JPS6227766A - Method for adjusting image quality of copying machine - Google Patents

Abstract

PURPOSE:To obtain always copy images of the best quality automatically by giving a prescribed charging current and exposure voltage to an electrostatic charger and an exposure device in a prescan cycle to measure the latent image characteristic of a photosensitive body and correcting the current and the voltage in accordance with the measured value of the latent image characteristic to copy an original image in a copy cycle. CONSTITUTION:A control circuit 17 which controls exposure due to an illuminating lamp 10 and the charging current of an electrostatic charger 3 is provided for the purpose of obtaining always the best picture quality. A potential detector 20 which detects the potential of a dark potential part formed in a prescribed position of a photosensitive drum 1 with scanning light L is provided to face the surface of the photosensitive drum 1. This dark potential part is formed in the prescan cycle before execution of a series of blue, red, and green latent image forming processes. At this time, the control circuit 17 controls an exposure light source 22 and a charging power source 23 so that the exposure voltage and the charging current given from the exposure power source 22 and the charging power source 23 to the illuminating lamp 10 and the charger 3 are preliminarily set values.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an image quality adjustment method for a copying machine in which an electrostatic latent image is formed on a photoreceptor, then developed with toner, and the image is transferred to recording paper. I'll go.

- [Conventional technology] As is well known, this type of copying machine ■ Charge the photoreceptor to give it photosensitivity.

■Exposing the photoreceptor to a light image creates an electrostatic latent image.

■Illuminating the electrostatic latent image with toner.

■Transfer the developed image to recording paper.

■Fix the transferred image.

■Clean the photoreceptor.

By performing a series of steps, the image read from the original is recorded on recording paper.

In addition, in a multicolor copying machine, the original image is separated into colors, and each color separation image is charged, exposed, and developed as described above.

Repeating a series of transfer, fixing, and cleaning processes,
By superimposing images of each separated color on the same recording paper, a multicolor print identical to the original image is obtained.

In such monochrome or multicolor copying machines, the surface potential of the photoreceptor that forms the latent image changes due to changes in temperature and humidity.
Alternatively, it may change due to changes over time, etc., and it may become impossible to obtain a copy image that is faithful to the original.

Therefore, in the past, a method has been adopted in which trial printing is performed while manually adjusting the charging current of the charger, the Sakai image voltage of the developer, etc. until a good image quality is obtained.

[Problems to be Solved by the Invention] However, the method of manually adjusting image quality through test printing requires a lot of time to obtain the desired image quality, and also involves wasteful consumption of recording paper and toner. I ran into problems.

The object of the present invention was made in view of the above-mentioned problems, and the object is to provide an image quality adjustment method for a copying machine that is economical and can obtain optimal image quality without tedious work. It's about doing.

[Means for Solving the Problems] The present invention divides one copy cycle consisting of charging, exposure, development, transfer, fixing, and cleaning steps into a pre-scan cycle and a copy cycle, and in the pre-scan cycle, the charger The latent image characteristics of the photoreceptor are measured by applying a predetermined charging current and exposure voltage to the exposure device, and in the copy cycle, the charger and exposure device The original image is copied by correcting the charging current and exposure voltage applied to the original image.

[Function] In the prescan cycle, the current latent image characteristics of the photoreceptor are measured, and in the copy cycle, the charging current and exposure voltage are corrected based on the measured values, and the original image is copied. Therefore, even if the photoreceptor changes over time or the ambient temperature changes, the best image quality can always be obtained.

[Example] The present invention will be explained below based on Examples.

The figure is an overall configuration diagram of a three-color separation type multicolor copying machine to which the present invention is applied. In the same figure, 1 is @! A drum-type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) rotated around A2 in the direction of the arrow at a circumferential speed V; 3 is a charger that imparts photosensitivity to the photosensitive drum 1; 4 is an exposure section; 5Y; 5M and 5C are color toner developing devices corresponding to separated light, and in this embodiment, they are yellow, magenta, and cyan color toner developing devices, respectively. 6 is a drum wrapped with transfer paper, and 7 is a photosensitive drum cleaner.

