JPS59123857A - Image reproduction controlling device - Google Patents

Abstract

PURPOSE:To enable correct control of copying density by exposing an original preliminarily and measuring density of a toner image. CONSTITUTION:An original scanning means is actuated to expose an original image on a photosensitive drum 1 before a copying process. When the scanning means finishes forward movement for the preceding copying step and returns to the initial position, said preliminary operation may be executed by using this returning means. The density of this toner image formed on the drum 1 by this preliminary exposure is detected with a sensor 11-1, and conditions for obtaining correct copying density are selected by adjusting bias potential of a developing device 6, voltage of a transfer charger 7, output of an exposure lamp 4, etc. The sensor 11-1 is arranged on the center of the image forming area on the drum 1 corresponding to a transfer paper having the min. width. Potential of a latent image on the drum 1 may be also measured at the time of preliminary exposure to serve setting of copying conditions. The sensor 11-1 is located downstream from a transfer section to avoid toner staining.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image reproduction control device. In particular, the present invention relates to a copying apparatus that detects the shading of an original and obtains a copy with the optimum density according to the original.

Conventionally, the image density of a copying apparatus has been selected by operating an image adjustment input means such as an exposure dial. Recently, there has been a system that uses a photoelectric device to read the shading of a document, forms a latent image on a rotating body, and detects the potential of the latent image, and controls the process according to these detection signals to form an image with an appropriate density. Proposed. However, factors that determine the image quality of actual copies include the performance of the optical system that guides the reflected light from the original to the rotating body, the sensitivity of the rotating body, and the performance of the developing device.

Therefore, even if process control is performed using the above-mentioned detection signals, the expected developed image may not be obtained due to the above-mentioned variations in performance.

The present invention solves the above-mentioned drawbacks, and one of them is to provide means for detecting shading on a rotating body, and a means for pre-exposing a document and developing a latent image resulting from the exposure, which is then used to detect the light and shade on a rotating body. a sequence control means for rotating the rotary body so as to achieve the following; a means for enabling a detection operation or a control operation by detection of the detection means after the rotation of the rotation body; and an exposure means and a latent image forming means according to the detection means. , a process control means for controlling at least one of a developing means and a transfer means.

Here, the detection means is a reflective photosensor provided one or two near the center of the rotating photoreceptor to detect the density of the developed image corresponding to the document latent image, or a large number of photosensors arranged in the axial direction of the rotating body. It can be composed of a sensor group or a linear sensor such as a COD arranged in the axial direction. The appropriate position of the detection means in the rotational direction of the rotating body is after development and before transfer, but preferably after transfer and before cleaning in order to prevent developer staining as much as possible.

Pre-exposure can be done using copy start command 9'A unit or
The optical system is moved back and forth to scan 1/4 to 1/2 of the document.

It is also possible to perform a full document scan.

In this case, if preliminary exposure is performed in the backward movement process, the cleaning surface of the rotating body can be exposed and the accuracy is good. Also, the document table usually stops at the center of the main body, moves once to the scan start position in response to a copy command, then changes direction and starts scanning, and after the movement is finished, changes direction and pauses. In a copying machine returning to its position, it is also possible to perform preliminary exposure during run-up. Further, by setting each process such as the rotating body and the developing means to the standard state before preliminary exposure, the accuracy can be improved. As a control target of the exposure means,
The voltage of the fluorocarbon lamp, the primary corona discharger as a latent image forming means, the corona voltage or current of the secondary corona discharger simultaneously with image exposure, or their grid voltage, the bias voltage to the developing roller as the developing means, the toner The amount of replenishment (in the case of a two-component developer), the corona voltage or current of a transfer corona discharger, or the grid voltage as a transfer means. The sequence control means is a timing output circuit using a timer or clock pulse, and the process control means is an analog node or average that compares the document reference concentration and the detected concentration and outputs an appropriate concentration. It is also possible to obtain the detected concentration by

The second is means for detecting the potential or concentration on the rotating body;
Sequence control means for performing preliminary exposure with a standard density member and φ semi-density member, and rotating the rotating body so that a latent image or a developed image resulting from the exposure reaches the detection means, and after the rotation, detection by the detection means. a first process control means for controlling at least one of the exposure means, the latent image forming means, the developing means, and the transfer means to a predetermined state according to a signal; and second process control means for detecting by the detection means and controlling at least one of the exposure means, the latent image forming means, the developing means, and the transfer means.

