JPS6035663B2 - Developer toner concentration detection method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for detecting the toner concentration of a two-component developer consisting of toner and carrier for use in electrophotographic copying devices, electrostatic recording devices, etc.

Conventionally, the method for detecting toner concentration in two-component developers is to irradiate light onto a developer using a carrier whose surface is different from that of the toner, and photoelectrically detect the mixing ratio of toner and carrier using the reflected light. A well-known method is to magnetically detect the mixing ratio of toner and carrier by detecting changes in the magnetic permeability of the developer using a magnetic carrier.Other methods include measuring the density or specific gravity of the developer. , a method of measuring the conductivity of a developer has also been proposed.

However, since the photoelectric detection method requires the carrier to be a different color from the toner, the type of carrier used is limited, such as a resin-coated carrier, and the developing method is also limited.

Furthermore, since the change in the tawny color with respect to the change in toner concentration is not large, the detection accuracy is poor. On the other hand, although magnetic detection methods are the most reliable among those put into practical use, their detection accuracy is not high and their sensitivity is not good.

Namely, special public service No. 46-828 Pi and Hakama Kai No. 51-195.
In the method shown in 4 beats, developed developer is passed through a non-magnetic cylinder around which a coil is wound, and changes in the mixture ratio of toner and carrier are detected by changes in the inductance of the coil. It looks like this. This is based on the fact that changes in the mixing ratio of toner and carrier cause an increase or decrease in the amount of carrier in the developer flowing inside the cylinder, which changes the magnetic permeability of the developer. . In other words, it utilizes the fact that a change in toner concentration causes a change in the bulk density of the developer. However, the toner concentration of commonly used developers is 1 to fine t%, but if the toner concentration changes by 1M%, the developer's concentration will be about 7%.
The change is approximately 8%. This is because the carrier has a specific gravity approximately 7 to 8 times that of the toner. Therefore, the inventors of the present invention conducted various experiments on toner concentration detection methods with high detection accuracy, and found that the fluidity of the developer changes significantly in response to changes in toner concentration.

The present invention is based on the principle that the fluidity of the developer has a very large correlation with the toner concentration.

First, the principle of the present invention will be explained.

FIG. 1 is a diagram for explaining the principle of the present invention, and reference numeral 1 denotes a hopper, which has a funnel shape with an apex angle of about 600 mm.

At the bottom of the hopper, an outlet 2 with a diameter of 2.5 mm and a length of 3 willows is formed. This device is usually installed in the hall (port 11).
) flow meter. In this hopper, 50 grams of a two-component developer 3 consisting of an iron powder carrier with a diameter of about 10 mm and a toner with a diameter of about 10 mm is stored. A coil 4 is arranged below the outlet 2 of the hopper so as to wind around the flow path of the developer 3 falling from the outlet 2. The time at which all the developer 3 in the hopper 1 finishes flowing out is detected using the change in inductance of the coil 4. The fluidity of the developer in the present invention is defined as the amount of developer flowing per unit time. Now, when the toner concentration of the developer was varied from 0 to 3% and the fluidity was measured, the results shown in FIG. 2 were obtained. The axis of FIG. 2 represents the toner concentration, and the vertical axis represents the fluidity of the developer. According to this,
When the toner concentration is between 1 and 3 wt%, the toner concentration is lw
It can be seen that if the fluidity changes by t%, the fluidity changes by about 20%.

This value is about 2 to 4 times larger than the change in the volume of the developer described above. Thus, it can be seen that the amount of magnetic carriers flowing out from the hopper 1 per unit time changes as the toner concentration changes.

This is considered to be due to the viscosity of the developer 3 when it flows out from the outlet 2 of the hopper 1. That is, when the toner concentration is low, the developer flows easily from the outlet, and the amount of magnetic carrier per unit time increases. As described above, an object of the present invention is to provide a toner concentration detection method and apparatus with high detection accuracy.

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 3, reference numeral 5 indicates a photosensitive drum, which is continuously rotated in the loss-of-loss direction.

