JPH0199073A - developing device - Google Patents

Abstract

PURPOSE:To maintain the toner concentration in a developer so as to be constant and to execute the development by a stable concentration by detecting a variation of the toner concentration before development and after development, respectively and replenishing a toner based on a signal from each detecting means. CONSTITUTION:As for a developer on a sleeve for development, its toner concentration drops gradually due to toner consumption caused by a developing operation. This toner concentration after development is detected by a sensor S2, and a detecting signal is sent to a comparing and detecting circuit 16. In the comparing and detecting circuit 16, with respect to an output of the sensor S2, the lower limit level is set in advance, and based thereon, a driving motor 17 of a toner replenishing roller is operated. On the other hand, the toner concentration of the developer before development is detected by a sensor S1, and its output signal is sent to the comparing and detecting circuit 16. In this case, since the upper limit level to an output of the sensor S1 is set in advance, in case of exceeding the upper limit level, based thereon, a stop signal is outputted to the driving motor 17 and the toner replenishment is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a developing device applied to an electrophotographic copying machine, and particularly to a developing device applied to an electrophotographic copying machine.
The present invention relates to a developing device that uses component developers and is equipped with a toner concentration detection means.

(Prior Art) Conventionally, when detecting toner concentration in this type of device, an optical detection method has generally been adopted.

This method detects toner concentration (the ratio of toner to developer) by utilizing the change in reflectance of the developer due to changes in the toner content in the developer. A toner concentration detection means lOO having a light emitting element that illuminates the developer and a light receiving element that receives light reflected by the developer is provided. In this case, the toner concentration detection means 100 is often disposed near the developing sleeve 101 or in the stirring passage 102 for stirring the developer, as shown in FIG.

(Problems to be Solved by the Invention) However, in such a conventional example, when the toner concentration detection means 100 is provided near the developing sleeve 101, when the toner concentration decreases due to development, the toner concentration detection The toner is detected by the means 100, and toner is replenished from the toner cartridge 103 in accordance with the decrease in toner concentration, but even after the toner supply reaches a sufficient concentration, the developer continues to flow through the screws 104, 105 and 106.
Since the toner is replenished until it reaches the toner concentration detecting means 100 after being stirred by the toner, there is a tendency to oversupply the toner, and the toner concentration sometimes increases.

On the other hand, a toner concentration detection means 100 is installed near the stirring passage 102.
is provided, toner is not replenished until the developer whose toner concentration has decreased due to development reaches the agitation passage 102 and is detected by the toner concentration detection means 100, and development is performed with the developer whose toner concentration is low. As a result, the copy density decreases.

That is, in the above-mentioned conventional technology, only one toner concentration detection means for detecting the concentration of toner in the developer is provided, so there is a problem that the density of the developed image becomes unstable. It had

Therefore, the present invention has been made to solve the above-mentioned problems of the prior art, and its purpose is to quickly replenish toner according to changes in toner concentration to maintain a constant toner concentration in the developer. It is an object of the present invention to provide a developing device capable of performing development at a stable density by maintaining the density.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a developing device that performs development by agitating and conveying a developer having toner and a carrier. The apparatus includes a detection means for detecting toner concentration and a detection means for detecting the toner concentration after development of the developer, and is configured to replenish the toner based on signals obtained by each of the detection means.

(Function) In the present invention having the above configuration, by detecting the change in toner concentration before development and the change in toner concentration after development with each detection means, the actual change in toner concentration can be quickly detected. By detecting and replenishing toner based on the signals obtained by each detection means, the amount of toner reduced by development can be quickly and accurately replenished.

(Example) The present invention will be explained below based on illustrated embodiments.

1 to 3 show a first embodiment of a developing device according to the present invention. In the figure, ■ is the developing device main body,
2 is a removable toner cartridge filled with toner, and 3 is a toner replenishing roller for replenishing the toner in the toner cartridge 2, which is driven in the direction of the arrow by a drive motor 17, which will be described later.

Reference numeral 4 denotes a sleeve for performing a developing operation, which includes a magnet (not shown) inside and rotates in the direction of the arrow during development. 5 is a doctor blade provided near the sleeve 4, and 6, 7, and 8 are screws for stirring and transporting the developer, each of which rotates in the direction of the arrow. Reference numeral 9 denotes a partition wall provided between the screws 7° and 8.

