JPS5912455A - Control device of image density in electrophotographic copying machine - Google Patents

Abstract

PURPOSE:To maintain the density of an image in a satisfactory state by detecting the densities of toner images in a reference batch and an insulator region with photosensors, and controlling the quantity of the light to be irradiated to an original and the amt. of the toner to be replenished in accordance with the two detected values. CONSTITUTION:A reference density batch 3 is adhered to the part near the end of an original plate 2, and an insulator region 14 is formed partly on a photosensitive drum 8. When a fluorescent lamp 4 starts lighting and an electrostatic charger 9 starts discharging electricity, the region 14 and an image region 15 are electrostatically charged. The electrostatic latent image 16 of the batch 3 and the electrostatic latent image of an original 1 in the region 15 are successively formed; thereafter, a toner image is formed by a developing roll 11. Photosensors 12, 13 detect the densities of the toner images in the batch 3 and the region 14 and the output signals thereof 21, 27 are supplied to a density setting part 22 and a potential setting part 23, by which the quantity of the light of the lamp 4 and the amt. of the toner to be replenished are controlled and the image is maintained at the satisfactory density.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image density control device for an electronic copying machine using a two-component developer.

In a two-component developing electronic copying machine, toner is triboelectrically charged using Kyrelia to develop an electrostatic latent image. In such a copying machine, in order to maintain the image density in a good condition, ■ Replenish the doboo into the river conveyor as appropriate. # It is necessary to keep the density constant and also control the surface electron ☆ of the sensitive material within a certain range.

Among these, a device using a standard 81 degree patch is widely known as a density control device for keeping the content of 1-toner in the developer constant. In this device, a 1wm batch with a predetermined degree of repulsion is transferred to a portion of the document table. When a projection operation is started, a toner image for a reference density patch is formed on the photosensitive material. 1. The density of the Hessey image depends on the toner density in the developer. Therefore, this device uses a reflective photosensor to detect the condition of the toner image on the photosensitive material, thereby controlling the supplies to the developing device.

1/] As a potential control device to control the surface potential of the sensitive material at a constant level, a potential sensor is installed in front of the developing device ().
tb is usually used. At this potential level, the dark area potential or the electrostatic latent image l of the reference m degree patch described above is measured, and the discharge m of the charger is controlled so that this becomes a desired value.

On the contrary, in such conventional copying machines, the density control of the gutter and the potential control of the sensitive material are not necessarily carried out properly in some cases. For example, if the environment in which the copying machine is installed or the degree of fatigue of the photosensitive material changes, the potential of the photosensitive material will fluctuate, and the toner flow will also fluctuate accordingly, causing the AT stamp sub-control to be performed incorrectly. was there.

Also, if the potential path is contaminated by trees etc.
The potential of the sensitive H was sometimes detected incorrectly, and the potential was set to an inappropriate range. If the image density was properly controlled at 4 f, fog would occur in the copied image, and the image could not be reproduced with good proportion f1 from low density to high f1.

The present invention has been made in view of these points, and provides an electronic copying machine that can reliably control both the toner density and the surface potential of the sensitive material, and can always maintain an image quality in a good condition. Picture @
The purpose of the present invention is to provide a concentration control device.

In the present invention, the density of the toner image obtained by exposure and development of the reference patch and the yA value of the 1-toner image obtained by charging and development of the insulator region are respectively detected by a sensor, and these two are detected. While controlling the potential of the C-sensitive material or the amount of light irradiating the document to a predetermined value based on the two detected values, the slope γ of the development curve is determined from the detected value of the density of the toner image in the insulator area. By controlling one henna and one supply group accordingly, the above-mentioned purpose can be achieved.

The present invention will be described in detail with reference to Examples below.

FIG. 1 shows the housing of a copying machine using the density control device of this embodiment. In this copying machine, a transparent original platen 2 on which an original 1 is placed is horizontally fixed to a section F of the main body of the copying machine (not shown). A reference 11 degree patch 3 is pasted on the lower surface near the end of the document table 2. The standard m degree patch 3 is a predetermined anti! ) is a rectangular piece set in J I U.

An elongated lamp 4 for irradiating the document is arranged below the IPiI platform 2 horizontally with the document platform 2 . Lamp 4 is the first
Together with the second mirror 5.6, it moves back and forth 11 in the direction of the arrow in the figure, and the irradiation position of the original 1 is continuously changed from one end to the other end.

