KR20010038693A - Method for controlling of developing bias voltage level in image forming apparatus - Google Patents

Abstract

PURPOSE: A developing voltage control method of an image forming apparatus is provided to optimize printing quality by automatically controlling a developing voltage responding to a temperature change of an inside of an image forming device. CONSTITUTION: When a printing instruction is received(S1), a transcription resistance of a transcription roller is measured(S2). A stored developing voltage of a developing roller responding to the measured transcription resistance of a transcription roller is detected(S3). A temperature of an inside of an image forming device is measured(S4). The measured temperature of an inside of an image forming device is compared with a reference temperature(S5). When the measured temperature is greater than the reference temperature, the detected developing voltage is provided to a developing roller(S7). When the measured temperature is smaller than the reference temperature, the developing voltage is increased by a set variable value and is provided to the developing roller(S6).

Description

TECHNICAL FOR CONTROLLING OF DEVELOPING VOLTAGE OF IMAGE FORMING DEVICE

The present invention relates to a developing voltage control method of an image forming apparatus. More particularly, in an image forming apparatus employing an electrophotographic developing method, the developing voltage is automatically adjusted in response to a change in the resistance value of the transfer roller and the cabin temperature. The present invention relates to a developing voltage control method of an image forming apparatus in which an optimum printing quality can be maintained by adjusting.

In general, the electrophotographic developing method refers to a method of moving a toner attached to a photosensitive member to a recording paper by using an electric field. In the electrophotographic developing method using a conventional dry toner, the toner on the photosensitive member is transferred to the recording paper with electrostatic force. Corona charger method and bias roller method are available.

The bias roller method is advantageous in miniaturization because the circumference of the transfer roller is in contact with the photosensitive member, and mechanically pressurizes the back surface of the recording sheet in contact with the photosensitive member to provide excellent adhesion and various configurations of the transfer structure of the recording sheet. In addition, since the transfer roller and the photoreceptor are in contact with each other, electrical efficiency can be obtained and the applied voltage can be lowered. Since it is not a discharge method, ozone is not generated, and transfer efficiency is excellent and a high quality output image can be obtained.

The bias rollers generally have an electroconductive soft roller method using a semiconductive sponge in contact with the back surface of a photosensitive member or a recording paper, and an ion conductive hard roller method using a semiconductive rubber.

The transfer voltage required to transfer the toner attached to the photosensitive member onto the recording paper can be expressed by the following equation.

The transfer voltage acts to transfer the transfer potential to the toner potential of the toner layer on the photoconductor to separate the toner layer from the photoconductor and to move it to the recording paper using an electric field. The remaining toner remaining in the photoconductor in the separated toner layer is charged again by a high-voltage charging voltage and recovered to the developing roller side. The electric field at this time is called a recovery electric field.

On the other hand, the formation of the toner layer on the image portion on the photoconductor is called development, and the development work is carried out using a development bias voltage ( ) And the toner is moved to the photoreceptor to form a visible image by using an electric field caused by the potential difference of the image portion on the photoreceptor.

However, according to the conventional electrophotographic image forming apparatus, the following problem (s) occur.

In other words, the transfer roller and the development roller used in the conventional hard roller type image forming apparatus generally use ion conductive rollers in which the current flow is made of ions, and these rollers have electric resistances that vary depending on the environment, particularly at low temperatures. There is a problem that the value of the electrical resistance increases sharply. In the case of the developing roller, when the resistance value increases at low temperature, the recovery electric field for recovering the residual toner remaining on the photoconductor after transfer to the developing roller is insufficient, resulting in afterimages on the previous printed image. As the amount of developing current increases, the image becomes darker and the output becomes darker overall.

On the other hand, if the standing time of the system becomes longer after continuous operation or after performing the initial process, the temperature in the cabin decreases and the resistance of the developing roller increases. It will descend sharply. As a result, the printing density is initially blurred and gradually increases.

Accordingly, the present invention is to solve such a problem (s), the object of the present invention is to detect the resistance value of the ion conductive transfer roller having a material characteristic similar to the development roller indirectly to the resistance value of the development roller. By measuring the temperature in the cabin and controlling the developing voltage automatically in response to the change in the cabin temperature, the developing voltage control method of the image forming apparatus can provide the optimum printing quality in response to the change in the cabin environment. In providing.