Sl, 57 is a sensor having the same configuration as a toner concentration detection means for detecting the toner concentration in the developer;
One sensor Sl is embedded in the developer regulating member lO located above the sleeve 4, and the other sensor S2
is the side of the partition wall 9 between the screws 7.8 and the opening 11
It is provided near B.

FIG. 3 shows the control system of this embodiment.

In the figure, sensors S1 and Sl have the same configuration. For example, to explain the configuration of sensor S1,
This sensor S1 includes a light emitting source 12A and two light receiving elements 1.
Consists of 3A and 14A. Here, the light emitting source 12A irradiates light onto both the developer and the monitoring light receiving element 13A, and the light receiving element 14A receives reflected light from the developer. Further, 15A is a normalization circuit that normalizes the output signal of the light receiving element 14A with the output signal of the light receiving element 13A in order to cancel the influence of the change in the light amount of the light receiving element 14A, and is connected to the light receiving elements 13A and 14A.

On the other hand, the sensor S2 also has a light emitting source 12B similar to that of the sensor S1,
It consists of a light receiving element 13B for monitoring and a light receiving element 14B for detecting reflected light, and each of the light receiving elements 13B and 14B is connected to a normalization circuit 15B.

A comparison calculation circuit 16 is connected to the normalization circuits 15A and 15B, and determines an appropriate amount of toner replenishment based on the difference in toner concentration detected by the sensor 511S2.

Reference numeral 17 denotes a drive motor such as a DC pulse motor that drives the toner supply roller 3 according to the output of the comparison calculation circuit 16.

In this embodiment having the above configuration, the developing operation and toner replenishment are performed as follows.

First, the developer near the sleeve 4 adheres to the sleeve 4 due to the magnetic force of the magnet inside the sleeve 4 and the electric reflection force due to frictional charging, and as shown in FIGS. 1 and 2, the developer moves upward as the sleeve 4 rotates. transported to. A portion of the transported developer is scraped off by the screw 6,
The remaining developer is transferred to the sleeve 4 by the developer regulating member 10.
The amount applied is regulated. At this time, the sensor S1 embedded in the developer regulating member 10 detects the toner concentration of the developer contributing to development. That is, the developer is irradiated with light emitted from the light emitting source 12A of the sensor Sl, and reflected light corresponding to the toner concentration of the developer is detected by the light receiving element 14A. Here, in order to eliminate the influence of light intensity fluctuations of the light emitting source 12A, the light intensity of the light emitting source 12A is directly transmitted to the light receiving element 13.
A, and the output obtained by the light receiving element 14A is processed by the normalization circuit 15A using the monitored output as a reference, and is used as the output signal of the sensor S1.

On the other hand, the developer regulated by the developer regulating member 10 is further made into a thin layer by the doctor blade 5, and is used for development near the position closest to the photosensitive drum (not shown) by the conveyance force of the sleeve 4. Therefore sensor S1
In this case, the toner concentration of the developer immediately before development is detected. The developer used for development has a lower toner concentration because only the toner flies, and is collected into the developing device by the rotation of the sleeve 4, transported to the back of the developing device by the screw 7, and further transferred to the screw 8 through the opening 11B. passed on. When passing through this opening llB, the toner concentration of the developer is detected by the sensor S2 in the same manner as the sensor S1. Then, based on the outputs of the sensors sl and s2, the drive motor 17 of the toner replenishment roller 3 is driven to replenish the developer with an appropriate amount of toner, and the screw 8 sufficiently stirs and mixes the toner, and the developer is transferred to the sleeve 4 again. supply

Here, the relationship between the output signal of the sensor S I * 52 and toner replenishment will be explained. The toner concentration of the developer on the developing sleeve 4 gradually decreases due to toner consumption during the developing operation. This developer is applied to screw 6.
7, the toner concentration is detected by a sensor S2 disposed in the partition wall opening 11B, and its output signal is sent to the comparison detection circuit 16. In the comparison detection circuit 16, a lower limit level is set for the output of the sensor S2, and when the output becomes Low with respect to this lower limit level, a signal is sent to the drive motor 17, and the drive motor 17 of the toner replenishing roller 3 is activated. Activate. In this case, the developer replenished with toner is mixed and stirred according to the output signal of the sensor S2, and is again supplied to the sleeve 4, but the toner concentration of the supplied developer before development is detected by the sensor S1. , its output signal is sent to the comparison detection circuit 16. In the comparison detection circuit 16, an upper limit level is set for the output of the sensor S1, and the old g
When the state h is reached, a stop signal is sent to the drive motor 17 to stop toner replenishment.

By replenishing the toner based on the toner concentration detected by the sensors S1 and S2 in this way, it is possible to replenish the amount of toner consumed by development and always stabilize the toner concentration immediately before development. Since the occurrence of defective images such as background fog and low density can be prevented, development can be performed with stable image density.

FIG. 4 shows a control system for replenishing, stirring, and mixing toner in a second embodiment of the developing device according to the present invention.
The same parts as in the first embodiment will be described with the same reference numerals. The sensor detection section A consists of the sensor S1 shown in FIG. 2 and a normalization circuit 15A for normalizing its output, and similarly the sensor detection section B consists of the sensor S2 and a normalization circuit 15B.

The sensor detection units A and B are connected to a motor drive circuit 21 via a comparison calculation circuit 16. This motor drive circuit 21 is connected to a drive motor 22 and a drive motor 23 such as a DC pulse motor, and the drive motor 22 rotates each screw 6.7, and the drive motor 23 rotates the screw 8 and the toner supply roller 3. It asks you to rotate it.

In the above configuration, the developer conveyed by the screw 7 adheres to the surface of the sleeve 4 due to the magnetic force of the magnet roller (not shown) in the sleeve 4 and the mirror force caused by the charging force of the developer itself, and further It is conveyed as the sleeve 4 rotates in the direction of the arrow, and by regulation by the developer regulating member 10 and the doctor blade 5, part of it is coated on the sleeve 4 as it is and contributes to development, and the rest is scraped off by the screw 6. It is again lifted up by the screw 7 and sleeve 4.

The developer that has contributed to the development has a reduced toner concentration, and is recovered into the developing device as the sleeve 4 rotates. Thereafter, it is passed to the screw 7, passes through the opening 11B in which the sensor S2 is arranged, and is sent to the screw 8. At this point, the sensor S2 detects the concentration of the developer whose toner concentration has decreased after development. Therefore, the output at sensor detection section B decreases. On the other hand, since the developer whose concentration has been adjusted is supplied to the sensor S1, the output of the sensor detection section A has not decreased. In the comparison calculation circuit 16, when receiving the output signals from the sensor detection units A and B, a lower limit level for the sensor detection units is set, and when the level falls below this level, the drive motor 23 is driven to replenish toner. Control. In this case, when the output difference between sensor detection section A and sensor detection section B exceeds a certain level, that is, when the amount of toner consumption is large, a signal is output that speeds up the rotation of motor drive circuit 21 and drive motor 23. By doing so, toner replenishment and density-adjusted developer supply are accelerated.

Next, the developer whose density has been adjusted is supplied to the sleeve 4, and when detected by the sensor S1, toner supply and rotation of the screw 8 are returned to their original state. In addition, when toner is being oversupplied, that is, when the detection signal from the sensor detection section A exceeds the upper limit level for the sensor detection section A in the comparison calculation circuit 16, the drive motor 22 is controlled to speed up the rotation. The agitation force of the entire developer is increased to mix the toner throughout the developer and give sufficient tripo to the toner. At the same time, the toner supply roller 3 and the drive motor 2
3 to stop toner replenishment, and when the toner is consumed by development and the detection signal at the sensor detection section A returns below the upper limit level, the rotation of the drive motor 22 is returned to normal.

As described above, by setting the upper and lower limit levels for sensor detection parts A and B, their outputs, and the limit level of the output difference between the two, and changing toner replenishment, stirring, and conveyance speed according to those outputs. , it becomes possible to always supply a developer with a constant toner concentration to the developing sleeve 4, and more stable image density can be obtained. The other configurations and functions are the same as those of the first embodiment, so their explanation will be omitted.

