JPH02266373A - Copying machine - Google Patents

Abstract

PURPOSE:To obtain a stable image for a long time by providing an exposure control means which controls irradiation intensity of an exposing means according to the output of a reflection intensity detecting means. CONSTITUTION:At the time of pre-scanning, the reflected light of a standard white board 22 detects the extent of contamination of an optical system (mirror, lens), and the light reflected from an original 6 detects blackness of the original (an original and newspapers written on white paper, and an original written on a colored paper). Thus, when the intensity of the light reflected from the standard white board 22 is weakened, a signal is sent to a lamp controller from a detector 23 to raise a scan/exposure voltage. The intensity of the light reflected from the standard white board 22 is constant. When the intensity of the light reflected from the original 6 is weak, the optical system is not contaminated. However, the detector decides that the original is black so that the scan/exposure voltage is raised. When both intensities of the lights reflected from the standard white board 22 and the original 6 are weak, the detector detects that there is contamination of the optical system and the original is black. Consequently, the scan/exposure voltage is raised. Therefore, a copied picture without fogging can be obtained for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to, for example, an electrophotographic copying machine.

BACKGROUND OF THE INVENTION The operation of a conventional copying machine will be explained using FIG. In the figure, reference numeral 1 denotes a photoreceptor which rotates in two directions of arrows. Reference numeral 3 denotes a charger, which applies an electrostatic charge to the photoreceptor 1. Reference numeral 4 denotes a solid black prevention lamp, which erases unnecessary portions of the static charge applied to the photoreceptor 1.

Reference numeral 6 is a light image, which is irradiated with the pattern of the original 6 by an exposure lander 7, and mirrors (a, e, 1o, 11) and a lens 1.
2 onto the photoreceptor 1.

Here, an image of electrostatic charge on the photoreceptor 1, a so-called electrostatic latent image, is formed. 13 is a developing device, in which the electrostatic latent image is visualized. A transfer charger 14 transfers the developer on the photoreceptor 1 onto the paper 15.

Is 16 a separation zone? 1! It neutralizes the static electricity between the photoreceptor 1 and the paper 15 and separates the paper 16 from the photoreceptor 1. A conveying section 17 guides the paper 16 to which the developer is attached to a fixing section. 1
A cleaning section 8 removes untransferred developer on the photoreceptor 1. Reference numeral 19 is a static elimination lamp, which uniformizes the static electricity on the photoreceptor 1 for the next charging.

Move on to the exposure cycle.

Furthermore, the image forming process will be explained in detail. FIG. 2 shows the light attenuation characteristics of the photoreceptor. The electrostatic charge applied to the charger 3 is attenuated by light. In FIG. 2, when the light intensity of (a) is applied, the potential due to the electrostatic charge of aoov becomes point A, and the potential becomes 100V. In addition, when the light intensity of (→ is applied, the point B is reached and the potential is 200V.Furthermore, the developer adheres according to the potential on the photoreceptor, so the higher the potential on the photoreceptor, the more developer will adhere. However, if the potential is low, only a small amount of developer will adhere.Normally, a developing bias voltage is applied to the developing device 13, and even if the potential on the photoreceptor 1 does not become 0, the developer will adhere. In this example, at the potential of point A, the developer hardly adheres, and at the potential of point B, the developer adheres to the extent that it becomes slightly darkened.

What is the potential at point 0?

It adheres to the developer so that it becomes completely black.

Therefore, when the exposure level is set to (G), a clear copy is obtained, but when the exposure level is set to (B)).

It will be a dirty copy. This is numerically referred to as "the background does not overlap" or "the background overlaps".

When you install a copy machine, you can get clean copies with no background in the beginning, but as you use it, the mirror becomes dirty with indoor dust and cigarette grease, and the exposure lamp deteriorates. The amount of light incident on the photoreceptor 1 was different from the initial setting value, resulting in a copy with background fog.