1 is an example of an image forming apparatus applied to the present invention, which is a system configuration diagram of a printer and a computer.

2 is a schematic structural diagram of a printer applied to the present invention,

3 is a schematic block diagram of a printer applied to the present invention,

4 is an operation flowchart showing a process of developing voltage control method according to the present invention,

5 is a voltage waveform diagram showing a developing bias voltage level corresponding to a change in resistance of a developing roller according to the present invention.

<Description of the code | symbol about the principal part of drawing>

200: printer 204: transfer roller

205: developing roller 213: central processing unit

214: memory 215: developing voltage control unit

216: sensor unit

A feature of the present invention for achieving such an object (s) is an image forming apparatus employing an electrophotographic developing method: when a print command is received, measuring a transfer resistance value of a transfer roller; Detecting a developing voltage value of the previously developed developing roller corresponding to the measured transfer resistance value of the transferring roller; Measuring a cabin temperature value of the image forming apparatus; Comparing the measured cabin temperature value with a preset reference temperature value; If the in-flight temperature value is greater than the reference temperature value, the detected developing voltage is supplied to the developing roller; If the in-flight temperature value is smaller than the reference temperature value, the detected developing voltage is boosted by a predetermined variable amount to supply the developing roller.

Here, the transfer voltage is varied and supplied to the transfer roller until a reference current having a predetermined size flows; When a reference current having a predetermined magnitude flows through the transfer roller, the current transfer voltage supplied to the transfer roller is detected to detect the transfer resistance value of the transfer roller.

In addition, the respective developing voltage values are stored in the form of a look-up table so as to correspond one-to-one to the transfer voltage value when the preset reference current flows in the transfer roller; Any developing voltage value corresponding to the transfer voltage value of the transfer roller changed in response to the resistance change of the transfer roller is detected from the look-up table.

At this time, it is preferable that the transfer roller and the developing roller are each made of the same material that reacts with the same characteristics to the change in the cabin temperature.

Hereinafter, exemplary embodiment (s) of the present invention will be described in detail with reference to the accompanying drawings. First, in adding reference numerals to the elements of each drawing, it should be noted that the same elements are denoted by the same reference numerals as much as possible even if they are displayed on different drawings. In addition, in the following description there are shown a number of specific details, such as components of the specific circuit, which are provided only to help a more general understanding of the present invention that the present invention may be practiced without these specific details. It is self-evident to those of ordinary knowledge in Esau. In describing the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

1 shows an example of an image forming apparatus applied to the present invention, a system configuration diagram of a printer and a computer is shown, FIG. 2 shows a schematic structural diagram of a printer applied to the present invention, and FIG. 3 is applied to the present invention. A schematic block diagram of a printer is shown. FIG. 4 is a flowchart illustrating an operation of a developing voltage control method according to the present invention. FIG. 5 is a developing bias corresponding to a resistance change of a developing roller according to the present invention. A voltage waveform diagram showing the voltage level is shown.

First, the configuration of the present invention will be described with reference to FIGS. 1 to 3.

As shown in FIG. 1, the computer 100 and the printer 200 are connected through a printer cable 300. As the print data is transmitted from the computer 100, the printer 200 images the print data. Then print.

On the other hand, an image forming apparatus employing an electrophotographic developing method such as a copying machine, a printer, or the like has a pickup roller 201, a charging roller 202, to print predetermined image data on a printing paper as shown in FIG. An organic photoconductive (OPC) 203, a transfer roller 204, a developing roller 205, a supply roller 206, a fixing unit 207, and an exposure apparatus 208 are formed. That is, when the charging roller 202 charged by the high-voltage charging voltage rotates to evenly charge the photosensitive member applied to the outer circumferential surface of the photosensitive drum 203, the photosensitive drum 203 in which the light generated by the exposure apparatus 208 is charged is charged. The electrostatic latent image to be printed is formed on the surface. Thereafter, a potential difference is generated between the supply roller 206 supplied with the high voltage supply voltage and the developing roller 205 supplied with a voltage lower than the supply roller 206. Thus, the negative charge moves from the feed roller 206 to the developing roller 205. The toner supplied to the developing roller 205 is applied to an electrostatic latent image formed on the surface of the photosensitive drum 203 to form a visible image. The high pressure transfer roller 204 transfers the visible image on which the toner applied on the surface of the photosensitive drum 203 is transferred to the recording paper 209 to be transferred. The visible image transferred to the recording paper 209 is fixed to the recording paper 209 by the high heat and pressure of the heating roller 210 and the pressing roller 211 constituted in the fixing unit 207, thereby completing the printing process.