Reference numeral 8 denotes a document mounting table, and the document G is placed on the table 8 with its image surface facing downward. Reference numeral 9 denotes an original scanning optical system that exposes the photosensitive drum 1 to light. Below the original mounting table 8, the system operates as an exposure light source from the left side of the table to the right side of the table along the lower surface at the same speed as the circumferential speed V of the photosensitive drum 1. Original illumination lamp 10
It consists of a first movable mirror 15 that reciprocates along with the scanner to scan the downward facing document surface on the table 8 through the table 8, and fixed second to fourth mirrors 12 to 14, and a print start button (not shown). When you press , the moving optical system 10.11 reciprocates and sequentially scans from the left to the right through the platform 8, and the scanning light is transmitted to the first mirror 11, the second mirror 12, and then the third mirror 13.
→ Photosensitive drum 1 in a rotationally driven state in the path of the fourth mirror 14
Images are sequentially formed on the surface by the exposure section 4.

15 is a color separation filter device, and a blue light transmission filter 15B and a green light transmission filter 15G are connected to the rotation axis thereof.
1 Red light transmission filter 15R1 Neutral filter 1
Install four 5N filters radially at 90 degree intervals.
'A: L'+ , :, t-j, and the rotation axis is 9
By rotating each filter by 0 degrees, each filter is positioned in the optical path of the scanning light. Further, this filter device 15 and the respective color developers 5Y, 5M, and 5C are related to each other, and when the blue filter 15B is switched to the optical path of the scanning light, the yellow toner developer 5Y is connected to the green filter 15G. When this happens, the magenta toner developer 5M operates, and when the red filter 15R operates, the cyan toner developer 5C operates.

On the other hand, the transfer paper wrapped drum 6 is driven to rotate in the direction of the arrow around the shaft 16 at the same circumferential speed as the photosensitive drum 1, and the transfer paper is fed to the drum 6 from a paper feed section (not shown). , and rotates together with the drum 6 while being wound around the circumferential surface of the drum 6.

Therefore, when you set the 1UiG on the stand 8 and press the print start button, after the color separation image of the original, it is charged, exposed, developed, and
A color print is created by repeatedly executing a series of image forming processes including transfer, fixing, and cleaning.

That is, if color separation is performed in the order of blue, green, and red, the blue filter 15B intervenes in the exposure optical path during the first image formation, and the yellow toner developer 5Y operates, so that A blue component image of the original image is formed on the surface of the photosensitive drum as a yellow toner image, which is a complementary color to blue, and the yellow toner image is transferred to the surface of the transfer paper wrapped around the circumferential surface of the drum 6. .

During the second image formation, the green filter 15G intervenes in the exposure optical path, and the magenta toner developer 5M works, so that the green component image of the original image is exposed as a magenta toner image, which is a complementary color to green. The magenta toner image is formed on the drum surface, and the yellow toner image is first transferred thereto, and then the magenta toner image is superimposed and transferred onto the transfer paper surface wrapped around the drum 6.

During the third image formation, the red filter 15R intervenes in the photosensitive optical path, and the cyan toner developing device 5C works, so that the red component image of the original image is converted to a cyan toner image complementary to red on the drum surface. The cyan toner image further transfers the already mentioned yellow and magenta toner images and is superimposed and transferred onto the transfer paper surface.

In this way, the same multicolor image as the original image is formed on the transfer sheet by superimposing the toners of each color. After the repetitive transfer process is completed, the transfer paper held on the drum 6 is separated from the drum 6 and sent to a fixing device (not shown) by a conveying device (not shown), where it is fixed.
The paper is ejected from the output tray as a multicolor print.

By the way, in this example, the best image quality is always 1q
In order to
A control circuit 17 is provided to control the charging current.

Roughly speaking, a potential detector 20 is provided facing the surface of the photosensitive drum 1 to detect the potential of a dark potential portion formed at a predetermined position of the photosensitive drum 1 using scanning light.

