JPS6111762A - Device for controlling image - Google Patents

Abstract

PURPOSE:To form a pattern for detection on a photosensitive body and to enable toner concn. to be adjusted by reducing an exposure amt. at a prescribed region at the time of forming an electrostatic latent image and detecting the development characteristics at said region. 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 detection pattern region P2 provided before or after the image forming region G2 can be changed in the luminance of an exposure lamp L from the image region G2. When the reflection density of the region P2 is judged that it is lower than the preset standard density, 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 a 9-electro 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 standard amount of light, and then this is developed. An image density detection device detects the toner adhesion amount of a toner image, and the toner supply amount is automatically controlled based on the toner adhesion amount 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 photoreceptor L: with a reference light amount forms a latent image on the photoreceptor of a reference tarded (reference density piece) placed near the document table (outside the document placement area). 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 area, 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 "2" is produced by illuminating a reference target placed near the document table with a document illumination lamp, and forming an image of the detection pattern on a photoreceptor whose surface potential has been set to a certain level by charging means in advance. However, a reference latent image was formed.

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. Furthermore, in copying machines that move originals, it is not easy to image the detection pattern on a photoreceptor, and a special mechanism is required.

[Purpose of the 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 tarp 7 on the document table or near the document table. With the goal.

[Structure of the invention]

The present invention aims to achieve the above object, and the present invention forms an electrostatic latent image by a charging means for charging an image carrier, and an exposure means for exposing a charged surface charged by the charging means, In an image forming apparatus having a step of developing, the image can be controlled by reducing the exposure amount of a predetermined area when forming the electrostatic latent image and detecting the development characteristics of the predetermined area. The present invention provides an image control device with characteristics.

〔Example〕

Figure tjS1 shows the structure of an electrophotographic copying machine equipped with the image control device of the present invention. 1 is a photoreceptor consisting of a rotating drum installed in the frame of the machine, and the photoreceptor is mounted on the circumference of the photoreceptor drum 1. There is a charging means 2 for fluorostatically charging the second surface potential.

Reference numeral 3 denotes an exposure unit that forms an image of the original placed on the original placing table 4-h onto the rotating, charged photosensitive drum 1 to form a latent image. Reference numeral 5 denotes a developing device, in which the latent image on the ram 1 is developed on the photoreceptor in the process of passing through the developing section of the developing device 5, and toner is electrostatically attached thereto to form a toner image.

6 is a transfer device, and 7 is a separation means. Photosensitive drum 1”
The second toner image is conveyed separately at a position facing the transfer device 6 and is transferred onto the grain transfer paper. The transfer paper with the transferred toner image attached is placed on the photoreceptor drum in the separating section 7.
After being separated from 1 and fixed, it is carried 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 mounting table 4 corresponding to the size of a specified size sheet document is fixed to the top of the copying machine, and a conveyor belt (transfer belt) rotated clockwise by drive rollers R1 and R2 is mounted on the top surface of the document table 4.
4a and the conveyor belt 4a are provided with a conveyance device consisting of a feed roller 4b that feeds the sheet FA document and a discharge roller 4c that discharges the sheet document from the conveyor belt 4a.

Further, below the document placement glass 4, an exposure lamp I,
An exposure optical system 3 comprising a first mirror unit 7) 3a, a second mirror unit) 3b and a projection lens 5C1 and a reflecting mirror 3d is further arranged. The speed related to the speed, that is, the speed of the first mirror unit) 3a is 2, the circumferential speed of the photoreceptor drum 1 is 3, and the copying magnification is at a speed that satisfies V2=■, /n, and The second mirror unit) 3b becomes capable of linearly moving the original document in the right' direction in parallel with the lath 4 at their respective speeds of J- and {circle around (2)}. Further, the position facing the left end of the document placement glass 4 is a document stopper 41.
is provided, and when copying a sheet original of the same size or shorter than the specified size, it protrudes from the original placement surface to stop the sheet original, and is retracted downward in response to an ejection signal. When copying a sheet original with a length longer than a specified size, it is possible to maintain the retracted state by using a special intermediary.

In such a copying apparatus, when copying a sheet document D1 that is equal to or shorter than the specified size, the sheet document DI inserted into the feed roller 4b is moved to the left on the document placement plus 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 first mirror unit 3a and the second mirror unit 3b move to the dotted line position while exposing and scanning, and the image on the document surface is projected by the projection lens 3C via the reflecting mirror 3d onto the photoreceptor which rotates at a peripheral speed of . An image is formed on the circumferential surface of drum 1.

