KR20050097676A - Image controlled electrophotographic printer and image control method thereby - Google Patents

Abstract

Disclosed are an electrophotographic printer in which an image is adjusted, and a method for adjusting the image. The printing machine in which the image is adjusted according to the present invention includes a photosensitive member charged by a charging voltage; Image forming means for forming an electrostatic latent image corresponding to the image on the charged photosensitive member; A developing device for developing an electrostatic latent image; A reflected light sensor for irradiating light onto an image portion on which the image is developed and a non-image portion on which the image is not developed, and measuring the intensity of reflected light reflected by the image portion and the non-image portion; And a control unit for measuring the density of the image unit and the non-image unit from the reflected light intensity, grasping the developing amount of the developing unit, and adjusting the charging voltage when the density and the developing amount satisfy a predetermined condition.

Description

Image controlled electrophotographic printer and image control method according thereto {Image controlled electrophotographic printer and image control method hence}

The present invention relates to a printing press for controlling an image and a method thereof, and more particularly to an electrophotographic printing press for adjusting an image and a method thereof.

In general, an electrophotographic printing machine forms an electrostatic latent image by scanning light onto a photosensitive member charged at a constant potential, and develops the electrostatic latent image with a toner of a predetermined color using a developing machine, and transfers it onto paper. Refers to an apparatus for fixing a monochrome image or a color image by fixing.

Electrophotographic printing presses are roughly classified into wet and dry electrophotographic printing presses, depending on the developer used. A wet electrophotographic printing press uses a developer in which powdery toner is dispersed in a liquid carrier. Dry electrophotographic printing presses use a two-component developer in which a powdered carrier and a toner are mixed or a one-component developer without a carrier. Hereinafter, a dry electrophotographic printer will be described. For convenience, a developer is referred to as a toner.

When printing color images, toners of yellow, magenta, cyan and black colors are usually required. Four developing devices are required. The color image forming method includes a single path method having four exposure units and a photoconductor, and a multipath method having one exposure unit and a photoconductor, respectively. In either case, the developing unit usually requires four developing units as described above.

The more the photoreceptor is used, the more the material encoded by mechanical friction is worn out and the thickness of the photosensitive layer becomes thinner. As the temperature inside the printer increases, the characteristics change. Also, in the case of the developer, the characteristics change while being mechanically driven. In particular, the toner is deteriorated after a certain period of time, and its characteristics deteriorate. As the amount of the toner decreases, the toner deteriorates, and thus the developing characteristics change. As a result, the developing amount increases under the same conditions, so that the image density is increased, and the reverse polar toner also increases in the toner, and the reverse polar toner adheres to the non-image area. As a result, toner is deposited on the non-image area of the paper, thereby deteriorating the image quality.

SUMMARY OF THE INVENTION An object of the present invention is to provide a printer and a method for controlling an image by detecting an amount of toner deposition on a photosensitive member, and adjusting a developing amount and a toner deposition amount by adjusting a charging voltage based on a developing parameter of a developer.

In order to achieve the above technical problem, the printing machine of the present invention is controlled by the photosensitive member charged by the charging voltage; Image forming means for forming an electrostatic latent image corresponding to the image on the charged photosensitive member; A developing device for developing the electrostatic latent image; A reflected light sensor for irradiating light onto an image portion on which the image is developed and a non-image portion on which the image is not developed, and measuring the intensity of reflected light reflected by the image portion and the non-image portion; And a control unit for measuring the density of the image unit and the non-image unit from the reflected light intensity, grasping the developing amount of the developing unit, and adjusting the charging voltage when the concentration and the developing amount satisfy a predetermined condition.

According to an aspect of the present invention, there is provided a method of controlling an image of a printer, the method including: forming an electrostatic latent image corresponding to an image on a charged photosensitive member, and developing the electrostatic latent image using a developer; Measuring image densities of the image portion where the electrostatic latent image is developed and the non-image portion that is not developed; Measuring a developing amount of the developing unit when the density of the image unit and the non-image unit satisfies a predetermined condition, respectively; And adjusting the charging voltage supplied to the photosensitive member when the developing amount satisfies the third condition.

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

FIG. 1 is a schematic block diagram of a multi-path electrophotographic printing press to which the present invention is applied. 1, a photosensitive drum 1, a charging roller 2, an exposure unit 3, four developing devices 4, and a transfer belt 5 are shown.

The photosensitive drum 1 is a photoconductive layer formed on the outer circumference of the cylindrical metal drum.

The charging roller 2 is an example of a charger for charging the photosensitive drum 1 to a uniform potential. The charging roller 2 supplies electric charge while rotating in contact or non-contact state with the outer peripheral surface of the photosensitive drum 1 so that the outer peripheral surface of the photosensitive drum 1 has a uniform potential. As the charger, a corona discharger (not shown) may be used instead of the charging roller 2.

