KR19990014692U - Toner contamination prevention device in an image forming apparatus employing an electrophotographic development method - Google Patents

Abstract

end. TECHNICAL FIELD OF THE INVENTION

An apparatus for preventing contamination due to toner in an image forming apparatus employing an electrophotographic development method.

I. The technical problem the invention seeks to solve

Provided is a pollution prevention device that can prevent contamination due to toner moving from a developing roller to a photosensitive drum surface in a non-printing section when a new printing is started.

All. Summary of solution of design

Each time a new printing is started, the surface potential on the photosensitive drum is kept constant from the start of charging the surface of the photosensitive drum until the charged region on the photosensitive drum reaches the developing region.

la. Important uses of the devise

In an image forming apparatus employing an electrophotographic developing method, it is used to prevent contamination due to toner moving from a developing roller to a photosensitive drum surface in a non-printing section.

Description

Toner contamination prevention device in the image forming apparatus adopting the electrophotographic development method

The present invention relates to an image forming apparatus employing an electrophotographic developing method, and more particularly, to an apparatus for preventing contamination due to a toner.

In general, electrophotographic development methods are widely used in image forming apparatuses such as copiers, laser beam printers (LPP), LED print head (LPH) printers, plain paper fax machines, and the like. The electrophotographic development process consists of a process of "charge" → "exposure" → "developing" → "transfer" → "settlement".

FIG. 1 illustrates a schematic engine mechanism of the electrophotographic image forming apparatus. In FIG. 1, the photosensitive drum 10, the charging roller 12, the developing roller 14, the supply roller 16, the register roller 18, the transfer roller 20, and the like are driven systems including an engine driving motor (not shown). In the direction of the arrow shown in FIG. 1 to correspond to the progress of the electrophotographic process. At this time, the recording paper is fed from a paper cassette (not shown) and conveyed along the paper feed path 24.

A typical electrophotographic process will now be described with reference to FIG. 1. First, in the charging process, the photosensitive drum 10 is uniformly charged to a negative potential of about -800 [V] by being charged by a charging roller 12 to a charging voltage Vch of negative bias, for example, about -1400 [V]. One charge is formed on the surface. The surface of the photosensitive drum 10 charged in this way is subjected to an exposure process in accordance with the rotation of the photosensitive drum 10. An electrostatic latent image is formed by being exposed by an exposure apparatus (not shown) corresponding to the image to be printed. At this time, the original potential of the non-exposed areas that are not exposed on the surface of the photosensitive drum 10 is maintained as it is, but the potential of the exposed image area is reduced to about several tens [V]. The exposure apparatus is, for example, a laser scanner unit in the LBP and an original scanner in the copier. As such, the surface of the photosensitive drum 10 having the electrostatic latent image reaches the developing region according to the rotation of the photosensitive drum 10. The developing area means an area where development is performed by moving the toner on the developing roller 14 onto the photosensitive drum 10, that is, a contact portion between the photosensitive drum 10 and the developing roller 14. At this time, the recording paper fed from the paper cassette is aligned with the front end by the register roller 18, and then starts to be transferred to the transfer roller 20 at the same time as the above exposure process is started.

The surface of the photosensitive drum 10 which has reached the developing region in this manner is subjected to a developing process, and the electrostatic latent image formed on the photosensitive drum 10 is converted into a visible image by being developed by the toner on the developing roller 14. . At this time, the toner is supplied to the developing roller 14 by the supply roller 16 and applied onto the developing roller 14. Further, the developing roller 14 has a negative developing potential of, for example, -250 [V] to -350 [V] due to the negative developing bias voltage Vb. The developing bias voltage Vb is also supplied to the supply roller 16 via a zener diode 22. In this way, the toner supplied to the developing roller 14 is frictionally charged to the developing bias potential Vb by the developing roller 14 and moves to the developing region. The toner moved to the developing area in this manner is developed by moving to the exposure area on the photosensitive drum 10 by the electrostatic force caused by the potential difference between the exposure potential of the photosensitive drum 10 and the developing potential of the developing roller 14.