An electrostatic latent image is formed on this surface by means such as charging and exposure. A magnetic brush developing device 6 is disposed at the lower left of the photosensitive drum 5, and develops the latent image on the photosensitive drum 5 with a magnetic brush. The magnetic brush developing device 6 includes a non-magnetic cylindrical sleeve 8 and a non-magnetic cylindrical sleeve 8 in a developing container 7.
The developing roller 10 includes a plurality of magnets 9, 92, 93 provided therein, and a magnetic brush is formed on the surface of the sleeve 8 rotated in the direction of the arrow by the magnets 9, 92, 93. A scraping plate 11 is provided close to or in contact with the surface of the sleeve 8, and a closing opening 12 is formed approximately in the center of the scraping plate 11. A hopper 13 connected to the opening is disposed below the scraping plate 11, and the hopper 13 has a funnel-shaped structure similar to that shown in FIG. The bottom of the hopper 13 has a diameter of 2
．． An outlet 014 with a length of 5 pigs and 3 ribs is provided, and a non-magnetic cylinder 15 is provided below this outlet 14. A coil 16 is wound around the cylinder 15, and the inductance L and capacitor C of the coil 16 constitute an LC oscillation circuit, and the coil 16 is connected to a frequency detector 17 that detects the oscillation frequency. . A comparing circuit 19 compares the outputs of the frequency detector 17 and the reference circuit 18.
A signal is given to the drive circuit 22 to control the rotation of the toner replenishing roller 21 provided at the lower part of the toner hopper 20 based on this output. On the other hand, hopper 1
As shown in FIGS. 3 and 4, a first shutter plate 23 is movably provided on the upper part of the hopper 13, and a second shutter plate 24 for blocking the outlet 14 of the hopper 13 is also movable. It is set in.

Next, to explain the operation of this device, normally the first shutter plate 23 covers the upper part of the hopper 13 as shown in FIG. This is to prevent it from flowing into the country.

At this time, the second shutter plate 24 is retracted from the outlet 14. Note that this state is the state at the time of non-detection, so the first
It does not matter if the shutter plate 23 is open or the detection circuit is inactive. The closing operation of the first shutter plate 23 is performed when the cam 25 is rotated half a rotation around the shaft 26, as shown in FIG. Shutter plate 23
is moved to the right and closes the closure 12. Now, when the toner concentration detection operation starts, the first shutter plate 23
While being moved to the dotted line position in the figure, the second shutter plate 24 is changed so as to close the outlet 14.

After a predetermined period of time, the developer is stored in the hopper 13 and begins to overflow. Next, the first shutter plate 23 and the second shutter plate 24 are returned to their initial positions, and at the same time, the developer in the hopper 13 begins to flow out from the outlet 14 and falls down the cylinder 15 at a predetermined flow rate. When the developer is not flowing down, the output value of the coil 16 is the lowest, but when the developer starts flowing into the cylinder 15, the output increases rapidly. The same 50 grams of developer is stored in the hopper so as to match the toner concentration-flow rate curve determined in advance as explained in FIGS. 1 and 2. However, after a predetermined period of time has elapsed, the developer runs out and the output drops sharply. This coil 1
The frequency detector 17 detects the time from the first sudden change in the oscillation frequency from 6 to the last sudden change. Detects the so-called flow rate. The reference circuit 18 is stored or programmed with a flow rate corresponding to a change in toner concentration that has been experimentally determined in advance, and the flow rate detected by the frequency detector 17 is determined by comparing both outputs with a comparison circuit 19. The current toner concentration is calculated from the current toner concentration and the amount of toner is replenished until a predetermined toner concentration is reached.The rotation of the toner replenishment roller 21 is controlled by the drive circuit 22. When the detection operation is completed, the next detection operation may be started immediately, but it is also possible to perform the detection after a predetermined period of time has elapsed. At this time, the first shutter plate 23 and the second shutter plate 24 repeat the above-described operation. Furthermore, the present invention measures the characteristic of developer fluidity, and this fluidity is largely determined by the difference in particle size between toner and carrier. Even if the difference in specific gravity is not large, sufficient measurement is possible even when the difference in specific gravity between the carrier and the toner is small, such as a small magnetic carrier such as ferride. Further, it is also possible to implement the present invention in the same manner even if the two-component developer uses a magnetic toner instead of a non-magnetic toner. As for the developing method, although the magnetic brush developing method has been described, it can be used for all developing methods that use a two-component developer such as cascade development. Now, when non-magnetic resin, glass beads, etc. are used as a carrier, the above-mentioned magnetic detection method cannot be used, but instead of that method, a photoelectric detection device consisting of a light emitting diode and a light receiving element is used. Hopper 13 in Figure 3
It is possible to detect the fluidity of the developer by providing it below the outlet 14 of the developer.

