JPS6111765A - Device for controlling image - Google Patents

Abstract

PURPOSE:To enable toner concn. to be adjusted without providing a standard target on an original platen or near it by rendering developing bias at the time of developing a prescribed region different from that to be given to the region except said region, and detecting development characteristics. CONSTITUTION:A detector 8 for detecting the density of the pattern for detection is provided at the circumference of a photosensitive drum 1 between a developing device 5 and a cleaning device 9. The detector 8 detects the density of the detection pattern and its background formed on a part of the drum 1 on the outside of a latent image area. The reflection density expressed by voltage of the detection pattern region P2 detected with the detector 8 is compared with the preset standard density expressed by voltage. When it is judged that the reflected density of the region P2 is lower than the standard value, the toner is replenished from a toner replenishing section 51 in the developing device 5 or toner replenishing rate is increased to raise toner concn. in the developer.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an image control device for an electrostatic recording device such as an electrophotographic copying machine or an electrostatic printer, and more specifically relates to an image control device for an electrostatic recording device such as an electrophotographic copying machine or an electrostatic printer. The present invention relates to an improvement in an image control device for an electrostatic recording device that detects the density of a visible image obtained by developing a reference latent image, and controls toner replenishment based on the detected development characteristics.

[Prior art]

Conventionally, in order to maintain a constant image quality, especially the density of a copied image, obtained using an electrophotographic copying machine, a part of the photoreceptor, which is an image carrier, is first exposed to a Jli amount of light, and then this is developed. The amount of toner adhesion in the obtained toner image is detected by an image density detection device, and the amount of toner supplied is automatically controlled based on the amount of toner adhesion detected by the image density detection device. In order to maintain a constant density of a copied image, it is necessary that the measured value by the image density detection device described above be accurate.

The detection pattern exposed and developed on the photoconductor with a reference light amount forms a latent image of a reference target (reference density piece) placed near the document table (outside the document placement area) on the photoconductor.
It is obtained by passing through a developing section and being developed. In order to detect the image density of this detection pattern, the reflected light from the toner image is detected by a detector. Since the detection pattern is limited to a relatively small portion, in order to accurately detect this reflected light at a predetermined detection timing, a detector is provided to receive and detect the regular reflection component of the reflected light. The detector provided in this manner responds sharply to the condition of the surface of the photoreceptor, provides highly accurate detection results, and can accurately detect image density.

Conventionally, the detection pattern described in "-" was created by illuminating a reference tarded placed near the document table with a document illumination lamp, and using a photoconductor L whose surface potential had been brought to a constant level by charging means in advance.
The detection pattern image was formed to form a reference latent image.

Providing such a reference target near the document table is useful for copying machines with a movable document table or a movable optical system.
The range of movement of these parts will be expanded, the copying speed will be reduced, and the durability of the illumination lamp will also be adversely affected. In addition, in copying machines that move originals, it is not easy to image the above-mentioned detection pattern on the photoreceptor.
It required a special mechanism.

[I of invention]

The present invention provides an image control device that adjusts toner density by providing a detection pattern on a photoreceptor without providing the reference target described in -1- on the document table or near the document table. The purpose is to

[Structure of the invention]

The present invention aims to achieve the above object, and the present invention provides an image forming apparatus having a step of forming and developing an electrostatic latent image on an image carrier, and developing a predetermined portion of the electrostatic latent image. Image control characterized in that the image can be controlled by varying the developing bias used when developing other than the predetermined portion of the electrostatic latent image and detecting the development characteristics of the predetermined portion. It provides equipment.

〔Example〕

FIG. 1 shows the structure of an electrophotographic copying machine equipped with an image control device according to the present invention. 1 is a photoreceptor consisting of a rotating drum installed in the frame of the machine; There is a charging means 2 for corona charging the surface potential on the photoreceptor. -3 is an exposure means which forms a latent image on the ram 1 by forming an image of the original placed on the original platen 4 on a rotating charged photoreceptor. 5 is a developing device, in which the latent image on the photosensitive drum 1-11 is developed in the process of passing through the developing section of the developing device 5;
The toner adheres in an energy-saving manner to form a toner image.

