JPS6019504B2 - Developer concentration adjustment method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for detecting the concentration of a developer used in electrostatic charge development, and a method of adjusting the concentration of the developer to an appropriate range using the device.

2. Description of the Related Art In electrophotographic systems, electrostatic printing systems, and the like, a developer consisting of a mixture of toner and carrier is used to develop an electrostatic image (static latent image). For example, when a magnetic development method is applied, a developer attached to a magnet detects an image in an electrostatic tank and develops the latent image with toner. As a result, toner is gradually consumed from the developer and the ratio of toner to carrier decreases, resulting in a decrease in the density of the developed image. Therefore, the density of the developed image is stabilized by replenishing an appropriate amount of toner, but if the amount of toner replenished exceeds the appropriate amount, not only will the density of the developed image become excessively high, but it will also cause fogging on the developed image. This may cause contamination around the developing device due to excessive toner scattering. Therefore, a method for accurately detecting changes in developer concentration and replenishing an appropriate amount of toner is required. Accordingly, one proposed method is to develop the surface of an insulating layer or conductive layer to which a reference potential or reference voltage is applied, and measure the transmission or reflection density of the precipitated toner layer.
There is a method for determining whether the toner concentration in the developer is excessive or insufficient.

This method has the advantage that the appropriate value of toner density can be determined fairly accurately because the developing operation is actually performed. However, it requires moving parts and has disadvantages in terms of device cost and reliability due to problems such as dirt on the detector. Another highly practical method is to measure the reflectance of the developer and find out the deviation of the toner density from the appropriate value. In this case, in order to prevent the detector from becoming dirty, it is preferable to measure the reflectance of the developer through a transparent plate, but toner may adhere to the transparent plate, which may greatly deviate the measured value. . Further, when used for a long time, toner components may adhere to the carrier 1 and the reflectance of the carrier 1 may change, but in this case, a large measurement error occurs. In addition, in order to prevent errors due to changes in the light intensity of the light source due to temperature, voltage, changes over time, etc., and changes in the sensitivity of the detection photocell, which are common to the above measurement methods, it is necessary to set a reference concentration and compare it with that. It must be measured under the condition. Therefore, the present invention avoids the drawbacks of conventional optical detection methods and provides a device for always accurately and sensitively detecting developer concentration, and a novel developer concentration adjustment method using the device. This is what we intend to provide. Specifically, it is a device for optically detecting the mixing ratio of one toner particle and one carrier particle through a transparent partition wall, and is equipped with means for repeatedly applying an electric field to the transparent partition wall. A developer concentration detection device characterized by: In addition, the first value obtained by leaking the reflected light from the developer through a transparent partition wall to which an electric field strong enough to attract the toner is applied, and the first value obtained by leaking the reflected light from the developer through a transparent partition wall to which an electric field strong enough to attract the toner, The toner concentration in the developer is detected from the difference from the second value obtained by applying light through a translucent partition wall to which an electric field of the strength obtained is applied, and the toner concentration is adjusted to an appropriate range. To provide a method for adjusting the concentration of a developer, characterized by supplying a necessary amount of toner to maintain the concentration. The present invention will be described below by way of specific examples with reference to the drawings.

FIG. 1 shows an outline of a developing device using a magnetic brush.

In this developing device, a developing sleeve 6 rotates around a fixed magnet portion 7 in the direction of the arrow.

A magnetic brush 8 is formed on the surface of the sleeve 6 by the magnetized developer 3, and the tip of the brush 8 is scraped off by a scraper 5 to make the length of the brush uniform. The static dragon latent image on the photoreceptor 1 is developed by this magnetic brush 8 having a uniform length. Incidentally, the developer 3 is constantly moved by a fly roller 4 so that the carrier and toner are sufficiently mixed. 9 in the diagram
indicates a developer container. Next, an embodiment in which the detection device of the present invention is incorporated into the device shown in FIG. 1 will be described. FIG. 2 is a diagram schematically showing a part of the developing device shown in FIG. 1 in which a detection device according to the present invention is installed.

