KR0177094B1 - Charge voltage control method to prevent contamination of contact charger - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

A charging voltage control method in an apparatus using an electrophotographic development method.

2. The technical problem to be solved by the invention

The present invention provides a charging voltage control method capable of obtaining an optimal image by preventing contamination of a contact charger caused by a reverse polarity toner and an unclean toner.

3. Summary of Maritime Method of Invention

During the printing operation or during the warm-up operation, the charging voltage is applied to the contact charger, the charging voltage is turned off after performing the transfer process, and the electrostatic latent image area is applied again to the charging charge after passing through the contact charger. To prevent it from adhering to the contact charger.

4. Important uses of the invention

Non-clean contact chargers can be used in laser beam printers, copiers, fax machines and the like.

Description

Charge voltage control method to prevent contamination of contact charger

1 is a schematic engine mechanism diagram of a laser beam printer using an electrophotographic development method.

2A and 2B are voltage application timing diagrams for preventing contamination of the contact charger according to the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus using an electrophotographic development method, and more particularly, to a charging voltage control method for preventing contamination of contact chargers caused by reverse polarity toner and unclean toner.

In general, the electrophotographic development method is a widely used method for outputting an image according to a video signal in a printer, a facsimile, etc. as well. An example of a device using a representative electrophotographic development method is a laser beam printer. The laser beam printer forms an image on paper through a series of electrophotographic processes of charging ⇒ exposure ⇒ development ⇒ transfer ⇒ settlement ⇒ media. Hereinafter, the electrophotographic process described above will be described in detail with reference to an engine mechanism configuration diagram of the laser beam printer using the electrophotographic development method as shown in FIG. 1. In addition, in the following description, a laser beam printer using a contact charging method will be described as an example to minimize ozone (O3) generation. The contact charging method refers to a method of forming a constant surface potential on the photosensitive member by contacting the photosensitive member with a conductive roller and a brush as a charging means.

First, the charging step, which is the first step of the electrophotographic process, is to make the surface of the photoconductor at a constant potential. That is, the conductive roller 10 of FIG. 1 has a potential of (−) by the charging voltage V _ch and the photosensitive drum 12 in contact with it also has a surface potential of (−). At this time, the surface potential of the photosensitive drum 12 has a potential of about -500 [V]. The second step of the electrophotographic process is to expose the portion corresponding to the image area to be printed using the exposure means (laser beam, LED head) 14 to form an electrostatic latent image on the photosensitive drum 12. will be. At this time, the potential of the non-exposed part is maintained and the potential of the exposed part is changed. In addition, the exposed portion has only a potential difference with the non-exposed portion, and thus is not visible to the human eye, so it is called an electrostatic latent image. The developing step, which is the third step of the electrophotographic process, is a step of converting the electrostatic latent image formed on the surface of the photosensitive drum 12 into a visible image. That is, the magnetic roller 16 of the developing part has a potential of (-) by the developing voltage V _D of about -450 [V]. Accordingly, the toner in the toner hopper is triboelectrically charged to the negative by the magnetic roller 16, thereby exhibiting a negative potential and moving to the developing region by rotating the sleeve. At this time, the amount of toner and carrier is controlled by the regulating blade 18, and the reverse polar toner having a positive potential is also moved to the developing area. The reverse polarity toner having the (+) potential refers to an abnormally tribocharged toner. Then, the toner moved to the developing area is developed by moving a part of the toner to the exposed area of the photosensitive drum 12 by the electric field around it. On the other hand, the fourth step of the electrophotographic process is a process of transferring the image generated on the photosensitive drum 12 to paper. A transfer portion (20), the positive charge generated by the transfer voltage V _T of about 800 ~ 1500 [V] is attached to the sheet (S). At this time, the pulling force between the (+) charge generated by the transfer voltage V _T and the (-) potential toner particles on the photoreceptor is greater than the pulling force between the toner particles and the photosensitive drum 12, so the toner is on the paper (S). It is left on the transfer unit 20. The toner placed on the paper S is then fixed on the paper S through a fixing step, which is the fifth step of the electrophotographic process. In the fixing step, the toner placed on the paper S is strongly adsorbed on the paper S by the pressure roller 26 and the heat roller 28, and is converted into an image which can be stored for a long time. After the fixing step paper (S) is discharged to the outside through the discharge process. Meanwhile, in FIG. 1, the conveying roller 22 conveys the paper S conveyed by the pickup roller (not shown) to the register roller 24, and the register roller 24 is conveyed to the conveying roller 22. Align the sheet S conveyed by. Also, in general, a laser beam printer is provided with a sensor for detecting an operating state of each part of the printer or a paper conveying state. Accordingly, the first sensor SI installed on the sheet conveying path between the conveying roller 22 and the register roller 24 in FIG. 1 detects a conveying state of the sheet conveyed to the register rollers 32a and 32b. The second sensor S2 provided on the paper discharge path at the rear end of the fixing unit 26 detects the paper discharge state from the paper discharge roller.

