KR0160558B1 - Control method for preventing pollution of contact charge - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

In an electrophotographic image forming apparatus employing a contact charging method, it is a charging control method for preventing contamination of a contact charger by an abnormal developer.

2, the technical problem to be solved by the invention

Provided is a charging control method capable of preventing contamination of contact chargers by an abnormal developer attached to a photoconductor due to untransfer or scattering.

3, the summary of the solution of the invention

A charging voltage of a predetermined level is applied to the contact charger for a first period of time at which the photosensitive member starts to rotate for at least one rotation, and after the first period of time, the charging voltage is cut off for a second predetermined period until the rotation of the photosensitive member is stopped. The developing bias voltage of the developing means is applied at a level equal to or higher than the surface potential on the photosensitive member.

4. Important uses of the invention

It is used to remove abnormal developer without using separate cleaning device.

Description

Charge control method for preventing contamination of contact charger in electrophotographic image forming apparatus

1 is a schematic engine mechanism configuration of an image forming apparatus employing a conventional electrophotographic development method.

2 is a timing diagram showing a charging control process according to the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus, and more particularly, to a charge control method for preventing a contamination rate of a contact charger caused by an abnormal developer when the contact charging method is used habitually.

In general, the electrophotographic development method is widely used in an image forming apparatus such as a copying machine, a laser beam printer, a light emitting diode (LED) printer, a plain paper fax machine, and the like. The process according to the electrophotographic development method is composed of a charging → exposure → development → transfer → fixing process as known.

FIG. 1 shows a schematic diagram of an engine mechanism of an image forming apparatus employing the electrophotographic developing method as described above, and shows a case where the contact charging method is adopted. The contact charging method is a charging method widely used to minimize the generation of ozone (O ₃ ) due to charging, and the surface of the photosensitive member is brought into contact with a photosensitive member by contacting a conductive roller or brush used as a contact charger. It means a method of forming a dislocation, in Figure 1 has shown an example using a conductive roller (10). In Fig. 1, reference numeral 5 denotes a conveyance path of recording paper.

The electrophotographic development process will now be discussed in more detail with reference to the engine mechanism diagram of FIG. First, the photosensitive drum 12 of FIG. 1 is rotated in the direction of an arrow by an engine driving motor (not shown) which is a main motor of the engine unit, corresponding to the progress of each process of the electrophotographic development process as described above. .

First, in the charging process, the photosensitive drum 12, which is the photosensitive member, is charged by the conductive roller 10, which is a contact charger, to form a uniform charge in the photosensitive drum 12. At this time, the conductive roller 10 has a negative potential due to the negative charging voltage V _CH , and the photosensitive drum 12 is charged by contact with the conductive roller 10, thereby causing negative. It has a surface potential. At this time, the surface potential of the photosensitive drum 12 has a potential of, for example, about -500 [V].

In the above state, the feed roller 22 transfers the recording paper fed from the paper feed cassette (not shown) to the register roller 24, and the register roller 24 is transferred by the feed roller 22. Align the leading edge of the transported recording paper along (5). As described above, the exposure process starts with the tip of the recording paper aligned, and the recording paper starts to be transferred to the transfer machine 20.

Secondly, in the exposure process, an electrostatic latent image is formed on the photosensitive drum 12 by exposing the charged photosensitive drum 12 to correspond to the original or image data. In this case, the electrostatic latent image is formed on the photosensitive drum 12 by exposing only a portion corresponding to the image area to be printed using the exposure apparatus 14. In this case, the surface potential of the unexposed portion is maintained as it is, and the exposed portion is changed in potential so that an electrostatic latent image having a potential difference between the non-exposed portion and the exposed portion is formed. The exposure apparatus 14 becomes a laser scanner unit (Laser Scanner Unit, hereinafter referred to as LSU) in the case of a laser beam printer and an original scanner in the case of a copying machine.

Thirdly, in the developing process, the developer is transferred and attached to the electrostatic latent image formed on the photosensitive drum 12 as described above. The above development means that a developer such as a toner is deposited on the photosensitive drum 12 on which the electrostatic latent image is formed. That is, this process is a process of converting the electrostatic latent image formed on the photosensitive drum 12 into a visible image by a developer. At this time, the developing roller 16 has a negative potential due to, for example, a developing bias voltage V _D of about -450 [V]. Accordingly, the developer in the developer feeder (not shown) exhibits negative potential while frictionally charged to the negative potential by the developing roller 16, and develops as the developer roller 16 rotates. Will move to the area. At this time, the amount of the developer is controlled by the regulating blade 18 and is uniformly applied on the developing roller 16. Then, the developer charged to the negative potential moved to the developing region is developed by attaching part of the developer to the exposed region on the photosensitive drum 12 by the potential difference.