At this time, the supply voltage, the developing voltage, the transfer voltage, and the charging voltage described above are continuously supplied to the supply roller 206, the developing roller 205, the transfer roller 204, and the charging roller 202 until the printing operation is completed. Supplied. Then, the heating roller 210 in the fixing unit 207 is kept turned on until the printing operation is completed.

In addition, a transfer transfer lamp 212 is provided between the developing roller 205 and the transfer roller 204 to scan the photosensitive drum 203 with light having a wavelength of 650 nm generated by the transfer transfer lamp 212. By lowering the potential of the toner applied to the photosensitive drum 203, the bonding force of the toner to the photosensitive drum 203 is lowered to improve the transfer efficiency.

Meanwhile, referring to FIG. 3, a schematic configuration of a developing voltage control device applied to the present invention will be described. The central processing unit 213 generally controls the printer according to a predetermined program. In particular, the central processing unit 213 sets the developing voltage corresponding to the measured resistance value of the transfer roller 204, and sets the developing voltage according to the cabin temperature. Variable by)

The memory 214 stores various programs for the CPU 213 to control the printer, and print data to be printed through the printer. In particular, in the memory 214, the developing voltage value corresponding to the transfer voltage value of the transfer roller 204 is stored in the form of a look-up table, and the variable amount of the developing voltage which is variable in response to the cabin temperature ( ) Is stored.

The developing voltage control unit 215 controls the developing voltage to be supplied to the developing roller 205 according to the control signal of the central processing unit 213. In particular, the developing voltage controller 215 first sets the developing voltage in response to the resistance value of the transfer roller 204 under the control of the central processing unit 213, and sets the developing voltage primarily set in response to the cabin temperature. Variable amount stored in (214) Change by) to set the secondary.

The sensor unit 216 detects the cabin temperature value in the printer and provides the detected cabin temperature value to the central processing unit 213.

Referring to Figures 4 and 5 with respect to the operation of the present invention having such a configuration as follows.

When a print command is received (S1), the central processing unit 213 measures the resistance value of the transfer roller 204 (S2). Here, the central processing unit 213 supplies the transfer voltage of the preset initial value to the transfer roller 204, thereby measuring the current value flowing through the transfer roller 204. If the detected current value is smaller than the preset current value, the CPU 213 increases the transfer voltage by a predetermined level from the preset initial value and supplies it to the transfer roller 204. When the current value flowing through the transfer roller 204 becomes the same as the preset current value by repeating this process, the CPU 213 forms a look-up table in the memory 214 corresponding to the corresponding transfer voltage value. The detected developing voltage value is detected and is temporarily stored in the memory 214 (S3). Here, since the transfer roller 204 and the developing roller 205 are made of the same or extremely similar material, the resistance variation of the transfer roller 204 and the resistance variation of the developing roller 205 have a proportional relationship with each other. Therefore, when the developing voltage of the developing roller 205 corresponding to the transfer voltage of the transfer roller 204 is set in accordance with a constant proportional relationship, the developing voltage value of the developing roller 205 corresponding to the resistance variation of the transfer roller 204 is set. Can be obtained. This is a method capable of detecting an optimum developing voltage value to be supplied to the developing roller 205 in an extremely simple method in an existing printer which cannot directly measure the resistance value of the developing roller 205.

Thereafter, the central processing unit 213 controls the sensor unit 216 to detect the cabin temperature value in the printer. Accordingly, the sensor unit 216 senses the temperature in the printer, and transmits the detected cabin temperature value to the central processing unit 213 (S4).

The central processing unit 213 determines whether the cabin temperature value detected by the sensor unit 216 is smaller than the preset reference temperature value (S5). If the temperature in the cabin is smaller than the preset reference temperature in this step S5, this means that the resistance of the transfer roller 204 and the developing roller 205 becomes high, resulting in a phenomenon that the print density of the printed matter is blurred. The central processing unit 213 sets the development voltage level based on a preset variation amount from the development voltage value temporarily stored in the memory 214. ) And supplied to the developing roller 205 (S6) ("A" waveform in FIG. 5).

