JPS6266286A - Electrophotographic copying machine - Google Patents

Abstract

PURPOSE:To prevent the wasteful consumption of toner which is not supplied for copying directly by forming a reference picture at the time of copying by a special copying magnification with a high copying frequency, executing the constant quantity supply of the toner in accordance with the copying quan tity at the time of the copying except for it. CONSTITUTION:When the density of the reference picture is lower than the reference density at the time of the magnification copying, the toner of the quantity is supplied in which the toner quantity necessary to develop the original with the black and white ratio of 20% an A4 size is applied to the toner quantity necessary to develop the reference latent image. When the density of the reference picture is higher than the reference density, the toner of the quantity is supplied in which the toner quantity necessary to develop the original with the black and white ratio of 2% by the A4 size is applied to the toner quantity necessary to develop the reference latent image. On the other hand, at the time of the variable power copying, the control by an AIDC is not required, and the toner of the quantity necessary to develop the original of the black and white ratio of 2% by the A4 size for one copying is supplied in the constant quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to electrophotographic copying machines, and more particularly to the control of toner replenishment therein.

In general, in electrophotographic copying machines, the toner in the developer is consumed as the electrostatic latent image is developed. The agent must be replenished with fresh toner. In order to achieve such toner replenishment, a latent replenishment control method is used to form a base latent image on the surface of the photoconductor, develop this to form a reference image, and then detect the amount of toner adhering to the reference image. There is a method (hereinafter referred to as AIDC) in which the amount of toner supplied to the developing device is controlled in accordance with this detected value in order to constantly maintain the toner concentration in the developer in the developing tank constant.

A typical method of such AIDC is to provide a black reference pattern in front of or behind the document placement glass, form a corresponding reference latent image on the surface of the photoreceptor via a copying optical system, and then print this pattern. It is known that after development, the amount of toner adhering to the latent image on the substrate is detected by a photosensor as a reflection density, and the amount of toner replenishment to the developing device is controlled according to the detected value (Japanese Patent Application Laid-Open No. 1983-1999). -61938, 56-128977, etc.). Since the reference pattern is black, the photoreceptor surface portion corresponding to the reference pattern is not substantially exposed to light during image exposure, and the potential of the reference latent image is approximately equal to the charged potential (constant) of the photoreceptor. The amount of toner attached to the developed reference image is proportional to the toner concentration in the developer. Therefore, the principle of AIDC is to know the change in the toner concentration in the developer by knowing the change in the amount of toner adhesion, and to control the amount of toner supplied to the developing device accordingly.

Problems to be Solved by the Invention By the way, when the AIDC is used in an electrophotographic copying machine in which copying magnification can be changed, the following problems occur.

That is, conventionally, AIDC is a process in which a reference latent image is formed and developed through a copying optical system for each copy, and the amount of toner adhesion is detected, not only during full-size copying but also during variable-magnification copying. has passed through. Then, the surface reference latent image (image I) is formed with an area corresponding to the copying magnification with respect to the reference pattern of a constant area. This reference image has a fixed installation position 1δ,! -1- It must have a size that can be reliably detected by the sensor, and the basic pattern should have an area that can form a reference image of a size that can be reliably detected even at the minimum copy magnification. There is.

However, in this case, the standard image becomes too large for the same-size copying or enlarged magnification copying, and since it is developed for each copy, wasted toner costs increase, and the base image becomes too large. The problem is that the toner adhering to the image goes to the cleaning device without being transferred, which increases the burden on the cleaning device. In particular, in a method in which the original is positioned on the original placing glass 2 by aligning one side of the original, changing the copying magnification causes the location where the original image and replacement image are formed to shift in the axial direction of the photoreceptor. The area of the reference chart is inevitably larger than that in the center alignment method, and the above-mentioned problem becomes more noticeable.

Means for Solving the Problems Therefore, the electrophotographic copying machine according to the present invention forms a reference image when copying at a specific copying magnification that is frequently used.
The present invention is characterized in that, while toner is replenished by IDC, when copying is performed at a copying magnification other than a specific one, toner is replenished in a fixed amount according to the copy amount.

That is, even if it is possible to change the copying magnification, in most cases copies are made at a specific magnification (usually equal magnification), and copies are made less frequently at other magnifications. Therefore, in the present invention, toner is replenished by AIDC when copying at a specific copying magnification with high copying frequency, and when copying at other magnifications, a fixed amount of toner is replenished according to the copying amount, thereby eliminating waste!・It was designed to prevent the consumption of ner.

First, an outline of an embodiment of an electrophotographic copying machine according to the present invention will be explained with reference to FIG.

The photoreceptor drum (1) has a surface coated with a Cd5-nCdCo3 resin photoreceptor, and can be rotated counterclockwise in the figure. Around this photoreceptor drum (1), there is a subcharger (2), a prior history exposure lamp (3),
Main charger (4), developing device (5), transfer DC
'Dianoya (15), separation AC charger (16)
, a cleaning device including a light emitting element (17), a light receiving element (18), and a cleaner blade (19) for detecting 4' the adhesion of toner to the reference latent image.