Fourth, in the transfer process, the developer attached to the photosensitive drum 12 is transferred to the recording paper by the transfer machine 20 as described above. A first pull the charged developer to the potential of, for example into the recording paper by a transfer voltage V _T of about 800~1500 [V] - () The imprinter 20. The photosensitive drum 12, part that is attached to the By attaching it to the recording paper.

Fifth, in the fixing process, the developer transferred to the recording paper as described above is fixed to the recording paper by the pressure and heat of the fixing roller, that is, the pressure roller 26 and the heat roller 28, respectively. After that, the fixing of the recording paper, which has been completed, is discharged to the outside of the image forming apparatus, thereby completing copying or printing of one recording paper.

The developer adhering to the photosensitive drum 12 during the electrophotographic development process as described above is mostly transferred to the recording paper during the transfer process, but usually some of the developer is not transferred and remains on the photosensitive drum 12. do. In addition, a part of the developer applied to the developing roller 16 is scattered and adheres to the photosensitive drum 12. If the untransferred or scattered abnormal developer is left as it is, the conductive roller 10 is contaminated, thereby degrading the print quality.

In order to prevent the conductive roller 10 from being contaminated by such abnormal developer, the abnormal developer remaining on the photosensitive drum 12 after transfer has been removed by using a separate cleaning device such as a cleaning blade. . However, this was not only to use a separate cleaning device, but the surface of the photosensitive drum 12 was damaged due to the cleaning device.

Accordingly, a technique of removing an abnormal developer without using a separate cleaning device has been used. This occurs when the region on the photosensitive drum 12 with the abnormal developer contacts the developing roller 16 in a state in which the developing bias voltage V _D is blocked due to the continuous rotation of the strong drum 12. The potential difference between the rollers 16 causes them to adhere to the developing roller 16. In this case, the potential of the developing roller 16 becomes positive (+) relative to the surface potential on the photosensitive drum 12, so that an abnormal developer having a negative potential remaining on the photosensitive drum 12 is developed. It is recovered by being attached to 16). Accordingly, the abnormal developer can be removed from the photosensitive drum 12 without using a separate cleaning device.

However, the abnormal developer is not only a normal developer having a negative potential, but also a reverse polarity developer having a positive potential as described above.

The normal developer means a developer normally tribocharged by a negative (-) potential in the developing roller 16. In contrast, the reverse polarity developer is a developer having a positive potential, and is caused by abnormally triboelectric charging in the developing roller 16 or the positive transfer voltage V _T as described above in the transfer machine 20. It means the developer which was generated by being charged by and not transferred.

Therefore, in the conventional technique as described above, the normal developer charged to the negative potential is attached to the developing roller 16 from the photosensitive drum 12, but the reverse polarity phenomenon having a positive potential The agent cannot be removed. Such a positive polarity developer having a positive potential is attached to the conductive roller 10 when contacted with the conductive roller 10 having a potential of negative (−) during charging. As a result, the conductive roller 10 is contaminated, and accordingly, when the photosensitive drum 12 is charged, the surface potential of the initial set value on the photosensitive drum 12 is changed, thereby causing image stains on the printed recording paper.

Accordingly, an object of the present invention is to provide a charging control method capable of preventing contamination of the contact charger by the abnormal developer attached to the photoconductor due to untransfer or scattering.

The present invention for achieving the above object is the process of applying the charging voltage of the prescribed level to the contact charger for a first period of at least one rotation from the start of the photosensitive member, and after the first period of time until the rotation of the photosensitive member is stopped It is characterized in that it comprises the step of interrupting the charging voltage for a second predetermined period and at the same time applying the developing bias voltage of the developing means to a level above the surface potential on the photosensitive member.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Many specific details are set forth in the following description and in the accompanying drawings to provide a more general understanding of the invention, such as specific control timings. It will be apparent to those skilled in the art that the present invention may be practiced without these specific details. And a detailed description of known functions and configurations that may unnecessarily obscure the subject matter of the present invention will be omitted.

First, in the electrophotographic image forming apparatus employing the contact charging method as described above, the charging control process according to the present invention is performed according to the timing as shown in FIG.

The control timing of FIG. 2 is divided into a warm-up operation and a printing operation. In the warm-up operation, a warm-up operation for preparing an engine unit in a standby state for printing is performed. In the printing operation, actual printing is performed on the recording paper. In addition, the control timing at the time of the printing operation is an example of printing one sheet of paper.

