KR100193816B1 - Developing bias voltage control method for printing environment recognition - Google Patents

Abstract

[Technical field to which the invention described in the claims belong]

An image forming apparatus employing a one-component nonmagnetic contact development method.

[Technical Challenges to Invent]

A development bias voltage control method for accurately recognizing a printing environment required for obtaining an optimal image density is provided.

[Summary of the solution of the invention]

The developing bias voltage is applied to the developing means before the printing environment recognition section to keep the potential between the developing means and the photosensitive member constant, and then check the amount of current flowing through the transfer roller so that the optimum transfer voltage can be applied.

[Important Uses of the Invention]

It can be used for laser beam printers.

Description

Developing bias voltage control method for printing environment recognition

1 is a diagram illustrating a connection state between a high voltage power supply unit (HVPS) and various rollers for explaining a bias voltage applied to various rollers of a laser beam printer using an electrophotographic development method.

FIG. 2 is a timing diagram of voltage application applied to various rollers in FIG.

3 is an equivalent circuit diagram showing the relationship between the impedance of the photosensitive drum 10 and the transfer roller 20 and the current I flowing to the transfer roller 20 by the transfer bias voltage.

4 is a flowchart illustrating various bias voltage application control according to an embodiment of the present invention.

5 is a timing diagram of bias voltage application according to FIG. 4;

6 shows an example of surface potential change of the photosensitive drum which is changed according to the printing environment and the developing bias voltage.

The present invention relates to an image forming apparatus employing a one-component nonmagnetic contact development method, and more particularly to a development bias voltage control method for correctly recognizing a printing environment.

In general, image forming apparatuses such as laser beam printers, LED printers, and digital copiers have developed process conditions for obtaining optimal image density at room temperature and humidity. That is, the general image forming apparatuses set the optimum development process conditions in order to minimize the problems caused by the change of the printing environment such as temperature and humidity. One problem that may occur when the printing environment changes is an example of a decrease in image density when the temperature of the air is increased. The reason why the image density decreases with temperature change is as follows.

If the temperature in the air is high, the electrical resistance value is relatively decreased, and thus the transfer bias voltage applied to the transfer roller is decreased. As a result, the amount of toner transferred from the photosensitive drum onto the paper is reduced, and the image density is lowered. Accordingly, in the image forming apparatus using the conventional electrophotographic development method, the current density applied to the transfer roller is fed back to recognize the change in the printing environment, and the new transfer bias voltage is newly applied to prevent the image density from dropping.

Hereinafter, a process of recognizing a printing environment of a conventional image forming apparatus will be described by using a laser beam printer employing a one-component nonmagnetic contact development method as an example.

1 is a diagram illustrating a connection state of a high voltage power supply (hereinafter referred to as HVPS) 22 and various rollers for explaining bias voltages applied to various rollers of a laser beam printer. In FIG. 1, the HVPS 22 is connected to a microprocessor unit (MPU) 24 which performs overall control operations of the laser beam printer, and applies bias voltages to various rollers under the control of the MPU 24. The charging roller 12 has a potential of about -1.4 [KV] by a charging bias voltage (hereinafter referred to as Vc) applied from the HVPS 22 and accordingly, the photosensitive drum (contacted with the charging roller 12) 10) It also has a surface potential of about -750 [V]. The laser scanner unit 14 as an exposure means generates a laser beam according to the image data to expose the photosensitive drum 10 to form an electrostatic latent image on the photosensitive drum 10. The developing roller 16 has a surface potential of about -400 [V] by the development bias voltage (hereinafter referred to as VD) applied from the HVPS 22. At this time, the toner in the toner hopper (not shown) is frictionally charged to (-) by the developing roller 16 to exhibit a potential of (-), and moves to the developing area by rotation of the sleeve. Meanwhile, the amount of the toner moved to the developing area is controlled by the regulating blade 18 '. On the other hand, the supply roller 18 receives a supply bias voltage (hereinafter referred to as VSP) from the HVPS 22 and supplies a toner in the toner hopper to the developing roller 16. Then, the toner of the negative potential moved to the developing region is moved to the exposure region of the photosensitive drum 10 by the electrostatic force with the surface potential on the photosensitive drum 10. The transfer roller 20 transfers the toner formed on the photosensitive drum 10 by the transfer bias voltage (hereinafter referred to as VT) of about 1.5 [KV] applied from the HVPS 22 onto the paper. The MPU 24 connected to the HVPS 22 has a built-in A / D converter and a memory, receives feedback of the amount of current applied to the transfer roller 20 through the A / D converter, recognizes a change in printing environment, and accordingly transfer transfer bias. The voltage VT is controlled.