The reflected light from the original 1 is reflected by the first mirror 5, the lens 7, and the second mirror 5.
The light reaches the photosensitive drum 8 through the mirror 6 and forms an image thereon.

Arranged around the photosensitive drum 8 are a charger 9 for charging, a developing roll 11 for developing, two non-conforming type A-transfers 12 and 13 for detecting mtxt of toner images, and other parts.

Now, when a start button (not shown) of this copying machine is pressed, the photosensitive drum 8 always starts rotating clockwise from its home position. At the same time, the fluorescent lamp 4 starts blinking, and the charger 9 starts discharging onto the photosensitive drum 8. A portion of the photosensitive drum 8 is coated with an insulator, as shown in FIG. 2, to form an insulator region 14. The charger 9 first charges the portion including the insulator region 14, and the image region 15) corresponding to I*g&1 is continuous therewith.

is charged. Insulator territory 1j! The optical components of the lamp 4 begin to move at the timing when the tip of the lamp 14 reaches the image forming position. First, the electrostatic latent image 16 of the reference density patch 3 is formed at a position that does not overlap with the 1 ml/1 insulator area as shown in the figure.

Subsequently, an electrostatic latent image of the document 1 is sequentially formed in the image area 15. Each charged portion of the photoreceptor drum 80 is developed by a developing roller 11 using a C magnetic brush method to form toner images 1 to 1.

FIG. 3 shows the relationship between developer concentration, sensitive material potential, and toner image depth for the photosensitive drum used in this embodiment. Three development curves shown in the figure 1
Numbers 7 to 19 represent the density characteristics of different developers. The development curve 18 shows an example when the degree of development is 1 to 100 degrees. An example of a high case is shown. This figure 7) s r et al., development It
, 'J ni ()ru! 8! ! There is a potential of i (approximately 9 in the figure)
00 V), 1 depending on the potential of the sensitive material.
~ I can see whether the degree of reluctance (rebelliousness) changes. In this region, the image depth depends on both the sensitivity + A potential and the developer temperature (as already pointed out, 1~) - It is necessary to accurately determine the development creation 1α from r [- I can't.

On the other hand, in the part where the potential of the sensitive material is higher than these values, there is
When development is performed (approximately 900V to 1400V in the figure), the depth of the toner image depends only on the concentration of the developer.

The insulator region 114 is temporarily charged to 1200V by the charger 9 and traced. The cable in this part is not affected by the environment
It is possible to accurately determine whether the concentration of the developer is higher or lower than the reference value.

1-1 located near the developing roll 11
3 detects the density of the toner image formed on the insulator region 14 when it reaches the opposing position. The obtained insulator m degree signal 21 is supplied to both the edge Tα setting section 22 and the potential setting section 23. FIG. 4 shows the structure of the temperature setting section. Insulator 54Ifi @21 CJ
', '+', y data 221 are supplied. A comparator 221 compares the voltage level with the reference voltage signal 2/I output from the reference voltage 11 generator 222. In this case, the reference voltage (rl 24 is the inverse 1 of the 1-ner image) J
It is No. 16 with an electric f level equivalent to about 1.3 m degrees. -1 amparator 221 is 1 in insulator region 171.
- When it is determined that the anti-OA density of the No. 11 image is lower than the reference J, a No. 1 replenishment signal 25 is generated. When the toner dispense signal 25 is supplied, the toner dispenser drive circuit 223 drives a toner dispenser (not shown) to replenish the developer with toner dispenser. 1 by insulator region 14
~ Detection of the concentration is carried out every copying cycle (
・As a result, the concentration of the developer cannot always be kept at an ideal state.

By the way, when the toner density is kept uniform as shown in FIG. 5, the slope γ of the development curve becomes constant at a potential of the sensitive material below a certain potential v1, as shown in FIG. If we now write the surface electric potential of the insulator region 14 as Vo (Vl<Vn), then
This toner image density D+ can be considered to be equal to that at the potential V1. If the developer concentration is expressed as -1,C, then the relationship between the slope γ, the developer temperature -',C and the developer i11 degrees F, and C and 1~'Image density 1]1 is as follows:・As shown.

γα−1, C・・・・・・・・・(1)'r, c (
Meni 1〕 1 ... ... (2) Follow -C
The relationship between the slope γ 1 and the image density D1 is expressed by the symbols a and b.
If both are constants, then J can be expressed by the following equation.