FIG. 2 (a) shows the driving timing of the engine driving motor MM, which is the main motor of the engine unit which rotates the photosensitive drum 12. The photosensitive drum 12 rotates during the whole section and the photosensitive drum during the off section. (12) stops. FIG. 2 (b) shows the control timing for applying or blocking the negative charging voltage V _CH to the conductive roller 10. FIG. 2C shows the control timing for turning on or off the exposure apparatus 14 such as the LSU. FIG. 2 (d) shows the control timing for applying or blocking the development bias voltage V _D to the developing roller 16. FIG. 2 (e) shows the control timing for applying or blocking the transfer voltage V _T to the transfer device 20.

The control process of the present invention according to the timing of FIG. 2 will now be described in detail with reference to the mechanism diagram of FIG. In general, in the electrophotographic development process, the configuration and operation of each part of the engine unit and the engine control unit which bears driving thereof are well known in the art, and thus, detailed description thereof will be omitted.

First, when the warm-up operation is performed, as the image forming apparatus starts the initialization operation, the engine driving motor MM starts to rotate from time t0, and accordingly, the photosensitive drum 12 also starts to rotate in the direction of the arrow, and the warm-up operation is performed until time t2. It continues to rotate. In the present invention, the charging control timing in the warm-up operation is divided into a first period T _W1 and a second period T _W2 . The first period T _W1 is a period for normal warm-up, during which the photosensitive drum 12 rotates several times. do. The second period T _W2 is a period during which the conductive roller 10 rotates at least one revolution before the rotation of the photosensitive drum 12 is stopped after the first period T _W1 . Accordingly, since the first period T _W1 is a normal warm-up time, it is applied as it is, but the second period T _W2 is set to a period shorter than the first period T _W1 .

First, a negative charging voltage V _CH is applied to the conductive roller 10 from the time t0 corresponding to the first period T _W1 to the time t1, the exposure apparatus 14 is turned off, and the negative development bias is applied. Cut off the voltage V _D and the positive transfer voltage V _T. In this state, the surface potential on the photosensitive drum 12 in contact with the conductive roller 10 is charged to a negative potential. When the charged region on the photosensitive drum 12 comes into contact with the developing roller 16 in a state where the development bias voltage V _D is blocked by the rotation of the photosensitive drum 12, an abnormality is attached to the photosensitive drum 12. The regular developer charged at the negative potential of the developer is attached to the developing roller 16 by the potential difference between the photosensitive drum 12 and the developing roller 16. In this case, the potential of the developing roller 16 becomes positive (+) relative to the surface potential on the photosensitive drum 12, whereby a regular developer having a negative potential among the abnormal developers on the photosensitive drum 12 It is recovered by being attached to the developing roller 16. In this manner, the operation is performed for at least one rotation of the photosensitive drum 12.

Therefore, the normal developer among the abnormal developers on the photosensitive drum 12 is removed during the first period T _W1 .

Next, the charging voltage V _CH and the positive transfer voltage V _T are cut off from the time t2 corresponding to the second period T _W2 to the time t3, the exposure apparatus 14 is turned on, and the negative development bias is turned on. The voltage V _D is applied to the developing roller 16 at a level lower than the prescribed level in the steady state. In this state, the charging voltage V _CH is blocked without being applied to the conductive roller 10 so that the inverse developer remaining separately from the normal developer removed during the first period T _W1 among the abnormal developers attached to the photosensitive drum 12 is prevented. Not only does the polar developer not adhere to the conductive roller 10, but also the reverse polar developer in the conductive roller 10 is transferred onto the photosensitive drum 12 and attached. Then, when the position of the exposure apparatus 14 is reached according to the rotation of the photosensitive drum 12, the photosensitive drum 12 is uniformly exposed by the exposure apparatus 14, thereby lowering the surface potential. When the area where the surface potential on the photosensitive drum 12 is lowered in accordance with the rotation of the photosensitive drum 12 comes into contact with the developing roller 16 in the state where the developing bias voltage V _D is applied, the photosensitive drum 12 is placed on the photosensitive drum 12. The attached reverse polar developer is attached to the developing roller 16 by the potential difference between the photosensitive drum 12 and the developing roller 16. In this case, the developing bias voltage V _D is applied at a level equal to or lower than the lowered surface potential on the photosensitive drum 12. Then, the potential of the developing roller 16 becomes negative (-) relative to the surface potential on the photosensitive drum 12, so that the reverse polarity developer on the photosensitive drum 12 is recovered by attaching to the developing roller 16. . In this manner, the operation is performed for at least one rotation of the photosensitive drum 12.

Therefore, the conductive roller 10 and the reverse polarity developer on the photosensitive drum 12 that are not removed during the first period T _W1 are all removed during the second period T _W2 .