In addition, when measuring the fluidity of the developer with respect to a change in toner concentration in advance, 50 grams of developing agent was stored in the hopper, but the present invention is not limited to this, and various types may be used.

However, if the amount is too large, it will take too much time to measure, and if the amount is too small, accurate values cannot be obtained. Therefore, the amount should be selected appropriately depending on the type of developer at the time of design. Next, instead of storing a fixed amount of developer in a hopper, in the developing device shown in FIG. 3, the developer is always allowed to flow down continuously without providing the first and second shutter plates 23 and 24. By configuring the apparatus as described above and measuring the fluidity of the developer per unit time, the toner concentration of the developer can be measured very easily. Here, the outlet 1 of the hopper 13
It is important to make the diameter of the cylinder 15 larger than the diameter of the cylinder 4 so that the amount of the phenomenon agent is not restricted by the cylinder 15.

With this configuration, instead of measuring the high density of the developer, the amount of carrier flowing out from the outlet 14 changes depending on the viscosity of the developer, which changes depending on the developer concentration, so the magnetic flux per unit time is measured. By measuring the amount of carrier, the toner concentration of the developer can be determined.

In this case, instead of using a coil wound around a non-magnetic cylinder as the fluidity measuring means provided at the lower part of the hopper 13, it is also possible to use a Hall element or the like. As described above, according to the present invention, it is possible to know the toner concentration by detecting the fluidity of the two-component developer, and therefore it is possible to perform toner concentration detection with good sensitivity and high detection accuracy.

This method has the advantage that it can be widely used regardless of the developing method. Furthermore, as the number of copies increases from 5,000 copies to 10,000 copies, conventional methods that measure toner concentration using the bulk density of developer initially set the toner concentration at 1%. If the toner concentration increases to 2% or more, and on the other hand, the toner density is maintained at 1%, the high density of the developer will change greatly from the initial 3.6 days/day to 4 days/day. According to this method, even if used for a long period of time, if the toner concentration is kept constant, the flow rate will hardly change, so it is possible to perform extremely stable toner concentration detection, and therefore it is possible to always maintain an appropriate toner concentration. This is possible.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the principle of the present invention, FIG. 2 is a diagram showing a toner concentration-flow rate curve, FIG. 3 is a sectional view of a developing device showing an embodiment of the present invention, and FIG. 4 is a diagram for explaining the principle of the present invention. FIG. 4 is a partial plan view of the developing device of FIG. 3; 1, 13... hopper, 2, 14... outlet,
3... Developer, 4, 16... Coil, 15
...Nonmagnetic cylinder, 23...First shutter plate, 24
...Second shutter plate. A total of 2 eagle figures and 4 rare figures.

Claims (1)

[Scope of Claims] 1. An electronic copying apparatus that develops an electrostatic latent image using a two-component developer consisting of toner and carrier, including a container in which a portion of the developer is stored, and a container that freely falls from the container. A magnetic detection means for detecting the developer is provided in the middle of the developer flow path, and the flow rate of the developer falling from the container is detected by the detection means as a change in magnetic permeability. A method for detecting the toner concentration of a developer so as to know the toner concentration of the developer. 2. The toner concentration detection method according to claim 1, wherein the inner diameter of the magnetic detection means is larger than the diameter of the outlet of the container storing a portion of the developer. 3. In an electronic copying device that develops an electrostatic latent image using a two-component developer consisting of toner and carrier, there is provided a hopper for storing a portion of the developer, and a magnetic hopper having a diameter larger than the discharge port of the hopper. a means for detecting the fluidity of the developer as a change in magnetic permeability by the magnetic detecting means and comparing it with a predetermined reference value; and controlling toner replenishment based on the output of the comparing means. A developer toner concentration detection device characterized by: