JPS6045276A - Developing device - Google Patents

Abstract

PURPOSE:To detect efficiently and exactly a toner concentration, to reduce a cost, and to make a device compact by controlling a toner concn. of a developer so that it becomes normal, basing on a recording picture information detecting signal. CONSTITUTION:A photodetector 20 is provided on a diameter of an image forming lens 14 in order to detect variable density information of an original 11. This position does not exert influence so much on an image forming performance and is capable of detecting variable density information of the whole original. A signal from the detector 20 is amplified by an amplifying circuit 22 and sent to a density control circuit 23. In the circuit 23, the variable density information is processed by a program determined in advance, and a control signal of a toner supply quantity and a timing is generated, and by this control signal, a clutch 26 is driven through a clutch driving circuit 25. The clutch 26 is provided on a power transfer system 28 between a driving source of a developing device 18 and a toner replenishing roller 27, brought to an ON-and-OFF control, and controls a motion of the roller 27.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a developing device having a toner density control function used in a recording device such as an electrophotographic copying machine.

[Technical background of the invention and its problems]

A typical developer used in a developing device is one consisting of a mixture of a magnetic carrier and a toner. The toner density of such developer decreases as printing is performed, which not only improves the quality of the copy image output by the copying device, but also improves the toner density by replenishing the toner consumed during copying as needed to keep the device in good condition. must be kept within an appropriate range.

Generally, toner is replenished to the developer by means of mechanically replenishing a certain amount of toner at regular intervals.

However, there are various kinds of documents to be recorded with different amounts of toner consumption, and it is impossible to always replenish the amount corresponding to the consumed amount by only replenishing a fixed amount of toner.

In order to solve the above problems, in recent years, the toner concentration of the developer has been detected by electrical, magnetic, optical, etc. means.
Various attempts have been made to maintain an appropriate density by automatically replenishing toner corresponding to the amount of consumed toner.

For example, as a method using optical means,
As described in No. 6095 (1), the floating toner of the developer during circulating transport is attached to a probe (pulley) provided for detection, and the change in light intensity caused by the toner attached to the probe is detected. There is a method of replacing the toner density with the density.As a method using magnetic means, there is a method of detecting the toner density based on a change in the magnetic permeability of the developer, as disclosed in Japanese Patent Publication No. 56-67872.

However, in the control based on these detection methods, the amount of toner adhering to the probe depends only on changes in toner concentration, and it is difficult to stably detect true concentration changes due to changes in toner charge amount and environmental humidity. Therefore, there were restrictions on the combination of toner and carrier, restrictions on usage conditions such as where to place the probe in the developer circulation path, and the device had a complicated mechanism, making it difficult to apply. Improvements were desired in terms of range, reliability, and cost.

Furthermore, when controlling the toner concentration in the developer, it is also required that the range be within a certain value. In particular, if the toner concentration becomes excessive due to some trouble, problems such as a sharp decrease in developer life and toner scattering to the surroundings occur. for that.

It was necessary to provide some kind of checkpoint in the toner concentration detection means or to adopt a complicated detection control method.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a toner concentration control device that can perform highly reliable toner concentration control with a simple and inexpensive configuration.

[Summary of the invention]

In order to achieve the above object, the present invention provides a method for replenishing toner consumed during each development to a two-component developer consisting of toner and carrier that is being circulated and conveyed, and the amount of replenishment is recorded in recorded image information. The system is controlled by a control signal based on the control signal.

The timing of toner replenishment can be continuous, intermittent, or a combination thereof. Also, the detection of recorded image information requires a new detection optical system in addition to the recording optical system that images the original on the recording surface. There are a method in which a photoelectric conversion element is placed directly in the optical path of the recording optical system, a method in which a semi-transparent mirror is placed in the optical path of the recording optical system and a part of the original signal is taken out and used, and a method in which a photoelectric conversion element is placed directly in the optical path of the recording optical system.

〔Effect of the invention〕

By adopting the configuration and control method of the present invention, there are no restrictions on usage such as applicable developers and environmental conditions that were problems in conventional systems, and in addition to the original functional configuration of the developing device, special It is possible to replenish toner to the developing agent in an extremely rational, efficient and accurate manner without adding any equipment.It is compact in shape and can reduce costs, and is excellent in terms of economy and performance. Toner density control can be performed.

Furthermore, by using the conventional basic detection means in combination, it is possible to realize extremely stable and reliable toner concentration control that can sufficiently cope with sudden changes in toner concentration due to abnormalities in the developing process.

[Embodiments of the invention]

An embodiment of the present invention will be described below.

FIG. 1 shows the main configuration of a general Shigeko photocopying machine.

The original 11 placed face down on the original table 10 is illuminated by a light source 1.
21 Reflection mirror 13. Condenser lens 141 Reflection mirror 15
6 original platens 10 are placed on the photosensitive drum 16 by
By rotating and hitting the photosensitive drum 16 in accordance with the movement of the photosensitive drum 16, the photosensitive drum 16 is uniformly charged by the charger 17.
An electrostatically magnified image corresponding to the shading of the original is formed thereon.