Hereinafter, a section in which the MPU 24 detects a change in printing environment by detecting an amount of current applied to the transfer roller 20 will be described with reference to FIG. 2.

2 is a timing diagram of bias voltages applied to various rollers 12, 16, 18, and 20 by the HVPS 22 in a conventional laser beam printer. In FIG. 2, section A represents a pre-rotation section of the main motor, section B represents a printing environment recognition section, that is, a section for detecting the amount of current applied to the transfer roller 20, Section D represents the transfer section, section E represents the post-rotation of the main motor, and section G represents the development section. In FIG. 2, section B is a section in which the MPU 24 checks the current I flowing through the transfer roller 20 to recognize the printing environment, and is calculated as the current I = VT / (ZD + ZTR). At this time, ZD represents the impedance of the photosensitive drum 10, ZTR represents the impedance of the transfer roller (20). That is, the MPU 24 reads the value of the current I according to the change of the overall impedance (ZD, ZTR) according to the printing environment in the section B to recognize the printing environment. The relationship between the VT, ZD, ZTR, and the current I is shown in an equivalent circuit as shown in FIG. 3. Although the impedance ZTR of the transfer roller 20 is constant in FIG. 3, when the surface potential of the photosensitive drum 10 (which is referred to as VOPC) varies, the current I also changes accordingly. This will be described in detail based on the experimental data described in the following [Table 1]. The following experimental data is the result measured by making the impedance of the transfer roller 20 constant.

Referring to [Table 1], even if the impedance of the transfer roller 20 is constant, if the VOPC fluctuates, the printing environment recognition resistance also fluctuates. The reason why the VOPC fluctuates in the laser beam printer employing the one-component nonmagnetic contact developing method is that the charge of the photosensitive drum 10 is transferred to the developing roller 18 due to the contact between the photosensitive drum 10 and the developing roller 16. Because it is a transition. In general, the potential VOPC of the photosensitive drum 10 is more greatly changed at high temperature and high humidity and when the potential difference between the developing roller 16 is large. Therefore, in the laser beam printer employing the one-component nonmagnetic contact phenomenon, the potential of Vopc fluctuates when the printing environment changes, so the printing environment should be recognized as the optimal state in order to obtain the optimal image density.

Accordingly, an object of the present invention is to provide a developing bias voltage control method capable of accurately recognizing a printing environment by maintaining a constant photoelectric surface potential before a printing environment recognition section in an image forming apparatus employing a one-component nonmagnetic contact development method. Is in.

The present invention for achieving the above object is a development bias voltage control method for recognizing a printing environment of an image forming apparatus employing a one-component nonmagnetic contact development method, charging for charging the surface of the photosensitive member to a predetermined level when receiving a print command A first process of applying a bias voltage to the charging means, a second process of applying a predetermined level of development bias voltage to the developing means for adsorbing the developer on the surface of the photoconductor, and a predetermined level of transfer bias for printing environment recognition A third process of applying a voltage to the transfer means, a fourth process of detecting an amount of current flowing through the transfer means for recognizing a printing environment, and reapplying a transfer bias voltage corresponding to the detected current amount to the transfer means by the photosensitive member And a fifth process of transferring the developer adsorbed on the surface onto the paper.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

4 is a diagram illustrating various bias voltage application control flow diagrams according to an embodiment of the present invention, which is performed by the MPU 24 shown in FIG. That is, the MPU 24 controls the application of various bias voltages by storing a control program according to an embodiment of the present invention in an internal memory. 5 shows various bias voltage timing diagrams according to an embodiment of the present invention, and VT, VD, and VC represent transfer, development, and charge bias voltages applied by the HVPS 22, respectively. Referring to the potential levels of the respective bias voltages in FIG. 5, first, Vc maintains a potential level of -1.4 [KV] to charge the photosensitive drum 10, and the photosensitive drum 10 is approximately-by VD. Assume we have a VOPC of 750 [V]. VD has a potential level of -400 [V] before the G section (developing section) and the printing environment recognition section (B) for attaching the toner to the electrostatic three on the photosensitive drum (10). VT has potential levels of -1.0 [KV], 1.0 [KV], 1.2 [KV] and 1.0 [KV] in section A, section B, section C, section D and section E, respectively.