Most of the toner adhering to the photosensitive drum 12 during the transfer process in the above-mentioned electrophotographic process is transferred to the paper S, but the reverse polarity toner of the positive potential or a very small amount of unclean toner is photosensitive drum. It remains on (12). Therefore, in the apparatus using the electrophotographic development system in which the surface potential is charged to the photosensitive drum 12 by the contact charging method (that is, the charging method using the conductive roller), the reverse polarity toner having a positive potential is negative. By attaching to the conductive roller 10 having a potential, the surface potential of the photosensitive drum 12 of the initial set value is varied. Therefore, there is a problem that the image stain occurs in the image quality due to the variation in the surface potential of the photosensitive drum 12.

Accordingly, an object of the present invention is to provide a charging voltage control method capable of obtaining an optimal image by preventing contamination of the contact charger caused by the reverse polarity toner and the unclean toner.

The present invention for achieving the above object is a charging voltage control method for preventing contact charge contamination of an apparatus for printing and outputting an image according to a video signal on a recording medium through a sequential process of charging, exposure, development, transfer, fixing A first step of applying a charging voltage for charging the surface of the photosensitive member during the rotation of the main motor for driving the rollers provided for the charging, exposure, development, transfer, fixing, and after the transfer process And a third step of turning off the charged voltage and a third step of reapplying the charged voltage when the electrostatic latent image region passes through the contact charger.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. And detailed descriptions of well-known functions and configurations that may unnecessarily obscure the subject matter of the present invention will be omitted.

FIG. 2A illustrates a voltage application timing diagram according to an exemplary embodiment of the present invention, in which one sheet of paper is used as an example, and FIG. 2B illustrates a voltage application timing diagram during warm-up of a laser beam printer. . In FIG. 2a, MM represents the rotation period of the main motor (MM) of the laser beam printer. V _CH shows a timing diagram of the charging voltage applied to the conductive roller 10. In the timing diagram of V _ch , sections a and c represent time being applied to the conductive roller 10, and section b represents time when the charging voltage V _ch applied to the conductive roller 10 was turned off. V _D and V _T represent timing diagrams of the developing voltage and the transfer voltage applied to the magnetic roller 16 and the transfer unit 20 of the developing unit, respectively. That is, the section d represents the time during which the developing voltage V _D is being applied, and the section e indicates the time during which the transfer voltage V _T is being applied. Meanwhile, in FIG. 2B, the MM indicating the rotation period of the main motor and the charging voltage V _CH are the same as the timing chart of FIG. 2A, and the developing voltage V _D and the transfer voltage V _T are turned off. Hereinafter, referring to FIGS. 2A and 2B, a charging voltage control process for preventing contamination of the conductive roller 10 that may occur due to the reverse polarity toner and the unclean toner will be described.