Here, the density detection means may be the same as described above, and the potential detection means may be a well-known cup-shaped tipper type probe, and the appropriate position thereof is after exposure and before development. The standard density member may include a standard white plate provided on a part of the mounting table, a separate standard light source, or a blank light source provided between the image exposure area and the development area to remove all charges on the photoreceptor. be. A latent image with a standard density is formed on the photoconductor in advance using the standard plate or a standard light source, and the process is set to a standard state depending on the density of the latent image or the developed image (standardization step). . After that, the document is exposed to light, and the density and type of the document are predicted from the resulting document image or developed image, and a transferred image with the appropriate density is obtained (optimization process). It is preferable to perform this when the switch is turned on or after 30 minutes of copying operation in order to increase the copying speed, but it is also possible to perform it every time the document is changed as in the optimization process. can be achieved by the above sequence.

FIG. 1 is a schematic cross-sectional view of an example of a copying apparatus according to the present invention. 1
1 is a drum having a sequential photoreceptor, 2 is a document, 3 is a primary corona discharger for charging the reciprocating document body, 6 is a single-component developer developing device for developing a latent image, 7 is a drum having a sequence photoreceptor;
8 is a transfer corona discharger that transfers the developed image onto the paper 20; 8 is a fixing roller that fixes the transferred paper sent by the belt 9;
Reference numeral 10-1 is a cleaner for removing residual toner, and reference numeral 10-2 is an erase lamp for removing residual charges and uniformizing the drum potential, which also serves as a pre-exposure for correcting the drum feel. 11-1 is a reflective photo sensor that detects the density on the drum, and the second cap is 11-2 to prevent stains from toner from the cleaner.
12 is a removable cassette in which paper 20 of different sizes can be inserted.
Photo sensor ti-i located approximately in the center corresponding to the B size exposure surface of the drum as shown in the figure (al), (b) is a line sensor 11-1' such as COD, which is provided in plural in the width direction of the drum. However, in the case of the type shown in Figure 3(b) where A and B size documents are placed with the drum center l as the reference, the sensor I
H is provided on the surface corresponding to e on the drum. These positional relationships are the same in the case of potential sensors. This makes it possible to appropriately determine the shading and type of documents of different sizes.

The operation will be explained below. Original 2 on glass stand 3 is lit by lamp 4
The reflected light is guided onto the photosensitive drum 1 which has been uniformly charged in advance by a charger 5, and a bias voltage is applied to the zero electrostatic latent image forming an electrostatic latent image. The image is developed by a developing device 6. Next, the developed image is transferred to a transfer paper 20 fed from the cassette 12 and guided by a guide 13 and conveyed by the action of a transfer charger 70.

The transferred transfer paper is guided to the fixing row 28 by the conveyor belt 9 and is fixed thereon.

A transformer H with D/A conversion converts the binary signal to determine the
In addition to the VTs 17, 18, and 19, a signal for determining the amount of lamp light is outputted to the 0VRI6, and the A/D conversion output of the sensor 11-1 is inputted. Sample timing signal S1 of sensor 11-1 Drum drive signal M11 Erase lamp on signal ER, Document platen advance signal FAD, Backward movement signal BAD, Transfer charger on signal TR1 - Next phase electric device on signal I8T, Lamp lighting signal EX is CPU, A signal SW and a copy button signal C0PY, which are output from the main switch and linked to the main switch, are input to the CPU.

The sequence will be explained using the time chart shown in FIG.

When the power switch SW is turned on, the main motor M is turned on, the drum is rotated, and the lamps 4 (signal EX) and 1O-
2 (signal E) and charger 5 (signal IST) are turned on. Accordingly, the rung 4 pre-irradiates the reference density plate 30 in advance.

The latent image obtained by this irradiation is developed by the developing device 6 and reaches the photodetector 11-1 by rotation of the rotating body t. The detector 11-1 detects the density of the area of the developed image at a predetermined timing, and the detection signal is converted into a digital signal via the A/D converter 15 and input to the CPU. CPU,
Based on this value, determines what density the standard plate has been developed with. If it is developed at a predetermined density, the CPU makes no change to each process means. However, if it is dark, the CPU,...
is the main scan (ms) of at least one of each process means.
Make corrections to obtain the correct density.

In addition, when rotating the drum 1 more than twice in '1,
Standardization due to correction can be confirmed by correcting it in the first rotation and detecting it again in the second rotation. If it is still inappropriate, a notification is given that the amount of toner in the developing device 6 is low.

In the manner described above, the process standardization process is completed. During this step, if the transfer charger 7 is turned off, a faithful developed image becomes the object of detection, which improves accuracy. Note that the paper is not fed during this process.