Secondly, in the printing operation, as the image forming apparatus starts the printing operation, the engine driving motor MM starts to rotate from the time t3, and accordingly, the photosensitive drum 12 also starts to rotate in the direction of the arrow and continues to rotate until the time t7. do. In the present invention, the charging control timing in the printing operation is divided into a first period T _P1 , T _{P1 ′} and a second period T _P2 before and after the printing section. The printing section is a time required for normal printing, and during this period, the photosensitive drum 12 rotates several times. The first periods T _P1 , T _{P1 ′} are periods during which the photosensitive drum 12 rotates at least one rotation before and after the printing section. The second period T _P2 is a period during which the conductive roller 10 rotates at least one revolution before the rotation of the photosensitive drum 12 is stopped after the first period T _P1 . At this time, the printing section from time t4 to time t5 is a period during which actual printing is performed on the recording paper.

First, the negative charging voltage V _CH is continuously applied to the conductive roller 10 for the time period t3 to t6 corresponding to the first period T _P1 , T _{P2 ′} and the printing section. Then, the exposure apparatus 14 is turned off during the first period Tp _P1 from t3 to t4 and the first period T _{P1 '} from t5 to t6, and the negative development bias voltage V _D is fixed. Cut the positive transfer voltage V _T. Therefore, in the first period T _P1 , T _{P1 ′} , the same operation as in the first period T _W1 during the warm-up operation as described above is performed. Since the printing section from t4 to t5 is the actual printing period, the exposure apparatus 14 is turned on / off according to the original or image data, and the negative development bias voltage V _D is positive. and a transfer voltage V _T respectively applied to the developing roller 16 and the imprinter 20.

Therefore, of the abnormal developer on the photosensitive drum 12, the normal developer charged to the negative potential is removed during the first period T _P1 , T _{P1 ′} before and after the printing section.

Next, the charging voltage V _CH and the positive transfer voltage V _T are cut off from the time t6 corresponding to the second period T _P2 to the time t7, the exposure apparatus 14 is turned on, and the negative developing bias is turned on. The voltage V _D is applied to the developing roller 16 at a potential lower than the prescribed level in the steady state. Therefore, the second period T _P2 has the same operation as in the second period T _W1 during the warm-up operation as described above.

Accordingly, the conductive roller 10 and the reverse polarity developer on the photosensitive drum 12 that are not removed during the first period T _P1 are all removed during the second period T _P2 .

As a result, all normal and reverse polarity developers attached to the photosensitive member due to untransfer or scattering can be removed without using a separate cleaning device.

As described above, the present invention has an advantage of preventing the deterioration of printing image quality by preventing contamination of the contact charger by any abnormal developer attached to the photoconductor due to untransfer or scattering.

Meanwhile, in the above description of the present invention, specific embodiments have been described, but various modifications can be made without departing from the scope of the present invention.

In particular, in the embodiment of the present invention, during the second period T _W2 , T _P2 , the exposure apparatus 14 is turned on to lower the surface potential on the photosensitive drum 12, and the developing bias voltage V _D is applied to the developing roller 16. 12), but the application of the developed bias voltage V _{D to the} developing roller 16 is applied at a level equal _to or higher than the surface potential _{of the} photosensitive drum 12 without turning on the exposure apparatus 14. You may also Also in this case, the potential of the developing roller 16 becomes a negative potential relative to the surface potential on the photosensitive drum 12, so that an abnormal developer having a positive potential on the photosensitive drum 12 develops. It collect | recovers by attaching to (16). In this case, the surface potential on the photosensitive drum 12 is a dark attenuation potential, and the dark attenuation potential means a potential at which the surface potential on the photosensitive drum 12 positioned in the dark in the image forming apparatus naturally decreases with time.

Therefore, the scope of the invention should not be defined by the described embodiments, but should be defined by the equivalents of the claims and the claims.

Claims (16)