If, in the above step (S5), the cabin temperature value is greater than the preset reference temperature value, this is a normal state or the resistance of the transfer roller 204 and the development roller 205 is lowered, so that the print density of the output is increased. In this case, the central processing unit 213 sets the developing voltage level to the developing voltage value temporarily stored in the memory 214 and supplies it to the developing roller 205 (S7) ("B" waveform in Fig. 5). ).

At this time, as shown in FIG. 5, when the cabin temperature is high, the resistance of the developing roller 205 is low, the image is darkened, and the resolution is low. In this case, the developing voltage is supplied at a level lower than room temperature.

In addition, if the resistance value of the developing roller 205 changes due to the characteristics of the developing roller 205, or if the temperature of the aircraft is lowered by preventing the device for a long time, the resistance value increases and the image is blurred. The voltage should be increased compared to the high temperature.

If the temperature in the cabin is drastically lowered or the system is initially driven, the resistance of the developing roller 205 becomes very high, and the recovery electric field is reduced so that the residual tuner cannot be recovered sufficiently. The developing voltage of the developing roller 205 is set to a lower value than that at the high temperature so that the residual toner magnetized by the charging roller 202 is sufficiently recovered by the developing roller 205 and the supply roller 206.

As the resistance of the developing roller 205 increases, the printing density is blurred. If the developing voltage of the developing roller 205 is further increased, the printing density increases, whereas the recovery electric field becomes smaller. The phenomenon that the afterimage of the image is printed occurs. Since the afterimage causes direct deterioration of the print quality, in order to prevent this, the deterioration of the print quality due to the afterimage is prevented by taking a method of increasing the recovery field by lowering the developing voltage when the recovery field is small.

Therefore, the development voltage is set by indirectly measuring the resistance value of the developing roller 205, which cannot be measured directly, using the transfer roller 204, and the developing voltage is changed by a predetermined level in response to a change in the cabin temperature. It is possible to maintain the optimum print quality by supplying the liquid.

As described above, although the specific embodiment (s) have been described in the detailed description of the present invention, various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiment (s) but should be defined by the claims below and equivalents thereof.

As a result, according to the developing voltage control method of the image forming apparatus according to the present invention, the following advantage (s) occurs.

In other words, the resistance value of the ion-conducting transfer roller having a material characteristic similar to that of the developing roller is detected to measure the resistance of the developing roller indirectly, and the cabin temperature is measured to automatically develop the developing voltage in response to the change in the cabin temperature. By controlling, it is possible to provide an optimum print quality in response to environmental changes in the cabin.

Claims (4)

In an image forming apparatus employing an electrophotographic developing method: Measuring a transfer resistance value of the transfer roller when a printing command is received; Detecting a developing voltage value of a previously developed developing roller corresponding to the measured transfer resistance value of the transferring roller; Measuring an in-flight temperature value of the image forming apparatus; Comparing the measured in-flight temperature value with a preset reference temperature value; Supplying the developing voltage detected in the detecting step to the developing roller when the cabin temperature value is greater than the reference temperature value; And And boosting the developing voltage detected in the detecting step by a predetermined variable when the in-flight temperature value is smaller than the reference temperature value and supplying the developing voltage to the developing roller. The method of claim 1, wherein the measuring of the transfer resistance value of the transfer roller comprises: Supplying the transfer voltage by varying the transfer voltage until a reference current having a predetermined magnitude flows into the transfer roller; And a resistance value of the transfer roller is detected by detecting a current transfer voltage supplied to the transfer roller when the reference current having a predetermined size flows through the transfer roller. The method of claim 1, wherein the detecting of the developing voltage value of the developing roller comprises: Each developing voltage value is stored in a look-up table form so as to correspond one-to-one to the transfer voltage value when the reference current preset in the transfer roller flows; And a development voltage value corresponding to the transfer voltage value of the transfer roller changed in response to the resistance change of the transfer roller is detected from the look-up table. The method according to any one of claims 1 to 3, And the transfer roller and the developing roller are each made of the same material that reacts to the change in the cabin temperature with the same characteristics.