Hereinafter, referring to FIGS. 4 and 5, when various bias voltages are applied by the MPU 24, first, a print command for printing an image according to predetermined image data from an external device such as a host computer is described. If it is received in step 30, the MPU 24 proceeds to step 32 to drive the main motor. Various rollers provided by the driving of the main motor rotate. After driving the main motor, the MPU 24 proceeds to step 34 so that the VC of -1.4 [KV] is applied to the charging roller 12, and the VT of -1.0 [KV] is applied to the transfer roller 20. 22). The VC of -1.4 [KV] causes the VOPC to have a potential level of about -750 [V] in section A. After applying the charging bias voltage Vc and the transfer bias voltage VT, the MPU 24 proceeds to step 36 to control the HVPS 22 to apply the developing bias voltage VD to the developing roller 16. At this time, the application time T1 of the developing bias voltage VD should be before the printing environment recognition section B for checking the current flowing in the transfer roller 20. The reason is to stabilize the potential level of Vopc by reducing the potential difference between the photosensitive drum 10 and the developing roller 16. Thus, when the developing bias voltage VD of -400 [V] is applied before the printing environment recognition section B, a potential difference of about 350 [V] occurs between Vopc and VD. On the other hand, the MPU 24 proceeds to step 38 to check whether the printing environment recognition section (B). As an inspection method, it is possible to check by checking the rotation time of the main motor. If the result of the 38th step is a printing environment recognition section, the MPU 24 controls the HVPS 22 so that the transfer bias voltage VT is 1.0 [KV], and then proceeds to step 40 to determine the amount of current applied to the transfer roller 20. Check it. Thereafter, the MPU 24 proceeds to step 42 to control the HVPS 22 such that a transfer bias voltage VT is applied to the transfer roller 20 to obtain an optimum image density according to the checked current amount. In this case, the transfer bias voltage VT for obtaining an optimal image density according to the amount of current may be implemented in the MPU 24 in a ROM table.

Hereinafter, referring to FIG. 6, the difference of the printing environment recognition effect according to the potential difference between Vopc and VD will be described.

FIG. 6 shows an example of the change of Vopc according to the printing environment and VD. As a result, the VC is constantly applied to the charging roller 12 at -1.4 [KV] and the Vopc is measured by the transfer roller 20. to be. In Fig. 6, the abscissa and the ordinate represent the printing environment (° C /% RH) and Vopc, respectively, and the solid and dashed lines represent the VDs of the -400 [V] and 0 [V] potential levels, respectively. Referring to FIG. 6, when VD has a potential of -400 [V], Vopc exhibits a stable potential level at about -750 [V] potential regardless of the printing environment change. On the other hand, when VD has a potential of 0 [V], Vopc shows a potential variation of -600 [V] to -720 [V] according to the printing environment change. Therefore, the MPU 24 can recognize the printing environment accurately when the Vopc potential fluctuation is small, and if the printing environment is correctly recognized, the optimal VT can be applied to the transfer roller 20 accordingly, thereby obtaining the optimum image density. It will be possible.

As described above, since the present invention recognizes the printing environment in a state in which the potential difference between the developing roller and the photosensitive drum is reduced, accurate printing environment recognition is achieved, and thus an optimum image density can be obtained.

Meanwhile, in the embodiment of the present invention, a laser beam printer using the one-component nonmagnetic contact development method has been described as an example, but may be applied to an image forming apparatus using the one-component nonmagnetic contact development method without any modification.

Claims (1)

A development bias voltage control method for recognizing a printing environment of an image forming apparatus employing a one-component nonmagnetic contact developing method, comprising: applying a charging bias voltage to a charging means for charging a photosensitive member surface to a predetermined level when a print command is received; A process of applying a predetermined level of developing bias voltage to the developing means for adsorbing the developer on the surface of the photoconductor; and a third process of applying a predetermined level of transfer bias voltage to the transferring means for recognizing a printing environment. And a fourth step of detecting an amount of current flowing through the transfer means for recognizing a printing environment, and applying a transfer bias voltage corresponding to the detected amount of current to the transfer means by applying a developer adsorbed on the surface of the photoreceptor. The development bias voltage control method comprising the fifth step of transferring to.