First, when a print command is received from an external (computer), the main motor MM starts to rotate from the time t1 time under the control of a control unit (not shown). At this time, the conductive roller 10 has a negative potential of about -500 [V] as the surface of the photosensitive drum 120 is supplied with a charging voltage of about -500 [V] from V _{ch under} the control of the controller. The electrostatic latent image corresponding to the image data received from the outside through the step is formed on the photosensitive drum 12. Then, the magnetic roller 16 of the developing unit is about -450 [V from V _D under the control of the controller at the time t2. The toner is triboelectrically charged with a developing voltage of [], and the toner triboelectrically charged with (-) is moved to the developing region by the rotation of the sleeve, and at the same time, the toner is positively triboelectrically charged (+). In addition, at the time t2, the transfer unit 20 receives a transfer voltage of about 800 to 1500 [V] from V _{T under} the control of the control unit, thereby causing an electrostatic latent image on the photosensitive drum 12. When the formed toner is attached to the paper S In this case, the reverse polarity toner (+) on the photosensitive drum 12 is attached to the photosensitive drum 12 to move to the conductive roller 10. Then, at the time t3, the controller is applied to the conductive roller 10. By _turning off the charging voltage V _ch , the reverse polarity toner (+) is continuously attached and moved on the photosensitive drum 12 without being attached to the conductive roller 10. Then, at the time t4, the control unit again performs the charging voltage V _ch. Is applied to the conductive roller 10 to convert the reverse polarity toner (+) adhering on the photosensitive drum 12 into a toner having a potential of (-). Is moved to the magnetic roller 16 of the developing part by the rotation of the photosensitive drum 12. On the other hand, the developing voltage V _D is turned off for c time while the charging voltage V _ch is being applied to the conductive roller 10. The electric potential of the magnetic roller 16 is higher than the electric potential of 12. Therefore, the toner having a negative potential on the photosensitive drum 12 is developed by moving to the magnetic roller 16. Then, the contact charger by the non-transfer toner, i.e., stops the rotation of the main motor MM at time t5. Contamination of the conductive roller 10 can be prevented to maintain an optimal image.

Meanwhile, a process of controlling the charging voltage V _ch for preventing contamination of the contact charger will be described with reference to FIG. 2B, which shows a voltage application timing diagram of the charging voltage V _ch , the developing voltage V _D , and the transfer voltage V _T during warm-up.

First, when the laser beam printer is turned on, the printer performs a warm-up operation by the initialization program. At this time, the main motor MM rotates from time t1 to time t4, and the charging voltage V _ch is applied to the conductive roller 10 at time t1. Then, by turning off the charging voltage V _ch applied to the conductive roller 10 from time t2 to time t3, the reverse polarity toner (+) adhered on the photosensitive drum 12 is developed due to the rotation of the photosensitive drum 12. Will be moved to. Then, by applying the charging voltage V _ch again at the time t3, the reverse polarity toner (+) adhered on the photosensitive drum 12 is converted to the toner having a negative potential to move to the magnetic roller 16 of the developing portion. do. At this time (at the time t3-t4), the developing voltage V _D is turned off and is higher than the potential of the photosensitive drum 12. Therefore, the toner having a negative potential on the photosensitive drum 12 is moved to the magnetic roller 16 to perform development cleaning. Therefore, it is possible to prevent contamination of the conductive roller 10 by the contact charger, that is, untransferred toner, thereby maintaining an optimum image.

As described above, the present invention controls the charging voltage applied to the contact charger, that is, the conductive roller, on / off during the rotation period of the main motor, thereby preventing contamination of the contact charger by the untransferred reverse polarity toner for an optimal image. There is an advantage that can be obtained.

On the other hand, the embodiment of the present invention illustrates a charging voltage control process that can prevent the contact charge contamination by the untransferred toner only in one sheet or warm-up period, but the invention without any modification even when performing a continuous printing operation Can be applied. For example, when 20 sheets of paper are continuously printed, the normal printing operation can be performed by printing the image on 18 sheets of paper and then turning off the charging voltage and applying the charging voltage again after a certain time. Before printing an image on only 19 sheets of paper, a PICK-UP delay process is required. In addition, in order to maximize the prevention of contamination of the contact electrode by the untransferred toner, an antistatic lamp is installed under the contact charger to zero the surface potential of the photosensitive drum 12, and then the charging voltage is sequentially turned off and on, thereby reducing the photosensitive drum 12 ) And the cleaning due to the potential difference between the magnetic roller 16 can be enhanced.

Claims (5)

A charging voltage control method for preventing contact electrocontamination of a device that prints and outputs an image according to a video signal on a recording medium through a sequential process of charging, exposing, developing, transferring, and fixing, wherein the charging, exposing, developing And a first step of applying a charging voltage for charging the photosensitive member surface while the main motor for driving the rollers provided for transferring and fixing is rotated, and a second for turning off the charging voltage applied after the transferring process. And a third step of applying the charging voltage when the electrostatic latent image region passes through the contact charger. The method of claim 1, wherein the second step is completed before the latent electrostatic image area contacts the contact charging unit. The method of claim 1, wherein the first to third steps are performed during warm-up. The method of claim 1, wherein the reverse polarity toner and the unclean toner adhered to the electrostatic latent image area after the third step are developed and cleaned. The charging voltage control method according to claim 1, wherein the second and third steps are repeatedly performed for each predetermined number of print outputs.