γ・-a l') 1+b...(3) The straight line part of the development curve in Fig. 55 passes through the point (Vl, D+), and the 1 to 1 images falling in this part are Degree and sensitive material potential■
Expression 1 is as follows.

D-γ(V-V+) 10F,) +-(a l)
+ +-b) (V-Vl) +I)I
------- (4) Now, set the potential of the electrostatic latent image 16 of the 14 t% L polishing pad to V2, and set the degree of 'a' of the toner image formed on this part to 1) 2. These numbers are (4
) to find the unknown potential V2, the following equation J,
I'm going to growl.

2 = VI + (+,)2-1)+ )/ (a l
)+ +ll )・・・・・・(5) In other words, the potential V1 of the bending part of the development curve that corresponds to the ideal degree of debooting is experimentally determined.
Using the 11 degrees D2, l)+ of the toner image detected by the first sensor 12.
It is possible to ask for.

Note 1] 12 detects the temperature of the hot water when the 1 to 1 images formed on the electrostatic latent image 160 reach the opposing position 16.
7 is the insulator Takidobutsu S → 21 obtained at the same timing
Both are supplied to the potential control section 2J.

FIG. 6 shows the configuration of the potential setting section. The potential V2 is calculated according to the body temperature signal 21 and the M semi-bap I h number 27. Operation result 281; i differential amplifier 234
and the reference voltage j is the reference voltage 1 output from the generator 233.
1'f: compared with signal 29. The reference voltage signal 29 in this case is a signal representing the ideal voltage level of the photoreceptor drum \8 relative to the exposure of the reference density batch 3.

The error signal 31 output from the differential amplifier 234 is supplied to a current value control circuit 235. The current value control circuit 235 receives the high voltage for discharge from the high voltage generator 236, and adjusts the current flowing to the charger 9 so that the error signal 31 becomes zero. Ru. As a result, the photoreceptor drum 8 is charged to an ideal potential in an external charging process.The surface potential is also controlled every time one copy is recycled, and an ideal potential state is always maintained.

Although the surface potential of the sensitive material is controlled in the embodiments described below, it is of course possible to control the amount of light from the lamp 4 that illuminates the original.

According to the present invention, both the toner stone content in the developer and the potential of the sensor are maintained at appropriate values, so even if environmental conditions change, high image quality can be achieved. It is possible to stably obtain a copy of the image.

[Brief explanation of the drawing]

The drawings are only for explaining one embodiment of the present invention.
The figure shows the main parts of a copying machine, and is a configuration diagram. Figure 2 is a perspective view showing the principle of measurement of the toner image on the photoreceptor drum. Figure 3 shows the developing characteristics of the photoreceptor drum. Characteristic diagram, 4th
Figure G, (11-1 ivy diagram of the part setting section, Figure 5 is an explanatory diagram for explaining the principle of potential detection using the straight part of the development curve, and Figure 6 is a block diagram of the potential setting section. .1... Manuscript 2...
1 Kyotodai 3... Standard m degree patch 4...
... Lamp 7 ... Lens 8 ...
...Photoreceptor 1 drum 9...Charger
11... Development 1-1-le 12.13...
...]]Al-Hinli 14...Insulator region 2
2...Warm stone setting section 23...Potential setting section N1 Hitobata Shige [Cox Co., Ltd. Patent attorney Ken Yamauchi nt

Claims (1)

[Claims] In an electronic copying machine that uses a two-component developer to perform C copying, a quasi-PIJ degree patch is provided on a part of the document table and set to a predetermined reflective electrical production. , an optical system that projects images of the original and the substrate t4 (density batches) onto the photosensitive material, respectively;
The densities of the toner images created in advance on the photosensitive material by development on the insulator area and the toner images of the reference tone patch at different positions on the photosensitive material are individually determined. Detection] A [~Lenri] and [Density setting] Compare the preparation of the toner image applied to the insulator area with the standard value and set the concentration of 1 to 8M in the developer to the desired value. The charging current of the C-sensitive material or the illumination light of the original is adjusted to the desired value based on the information regarding the development characteristics obtained by controlling the 8M degree of the two toner images on the photosensitive material and the preparation control means. 1. An image density control device for an electronic copying machine, characterized by comprising a potential setting means for setting a value.