JPS6167047A - Automatic density control method - Google Patents

Abstract

PURPOSE:To prevent an overshoot due to toner dispensing and an undershoot which occurs thereafter, and to obtain copy paper stable in picture quality by determining the new amount of toner to be dispensed in consideration of the last amount of dispensed toner and last toner density which are stored. CONSTITUTION:An automatic density control circuit 20 consists basically of an A/D converter 21, microcomputer, and motor driving circuit 27. An automatic density control program is stored in the ROM24 of the microcomputer and the amount of dispensed toner in the last cycle and other necessary data are stored in the RAM25. When a signal from a photosensor is inputted, the CPU perfoms arithmetic processing and outputs the proper amount of toner to be dispensed to the motor driving circuit 27 through an I/O. The motor driving circuit responds to the signal from the CPU to drive a motor 18, supplying toner to a developing device 8.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an automatic density control method for an electronic copying machine using a two-component developer.

Conventional technology A conventional electronic copying machine exposes and develops a reference density (R) image on a document table, detects the density of a reference image formed on a photoreceptor using an optical detection element, and compares this value with the reference. When the detected density was lower than the reference value, the toner dispenser was driven to supply a certain amount of toner (for example, Sho@
1943, Chikushideho Public Notice No. 16,199).

However, in this method, it takes quite a long time until the toner dispenser is driven, the toner is supplied into the developing device, and the toner density of the ξT image formed on the photoreceptor increases by one. I'll be late.

Therefore, when the density of the patch latent image is measured again during this period, the detected value always does not reach the reference value, so the automatic density control circuit continues to output a supply signal to the toner dispenser. Therefore, even if the signal from the optical detection element reaches the desired density, the toner supplied to the developing device increases until it becomes uniform on the photoreceptor, resulting in the toner density becoming higher than necessary. However, there was a rare problem that fog appeared on the resulting copy paper.

As a way to prevent this drawback, the toner dispense amount is set to about 1.5 times the toner consumption amount during normal copying, but the toner consumption amount is determined by differences in the document size, the area ratio of the black portion of the document, etc. Due to this difference, toner shortages often occurred, especially when copying originals with a large amount of black background.

In addition, if the developing density changes due to changes in humidity, etc., if the toner dispense amount is about 1.5 times the average toner consumption, it will take a long time for the toner density to reach the standard value, and during this period, satisfactory copying will not be possible. The disadvantage is that it is rarely possible to do so.

Therefore, with conventional devices, it is extremely difficult to determine the amount of toner dispensed that can accommodate various usage conditions.

Purpose of the Invention The present invention has been made in view of the above-mentioned drawbacks, and it aims to minimize the change in the density of the toner image formed on the photoconductor, and to reduce the change in the consumption amount due to changes in the usage environment and the size of the original and the same pressure. Another object of the present invention is to provide an automatic concentration control method that can quickly converge to a reference concentration.

EXAMPLE Hereinafter, the present invention will be described in detail using an example shown in the accompanying drawings.

FIG. 1 is a schematic illustration of a copying machine using the automatic density control method according to the present invention.

Standard density patch 6 is placed between platen 1 and guide 2 of the copier.
is installed. This patch uses, for example, gray with a density of 0.7 to 1.0 on a 20×20 scale.

When START/Zeta/ is pressed, the copying machine enters the density control cycle that normally precedes the copying cycle, and the latent image of the reference density/sensor 6 on the platen 1 is formed on the photoconductor 6, and the latent image is formed on the photoconductor 6, and then the latent image is formed on the photoreceptor 6. The toner image 19 is visualized. This toner image is measured by the photo sensor 12, and the detected density signal is supplied to an automatic density control circuit 201C shown in FIG.