When the exposure scan is completed in this way, the exposure lamp L is turned off and the first and second mirror units 3a and 3b return to the positions indicated by solid lines, but in conjunction with this, the document stopper 41 is retracted downward. After the sheet original D1 is moved by the transport bell 11f and 4a and is ejected out of the apparatus via the ejection roller 4c, it again protrudes onto the original placing surface as shown in the figure to prepare for the next sheet original. It has become.

- On the other hand, when copying a sheet original D2 with a length exceeding the specified size, the exposure optical system 3 does not stop at a fixed position and scan, and the sheet original inserted into the feed roller 4b is transported. An image is formed on the circumferential surface of the photosensitive drum 1, which moves to the left at a speed of {circle around (2)} and rotates at a circumferential speed of {circle around (3)} by the bell) 4a. 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 tarp like the conventional one.

In the copying machine as described above, in the present invention, a detector 8 for detecting the density of a detection pattern to be described later is provided at the peripheral edge of the photosensitive drum 1 between the developing device 5 and the cleaning device 9. ing. The detector 8 is a reflective type 7-to-coupler 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 of the background part and the density of the background 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 an image carrier to form a detection pattern without particularly providing a reference tarded (reference density piece) outside the document placement area.

That is, as shown in FIG. 2, the image area G2 and the image area G2
The detection pattern area P2 provided before or after is configured to change the brightness of the exposure lamp L.

The detection pattern area P2 formed by the copying machine shown in FIG.
- is a detection pattern formed at .

Since the image area C2 and the non-image area including the detection pattern area P2 are uniformly charged by the charging means 2, the detection pattern area P2 on the photosensitive drum 1 has a latent image of a constant voltage. Kotonasu, developing device 5
As the toner passes through the detection pattern area P2, toner adheres 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 concentration 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 preset reference density, toner is replenished from the toner replenishing section 51 in the developing device 5 shown in FIG. 1, or the amount of toner replenishment is It acts to 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 The variable resistor VR''Chll is adjusted and set so that the potentials of the points are equal, and the developed detection pattern on the photoreceptor 1 is irradiated with infrared light from the light emitting element 8a each time it is copied, and the reflected light is emitted from the light emitting element 8a. is received by the light receiving element 8b.Then, the comparator COMP judges whether the output voltage level at the four points due to the light reception has become higher or lower than the set level B4, and based on that signal, the toner replenishing section 5
The supply of toner to the developing device 5 is controlled by stopping or operating the first swinging rod 51a.

,: Here, when irradiating the detection pattern area P2, the brightness of the exposure lamp was changed to form a constant electrostatic latent image on the photoreceptor. This can be done by lowering the voltage of incandescent lamps or controlling the brightness of fluorescent lamps using Cyrisk or the like. Furthermore, even without changing the brightness of the light source, it is possible to reduce the amount of light exposed onto the photoreceptor by inserting a filter or the like on the optical path, which is included in the present invention. In carrying out the present invention, the detection pattern area P
The 2NS electrostatic latent image is set 100 to 150 V lower than the black paper potential of the image area (corresponding to an optical reflection density of 1.30), but the setting can be varied depending on the image density level of the machine.

〔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 copying speed. image con,
An effect has occurred that allows you to troll.

[Brief explanation of the drawing]

FIG. 1 is a front view of an electrophotographic copying machine showing an example of the present invention, FIG. 2 is a graph showing an example of charging and exposure according to the present invention, and FIG. 3 is a graph showing toner on the surface of a photoreceptor according to the present invention. An example of a circuit for detecting the amount of adhesion is shown. 1... Photoreceptor 2... Charging means 3... Exposure means 5... Developing device 8... Detector
8a... Light emitting element 8b... Light receiving element 5
1... Toner supply section 51a... Swing rod agent, patent attorney field 1) Foster parent Figure 1

Claims (1)

[Claims] An image forming apparatus comprising a step of forming an electrostatic latent image by a charging means for charging an image carrier and an exposure means for exposing a charged surface charged by the charging means, and developing the charged latent image. 1. An image control device that is capable of controlling an image by reducing the exposure amount of a predetermined area when forming the image and detecting the development characteristics of the predetermined portion.