In conventional machines, service personnel regularly inspected them, cleaned the optical system, and adjusted the brightness of the exposure lamp. Furthermore, as shown in Japanese Patent Publication No. 63-81685, an attempt was made to stabilize the surface potential in the dark and after exposure by incorporating a surface electrometer and adding complex control functions.

Problems to be Solved by the Invention However, with the above configuration, when the optical system (mirrors and lenses) becomes dirty due to long-term use of the copying machine due to dust in the air, the photoconductor 1 may The disadvantage is that the irradiation light becomes weaker, resulting in poorer copied images.

In view of the above problems, the present invention provides a control method for correcting the brightness of an exposure lamp so that the post-exposure position on a photoreceptor is always constant, and a control method for keeping developing conditions constant. The objective is to provide a copying machine that can provide stable images over a long period of time.

Means to solve problems In order to solve the above problems, a copying machine of the present invention is provided.

an exposure means for irradiating the original, an optical means for guiding the light image to the photoreceptor surface, and a reflection plate having a predetermined reflectance;
A reflection intensity detection means for detecting the reflection intensity of the reflection plate obtained through the optical means, and the irradiation intensity of the exposure means is controlled according to the output of the reflection intensity detection means, or the irradiation intensity of the developing device is controlled. It has a configuration for controlling the developing bias voltage.

Effects of the present invention, due to the above-mentioned B11 feature, the intensity of the light incident on the photoreceptor can be kept constant at all times, so the developing conditions can be kept constant for a long period of time.

The same stable copy image quality as the initial one can be maintained.

Embodiment A first embodiment of the copying machine of the present invention will be described below with reference to the drawings.

Note that the same components as in the conventional example are given the same reference numerals.

In No. 1, amorphous selenium, which is a photoreceptor, was used.

The material of the photoreceptor is not limited to amorphous selenium, as long as it is a material commonly used in electrophotography, such as OPC or a-silicon.

When the original 6 is set and a copy start button (not shown) is pressed, the photoreceptor 1 is rotated in the direction of the arrow 2 and the static elimination lamp 19 is turned on. Almost at the same time, the optical system begins to operate. First, the exposure lamp γ and the mirror 8 are located at the origin 2o, and begin to move toward the end point 21 at a speed of 120 W/sec.

At this time, a predetermined voltage is applied to the exposure lamp. This voltage is determined at the time of initial setting of the copying machine.

22 is a standard white plate. The reflectance is 82%.

Although the reflectance does not have to be this value, it is desirable that it be close to the reflectance of the original, and therefore it is preferably 70% or more.

23 is a detector, which moves in the direction of arrow 24 at the same time as the copy button is pressed, and blocks the optical path of the optical image. It comes to the position indicated by the broken line in the figure.

When the exposure lamp 7 and mirror 8 begin to move from the origin 2o toward the end point 21, they first pass under the standard white plate 22. At this time, the reflected light from the standard white plate 22 reaches the detector 23, and the intensity of the reflected light is measured. The detector outputs a signal 8p according to the intensity of the reflected light, and compares it with the initially determined output Spa when the optical system is clean, to determine whether the optical system is dirty. Further, the exposure lamp 7 and the mirror 8 scan the bottom of the document 6. At this time, the reflected light from the original 6 reaches the detector 23, and the intensity of the reflected light is measured.

The reflected light from the standard white plate 22 is t1 and Δt1 after pressing the copy button. The reflected light from the original 6 is the light that enters the detector 23 during t2±Δt2.

Here, tl<t2, and this time is stored in the copying machine in advance.

The exposure lamp 7 and the mirror 8 move toward the origin 2o at the same time as they pass the original 6. Since the size of the original 6 is stored in advance in the copying machine, the edges of the original 6 can be identified. At the same time that a signal is generated from the original 6 toward the origin 2o, the detector 23, which was in the optical path of the optical image, moves in the direction of the arrow 25 and returns to its original position. The above operation is called prescan. A predetermined voltage applied to the exposure lamp 7 during prescanning is called a prescanning exposure voltage. This prescan exposure voltage is always constant and never changes.