A charging control method for preventing contamination of a contact charger which charges a rotating photosensitive member by a contact charging method in an electrophotographic image forming apparatus, wherein the photosensitive member starts to rotate during a warm-up operation of the image forming apparatus. Applying a charging voltage of a prescribed level to the contact charger only for a first period of at least one rotation, and interrupting the charging voltage for a second predetermined period after the first period of time until the rotation of the photosensitive member is stopped; And applying a developing bias voltage to a developing means at a level equal to or greater than the surface potential on the photosensitive member. 2. The developer according to claim 1, wherein, among the abnormal developer adhered to the photoconductor due to untransfer or scattering from the developing means during the first period, the regular developer charged by the developing means to a potential of a normal polarity on the photoconductor. And a charge control method characterized in that it is attached to said developing means by a potential difference between a surface potential and said developing means and removed from said photosensitive member. The developing method according to claim 2, wherein the developer charged in the reverse polarity with respect to the regular developer among the abnormal developers during the first period is attached onto the photosensitive member from the contact charger according to the blocking of the charging voltage. And the charge control device is attached to the developing means by the developing bias voltage of the means and removed from the photosensitive member. 4. The charging control method according to claim 3, wherein the second period is set to a period in which the conductive roller rotates at least one rotation when the contact charger is a conductive roller. In a charging control method for preventing contamination of a contact charger which charges a rotating photosensitive member by a contact charging method in an electrophotographic image forming apparatus, printing is performed on actual recording paper during printing of the image forming apparatus. A process of applying a charging voltage of a predetermined level only to the contact charger during the first period in which the photoconductor rotates at least one rotation before and after a section, and during the second preset period before the rotation of the photoconductor is stopped after the first period. And applying a developing bias voltage to a developing means at a level equal to or higher than the surface potential on the photoreceptor. 6. The developer according to claim 5, wherein among the abnormal developer adhered to the photoconductor due to untransfer or scattering from the developing means during the first period, the regular developer charged to the potential of the normal polarity by the developing means on the photosensitive member. And a charge control method characterized in that it is attached to said developing means by a potential difference between a surface potential and said developing means and removed from said photosensitive member. 7. The development according to claim 6, wherein the developer charged in the reverse polarity with respect to the regular developer in the abnormal developer during the second period is attached onto the photosensitive member from the contact charger according to the blocking of the charging voltage. And the charge control device is attached to the developing means by the developing bias voltage of the means and removed from the photosensitive member. 8. The charging control method according to claim 7, wherein the second period is set to a period in which the conductive roller rotates at least one rotation when the contact charger is a conductive roller. A charging control method for preventing contamination of a contact electrifier that charges a rotating photosensitive member by a contact charging method in an electrophotographic image forming apparatus, wherein the photosensitive member starts to rotate during a warm-up operation of the image forming apparatus. Applying a charging voltage of a prescribed level to the contact charger only for a first period of at least one rotation, and interrupting the charging voltage for a second predetermined period after the first period of time until the rotation of the photosensitive member is stopped; And exposing the photoconductor uniformly to lower the surface potential on the photoconductor and applying a developing bias voltage to a developing means at a level equal to or lower than the lowered surface potential on the photoconductor. 10. The surface of the photoconductor according to claim 9, wherein, among the abnormal developer adhered on the photoconductor due to untransfer or scattering from the developing means during the first period, the regular developer charged by the developing means to a potential of a normal polarity And a charge control method, characterized in that it is attached to said developing means and removed from said photosensitive member by a potential difference between said potential and said developing means. The developing method according to claim 10, wherein the developer charged in the reverse polarity with respect to the regular developer in the abnormal developer during the second period is attached onto the photosensitive member from the contact charger according to the blocking of the charging voltage. And the charge control device is attached to the developing means by the developing bias voltage of the means and removed from the photosensitive member. 12. The charging control method according to claim 11, wherein the second period is set to a period in which the conductive roller rotates at least one rotation when the contact charger is a conductive roller. In a charging control method for preventing contamination of a contact charger which charges a rotating photosensitive member by a contact charging method in an electrophotographic image forming apparatus, printing is performed on actual recording paper during a printing operation of the image forming apparatus. Applying a charging voltage of a predetermined level to the contact charger only for a first period in which the photoconductor rotates at least one time before and after a section; and the second period which is set in advance before the rotation of the photoconductor stops after the first period. Blocking the charging voltage and uniformly exposing the photoconductor to lower the surface potential on the photoconductor and applying a developing bias voltage to a developing means at a level above the lowered surface potential on the photoconductor. 14. The surface of the photosensitive member according to claim 13, wherein, among the abnormal developer adhered on the photoconductor due to scattering from the developing means during the first period, the regular developer charged by the developing means to a potential of a normal polarity. And a charge control method, characterized in that it is attached to said developing means and removed from said photosensitive member by a potential difference between said potential and said developing means. 15. The method according to claim 14, wherein the developer charged in reverse polarity with respect to the regular developer in the abnormal developer during the second period is attached onto the photosensitive member from the contact charger in response to the blocking of the charging voltage. And the charge control device is attached to the developing means by the developing bias voltage of the means and removed from the photosensitive member. 16. The charging control method according to claim 15, wherein the second period is set to a period in which the conductive roller rotates at least one rotation when the contact charger is a conductive roller.