6 is a transfer device, and 7 is a separation means. The toner image on the photosensitive drum 1 is separately conveyed and transferred onto a sheet of transfer paper at a position facing the transfer device 6. The transfer paper to which the transferred toner image is attached is separated from the photoreceptor drum 1 in a separating section 7, fixed thereon, and then transported out of the copying machine.

On the other hand, the circumferential surface of the photosensitive drum 1 after the transfer is further rotated and cleaned by the cleaning device 9 in preparation for the next copying cycle.

The illustrated electrophotographic copying machine is constructed so that it can copy sheet originals of a specified size as well as sheet originals with a length longer than the specified size, so this will be explained.

A document placement table 4 corresponding to the size of a specified size sheet document is fixed to a part of the copying machine, and a conveyor belt rotated clockwise by drive rollers R1 and R2 is mounted on the top surface of the document table 4. ) 4a and a conveyor belt 4a, there is provided a conveyor device comprising a feed roller 4b for feeding a sheet document to the conveyor belt 4a, and a discharge roller 4c for discharging the sheet document from the conveyor belt 4a.

Further, below the lath 4 on which the original is placed, there are a first mirror unit 3a equipped with an exposure lamp L, and a second mirror unit 3a equipped with an exposure lamp L.
(b) Further, an exposure optical system 3 consisting of a projection lens 5c and a reflection mirror 3d is arranged, and the first mirror unit)
311 is a speed related to the circumferential speed of the photoreceptor drum 1, that is, the speed of the first mirror (uniform) 3a is 2, the circumferential speed of the photoreceptor drum 1 is 3, and the copying magnification is n, then V 2 = V , / At a speed that satisfies n, and the second mirror unit) 3b is their speed (-
・■, both allow the document to be moved linearly to the right in parallel with the document placement glass 4. Furthermore, a document stopper 41 is provided at a position where the document placement faces the left end of the lath 4.
is provided, and when copying a sheet original that is equal to or shorter than the specified size, Although it is designed to be able to be retracted flat, when copying a sheet original longer than a specified size, it is also possible to maintain the retracted state by special operation.

In such a copying apparatus, when copying a sheet document D1 that is equal to or shorter than the specified size, the sheet document D1 inserted into the feed roller 4b is moved to the left on the document placement glass 4 by the conveyor belt 4a as shown in the figure. direction, and comes into contact with the document stopper 41 and stops.

Thereafter, the 1jS1 mirror unit) 3a and the second mirror unit) 3b move to the dotted line position and perform exposure scanning, and the image on the document surface is transferred to the reflection mirror 3d by the projection lens 3C.
The photosensitive drum 1 rotates at a circumferential speed of 3 through the
The image is formed on the circumferential surface of the

After completing the exposure scan in this way, the exposure lamp L is turned off. The first and second mirror units 3a and 3b return to the positions shown by the solid lines, but in conjunction with this, the document stopper 41 retreats downward, and the sheet document is moved back to the conveyor belt 4a. After being moved by the sheet and being discharged out of the apparatus via the discharge roller 4c, it is again projected onto the document placement surface as shown in the figure to prepare for the next sheet document.

On the other hand, when copying a sheet original D2 whose length exceeds the specified size, the exposure optical system 3 stops at a fixed position and scans it, while the sheet original D2 inserted into the feed roller 4b is transferred to the conveyor belt 4a. Place the manuscript on the last 4th v
The image is formed on the circumferential surface of the photosensitive drum 1, which moves to the left at a speed of V, and rotates at a circumferential speed of V. In this case, since the document stopper 41 is retracted downward, the exposed sheet document D2 is continuously discharged from the apparatus via the discharge roller 4c. In such a copying machine, it is not easy to provide a reference coupe 76 as conventionally used.