After the prescan is completed and the exposure lamp 7 and mirror 8 return to the origin 2o, a normal copying operation begins. That is, at the same time as returning to the origin 20, charging by the band 7ri and the container 3 starts, and light image exposure and development start. The developing device 13 contains a developer consisting of toner and carrier. The toner is a magnetic toner containing 16% magnetic material, and the carrier is a resin carrier containing 76% magnetic material. Friction between the toner and the carrier imparts an electric charge to the toner, which contributes to development. The best copies are made when the developing bias is DC 160v and the potential of the white background is 80 to 1 oov. Therefore, the potential of the photoreceptor is set to 800 V for the text portion and 90 V for the white background portion.
By adjusting the exposure amount so that V is obtained, a stable copy image can always be obtained.

The normal copy operation after completing pre-scanning is called scanning. The voltage applied to the exposure lamp during scanning is called the scan exposure voltage. The scan exposure voltage will vary depending on the dirt on the optical system and the type of document.

During pre-scanning, the light reflected from the standard white plate 22 detects the degree of dirt on the optical system (mirrors, lenses), and the light reflected from the original 6 detects the blackness of the original (such as originals written on white paper and newspapers). , a manuscript written on colored paper) is detected. Therefore, when the intensity of the reflected light from the standard white plate 22 becomes weak, the detector 23 sends a signal υ to the lamp controller GG B (not shown), which operates to increase the scan exposure voltage. The intensity of the reflected light from the standard white plate 22 is constant, but when the intensity of the reflected light from the original 6 is weak, the optical system is not dirty.

It determines that the document is black and increases the scan exposure voltage. When the intensity of the reflected light from the standard white plate 22 and the original 6 are both weak, the trap determines that there is dirt in the optical system and that the original is black, and increases the scan exposure voltage.

When the copying machine was initially set, the prescan voltage was set to s6y. The scan exposure voltage when using an original with a normal white background was esv, and when a newspaper was used as an original, the scan exposure voltage was 69V. After using this copier for a month in a dusty environment near a window, the scan exposure voltage when using an original with a normal white background was eav.
The scanning exposure voltage when using a newspaper as an original was 73V, but the voltage for copying was the same as in the initial stage.

(Sugyan exposure after cleaning the optical system mirror and lens)
- “The pressure has returned to its original value.

As mentioned above, depending on the dirt on the optical system and the type of original,
By changing the scan exposure voltage, stable copies can be obtained over a long period of time.

Next, a second embodiment of the copying machine of the present invention will be described using FIG.

When the original 6 is set and the copy start button is pressed, the photoreceptor 1 begins to rotate in the direction of the arrow 2, and the static elimination lamp 19 lights up. Almost at the same time, the optical system begins to operate. The exposure land 7 and the mirror 8 are located at the origin 20, and the speed is 250.
It starts moving towards the end point 21 at wx, /B. At this time,
A predetermined voltage is applied to the exposure lamp. This voltage is.

It is determined when the copier is initially set up. 22 is a standard white plate with a reflectance of 82%. When the copy button is pressed, the detector 23 moves in the direction of the arrow 24 and enters the optical path. When the exposure lamp 7 and the mirror 8 start moving from the origin 20 toward the end point 21, they first pass under the standard white plate 22. At this time, the light reflected from the standard white plate 22 is transmitted to the detector 23.
The intensity of one reflected light is measured. The detector outputs a signal depending on the intensity of the reflected light. Let this signal be Sr1. The signal output when the optical system is clean is determined at the time of initial setting and is set to Sps. The signal levels of Spg and S are compared to determine whether the optical system is contaminated. Furthermore, the exposure lamp 7 and the mirror 8 scan the bottom of the document 6. At this time, the reflected light from the original 6 reaches the detector 23, and the reflection intensity is measured. This measures the density of the background of the original, and if the optical system is clean and the background is normal white, the signal will be at the same level as the signal from the standard white plate 22.

Even when there is no dirt on the optical system, a document with a dark background, such as a newspaper, will have a lower value than the signal from the standard white plate 22.