After the above-described exposure and development process, the photosensitive drum 10 continues to rotate to reach the transfer position, thereby transferring. At this time, a transfer voltage Vt of positive bias of several hundred [KV] to several thousand [KV] is applied to the transfer roller 20. As a result, the transfer is performed by transferring the toner adhered to the photosensitive drum 10 to the recording paper by an electromotive force due to the potential difference between the transfer roller 20 and the photosensitive drum 10. The toner transferred to the recording paper in this manner is fixed to the paper by the pressure and heat of the fixing unit (not shown), and the recording paper on which the fixing is completed is discharged to the outside, thereby ending the process for printing one sheet of paper.

On the other hand, the surface of the photosensitive drum 10 from the position in contact with the charging roller 12 to the position in contact with the developing roller 14 in the photosensitive drum 10 in the stopped state after the previous printing is finished, that is, The portion corresponding to section T shown in FIG. 1 is in contact with the developing roller 14 in an uncharged state when printing is newly started. Accordingly, since the surface potential of the portion corresponding to the T section on the photosensitive drum 10 is unstable, the toner on the developing roller 14 moves to the photosensitive drum 10 by mechanical friction despite the non-printing section. As such, the toner moved to the photosensitive drum 10 in the non-printing section moves to the contact portion between the photosensitive drum 10, the transfer roller 20, and the charging roller 12 as the photosensitive drum 10 rotates. 20) and the charging roller 12 is contaminated. As a result, each time a new print was started, this toner contamination contaminated the leading or back side of the first sheet of paper.

As described above, the toner is moved from the developing roller to the photosensitive drum surface in the non-printing section each time a new printing is started, which causes a problem of contaminating the front end or the back of the first recording sheet.

Accordingly, an object of the present invention is to provide a toner contamination prevention device that can prevent contamination due to toner moving from a developing roller to a photosensitive drum surface in a non-printing section when a new printing is started.

1 is a schematic engine mechanism configuration diagram of an image forming apparatus employing a conventional electrophotographic developing method;

2 is a block diagram of a toner contamination prevention apparatus according to an embodiment of the present invention.

The present invention for achieving the above object keeps the surface potential on the photosensitive drum constant from the start of charging the surface of the photosensitive drum every time a new printing is started until the charged region on the photosensitive drum reaches the developing region. It is characterized by.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail. In the following description and the annexed drawings, many specific details are set forth in order to provide a more thorough understanding of the present invention, such as specific circuit configurations or components. 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.

2 is a block diagram of a toner contamination prevention device according to an embodiment of the present invention. In the image forming apparatus shown in FIG. 1, a zener diode 26, a switch 28, and a switching driver 30 are added. The controller 32 is configured to switch the switch 28 through the switching driver 30. Therefore, in FIG. 2, except for the Zener diode 26, the switch 28, the switching driver 30, and the controller 32, the other components are the same as in FIG. 1, and accordingly, reference numerals are the same.

In FIG. 2, the ground plate of the photosensitive drum 10 is connected to the switch 28 as well as to the ground through the zener diode 26, unlike in FIG. 1. At this time, the zener diode 26 has a cathode connected to the ground plate of the photosensitive drum 10 and an anode connected to the ground. The switch 28 is connected between the connection point between the ground plate of the photosensitive drum 10 and the zener diode 26 and ground. In FIG. 2, the switch 28 is an example of using a solenoid switch, and is switched on and off by the switching driver 30. The switching driver 30 is connected between the switch 28 and the controller 32 and switches the switch 28 under the control of the controller 32. In the switching driver 30, a driving coil 36 installed corresponding to the switch 28 is connected between the power supply voltage B + and the collector terminal of the transistor 38, and the diode 34 is connected in parallel with the driving coil 36. Is connected, the emitter terminal of the transistor 38 is grounded and the base terminal is connected to the control signal output terminal of the controller 32. Therefore, when the control signal is output from the controller 32 at the "high" level, the transistor 38 is turned on and the switch 28 is turned on by the current flowing in the drive coil 34 accordingly. Alternatively, when the control signal is output from the controller 32 to the "low" level, the transistor 38 is turned off and thus the switch 28 is turned off because no current flows in the drive coil 34. The controller 32 uses a controller provided in a conventional image forming apparatus. According to the present invention, the controller 32 switches the switch 28 from the time of starting to charge the surface of the photosensitive drum 10 each time printing starts. The switch 28 is then turned on when the charged region on the photosensitive drum 10 reaches the developing region.