In the present invention, in the copying machine as shown in FIG.
is provided. The detector 8 is a reflective type 7-otocoupler consisting of a light-emitting element 8a such as a light-emitting diode, and a light-receiving element 8b such as a 7-ototransnoster, and detects a detection pattern formed outside the latent image surface on the photoreceptor drum 1. The density and the density of the back a part can be detected.

Here, the formation of the detection pattern according to the present invention will be explained. In the present invention, a reference latent image is created on the image carrier without providing a reference target (reference density piece) outside the document placement area, and the same effect as that obtained by forming a detection pattern is obtained. It is. That is, in the case of copying shown in FIG. 1, the detection pattern area P2 provided before or after the image area G2 on which the original image is projected is the lamp L
This is a latent image formed on the photoreceptor 1 when the light is off.

- On the other hand, since both the image area G2 and the non-image area including the detection pattern area P2 are uniformly charged under the same conditions by the charging means 2, the detection pattern area P2 of the photoreceptor drum 11- is , it has a latent image with a constant surface potential.

As is well known, the amount of adhering toner 5 when a latent image is developed differs depending on the developing bias applied to the developing sleeve 52, so in the present invention, as shown in FIG. When the pattern area P2 passes through the developing device 5, the developing bias applied to the developing sleeve 52F is changed to a constant value, and the toner density is controlled so that the image density is at the level required for the machine. By passing through such a developing device 5, toner becomes attached to the detection pattern area P2, and the reflection density is measured by the detector 8 shown in FIG.

The reflection density displayed by the voltage of the detection pattern area P2 detected by the detector 8 in this way is
It is compared with a reference i degree indicated by a preset voltage using a known comparison circuit. When it is determined that the reflection density of the detection pattern area P2 is lower than the fth set reference density, toner is replenished from the toner replenishing section 51 in the developing device 5 shown in FIG. It acts to increase the amount and increase the toner concentration of the developer.

Figure 3 shows the basic electrical circuit diagram.
P is a comparator built into a circuit consisting of a light emitting element 8a, a light receiving element 8b, etc., and the comparator COMP compares the potential at 4 points generated by the reflected light received from the detection pattern area when the toner standard density is reached and 84 Adjust and set the potential of the points using the variable resistor VR so that the potentials of the points are equal, and then
The developed detection pattern above is irradiated with infrared light from the light emitting element 8a, and the reflected light is received by the light receiving element 8b. Then, the comparator CO detects whether the output voltage level of the four points due to light reception has become higher or lower than the set level B4.
It is determined by MP, and the swinging rod 51a of the toner replenishing section 51 is stopped or activated based on the signal to control the replenishment of toner to the developing device 5.

〔Effect of the invention〕

The image control device according to the present invention eliminates the need to optically scan a reference target, which was required in the past, and increases the speed of image processing. This has the effect of making it possible to easily control the image.

[Brief Description of the Drawings] Fig. 1 is a front view of an electrophotographic copying machine showing an embodiment of the present invention, Fig. tJS2 is a graph showing an example of the developing bias according to the present invention, and Fig. 3 is a graph showing an example of the developing bias according to the present invention. An example of a circuit for detecting the amount of toner adhering to the surface of a photoreceptor is shown. 1... Photoreceptor 2... Charging means 3... Exposure means 5... Developing device 8... Detector
8a... Light emitting element 81)... Light receiving element
51... Toner supply section 51a... Swinging rod 5
2...Developing sleeve agent Patent attorney No 1) Yoshi
Parent figure 1 figure 3

Claims (1)

[Claims] In an image forming apparatus having a step of forming and developing an electrostatic latent image on an image carrier, a developing bias for developing a predetermined portion of the electrostatic latent image is set to a portion other than the predetermined portion of the electrostatic latent image. An image control device characterized in that it is possible to control an image by varying a developing bias during development and detecting development characteristics at the predetermined location.