JPS6028675A - Controller for developer density - Google Patents

Abstract

PURPOSE:To eliminate an over toner or the like to develop always an image with a normal developer denisty, by providing a position detecting means which detects the steady position of a developing device and controlling the toner supply independently of the detection signal of a density detecting means for a certain time after the operation of a copying machine. CONSTITUTION:A developing device 1 is provided with an agitating roll 8 of a developer 2 and a rotary developing roll 9. In a tank, an element 4, which detects a surface level 3 when a mixture ratio of the developer 2 is normal, is provided in a certain position. If this element 4 detects a level lower than the surface level 3, a toner 7 is supplied from a toner supply device 5. Then developer 2 is agitated by this supply; and when detected level is raised to detect the level 3, the toner supply is stopped. The device 1 is attachable and detachable. When the detecting means detects that the device 1 is pulled out, driving of a motor for supply of the device 5 is stopped independently of the detection state of the element 4.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to control of development density of a two-component developer used in electrophotographic copying devices and the like.

<Prior art> When an electrostatic image is visualized using a two-component developer, the concentration of the two components, that is, the carry Thv'i"8
2.' and the Ff-o mixing ratio "suitable EC'fx" - The problem arises that the density of the first image becomes thin and hard to see, or it becomes too dark and the capri increases. On the other hand, until a certain period of time, a manual toner supply amount adjustment device (1J,
The user was able to adjust this at 06 points depending on the change in copy density. However, even if the amount of toner supplied is adjusted, the mixing ratio within the developing device does not change rapidly, and there is a problem in aging properties. Moreover, it was therefore difficult to adjust the concentration to an appropriate level. Furthermore, it was a tedious task for the user to have to make every adjustment.

In order to overcome the above drawbacks, various automatic development density control methods have been proposed and put into practice.

Among these, there are those that detect and control magnetic permeability that changes depending on the mixing ratio of carrier and toner, and those that detect and control magnetic permeability that changes depending on the mixing ratio of carrier and toner colored in different colors. There are some that control by detecting the amount of carrier, and others that control by capturing the change in the amount of toner relative to a fixed amount of carrier as a change in volume.

The control method using level detection described above is often used because the reference value can be easily detected. This method will be explained with reference to FIG. 1. The developer 2 is sufficiently stirred and placed in the developing device 1, and the height of X (surface level 3) is approximately constant as long as the concentration is constant. Now, when the toner in the developer is consumed by copying, the volume decreases and the developer surface position 3 lowers by that amount. When the developer surface position falls below the reference position in this way, the developer 2 is no longer in contact with the ceramic vibrator 4 (detection device) installed at the reference position. This causes the vibrator 4 to start vibrating, and a detection signal is sent to the control circuit. Based on this signal, the control circuit controls the toner supply device 5.
The first small motor (not shown) for the toner supply roller is activated and the supply roller 6 rotates, so that supply of the toner 7 is started. Thereafter, when the volume of the developer increases again and reaches the reference position, the vibration of the vibrator 4 stops, and the toner supply also stops. Thereafter, by repeating these steps, the density of the developer 2 is automatically controlled, and fog-free copies with proper density can be obtained. In this method, in order to accurately control density, the developing device 1 must be correctly mounted in a horizontal plane.

However, when putting in and taking out the developing device A1 during maintenance or troubleshooting of the copying machine, or when replacing the developer 2, the developing device 1 is not always kept in a horizontal position, and the PJ In this case, there is a risk that the replaced developer 2 in the current device may be biased to one end, making it impossible to detect and control it in accordance with the intended purpose.

For example, the detection device 4 is provided at one end of the developing device 1, and if salt 9 is taken out from the copying machine and held diagonally with this end 11 facing up, the developer will be placed on the other end. will be concentrated on. If this size is reinstalled in the copying machine, the developing device will be in the horizontal position f'13. Since it has returned to normal state, the developer in 2 also tries to return to its normal state, but it does not return completely. When the power is turned on in this state, the detection device 4 determines that the height of the developer 2 has not reached a predetermined height even though the volume of the developer 2 is normal, and issues a signal accordingly. become. Then, the toner 7 is supplied from the toner supply device 5,
The developer 2 is in an overtoner state. In this case, an undesirable copy with a lot of fog will be obtained.