The detection device 2 is mounted adjacent to a sleeve rotating magnetic brush developing device 21 for developing the electrostatic latent image.

A developer 23 made of a mixture of carrier and toner passes through the transparent partition wall 22 made of a material such as glass, resin, metal, or metal compound while coming into contact with or in close proximity to it. Light from a suitable light source 24 is reflected by the developer and reaches a photodetector 25 . Here, the amount of reflected light is measured. Note that it is advisable to take measures to cut the specularly reflected light from the partition wall 22 surface. A conductive layer is formed on the transparent partition 22 using tin oxide, indium oxide, iodized steel, conductive resin, etc., and the toner in the developer is attracted to the surface of the 22 by the voltage application means 26. Process it in such a way that it is possible to create a situation where it is rejected or repulsed. If the conductive layer has a strong film such as tin oxide, it may be provided on the side that comes into contact with the developer, but if a material that is likely to be abraded due to sliding contact with the developer is used, it may be provided on the side that comes into contact with the developer. It is best to place it on the opposite side.
However, in this case, it is necessary to use a material such as glass that has a conductivity that does not cause charge-up as the substrate. In the present invention, the reflected light from the developer is measured under two conditions: one is applying an electric field to attract the toner to the surface of the transparent partition wall 22, and the other is applying an electric field to repel the toner from the surface of the transparent partition wall 22. sidelight.

3A is an enlarged view of a state in which an electric field that repels toner is applied to the transparent partition wall 32, and FIG. 3B is an enlarged view of a state in which an electric field that attracts toner is applied to the transparent partition wall 32. This is a mock-up. 31 indicates toner, and 33 indicates carrier.

When the toner concentration in the developer is at a proper value or higher, the carrier 33 is almost entirely covered with the toner 31. In this condition, the light reflected from the developer is the toner.
The reflected light from is dominant. Therefore, when the toner 31 is attracted to the transparent partition wall 32 as shown in FIG. 3B, the measured value of the reflected light from the developer is larger than in the case shown in FIG. 3A. . In the state shown in FIG. 3A, only a small amount of light is reflected from the toner close to the translucent partition wall 32, and most of the light enters the carrier and hardly affects the spotlight value. Even if it were to be reflected back repeatedly, the amount would be negligible. On the other hand, when the toner concentration in the developer falls below the appropriate value and the ratio of covering the carrier 33 with the toner 31 decreases, the light reflected from the developer
Most of the light is reflected from the

Under the condition shown in FIG. 3A, the absolute value of the amount of reflected light from the carrier is larger than that from the toner, so it contributes greatly to the measured value, and under the condition shown in FIG. 3B, Due to the influence of the toner 31 attracted to the transparent partition wall 32, the reflected light from the carrier does not contribute much to the side light value. Therefore, in such a case, the dimming value under the condition illustrated in FIG. 3A will be greater than the sidelight value under the condition illustrated in FIG. 3B. Furthermore, when the toner concentration in the developer decreases, even when an electric field is applied to attract the toner to the transparent partition wall surface, there is almost no toner adhesion to the partition wall surface, and the leakage light value decreases. It is mostly affected by the reflected light from the carrier. FIG. 4 specifically shows the above development, in which the reflected light from the developer is collected under the conditions shown in FIG. 3A and under the conditions shown in FIG. 3B. This is a graph of the results obtained.

The axis shows the toner concentration in the developer in weight %, the vertical axis corresponds to the amount of light incident on the dS photoconductive cell, and the current value is shown on an arbitrary scale. The detection device of the present invention was attached to the rotating sleeve type magnetic brush developing device shown in FIG.

As the carrier, magnetic iron powder pulverized to 200 to 300 mesh was used, and as the toner, positive polarity particles of 5 to 10 mesh were used. The light-transmitting partition wall was placed at a distance of three ribs from the sleeve surface, with the surface of the blue plate glass on which the tin oxide film was formed facing the developer side. In Figure 4, the curve a shows the measured value when an electric field that repels toner is applied to the transparent partition wall, and the curve b shows the measurement value when an electric field that attracts toner is applied to the transparent partition wall. Each corresponds to the measured value at . For example, in the former case, the potential of the sleeve is zero (grounded) on the conductive layer of the partition wall.
When applying a voltage of 1100V, in the latter case,
A low voltage was applied.