FIG. 5 shows a third embodiment of the developing device according to the present invention, and the same parts as in the second embodiment are denoted by the same reference numerals. In this embodiment, the partition wall 9 The configuration is the same as that of the second embodiment except that sensors s, , s2 are disposed in the openings 11AjlB on both sides.

In FIG. 5, the developer flows as indicated by the arrows in the figure. That is, the toner concentration is adjusted, stirred and mixed by the screw 8, the concentration at this time is detected by the sensor S+ located at the mouth 11A of the partition wall, and the toner is supplied to the sleeve 4 by the screw 7. In this case, part of the developer is used for development, and the rest is scraped off by the screw 6 and supplied to the sleeve 4 again. Further, the developer used for development is scraped off by the screw 7 and passes through the opening 11B on the side of the partition wall 9.

At this time, the toner concentration is detected by the sensor S2, and the necessary toner is further supplied to the toner supply port 2 of the toner cartridge 2.
4, and the developer is stirred and mixed again by the screw 8.

In a normal copying process, the developer passing through the sensor S1 is replenished with toner, so the output from the sensor S1 is stable. However, since the sensor S2 detects the developer used for development, the output from the sensor S2 decreases. Here, the comparison calculation circuit 16 shown in FIG. 4 detects the difference between the outputs of the sensor S1 and the sensor S2 and the absolute value of each output, thereby controlling the drive motor 23 for toner replenishment.
is appropriately driven to supply toner, and the screw 8 stirs and mixes the developer. Thereafter, the developer supplied with toner passes through the sensor S1, and the density at that time is detected. When the density reaches a predetermined level, the comparison detection circuit 16 stops the drive motor 23 to stop toner supply.

On the other hand, when the amount of toner consumption is large, the output of the sensor S2 decreases rapidly. For this reason, if the output difference between the sensor detection parts A and B increases and the difference exceeds the permissible range within the comparison detection circuit 16, toner replenishment and density adjustment are performed by increasing the rotation speed of the drive motor 23. speed up the supply of developer.

Here, the sensor S1 monitors how much the toner concentration increases by speeding up the rotation of the drive motor 23, and when the reference concentration is reached, the stirring speed of the screw 8 is returned to the original speed. Furthermore, if the toner-replenished developer is not sufficiently supplied by such fast feeding of the drive motor 23,
The rotational speed of the drive motor 22 is increased to speed up the circulation of the entire developer. As described above, in this embodiment, since the toner concentration after development and the toner concentration of the agent supplied for development are detected before and after the partition wall 9, the toner replenishment timing becomes accurate and the toner concentration can be accurately managed.

(Effects of the Invention) As described above, the present invention includes a detection means for detecting the toner concentration of the developer before development, and a detection means for detecting the toner concentration of the developer after development. By replenishing toner based on the signal obtained by the detection means, it is possible to quickly and accurately replenish toner that has decreased due to development and maintain a constant toner concentration in the developer, which is different from conventional devices. This has the effect of significantly reducing the instability of image density such as density reduction or background fog caused by excess or deficiency of toner replenishment, which occurred in the previous embodiment.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing a first embodiment of a developing device according to the present invention, FIG. 2 is a sectional view taken along line I-I' in FIG. 1, and FIG. 3 is a sensor and toner replenishment system of the same embodiment. A block diagram showing
FIG. 4 is a block diagram showing a sensor and toner replenishment system in a second embodiment of the developing device according to the present invention, FIG. 5 is a cross-sectional view showing a third embodiment of the developing device according to the present invention, and FIG. FIG. 2 is a vertical cross-sectional view showing a conventional developing device. Explanation of symbols 3... Toner supply roller 4... Sleeve 6.7.
8... Screws 12A, 12B... Light emitting sources 13A, 13B, 14A, 14B... Light receiving element 15A
, 15B... Normalization circuit 16... Comparison calculation circuit 17... Drive motor S
l, 32...Sensor (detection means)

Claims (2)

[Claims] (1) In a developing device that performs development by agitating and conveying a developer including toner and carrier, a detection means for detecting the toner concentration of the developer before development, and a detection means for detecting the toner concentration of the developer after development. A developing device comprising: a detection means, and replenishing the toner based on signals obtained by each of the detection means. (2) The developing device according to claim 1, wherein the developer is stirred and transported based on the signals obtained by each of the detection means.