The exposure device (20) is a moving optical system type, and includes a light source lamp (
21), reflecting mirrors (22), (23), (24), (25
), a projection zoom lens (27), and a light source lamp (21) and a reflecting mirror (22) have a speed of (v/n, n+ copying magnification) with respect to the circumferential speed (V) of the photoreceptor drum (1). The reflecting mirrors (23) and (24) can each scan to the left in the figure at a speed of (v/2n). This exposure device (20) has a projection lens (2) consisting of a zoom lens.
7), the copy magnification can be changed from 0647 to 1.
It can be changed steplessly between 414 times. The reference pattern (29) is provided in front of the document placement glass (28), that is, upstream in the exposure scanning direction, and is formed as a phantom image on the cleaning body drum (1) J: before exposing the document image. , and developed. By the way, in this embodiment, toner replenishment is controlled by AIDC only when copying at the same size, which is a frequent copying process, as will be described in detail below. Therefore, the reference pattern (29) has a minimum area that allows the light receiving element (18) to measure the reflection density of the reference image that is formed only when copying at the same size. The reference image formed based on this reference pattern (29) is not subjected to reflection density measurement by the light emitting element (+7) and the light receiving element (18) during variable magnification copying, or the potential of that part is is not erased by an eraser and formed as a reference image.

On the other hand, the developing device (5) is a well-known magnetic brush type device equipped with a developing sleeve (7) containing a magnetic roller (6), and the toner is cut into a peripheral surface provided at the bottom of the toner tank (8). It is replenished by rotation of the l/ner replenishment roller (9) which has a gap. The developing sleeve (7) has a self-bias resistance (
Ro) and a developing bias power supply (lO). The light receiving element (18) detects the toner adhesion amount of the basic image as a reflection density, and the detection output is manually inputted to the toner adhesion amount detection circuit (II) and the control circuit (12).
) to control the replenishment roller drive mechanism (13).

Next, the control circuit will be explained with reference to FIG.

The connection point between the output of the light receiving element (18) and the resistor (R4) is connected to the input terminal (Il, ) of the comparator (C),
A connection point between a resistor (R5) and a variable resistor (no) connected in parallel with the light receiving element (18) is connected to the other input terminal (R3). Microcomputer (CP)
At tJ), the output of the comparator (C) and the output of the magnification data storage section (14) are manually input, and the operating time of the replenishment roller drive mechanism (I3) is controlled from the output data of the rain sound.

The input voltage to the terminal (J-i2) of the comparator (C) changes depending on the resistance value of the variable resistor (R6), and the reference image when the toner ajy of the developer in the developing device (5) is at the set value. The light receiving element (!8) detected as the reflection density of
output voltage (reference voltage).

The output voltage of the light receiving element (18) increases in inverse proportion to the reflection density. Therefore, the comparator (C) turns on when the input terminal to the terminal (H,) [toner adhesion amount detection voltage of the light receiving element (18)] becomes larger than the input voltage (reference voltage) to the terminal (H,). The replenishment roller drive mechanism (13) is operated for a certain period of time, and the toner replenishment roller (9) is rotated by a certain amount to replenish toner.

Specifically, [1] When copying at the same size, [I a] If the density of the reference image is lower than the reference density, the amount of toner required to develop the reference latent image is 20% of the black and white ratio for A4 size. (Necessary to develop a manuscript)・The toner with the addition of a toner claw is caught by insects. [Ib] If the density of the reference image is higher than the base density, add the amount of toner required to develop the standard latent image to the amount of toner required to develop an A4 size document with a black and white ratio of 2%. amount of toner is replenished.

[11] On the other hand, during variable magnification copying, without controlling by AIDC, When control by λ1 AIDC is not performed on the 11th frame, the reference latent image formed on the surface of the photoreceptor drum (+) by the exposure device (20) is not shown before reaching the developing device (5). It is erased by irradiation with laser light, and as a result, no reference image is formed. In addition, in the case where such a first-order item is not destroyed, it is formed as an image in the developing device (5), but the light emitting element (17).

The light receiving element (18) does not operate, and AIDC control is not performed. This control is carried out by the magnification data storage section (14).
This is done by controlling the eraser etc. with a microcomputer (CPU) using signals from the CPU.

Furthermore, in this embodiment, the amount of toner replenishment per time is controlled to three types, [1a], [lb], and [11], which are determined by the operating time of the stepping motor for driving the roller. This is done by controlling with a timer.

In the case of [[b] above, not only the amount of toner required to develop the reference latent image but also the amount of toner required to develop the original with a black and white ratio of 2% is supplied in the developer. This is to minimize the level of variation in toner density. In addition, in the case of [+1] above, statistically most commonly used originals have a black-and-white ratio of 6%, but only the amount of toner needed to develop an original with a black-and-white ratio of 2% is supplied. The reason for this is to prevent excess toner as much as possible.