In the image forming apparatus of FIG. 2 as described above, each time the printing starts anew, the controller 32 turns off the switch 28 during the section T of FIG. The ground plate of the photosensitive drum 10 is then connected to ground via a zener diode 26. Accordingly, in the photosensitive drum 10, the portion of the surface of the photosensitive drum 10 from the position in contact with the charging roller 12 to the position in contact with the developing roller 14, that is, the portion corresponding to the T section shown in FIG. Unlike, a constant surface potential is formed by the voltage of the zener diode 26. Accordingly, when the uncharged region of the photosensitive drum 10 corresponding to the T section comes into contact with the developing roller 14, the potential difference with the developing roller 14 is reduced. Therefore, movement of the toner from the developing roller 14 to the photosensitive drum 10 in the non-printing section is prevented. Therefore, a phenomenon in which the leading end or the back side of the first sheet of paper is contaminated due to toner contamination every time a new printing is started conventionally is prevented.

Then, when the charged region on the photosensitive drum reaches the developing region, that is, after the T section, the controller 32 turns on the switch 28. The ground plate of the photosensitive drum 10 is then directly connected to ground via switch 28 instead of through the zener diode 26. As a result, a normal electrophotographic process is then performed as usual.

Therefore, the surface potential on the photosensitive drum 10 is kept constant from the start of charging the surface of the photosensitive drum 10 each time a new printing is started until the charged region on the photosensitive drum 10 reaches the developing region. Contamination due to toner moving from the developing roller 14 to the photosensitive drum 10 surface in the non-printing section can be prevented.

Meanwhile, in the above description of the present invention, specific embodiments have been described, but various modifications may be made without departing from the scope of the present invention. Particularly, in the embodiment of the present invention, the surface potential on the photosensitive drum 10 is kept constant by the zener diode 26 voltage in the non-printing section, but other components capable of providing a constant potential instead of the zener diode 26 are provided. Can also be used. Therefore, the scope of the invention is not to be determined by the described embodiments, but should be determined by the equivalent of the utility model registration claims and utility model registration claims.

As described above, the present invention has an advantage of preventing contamination of the recording paper due to the toner by preventing the toner from moving from the developing roller to the photosensitive drum surface in the non-printing section at the start of a new printing.

Claims (5)

An image forming apparatus employing an electrophotographic developing method, Toner contamination prevention device characterized in that the surface potential on the photosensitive drum is kept constant from the time of starting to charge the surface of the photosensitive drum each time a new printing is started until the charged region on the photosensitive drum reaches the developing region. . An apparatus according to claim 1, wherein the developing region is a contact portion between the photosensitive drum and the developing roller. An image forming apparatus employing an electrophotographic developing method, A zener diode connected between the ground plate of the photosensitive drum and the ground; A switch connected between the connection point between the ground plate of the photosensitive drum and the zener diode and the ground; A controller for turning off the switch from starting to charge the surface of the photosensitive drum each time a new printing is started and turning on the switch when the charged region on the photosensitive drum reaches the developing region; And a switching driving unit connected between the switch and the controller and switching the switch according to the control of the controller. 4. The toner contamination prevention device according to claim 3, wherein the switch is a solenoid switch. 4. The toner contamination prevention device according to claim 3, wherein the developing area is a contact portion between the photosensitive drum and the developing roller.