second means is applied after the first voltage is applied to the discharge member and before the development bias is applied to the developer carrier. The state is changed from the state where the voltage is applied to the state where the voltage is not applied (0 V) (the application of the voltage is stopped during development).

In the above-described embodiment, the photosensitive drum 61 is employed as an example of the photosensitive member. However, the present invention is not limited thereto, and for example, a photosensitive belt may be employed.
In the embodiment, the cleaning brush 64 is used as an example of the cleaning member. However, the present invention is not limited to this, and for example, a cleaning roller may be used.

  In the above-described embodiment, an example in which the exposure apparatus 4 that exposes the photosensitive drum 61 (photosensitive body) with laser light is used has been described. However, the present invention is not limited to this. For example, you may employ | adopt the exposure apparatus which exposes a photoreceptor with the light radiate | emitted from LED (light emitting diode), EL (electroluminescence) element, a fluorescent substance, etc.

  In the above embodiment, the laser printer 1 is employed as an example of the image forming apparatus. However, the present invention is not limited to this, and may be, for example, a copying machine or a multifunction machine. In the embodiment, the image forming apparatus (laser printer 1) that forms a monochrome image is exemplified. However, the present invention is not limited to this, and an image forming apparatus that forms a color image may be used.

1 is a cross-sectional view illustrating an overall configuration of a laser printer as an example of an image forming apparatus. It is a flowchart which shows control of the laser printer by the control apparatus at the time of image formation. 4 is a time chart showing a voltage application state and a main motor output state to a developing roller, a charging wire and a transfer roller. It is the schematic which shows the principal part of a laser printer. It is a flowchart which shows control of the laser printer by a control apparatus at the time of warming-up operation | movement, cleaning operation | movement, etc. 6 is a time chart illustrating a voltage application state and a main motor output state to a developing roller, a charging wire, a transfer roller, and a cleaning brush.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser printer 4 Exposure apparatus 7 Developing cartridge 10 Control apparatus 61 Photoconductor drum 62 Charger 62A Charging wire 63 Transfer roller 64 Cleaning brush 71 Developing roller C Charging position D Development position P Paper T Movement time V1 Charging bias V2 Transfer bias VD Development Bias VT Transfer bias

Claims (10)

A photoreceptor,
A charger having a discharge member for performing corona discharge, and charging the photoreceptor;
An exposure device that exposes the charged photoreceptor to form an electrostatic latent image;
A developing device having a developer carrying member for carrying the developer, and developing the electrostatic latent image formed on the photoreceptor;
First means acting on the photoreceptor;
A controller for controlling a voltage applied to the discharge member and the first means,
The control device includes:
A mode in which a first voltage is applied to the discharge member;
A second voltage having the same polarity as the first voltage with respect to the first means and having an absolute value larger than the surface potential of the developer carrier without applying a voltage to the discharge member. An image forming apparatus configured to execute a mode for applying a voltage.   The image forming apparatus according to claim 1, wherein the first unit is a transfer member that transfers a developer image formed on the photosensitive member to a recording sheet.   The image forming apparatus according to claim 1, wherein the first unit is a cleaning member that collects the developer attached to the photosensitive member. The control device includes:
The application of the first voltage to the discharge member is started at a time before the development bias is applied to the developer carrying member and before the time required for the charged position of the photoconductor to move to the development position. ,
The voltage applied to the first means is changed from the second voltage after applying the first voltage and before applying the developing bias. The image forming apparatus according to claim 3.   The image forming apparatus according to claim 4, wherein the second voltage has an absolute value larger than that of the developing bias. A photosensitive member, a discharger that discharges corona discharge, a charger that charges the photosensitive member, an exposure device that exposes the charged photosensitive member to form an electrostatic latent image, and a developer carrying a developer A control method for an image forming apparatus, comprising: a developing device that has an agent carrier and develops an electrostatic latent image formed on the photoconductor; and a first unit that acts on the photoconductor.
Applying a first voltage to the discharge member;
A second voltage having the same polarity as the first voltage with respect to the first means and having a larger absolute value than the surface potential of the developer carrying member without applying a voltage to the discharge member. Applying the voltage, and a method for controlling the image forming apparatus.   The method of controlling an image forming apparatus according to claim 6, wherein the first unit is a transfer member that transfers a developer image formed on the photosensitive member to a recording sheet.   7. The method of controlling an image forming apparatus according to claim 6, wherein the first unit is a cleaning member that collects the developer attached to the photosensitive member. The application of the first voltage to the discharge member is started at a time before the development bias is applied to the developer carrying member and before the time required for the charged position of the photoconductor to move to the development position. ,
7. The voltage applied to the first means is changed from the second voltage after applying the first voltage and before applying the developing bias. The method for controlling an image forming apparatus according to claim 8.   The method of controlling the image forming apparatus according to claim 9, wherein the second voltage has an absolute value larger than the developing bias.

Images