In this way, since the process system can be set in advance to a reference state, it is possible to correct for deterioration of process performance, etc., and the reliability of control of the concentration optimization process described later is increased.

Next, when the copy button is turned on, the main motor is driven, the document table moves forward, and the lamp 4 moves the document 2 by a predetermined distance.
A preliminary scan PS is performed, but this may be a part of the document regardless of the size of the document.

It is also possible to scan the entire area by making the speed at 28 o'clock twice the speed at m8. The latent image obtained by this scanning is developed by a developing device 6, and reaches a detector 11-1 due to the rotation of the rotating body. The detector 11-1 detects the density of the area of the developed image of the lever at a predetermined timing T. The detection signal obtained by the detector 11-1 is converted into a digital signal via the A/D converter 15 and input to the CPU. The CPU determines what kind of document the document is based on this value. If there are many white parts and few black parts, it is judged that it is a normal printed matter with black characters written on a white background, and the CPU 1 determines each process means (exposure rung, bias voltage, charging high voltage), etc. Do not make any changes to 〇 However, if the background is gray, the copy will be easier to see if the background is erased, so CPU1. controls at least one of the process means so that the gray background is copied to white. At this time as well, the transfer paper 20 is controlled not to be fed, and the transfer charger 7 is also not energized. Next, the CPU,
At least one of the process means is controlled as soon as the performance of the process is completed. Figure 6.7 shows the calculation when the lamp light amount is used as the process control target.

If the PS speed is fast, the second performance is taken into consideration.Next, the main scanning ms starts at timing T8, and the original is scanned in accordance with the size of the original to create a copy with an appropriate density.

At this time, the transfer charger 7 is energized for transfer and paper feeding is also performed. The copy cycle time can be shortened by starting the main scan ms immediately in response to the end signal of the backward movement BAD of the PS.

Note that the sensor 11-1 performs a detection operation at timing T4 even during this cycle. And OPU.

During this period, if white is detected continuously, the CPU.

Sends signal J to , cuts the output of Ml, etc., and stops the sequence from continuing. First, the machine stops when it determines that the paper has become wrapped around the drum due to a paper separation error.

In the above, the density of the developed image is detected, the density of the original is determined, and optimization control is performed. For example, in the sequence control shown in FIG. It is also effective when directly detecting and controlling the density of the original.

[Brief explanation of the drawing]

Fig. 1 is a schematic sectional view of a copying machine to which the present invention can be applied, Fig. 2 is a perspective view of the top of the drum, Fig. 3 is a top view of the glass, Fig. 4 is a time chart diagram of Fig. 1, and Fig. 5-1. Figure 5-2 is a sequence control flowchart, Figure 6 is a process control flowchart, and Figure 7 is an explanatory diagram of Figure 6.
2 is a rotating body, 2 is an original, 30 is a standard plate, and 11-1 is a 7-point sensor.

Claims (3)

[Claims] (1) A rotating body, a document exposure means, a means for forming a latent image on the rotating body, a means for developing an IA image, a means for transferring the developed image, a means for detecting the density on the rotating body, a means for pre-exposing a document, and Sequence control means for rotating the rotary body so that a latent image formed by exposure is developed and reaches the detection means, and means for enabling a detection operation of the detection means or a control operation based on the detection after the rotation of the rotor. and a wood process control means for controlling at least one of the exposure means, the latent image forming means, the developing means, and the transfer means using the detection means. (2) Rotating body, document exposure means, means for forming a latent image on the rotating body, means for developing the latent image, means for detecting the potential or density on the rotating body, standard plate, preliminary exposure of the standard plate, and the exposure a sequence control means for rotating the rotating body so that a latent image or a developed image reaches the detection means; after the rotation, the exposure means, the latent image forming means, the developing means; a first process control means for controlling at least one of the transfer means to a predetermined state; a first process control means for exposing the document to light; detecting the latent image potential due to the exposure or the density of the developed image by the detection means; a second controlling at least one of the forming means, the developing means, and the transfer means;
An image reproduction control device having a process control means. (3) A rotating body, a document exposure means, a means for forming a latent image on the rotating body, a means for developing the latent image, a means for transferring the developed image onto a transfer material, and a feeding section capable of feeding transfer materials of multiple sizes. , means for detecting the density or electric potential on a rotary body provided corresponding to substantially the center of the transfer material; at least one of the above-mentioned exposing means, latent image forming means, developing means, and transfer means according to the detection signal; An image reproduction control device having means for controlling.