This dark potential area is formed in a prescan cycle before executing a series of blue, red, and green latent image forming processes. At this time, the control circuit 17 controls the exposure power source 22 and the charging power source 23 so that the exposure voltage and charging current applied from the exposure power source 22 and the charging power source 23 to the illumination lamp 10 and the charger 3 become set values set in advance. do. That is, the control circuit 17 forms a dark potential portion in a portion of the photosensitive drum 1 under predetermined exposure voltage and charging current conditions.

After forming a dark potential area for measuring the latent image characteristics of the photosensitive drum 1 in this manner in the first time period of the prescan cycle, the control circuit 17 controls the potential of this dark potential area at the position of the detector 20. is detected, and the latent image characteristics of the photosensitive drum 1 are measured. That is, the latent image characteristics of the photosensitive drum 1 are measured by detecting the tendency of potential attenuation when a dark potential is formed with a predetermined exposure amount and charging current. Then, when the copy cycle after the pre-scan cycle begins, the output voltages of the exposure power source and the charging power source are controlled to increase or decrease depending on the measured value of the latent image characteristics.

Incidentally, the prescan cycle may be performed in one copy cycle for copying one TL image or every time the copying process for each color is started, but considering the copying speed, it is necessary to start copying the first original image. It is more effective if you do it just before. This has the advantage that the image quality of the first document image and the image quality of subsequent document images are uniform.

Therefore, if the process of copying the original image is started after correcting the exposure amount of the exposure device and the charging current of the charger in this way, the latent image characteristics of the photosensitive drum may change over time, or the ambient temperature conditions etc. Color prints that are faithful to the original image can always be obtained even if the original image changes.

Although this embodiment has been described with reference to an example in which the present invention is applied to a multicolor copying machine, the present invention can also be applied to a black/white monochrome copying machine in exactly the same manner.

[Effects of the Invention] As explained above, the present invention divides one copy cycle consisting of charging, exposure, development, transfer, fixing, and cleaning steps into a pre-scan cycle and a copy cycle,
In the prescan cycle, the latent image characteristics of the photoreceptor are measured by applying a predetermined charging current and exposure voltage to the charger and exposure device, and in the copy cycle, the latent image characteristics of the photoreceptor are measured according to the measured values of the latent image characteristics of the photoreceptor measured in the prescan cycle. Since the original image is copied by correcting the charging current and exposure voltage applied to the charger and exposure device, it is possible that the latent image characteristics of the photoreceptor may change over time or the surrounding humidity conditions may change. Also, there is an effect that a duplicate image of the best image quality can always be obtained automatically.

[Brief explanation of the drawing]

The figure does not show one embodiment of the present invention, but is a block diagram. 1... Photosensitive drum, 3... Charger, 4... Exposure device, 5G, 5 yen, 5M:... Developing device, 6... Transfer paper wrapped drum, 7... Cleaner, 8...・・Manuscript mounting table,
9... Original scanning optical system, 10... Original illumination lamp,
15... Color separation filter device, 17... Control circuit,
20...Potential detector, 22...Exposure power supply, 23...
・Charging power supply.

Claims (3)

[Claims] (1) A charger that charges a photoconductor to give it photosensitivity, an exposure device that exposes the photoconductor with a light image to form an electrostatic latent image, and develops the electrostatic latent image with toner. In a copying machine equipped with a developing device and a transfer device that transfers the developed image onto recording paper, one copy cycle consisting of each process of charging, exposure, development, transfer, fixing, and cleaning is called a prescan cycle and a copy cycle. In the pre-scan cycle, a predetermined charging current and exposure voltage are applied to the charger and exposure device to measure the latent image characteristics of the photoreceptor, and in the copy cycle, the latent image characteristics of the photoreceptor measured in the pre-scan cycle are measured. A method for adjusting image quality of a copying machine, characterized in that a document image is copied by correcting a charging current and an exposure voltage applied to the charger and the exposure device according to a measured value of a characteristic. (2) The image quality adjustment method for a copying machine according to claim 1, wherein the latent image characteristics are measured by detecting a dark potential at a predetermined position on the surface of the photoreceptor. (3) The prescan cycle is performed prior to a copy cycle in which a first document image is copied among a plurality of copy cycles in which a plurality of document images are copied. How to adjust the image quality of a copying machine as described in section.