The exposure unit 3 is provided below the photosensitive drum 1, and forms an electrostatic latent image by scanning light corresponding to image information onto the photosensitive drum 1 charged to have a uniform potential. Generally as the exposure unit 3, the laser scanning unit (LSU) which uses a laser diode as a light source is used.

The four developing units 4C, 4M, 4Y, and 4K each contain toners in solid powder of cyan (C), magenta (M), yellow (Y), and black (K) colors. Each of the developing rollers 25 is supplied to the electrostatic latent image formed in 1) to form a toner image. The four developing devices 4C, 4M, 4Y, and 4K are provided so that the developing roller 25 is spaced apart from the outer peripheral surface of the photosensitive drum 1 by a developing gap.

Toner images of cyan (C), magenta (M), yellow (Y) and black (K) colors sequentially formed on the photosensitive drum 1 are sequentially transferred and superimposed on the transfer belt 5 in a predetermined order. Color toner images are formed.

Reference numeral 12 denotes a transfer roller. The transfer roller 12 is installed to face the transfer belt 5. The transfer roller 12 is spaced apart from the transfer belt 5 while the color toner image is transferred to the transfer belt 5, and then transferred to the paper when the color toner image is completely transferred to the transfer belt 5. The belt 5 is contacted with a predetermined pressure.

Reference numeral 10 denotes a pre-transfer eraser. The transfer prestatic unit 10 removes the electric charges in portions (non-image regions) other than the portion where the toner image on the photosensitive drum 1 is formed before the toner image on the photosensitive drum 1 is transferred to the transfer belt 5. . Thereby, the transfer efficiency from the photosensitive drum 1 to the transfer belt 5 can be improved.

Reference numeral 7 denotes an antistatic lamp. The antistatic lamp 7 is an example of a static eliminator which removes electric charges remaining on the outer circumferential surface of the photosensitive drum 1 in the pre-charging step. The antistatic lamp 7 irradiates a predetermined amount of light to the outer circumferential surface of the photosensitive drum 1 to remove electric charges remaining on the surface of the photosensitive drum 1.

Reference numeral 8 is a power supply. The power supply 8 includes a developing bias for developing the toner from the developer 4 to the photosensitive drum 1, a first transfer bias for transferring the toner image from the photosensitive drum 1 to the transfer belt 5, and a transfer belt. A second transfer bias for charging the toner image from the paper (5) to the paper, and a charging bias provided to the charging roller 2 are provided.

Reference numeral 11 denotes a reflected light sensor. The reflected light sensor is used to measure the amount of development. That is, after exposing and developing an image of a certain size on the photosensitive member of the photosensitive drum 1, irradiating infrared rays to the developed image using a reflected light sensor, the intensity of the reflected light reflected from the image or non-image can be measured. have. The intensity of the reflected light appears in proportion to the amount of development, and the reflected light sensor 11 converts the intensity of the reflected light into an electrical signal and outputs the electrical signal. The reflected light sensor 11 is a CTD (Color Toner Density) sensor.

Reference numeral 6 denotes a control unit, which refers to a reference value stored in the storage unit 9 from the tone reproduction curve (TRC), which classifies the signal detected by the CTD sensor 11 according to each toner area density. Adjust

Now look at the image forming process by such a configuration.

The color image information is a mixture of information corresponding to cyan (C), magenta (M), yellow (Y), and black (K) colors, respectively. In this embodiment, cyan (C), magenta (M), yellow (Y), and black (K) are sequentially superimposed on toner images of each color on the transfer belt 5 in a specified order, and then transferred to paper. By fixing, a color image is formed.

The outer circumferential surface of the photosensitive drum 1 is charged to a uniform electric potential by the charging roller 2. When the optical signal corresponding to the cyan (C) color image information is scanned by the exposure unit 3 onto the rotating photosensitive drum 1, the light is scanned in the charge generating layer and the charge is generated through the charge transfer layer. The charge moves to the photoreceptor surface, canceling out the charge and lowering the surface potential. Therefore, a potential difference occurs between a portion where light is scanned and a portion where it is not, thereby forming an electrostatic latent image on the outer circumferential surface of the photosensitive drum 1.

When the electrostatic latent image approaches the cyan developer 4C while the photosensitive drum 1 rotates, the developing roller 25 of the cyan developer 4c starts to rotate. A developing bias is applied from a power supply (not shown) to the developing roller 25 of the cyan developer 4C. Then, only the cyan toner is attached to the electrostatic latent image formed on the outer circumferential surface of the photosensitive drum 1 across the developing gap Dg to form a cyan toner image.

When the cyan toner image approaches the transfer belt 5 by the rotation of the photosensitive drum 1, the toner image is changed by the first transfer bias and / or the contact pressure between the photosensitive drum 1 and the transfer belt 5. The transfer belt 5 is transferred.