The reflected light from the standard white plate 22 enters the detector 23 between t5±Δt3 after pressing the copy button, and the reflected light from the original enters the detector 23 during t4±Δt4 after pressing the copy button. It is light.

Here 1. <14, and this time is stored in the copying machine in advance.

The exposure lamp 7 and the mirror 8 move toward the origin 20 at the same time as they pass the original θ. At the same time as it heads toward the origin 20, the detector 23 moves in the direction of the arrow 26 and returns to its original position. The operation up to this point is called prescan. Therefore, during pre-scanning, the reflected light from the standard reflector 22 and the document e is measured and fed back to the developing bias in order to obtain a constant copy in the next copying operation.

After the grease scan is completed and the exposure lamp 7 and mirror 8 return to their original positions, a normal copying operation begins. That is,
At the same time as returning to the origin 20, obi tl! 3, charging begins, light image exposure, and development begins.

As the developer, a two-component developer consisting of 7Elite Kya 1)-%t and a non-magnetic toner was used. When the original has a normal white background, the developing bias voltage is 260V, and the best copy can be obtained when the potential of the white background is 150V. Therefore, in the initial settings, the potential of the photoconductor is set to 5oov
, white background portion 1507° development bias is set to 250V. Furthermore, in the case of a newspaper manuscript with a dark base, the potential of the base portion of the photoreceptor is 230V. In this case, if the developing bias voltage is set to 360V, there will be no fog in the copy.

When the optical system (mirrors and lenses) becomes dirty with dust, etc.

The amount of light reaching the photoreceptor decreases, and the potential of the underlying portion increases. In order to obtain a clear copy, the increased potential of the underlying portion is compensated for by increasing the developing bias.

During prescanning, the light reflected from the standard white plate 22 is detected by the degree of dirt on the optical system (mirror, lens), and the light reflected from the original 6 is detected by the blackness of the base of the original. Therefore, when the intensity of the reflected light from the standard white plate becomes weaker than the initially set intensity, the developing bias is increased. The intensity of the reflected light from the standard white plate 22 does not change, but when the intensity of the reflected light from the original 6 is weak, the optical system determines that the original is black, although it is not dirty, and increases the developing bias. do.

Effects of the Invention During pre-scanning, the reflected light from the standard white plate and the reflected light from the original are measured separately, and compared with the initially set values, it is possible to detect dirt in the optical system and blackness of the base of the original. Both can be detected. Is it possible to detect the strength of the reflected light and lower the potential of the white background due to the light?

Copy images without fogging can be obtained for a long period of time by feeding back to the developing bias, correcting the potential of the white background area, or a combination thereof.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the operation of the present invention, FIG. 2 is an electrophotographic characteristic diagram of the photoreceptor used in the present invention, and FIG. 3 is an explanatory diagram of the conventional operation. 1...Photoreceptor, 3...Charger, 6...
...Light image, 6...Original, 7...Exposure lamp, 8,9,10°11...Mirror, 12
・・Mark・Lens, 13・・・・Developer, 20・・・・
...Origin, 21...River/end point, 22...Internal standard white plate, 23...Detector. Name of agent: Patent attorney Shigetaka Awano and one other person;
~&lPortrait of Shikaku Cliff

Claims (2)

[Claims] (1) An exposure means for irradiating a document, an optical means for guiding a light image to a photoreceptor surface, a reflection plate having a predetermined reflectance, and a reflection intensity of the reflection plate obtained through the optical means. 1. A copying machine comprising: a reflection intensity detection means for detecting the reflection intensity; and an exposure control means for controlling the irradiation intensity of the exposure means in accordance with the output of the reflection intensity detection means. (2) an exposure means for irradiating the original, an optical means for guiding a light image to the photoreceptor surface, a reflector having a predetermined reflectance, and a reflection intensity of the reflector obtained through the optical means; What is claimed is: 1. A copying machine comprising: a reflection intensity detection means for detecting reflection intensity detection means; and a development bias control means for controlling a development bias voltage of a developing device according to the output of the reflection intensity detection means.