Therefore, when continuous copying is performed with variable magnification, there is a risk that the toner concentration in the developer will decrease.

To this end, it is conceivable to count the number of copies to be made at variable magnification and replenish an amount of toner equal to or greater than [+1] constant replenishment for every predetermined number of copies.

Next, the toner replenishment control means will be explained with reference to the flowchart shown in FIG.

First, in step (Sl), the reading timing of the reference image is checked. The reading timing is such that the reference image is the light emitting element (17) for each copying operation.

It is determined by another control routine that the detection point of the light receiving element (18) has been reached. If it is the reading timing, it is determined in step (S2) whether or not the copy magnification is equal to the same magnification. If it is the same size, AIDC will be executed, and in step (S3) it is determined whether the output state of the comparator (C) is on or not. If it is on, that is, the l-ner concentration is lower than the reference density. If it is determined that
) to set the timer (T-0). Timer ('I'-
0) is set to the time required to replenish toner in the amount of [j a], and it is determined in step (SIO) whether or not this count has ended, and if the count has ended, step (SIO) is set. Sll), the operation of the replenishment roller (9) is stopped.

Further, if the output of the comparator (C) is in the OFF state in the step (S3), that is, if it is determined that the toner density is higher than the reference density, in the step (S6), the replenishment roller (9) is avoided and , a timer (T-1) is set in step (S7). The timer (T-1)
The time required to replenish the amount of toner b] is set, and when the end of the count is confirmed in step (SIO), the operation of the replenishment roller (9) is stopped in step (Sll).

On the other hand, if it is determined in step (S2) that the copy magnification is variable, the replenishment roller (9) is operated in step (S8), and the timer (T-2) is activated in step (S9).
). The timer (T-2) is set to the time required to replenish the toner in the amount of [+1], and similarly to the above, when it is confirmed in step (SIO) that the count is completed, step (Sll) is set. with HLT feed roller (
9) is stopped.

Note that the present invention is not limited to the above embodiments, and can be variously modified within the scope of the gist. For example, the amount of toner replenishment shown in [1a], [Ib], and [11] above is just an example, and the copy size that should be used as the standard for the amount of replenishment may be set for each size other than A4, and in actual use. It is best to supply an amount of toner commensurate with the size selected for copying. Further, the specific magnification for controlling toner replenishment by AIDC may be other than the same magnification, or as in the above embodiment, a zoom lens is used for the projection lens (27) to make the magnification variable steplessly. In the case of a machine, toner replenishment control using AIDC may be performed in a range of 0.95 to 1.05 times before and after the same magnification.

Furthermore, toner replenishment by AIDC is performed using a comparator (C
) The nails may be replenished in proportion to the tapped toner concentration based on the voltage difference input to the input terminals (H1) and (I-12) of the toner.

Effects of the Invention As is clear from the above explanation, according to the present invention, when copying is performed at a specific copying magnification with high copying frequency, a base ω image is formed and toner is replenished by the AIDC method, while at the same time When making copies other than the above, a fixed amount of toner is supplied according to copy 1, so that the reference image is formed only to the minimum size required for a specific copying magnification, and wasteful information that is not directly used for copying is created. Consumption of toner can be prevented and excessive burden on the cleaning device can be eliminated.

[Brief explanation of drawings]

The drawings show an embodiment of an electrophotographic copying machine according to the present invention,
FIG. 1 is a schematic diagram of the main parts, FIG. 2 is a control circuit diagram for l/ner replenishment, and FIG. 3 is a flowchart showing the control procedure. (1)...Wq Photo drum, (4)...Main charger, (5)...Developing device, (8)...Toner tank, (9)...Toner replenishment roller, (11 )・
... Toner adhesion amount detection circuit, (12) ... Control circuit,
(13) Replenishment roller drive mechanism, (17) Light emitting element, (18) Light receiving element, (20) Exposure device, (29) Reference chart. Patent Applicant: Minolta Camera Co., Ltd. Representative Patent Attorney: Mr. Maeda and 2 others III Figure 4: Main charger 1, 1, toner tongue 7 9: toner replenishment roller 17: 9E, 18; light receiving 41 Number 2o: N, fold 1 29: 1;

Claims (1)

[Claims] 1. Copying magnification can be changed, and after developing a reference latent image formed on the surface of an electrophotographic photoreceptor through a copying optical system to form a reference image, the toner of the reference image is In an electrophotographic copying machine that detects the amount of adhesion and controls the amount of toner replenishment according to this detected value, when copying is performed at a specific copying magnification that is frequently used, the reference image is formed and the toner replenishing means is activated. What is claimed is: 1. An electrophotographic copying machine characterized in that, on the one hand, when copying is performed at a copying magnification other than a specific one, a fixed amount of toner is replenished according to the amount of copying;