The automatic concentration control circuit 20 shown in FIG.
It consists of a /D converter, a microcomputer, and a motor drive circuit. A signal from a photo sensor t-12 shown in FIG. 1, for example, an infrared light emitting diode and a photo transistor, is input to the A/D converter 21. The input signal (after being amplified with a suitable amplifier) is converted from an analog signal by an A/D converter 21, e.g.
It is converted into a bit digital signal and input to the micro combinator. The microcomputer has a known configuration and is composed of a CPU (computation unit) 26, ROM 24, RAM 25, and related components 11022 and 26. ROM
An automatic density control program, which will be explained later using a flowchart, is stored in the RAM 24, and the RAM internal pressure stores the toner dispense amount of the previous density control cycle and other necessary data. This IIAM is preferably powered up by a battery so that it remembers the previous amount of toner dispensed even when the copier is turned off.

CPUt-! When the copying machine is powered on, the density control program in the RAM is read and the previous toner dispense amount in the KRAM is input as one of the reference values. Then, it enters a state of waiting for an input signal from the photo sensor 12 to be inputted via the A/D converter 21 and Ilo.

When the signal from the photo sensor is input, the CPU performs arithmetic processing and determines the appropriate toner dispense amount'&l1
0ft intervention.

and outputs it to the motor drive circuit 27. The motor drive circuit is C
The motor 18 is driven in response to a signal from the PU to supply toner to the developing device 8.

The program used to implement the method of the present invention is shown in FIG. 6 and will be explained below using a flowchart.

1) When the density control cycle is started, the density of the reference density patch is input to the CPU as Vp.

2) A comparison band having a width Vw with respect to the reference value Vs is set in the CPU according to the program in the ROM, and vp is set such that Vp <Vs −Vw (low density), Vs −Vw
<Vp<Vs+Vw (normal concentration control range), Vp>Vs
It is determined which IC of +Vw (9th degree is dark) belongs to.

For the following explanation, the toner dispense amount is assumed to be tjllR, and 'r, , T2. 'r, are respectively 0.2 times, 2 times, and 4 times the normal toner consumption amount, and the basic preparation Vs for density determination is toner density 0.9 (patch 0.7 G)
, the width Vw is set to ±0.07.

3) If Vp>Vs-Vw, then it is determined whether or not the previous toner dispense amount was T3, and if it was T3, the new toner dispense amount is set as T2, and if it was not T3. In this case, T1 is set.

4) If Vp<Vs+Vw, then it is determined whether or not the previous toner dispense amount was at T1, and if T1 was not successful, a new toner dispense amount is set as T2, and if T1 is not, then T6 is set.

5) If Vs - Vw<Vp<Vs +Vw, then it is determined whether Vp dl is greater than Vs.

6) If Vp > Vs, the previous toner dispense amount is 'r1. 'r2. 'r, and if it is T1, T1 is selected as the expected toner dispense amount, if T6, T2 is selected, and if T2, it is determined whether Vp is the same as the previous value. If they are the same, T2 is selected, and if they are different, T1 is selected.

7) If ■, > vs, the previous toner dispense amount is T4. T2. Determine which of T3 it was, and in case of T6, '! When T3 is the toner dispense amount, T2 is selected when T1 is selected, and in the case of T2, it is determined whether or not ■ is the same as the previous value, and if the same, T2 is selected.
If they are different, T3 is selected.

Based on the above, if the current toner density is out of the range vs. vw based on the judgment (2), the maximum or minimum toner dispensing amount is set, respectively, so that the toner density quickly converges to the reference density. In (2), the previous toner dispense amount is taken into account, and if the previous toner dispense amount is the same and rarely occurs, the density change due to the previous toner dispense amount is predicted and the value is lowered (or raised) by one rank. If the current toner density is within the normal control range in ■,
In , it is determined whether the value of VP is v,>vs or vP<vs, and in each case φ, if the previous toner dispense amount is 'r1. 'r2. It is determined which one of 'r' is the 6th nen. In the case of vPn v8, if the previous value is T1, the previous toner dispense amount setting is based on the previous control and is operating in the direction of decreasing the toner density, so a new toner dispense, In the case of a private customer who sets the toner dispense amount to T, it is considered that the toner concentration has increased and vP>vs based on the previous control, so the toner dispenser is set to T2, which is one step lower. In the case of T2, it is determined whether or not ■2 is the same as the basket measured last time. If the toner concentration has to be supplied (or the supply time is short), T2 is further set. If the value of V increases, an increase in toner concentration is observed and vs<v. , <vs+■, so T1 is set as the new toner dispense amount.