This toner supply continues until the developer 2 is agitated by the agitation roller 8 in the developing device and the developer returns to a substantially horizontal state.

<Objective of the Invention 2 An object of the present invention is to prevent overtoner, etc., when the developing device returns to its normal position after being attached and detached.

<Embodiment> In order to prevent overtoning, the present invention detects whether the developing device is attached or detached, and based on the detected signal, the toner is This is to stop the supply. Not only when the developing device is installed and removed, but also when the copying machine is tilted.
Performs the same control as the double series.

4. The present invention will be explained below with reference to the drawings. In FIG. 1, there is a developing device 1r/'J, a stirring roller 8 that stirs the carrier and toner of the developer 2 in a developing tank containing the developer 2, and a stirring roller 8 that stirs the carrier and toner of the developer 2. :Developer 2
It has a rotating developing roller 9 that magnetically attracts and conveys the image to the developing area of the opposing photoreceptor 1o.

Further, a detection element 4 is provided at a fixed position in the developer tank to detect the surface level 3 when the mixing ratio of the developer 2 is normal. , the toner 7 is supplied from the toner supply device 5 described above. As a result of this replenishment, the developer 2 is agitated and its volume increases, and when the detection element 4 detects a certain surface level 3, the toner replenishment is stopped at 04.

The developing device 1 as described above is detachably installed in the main body of the copying machine. That is, the carrier of the developer 2 has lines of force, and it is necessary to replace the entire developer 2 including the backward-tilting carrier for a considerable period of time. Therefore, in order to facilitate replacement of the developer 2, it is provided so as to be detachable from the main body of the copying machine. It is clear that the present invention can be carried out even if the developing device 2Jt/'i is not provided in a detachable manner but is provided in a manner that it can be pulled out to a certain extent along a guide rail etc. so that the developer can be easily replaced. .

According to the present invention, a detection device for detecting attachment and detachment of the developing device 1 is provided. For example, if the developing device 1 is installed in a normal position, the switch state of this detection device is ON,
It can be easily constructed by using a switch means or the like that turns off when it is pulled out and not in the normal position. This detection device is the image device 1.
When the withdrawal of the toner is detected, the supply motor of the toner supply device 5 shown in FIG.

The above control example is shown in FIG.
12 is a flip-flop whose output is switched from "L" to "'H" based on the attachment/detachment of the developing device 1, and 12 is a flip-flop whose output is switched for a certain period of time only when the flip-flop 11 rises from "°L" to "H". This is a timer circuit that sets the signal to "L". The output of the timer circuit 12 is normally It H
#, maintains that state even if the input side is "II", operates when it rises from II Ln to "H", and outputs a "L" signal for a certain period of time, then becomes °H".
to be reversed. The output of this timer circuit 12 is supplied to one input terminal of a three-way AND gate 13.

Backup power is supplied to the flip-flop 11 in order to memorize the attachment/detachment status of the developing device 10 when the power is 01"F. The set input terminal of the flip-flop 70 knob 11 is connected to the main The motor drive borrow (ON or OF By inputting the signal, the flip-flop is set, and its set output becomes "II".The above-mentioned main motor drive signal is also supplied to one input terminal of the three-person customer gate 13. ing.

On the other hand, the glue set input terminal of the flip-flop 11 has
The input signal from the developing device 10 attachment/detachment detection device is input. In other words, the flip-flop 11 is the developing device 1
It is reset when the developing device is attached or detached, especially when the developing device is pulled out from its home position, and its state is memorized. The output of the 7-linopfronog 11 at this time becomes It L II.

In this case, the detection device also supplies backup power to detect whether the developing device 1 is attached or detached.

Furthermore, a detection signal from a detection element 4 for detecting the level of the developer 2 is input to another input terminal of the AND gate 13. The output signal of this AND gate 13 is sent to the control device 14, and the motor 15 of the toner supply device 5 is
is under control.

The main motor is fully driven when the copying machine starts operating, and rotates the stirring roller 8 and the like of the developing device 1.

The operation of the system configured as described above will be explained below with reference to the time chart shown in FIG.