When the toner image of cyan color is completely transferred to the transfer belt 5, the toner images of magenta (M), yellow (Y) and black (K) color are also superimposed on the transfer belt 5 through the above-described steps. Is formed.

The transfer roller 12 is spaced apart from the transfer belt 5 during the process. When toner images of four colors are all transferred to the transfer belt 5 in a superimposed manner, and a color toner image is formed on the transfer belt 5, the transfer roller 12 transfers the transfer of the color toner image to paper. Contact with the belt (5).

When the paper passes between the transfer belt 5 and the transfer roller 12, the color toner image is transferred to the paper by the second transfer bias, and the color toner image is subsequently formed by heat and pressure in the fixing unit (not shown). The color image formation is completed by sticking to and discharging it.

2 is a flowchart illustrating an image adjusting method according to the present invention. The illustrated image control method is performed by the controller 6 shown in FIG.

In general, in the case of a color printer, by adjusting the TRC to maintain image quality, the amount of toner developed for each color is adjusted to achieve an optimal development. In the present invention, the non-image part density is measured from the density of the image part and the amount of toner abnormally attached to the non-image part in the TRC adjusting function. The control unit 6 also grasps the amount of usage from the developer 4 attached to the printer. The controller 6 adjusts the image by adjusting the TRC by comparing the measured values with the reference value stored in the storage unit 9, or by adjusting the charging voltage to adjust the developing amount of the image portion and the toner adhesion amount of the non-image portion. This will be described in more detail as follows.

First, an electrostatic latent image corresponding to an image is formed on the photosensitive member of the photosensitive drum 1, and the electrostatic latent image is developed using the developing device 4 (step 31). The control unit 6 detects the intensity of the reflected light after irradiating infrared rays to the image portion developed on the photoconductor and the non-image non-developed image through the reflected light sensor 11, thereby detecting the density of the image portion and the non-image portion on the photoconductor. Measure (step 32).

The control unit 6 compares the density of the image unit obtained through the reflected light sensor 11 with the first reference value stored in the storage unit 9 (step 33). When the density of the image unit is less than the first reference value, the control unit 6 Adjust the TRC (step 37). If the image portion density is greater than the first reference value, the controller 6 compares the non-image portion density with the second reference value (step 34). If the non-image concentration is less than the second reference value, the TRC is adjusted (step 37). If the non-image portion concentration is larger than the second reference value, the usage amount of the developer 4 is checked (step 35). If the usage amount of the developer 4 is less than the third reference value, TRC is executed (step 37). If the usage amount of the developer 4 is greater than the third reference value, after adjusting the charging voltage through the power supply 8 ( Repeat step 36). The charging voltage is adjusted by increasing a prescribed value. When the charging voltage is increased, the surface potential of the photoconductor is increased, thereby reducing the developing amount of the image portion, and reducing the toner adhesion amount of the non-image portion to obtain an optimized image.

According to the present invention, by detecting the concentration of the image portion and the non-image portion using a CTD sensor, and by determining the amount of use of the developer to adjust the charging voltage, to minimize the amount of the attachment of the non-image portion of the imager and increase the amount of developer on the developing roller An increase in density can be suppressed to obtain an optimal image.

FIG. 1 is a schematic block diagram of a multi-path electrophotographic printing press to which the present invention is applied.

2 shows a flowchart of an image control method according to the present invention.

Claims (5)

A photosensitive member charged by a charging voltage; Image forming means for forming an electrostatic latent image corresponding to the image on the charged photosensitive member; A developing device for developing the electrostatic latent image; A reflected light sensor for irradiating light onto an image portion on which the image is developed and a non-image portion on which the image is not developed, and measuring the intensity of reflected light reflected by the image portion and the non-image portion; And And a control unit for measuring the density of the image unit and the non-image unit from the reflected light intensity, grasping the developing amount of the developing unit, and adjusting the charging voltage when the density and the developing amount satisfy a predetermined condition. Printing machine adjusted. The method of claim 1, wherein the reflected light sensor An image-controlled printing press, characterized in that the CTD sensor. Forming an electrostatic latent image corresponding to the image on the charged photosensitive member, and developing the electrostatic latent image using a developing device; Measuring image densities of the image portion where the electrostatic latent image is developed and the non-image portion that is not developed; Measuring a developing amount of the developing unit when the density of the image unit and the non-image unit satisfies a predetermined condition, respectively; And And adjusting the charging voltage supplied to the photosensitive member when the developing amount satisfies the third condition. The method of claim 3, wherein the density measurement of the image portion and the non-image portion And irradiating light to the image portion and the non-image portion, respectively, and measuring the intensity of light reflected from the image portion and the non-image portion, respectively. The method of claim 3, And adjusting the TRC if the density and the developing amount do not satisfy the respective conditions.