8) Similarly, when vP>Vs, the previous (b) toner dispense amount is T, , 'r2. 'r, and if the previous value is T5, the previous toner dispensing turtle setting is operating in the direction of increasing the toner concentration σ based on the control of the Ail times. Since the toner concentration has not yet increased sufficiently, T5'fr is set as a new toner dispense amount.

In the case of T1, it indicates that the toner ζ degree has begun to decrease, so T2 is set as the new toner dispense amount. In the case of T2, it is determined in (2) whether V is the same as the previous value, and if it is the same, there is no change in toner density related to the previous toner dispensing, so T2 is further set.

If they are different, that is, if the value of vP is decreasing, the toner dispense amount T2 will be insufficient and T6 will be set as the new toner dispense amount.The above control is shown using 2 as follows. become.

As can be easily understood from Table 1, once is the center of judgment vs. Since the dispensed amount is determined, there is a lack of accuracy caused by the time delay between when the toner dispenser operates and when the density change of the image appears, and overshoots and undershoots caused by excessive or minute amounts of toner dispensed. can be resolved.

In the present invention, the area coverage is usually about 5%.
! For oaks, repeat T1 and T2! 13 m,
Even if the number of area/9 registers increases and the number of toner erased 5R discrepancies increases, it can be sufficiently coped with by repeating T2 and T6, and the density can be maintained as always<vs1.

FIGS. 4(a) and 4(b) tr1 are diagrams showing toner density changes when using the method according to the present invention and when using conventional on/off control. As can be easily understood from the above, the method of the present invention has much less change in density than the conventional method, and it is possible to obtain copy paper with stable image quality. Further, more precise toner density control can be performed by detecting the number of copies, document size, etc., and controlling the density by @N processing using a microcomputer in conjunction with the density signal from the toner sensor.

Effects of the Invention As described above, in addition to the conventional toner concentration measurement, the present invention takes into account the previous toner dispense amount and the previous toner concentration that are stored, and calculates a new toner dispense amount.
Therefore, toner dispensing is performed based on the lack of density due to the time delay between the operation of the toner dispenser and the change in the density of the patch image, which is a rare problem with the conventional method, and the density measurement is performed again after the shortcoming of the toner dispenser. It is possible to prevent the occurrence of overshoot and undershoot that occurs thereafter, and it is possible to obtain copy paper with stable image quality.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of an electronic copying machine according to the present invention, FIG. 2 is a block diagram of an automatic density control circuit according to the present invention, and FIG. 3 is a flowchart of an automatic density control method according to the present invention. FIGS. 4(a) and 4(b) are diagrams showing all the changes in toner density according to the present invention and the conventional method. ξ
Tsuchi, 4... line light lamp, 5... line light section, 6...
Photoreceptor. 7... Charge corotron, 8: Developing machine, 12: Photo sensor, 13: Toner dispenser, 18: Motor, 20: Automatic! # degree control circuit, 2 A/D converter,
22: Ilo, 23: CPU, 24: ROM
, 25: RAM, 26: Ilo, 27: Motor rotation circuit

Claims (1)

[Claims] In an electronic copying machine that uses a two-component developer, a standard density patch is exposed prior to the original, the density of the patch exposed and developed on the photoconductor is detected, and the density of the patch is detected based on that value and a plurality of preset standards. In addition to selecting a predetermined amount from a plurality of toner dispensing amounts based on the result, the toner dispensing amount to be newly set is changed in relation to the previous toner dispensing amount stored. Features automatic concentration control method.