After this electrostatic wave is developed by the developing device 18, it is transferred onto plain paper by the transfer charger 19, and the copying is completed. Thereafter, the sensing drum 16 returns to its initial state through a cleaning and cleaning process (not shown).

FIG. 2 shows an example of a configuration in which the electrophotographic copying machine configured as described above is provided with a toner density control device according to the present invention.

In order to project the density information of the original Bf411, a photodetector 20 is placed immediately after the condensation lens 14.This position is as follows.
It is possible to detect the shading information of the entire document without significantly affecting the imaging performance.

The signal from this photodetector 20 is amplified by an amplifying circuit 22.
L, sent to the concentration control circuit 23; The density control circuit 23 processes the density information according to a predetermined program and generates control signals for toner replenishment amount and timing. This control signal passes the clutch 2 through the clutch drive circuit 25.
Drive 6. A clutch 26 is connected to a power transmission system 28 between a drive source (not shown) of the developing device 18 and a toner supply roller 27.
The toner replenishing roller 27 is provided in the toner replenishing roller 27, and is turned ON and OFF by a control signal to control the movement of the toner replenishing roller 27.

FIG. 3 shows an embodiment of a magnetic brush type developing device according to the present invention.

This developing device includes a case 30 whose front end opening edge is close to the circumferential surface of the photosensitive drum 16, and a magnet roller 3 which attracts the developer 31 inside the case 30 and forms a magnetic brush 32.
3, and a doctor blade 34 that is attached along the lower edge of the opening of the case 30 and adjusts the magnetic brush 32 to a constant thickness.

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It is composed of a rotating sleeve 35 of "6", ;11, a plurality of magnets 36 disposed inside this, and a fixed shaft 37 that holds these magnets 36.

Further, a stirring blade 39 is provided at the rear of the developer accommodating portion 38 formed at the inner bottom of the case 30, that is, at a portion not affected by the magnetic force of the magnet roller 33. Development area 4 on the rear side
A scraper 41 is provided to separate and guide the developer 31, which has passed through zero and is no longer affected by the magnet 36 located above, onto the stirring blade 39.

Case 3 is located at the rear of the upper surface of the developing device configured as described above.
A toner replenishing device 43 for replenishing toner 42 is connected to the inside of the toner. The toner replenishing device 43 has a toner replenishing port 44 as described above (consisting of a toner box 45 facing the agitating blade 39 and a toner replenishing roller 27 made of a porous member provided to close the toner replenishing port 44). This replenishment roller 27 is rotationally driven by a power transmission system 28 (not shown) through a clutch 26 to replenish toner.

Next, the operation of the above embodiment will be explained. Rotating sleeve 3
On the surface of the rotary sleeve 35 , the developer 31 is attracted to the area where magnetic lines of force are formed by the magnet 36 like a brush with flocked hairs, forming a so-called magnetic brush 32 .
As the magnetic brush 32 rotates, the magnetic brush 32 also moves in the same direction. After being made uniform in thickness to a predetermined thickness by the doctor blade 34, the toner slides into contact with the surface of the photosensitive drum 16, converting the electrostatic latent image previously formed on the surface of the photosensitive drum 16 into a toner image, thereby performing so-called development.

Next, the magnetic brush 32 that has passed through the development area 40 is peeled off from the surface of the rotating sleeve 35 by a scraper 41, and is dropped into the developer storage section 38, which is not affected by magnetic force, where the magnetic brush 32 is divided into magnetized, non-magnetized, metal, and non-magnetic. Regardless of the metal, it is made of the most suitable material for this developing device (it will be stirred by the stirring blade 39).

On the other hand, the toner in the developer 31 moves to the photosensitive drum 16 due to development, and the toner concentration of the developer 31 decreases, and
This will cause local density unevenness. The amount of toner consumed by this development is basically based on the density pattern of the document. The capacity of the developer 31 accommodated in the developer accommodating portion 38 of the developing device is limited, and the developer 31 is used within the case 30 in extremely short cycles.

Ideally, it is desirable that the reduced density and density unevenness be restored to their normal state before moving on to the next cycle.

For this reason, a signal detected from a document that requires appropriate toner replenishment is guided to a density control circuit 23 through an amplifier circuit 22. This density control circuit 23 estimates the amount of toner consumption based on a predetermined program based on the area and density of the pattern drawn on the original and the characteristics of the developing device.

Determines the optimal toner replenishment amount and replenishment timing and generates a control signal.

In this case, various combinations and modified programs can be considered depending on the method of processing the density information of the original and the replenishment timing, but the optimal program is selected based on the state of the electrophotographic process and development at that time.

That is, the amount of toner to be consumed is calculated from an electrical signal corresponding to the area of the pattern drawn on the document and a density value set by the user for the device.

Once the toner consumption amount is calculated, the toner supply amount and replenishment timing are determined. A case where the developer storage capacity is large will be explained. At this time, the response of toner concentration change to toner consumption is slow.

Therefore, toner replenishment may be performed intermittently. For example, the toner consumption amount calculated from the image information amount and the density setting value is compared with a threshold value, and a control signal is generated when the threshold value is exceeded.

On the other hand, when the developer storage capacity is small, the response of toner concentration change to toner consumption is quick.

Therefore, it is preferable that toner be replenished continuously.

Therefore, the pulse frequency is subjected to F-V conversion to obtain a voltage corresponding to the amount of image information. A control signal is constantly generated from this voltage value and concentration setting value. This control signal controls the rotation speed of the feed roller.

In this way, toner is continuously replenished.

The control signal generated in this way operates the clutch 26 of the power transmission system 28 of the toner replenishing device 43, and the replenishing roller 27 rotates, so that the toner 41 is dropped and replenished into the developer storage section 38.

By stirring and mixing the developer 31 and replenishment toner in the developer storage section 38, the decreased density and unevenness are restored to the normal state, and the circulation action gradually moves toward the magnet roller 33, and the magnetism is restored. This becomes the brush 32.

In this way, the toner concentration of the developer 31 is maintained within the specified concentration range by detecting the density information of the original and automatically linking toner replenishment based on the detection, thereby ensuring stable operation as a copying device and making the device easy to handle. become.

In addition to the original density detection method used in the above-mentioned actual example, Fig. 4
There are methods such as those shown in FIG. 2.

In FIG. 4, a mirror 46 behind the imaging lens 14 between the original 11 and the photosensitive drum 16 is used as a semi-transparent mirror to extract a part of the reflected light from the original, and a photodetector 47 is placed after that. It is something. A sufficient detection signal can be obtained by setting the transmittance of the semi-transparent mirror 46 to a level that does not affect the amount of light from the imaging optical system.

In FIG. 5, recorded image information detection means consisting of a lens 50 and a photodetector 51 is provided in addition to the imaging system of the original 11 and the photosensitive drum 16 in order to obtain density information of the original.

Further, in the above-described embodiment, the case where the present invention is employed in a magnetic brush developing device of a copying machine has been described, but it is also applicable to developing devices of other types.

In addition, it goes without saying that the present invention is not limited to the above-mentioned embodiments, and that various modifications can be made without departing from the gist of the present invention.

As explained above, the present invention detects image @ information (shade information) of a copy document in a dry type developing device that circulates and conveys a powder developer made of a mixed component of toner and carrier. This is a toner concentration side device in a developing device that determines the replenishment amount and timing based on the toner replenishment device and controls the toner replenishment device so that the toner concentration in the developer becomes appropriate.

Therefore, the limitations on usage, such as applicable developers and environmental conditions, which were problems in the conventional method, have been significantly improved, and there is no need to add special equipment in addition to the original functional configuration of the developing device (an extremely rational method). , it is possible to efficiently and accurately detect the toner concentration of the developer, and it is also compact in size, reducing costs, and it has the advantage of being able to perform toner production control that is excellent in terms of economy and performance. be.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing the main structure of a general electrophotographic copying machine, FIG. 2 is a schematic sectional view showing the structure of an embodiment of the present invention, and FIG. 41 and 5 are schematic sectional views showing other different embodiments of the original density detection system of the present invention. DESCRIPTION OF SYMBOLS 11... Document, 12... Illumination light source, 14... Imaging lens, 16... Photosensitive drum, 18... Photosensitive drum, 21... Photodetector, 23... Density control circuit , 26
... clutch, 27 ... replenishment roller, 31 ... developer, 39 ... stirring blade, 42 ... toner, 46
...Semi-transparent mirror. Figure 1 Figure 2 Figure 3

Claims (6)

[Claims] (1) A means for detecting recorded image information in a developing device that includes a means for storing toner and a means for supplying the toner to a carrier, and that circulates and conveys a two-component developer consisting of toner and carrier to develop an electrostatic image. and a means for controlling the amount of toner supplied so that the toner concentration in the developer becomes appropriate based on this detection signal. (2) The developing device according to claim 1, further comprising means for continuously controlling the amount of toner supplied based on the detection signal. (3) The developing device according to claim 1, further comprising means for storing a detection signal and supplying toner intermittently according to the value of the detection signal. (4) The developing device according to claim 1, wherein the means for detecting recorded image information comprises means for illuminating the original and a photoelectric conversion element that receives reflected light from the original. (5) means for optically imaging the original to obtain a recorded image;
It is characterized by having means for extracting an optical signal by disposing a semi-transparent mirror in the middle of the imaging optical path, means for converting it into an electric signal by a photoelectric conversion element, and means for using the electric signal as a detection signal. A developing device according to claim 1. (6) means for optically imaging the original to obtain a recorded image;
2. The developing device according to claim 1, further comprising means for using an electrical signal obtained by disposing a photoelectric conversion element in the middle of the imaging optical path as a detection signal.