JPS5922067A - Image density controller of copying machine - Google Patents

Abstract

PURPOSE:To control an image density stably by comparing the density difference between toner images developed at two different development potentials with a reference value. CONSTITUTION:A density detection signal 23 is supplied to both delay element 241 and differential amplifier 242 in a controlling circuit 24, and the delay element 241 delays the detection signal 23 by the time obtained by dividing the distance between the centers of the 1st and the 2nd electrostatic latent images by the peripheral speed of a photosensitive drum 8. The delayed detection signal 243 is supplied to the other input terminal of the differential amplifier 242. A timing circuit 244 is a kind of counter circuit and starts counting by a copy cycle signal 25 every time a copy cycle starts for every sheet to output an enable signal 245 at the timing that the toner image of the 2nd reference density patch. At this time, the differential amplifier 242 outputs a density difference signal 246 showing the density difference between both reference density patches 2 and 3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image density control device for controlling the image depth of a copying machine.

In order to maintain good density of copied images in the electronic copying machine C, it is necessary to maintain the 1-ner in the developing device at an appropriate value at all times. The device used for this purpose is a photoreceptor (sensitive material).
There is an image density control device that detects the density of the toner image formed on F and controls the supply of toner to the C developing device based on this.

In this setup, the photoreceptor is first charged in the same way as the normal duplication process.Next, an image of the document in this state (or a reference density) is formed on the photoreceptor. Now, the photoreceptor is brought to a certain surface potential state. When this area is developed, a tonneau image with a density corresponding to the amount between the developing stations is formed. The density of this toner image is determined by a reflective film A1.
- Detection is made with the lens and compared with the image (reference density) at an ideal amount of toner in the developing device. If the detected toner density is lower, the toner is supplied to the developing device, whereas if the detected toner density is higher, the supply is stopped.

However, in such an apparatus, it is not always the case that the current output of the apparatus is properly controlled, and thus an inappropriate image-generated copy image may be obtained. Fluctuations in the surface potential on the sensitive material are cited as the cause of this. That is, if the charging device becomes contaminated with toner particles or the like, or if the light intensity of the illumination lamp fluctuates, the surface potential before development will differ from the desired value. In this case, if the developing device changes from 1 to 4'' iJi, then the image portion will not change. If control is carried out based on these 1 to 1 to 1 to 10 concentrations, 2 to 3 to 10 to 10% of toner will be supplied to the developing device in excess, or an insufficient amount will cause fogging. Or,
1-min (, not the density of the copied image will be ('J).

The present invention is based on these four points (J, ゛) (゛, feeling (A1)
- surface type (i/or 1- to the developing device with some variation)
It is an object of the present invention to provide an image density control device for a copying machine which can appropriately control the no-feed.

In the present invention, the surface charge of the 4f/2+iF type is different from that of the sensitive material.
7'a is generated and the image density is controlled by controlling the amount of 1-boo supplied to the C developing device in accordance with the a degree difference between the two developed images.

The detailed description of the present invention is given above with reference to the embodiments.

FIG. 1 shows the main parts of the duplex machine.

The reciprocating port of this copying machine (near the end of chinoan 1 of j (5
: The first and second standard 'fA degree badges 2.3 and 2.3 have different degrees of repulsion, respectively. When a star 1 button (not shown) is pressed to start copying, the fluorescent moon 4 arranged perpendicularly to the moving direction of the brown 1 shown by the arrow points to the first reference sheet at the start position. The electric pad 2 is first irradiated with light.

The reflected light from the first reference density batch 2 passes through the first minnow 5, the lens 6 and the second lens 7, and is illuminated onto the photoreceptor drum 8. Ru.

At this point, the photosensitive drum 8 starts rotating in the direction of the arrow C.
The surface ffi level of the drum charged with C by the heron (charging device) 0 decreases to a level corresponding to the exposure tH, and the electrostatic latent image of n) 1 is formed. . Similarly, a second electrostatic latent image C is formed for the second reference temperature pad y3 adjacent to the area on the photoreceptor drum E3 where the first electrostatic latent image is formed. Furthermore, next to it,
A third electrostatic latent image is formed on the document 11 placed on the platen 1-L.

These electrostatic latent images are sequentially developed by a developing device 12 as the photosensitive drum 8 rotates, forming a tonneau image.

Then, from the paper supply 1 to the lay 133 to the feed roller 14
Copy paper 1 fed out at a predetermined gluing temperature °C
5 or dashed line 16 (along the small path - CI Heransno)
'-j When the image reaches the position directly above the transfer device 17, the 33rd electrostatic latent image is transferred to the copy paper 11. After the copy paper 15 is fixed, it is ejected to an ejection tray (not in the same vehicle) at ejection 11-18.19.

The J, I, and No images on the first and second electrostatic latent images are not transferred to the copy W115 (and remain on the photosensitive drum 8). is cleaning device 1
In the if-t series 22 provided between 9 and DITAC 1 to 21, the density of J, . /
1 is supplied.

FIG. 2 shows the specific structure of the control circuit. Ia degree detection signal 2ζ3 is connected to the delay element 241 in the control circuit 2/'I and the differential amplifier? 42. Delay element 2 /l i LL, 1st tJ J:Hi 20th
) between each center point of the electrostatic latent image '! Separate the photoreceptor!
・This is a circuit that delays M interval detection (A) divided by the circumferential speed of the ram 8. The delayed detection signal 243 is supplied to another input terminal of the differential amplifier 242.The timing circuit 244 is It is a type of counter circuit, and is generated every time one copying cycle starts at one copy fσ.
The group fF−iGi! Degree batch 3 tonneau image is 77+1 ~
The enable signal 24 is output at the timing detected by the sensor 1) 22. At this time, the differential amplifier 242
outputs a degree difference number 246 representing a 1li11 degree difference between both bases t4=ilJ degree patch 2.33.

However, if the amount of charge on the photoreceptor drum 8 fluctuates, then the first and second group #; a degree pad 2.3
The potentials of the first and second electrostatic latent images of C vary accordingly. However, when the fluctuation range of charge h) is not large, the potential difference between these electrostatic latent images remains almost constant (
There is. If this is assumed to be constant, the temperature difference X between the toner images due to these patches 2.3 will be proportional to the slope T of the 1 to 1 image clarity with respect to the development potential. Here, the development potential refers to the potential obtained by subtracting the bias potential of the developing device 12 from the depth of each electrostatic latent image.

As shown in FIG. 3, the ratio .gamma. differs depending on the humidity condition, but in the same condition of 1!111 stones, it is proportional to the 1.J-containing hh) in the developer. In other words, if the amount of charge on the photoreceptor changes rapidly due to swearing and the projection recycle, the difference in density of the image (X) is 1. A] It seems that it is proportional to the hanging. Since the density difference 11/246 represents the density difference It's bright.

The comparison circuit 247 shown in FIG. A level 1-no supply request signal 24E3 is output.

1 Non-Shot 1~Nrujibyebreak 27'I9 detects the rise of this signal 24ε3 and repeats the dispensing smoke drive signal for a period slightly longer than one recycle. Outputs 6. Tsunsho 1 ~ Marujibye Break 245) Hari 1 ~ Rigable 4c
When the element 248 outputs the 1--supply number * signal 248 over a plurality of copy recycles, the dispensing drive signal 26 is output continuously during that period.

- The supply device 27 receives the dispense motor drive signal 2.
When the toner is supplied to the C developing device 12, the internally installed gas-spense motor is driven to supply toner to the C developing device 12. As a result, when the hebu-containing group becomes appropriate, the concentration difference X becomes a predetermined value, and the replenishment of 1 to ')- is stopped. With such control, the copied image of the original can maintain a good quality with high density and no fog.

In the embodiment described above, the image forming process was controlled by determining the density difference X, but the ratio γ of the photoreceptor potential difference between the two batches was determined, and the image temperature was controlled based on this. It is also possible.

In addition, in the example, the density difference It is also good to change the bias potential to two levels and set it to C. π) When the ink position is changed, the development potential differs (
It is possible to find the concentration difference X or the ratio γ using the same principle.

If the photoreceptor is developed with two types of bias potentials C, which is not charged while avoiding the illumination illusion, it is also possible to control the image @density without using the base 1v-m melon patch.

Furthermore, Embodiment C can be used to control the 1-no content of the developing device. I adjusted the turtle, but the photoconductor was charged! ■, Mitsuharu Ryo, or the bias potential of the current □□□ device, in Class A or in combination l! By controlling the image @i1! There is an effect of adjusting the degree.

In other words, does the b ratio γ remain unchanged due to a change in the surface potential of the photoreceptor, or is it an absolute 1 to 1 degree according to the standard Fuchimaro Pat-f?■
It is possible to control the charge on the photoreceptor, etc., and correct the fluctuation of the absolute toner density.

As explained above, the present invention has two responsibilities: (1) The density difference of the tonneau image developed at the developing potential is compared with a reference value, and the image temperature is controlled based on this result. This has the advantage of stabilizing the control of the C1 image in particular and facilitating maintenance of the copying machine.

[Brief explanation of drawings]

The drawings are for explaining one embodiment of the present invention, and the first
The figure is a schematic configuration diagram of the copying machine, and the second figure is the machine 911.
The block diagram of the circuit, FIG. 3, is a characteristic diagram C showing the relationship between the toner content ω and the ratio γ of the developer. 2...First standard 'a degree pap 3...
Second standard FM degree buffer f8...Photosensitive drum 9...Charge'I]1 to 11n12...
・・Developing device 22 ・・・・・・・・・A] Herensa 2/I ・・・・・Control circuit 27 ・・・Nor supply device Applicant Hatakeshi U1-1 Tsukusu Co., Ltd. Ne1 agent
Patent attorney Ken Yamauchi

Claims (1)

[Claims] a potential setting means for setting two different surface potentials on the sensitive material; a density detecting means for detecting 83 degrees of a 1-toner image obtained by developing these potential portions; and said means. From the two types of densities detected, find the difference in these densities or the development type (ratio γ of 1 to 1 m degrees of the toner image to 0, and compare this with the reference value. 5. An image density control device for a copying machine, characterized in that it comprises a temperature adjusting means for adjusting the image depth and temperature according to the comparison result.5.