It is now assumed that the developing device 1 contains an appropriate amount of developer 2 at an appropriate moisture level. Therefore, normally, the toner concentration detection element 4 should output a "'L" signal indicating an appropriate density (appropriate high or volume).

Here, in order to replace the developer 2, the door of the copying machine is opened, and the developing device 1 is taken out and replaced and then installed. As a result, if the detection device detects the drawer, the flip-flop 1
1 is reset. In this case, if the developing device 1 is tilted during handling, the developer 2 in the developing device 1 will be biased toward one end. At this time, the amount of developer 2 at the location where the toner concentration detection element 4 is attached is reduced compared to before the tilting, and even after maintenance or repair is completed and the developing device is installed in the copying machine, the amount of developer 2 remains at the predetermined height. It may not recover until then. As described above, when the developing device is reinstalled, the power is turned on, and the main motor rotates after a predetermined operation, the reset flip-flop 11 is set. Therefore, the output of the flip-flop 11 is "L"
The timer circuit 12 operates and the output becomes "L" for a certain period of time T. At this stage, even if the output of the toner concentration detection element 4 is °H,
The output of the ant gate 6 is the exact size of II, II. Therefore, the control device 14 controls the toner supply motor 15 to 1.
Without being driven, the toner supply device 5 will never run out of supply of toner.

Then, the output of the timer circuit 12 becomes "L" after one hour.
Before changing to II and HII and supplying toner, the developer 2 is agitated by an agitation roller 8, etc. normally installed in the developing device, correcting the unevenness, and determining which part of the developer surface is on the surface. The height is also leveled to be approximately constant.

That is, the time T of the timer circuit 12 is set so as to satisfy the condition that the developer 2 is normalized by stirring by the stirring roller 8 described above. So timer circuit 1
2 times up, its output becomes °゛H'', but at this time, the surface level 3 of the developer 2 in the developing device 1 has already returned to its original state. The output of the element 4 is inverted to II L II. Therefore, toner is rarely supplied from the toner supply device 5.

Thereafter, the printer 11 is not reset unless the developing device 1 is attached or detached, and the set state is maintained. Unfortunately, the output of the timer circuit 12 is also °゛H.
'', and if the toner concentration detection element 4 detects a certain level 3 or lower, toner supply is executed by driving the main motor.

In the example shown in FIG. 2, the timer circuit 12 is activated only when the developing device is attached or removed, but in short, the timer circuit 12 is activated only when the surface level of the developer in the developing device changes significantly. All you have to do is get it. For example, in order to facilitate jam removal in the copying machine main body, the copying machine main body is provided along the paper conveyance path so that the copying machine main body can be opened and closed up and down. Unfortunately, the developing device etc. installed in the upper body tilts when opened.
The same l(fffi) occurs when the developing device is attached or removed. Therefore, when the copying machine main body is opened, the developing device 1 is not in the normal position, and by detecting this, the 7-linopfronop 11 is reset and the timer circuit 12 is activated. However, the present invention is not limited to this, but it is sufficient to provide a means for detecting the inclination q of the developing device 1 and operate the timer circuit in connection therewith.

<Effects of the Invention> According to the developer concentration control device of the present invention, if the detection means for detecting the predetermined position of the developing device detects that the developing device is not in the predetermined position, after the copying machine is operated, the Since the toner supply is regulated regardless of the detection signal of the detection means,
By not supplying toner when the developer concentration is normal, it is possible to prevent overtoning and the like. In other words, development can always be performed with a normal developer concentration.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a developing device equipped with a developer concentration control device according to the present invention, and FIG.
A block diagram showing an example of the supply control circuit, and FIG. 3 is a time chart of FIG. 2. 1: Developing device 3 Surface level 4: Detection element 5 Toner supply device 7 Toner 8: Stirring roller 9 Developing roller 1o Photoreceptor 11 Linopfronop 12. Kuimer circuit 14. Control device J5 supply morph

Claims (1)

[Claims] 1. In a developer concentration control device that replenishes toner and controls the developer concentration by detecting the surface level of the developer in the developing device using a detection device, a position detecting device that detects the steady position of the developing device; and a control means for regulating toner replenishment for a certain period of time based on the detection signal of the position detection means during operation of the development device, regardless of the detection signal of the detection means.