When the toner concentration is about 5% or less, the relationship between a and b is almost the same, with the value of a being slightly larger than the value of b.

On the other hand, at 5% or more, the above relationship is reversed, and the value of b exceeds the value of a. In this example, the appropriate toner density for obtaining a good image was 5 to 7%.

Therefore, under the conditions shown in FIGS. 3A and 3B, measurements are performed sequentially to detect when the value of b becomes smaller than or equal to the value of a, and at that time, toner replenishment is performed. By doing this, the toner concentration can be maintained within an appropriate range. Of course, the value of b will be smaller than the value of a plus a certain value, or
It is also possible to replenish toner when the concentration is the same, and in this case, the toner concentration will be maintained at a higher concentration. As a method of applying an electric field to the transparent partition wall, various methods other than the above-mentioned example can be used.

For example, the present invention can be practiced by setting one of the repetitive electric fields to ground, or by setting both of the electric fields to the same polarity but at different voltages. Furthermore, even when the particle size of the carrier was changed, as shown in FIG. 4, a relationship was observed in which the values of a and b were reversed near the appropriate toner concentration.

As described in detail above, according to the present invention, there is no need to provide a special reference value as seen in conventional optical detection methods, and there is no need for moving parts for this purpose, reducing device cost and reliability. Significant improvements can be seen in terms of

Furthermore, there is no need to worry about contamination of the light source or photodetection element, and there is no influence from changes in their characteristics.

Furthermore, since an electric field that repels the toner is always applied to the light-transmitting partition wall serving as the detection window, cleaning can be accomplished at the same time as the detection operation, and accurate leakage light can be obtained. Although the above-mentioned embodiments have been described in detail by taking the magnetic brush development method as an example, the present invention is not limited to application to this method, but can also be applied to, for example, a cascade development method.

[Brief explanation of drawings]

Fig. 1 is a layout diagram showing an outline of a developing device in the magnetic brush development method, Fig. 2 is a device layout diagram showing an example of a magnetic brush development device incorporating the detection device of the present invention, and Figs. 3A and B are FIG. 4, which is an explanatory diagram showing a part of the embodiment of the present invention in an enlarged manner, is a graph showing the relationship between the developer concentration and the side light value of its reflected light in the present invention. 20...detection device, 21...rotary magnetic brush developing device, 22, 32...transparent partition wall, 2
3...Developer, 24...Light source, 25...
...photodetector, 26. ．． ．． . . . Repeated voltage application means, 31 . . . Toner, 33 . . . Carrier. Figure A Figure 2 Dancing figure Figure 4

Claims (1)

[Claims] 1. Light reflected from a developer containing toner and carrier is photometered through a translucent partition wall having a conductive detection window to which an electric field capable of attracting the toner is applied. Development is performed based on the difference between the first value and a second value obtained by photometrically measuring the reflected light through a transparent partition wall having a conductive detection window to which an electric field capable of repelling the toner is applied. A developer concentration adjustment method characterized by detecting the toner concentration in the developer and replenishing the necessary amount of toner to keep the toner concentration within an appropriate range. 2. The developer concentration adjustment according to claim 1, wherein toner is replenished when the first value becomes smaller than or equal to the second value. Method. 3. Claim 1, characterized in that toner is replenished when the first value is smaller than or equal to the second value plus a certain value. The developer concentration adjustment method described. 4. A translucent partition wall having a conductive detection window disposed in contact with or in close proximity to the developer containing toner and carrier, a light source for irradiating light to the developer via the translucent partition wall, and a light source from the developer. a photodetector for detecting the reflected light; a voltage applying means for repeatedly applying a voltage to the conductive detection window to attract the toner to the transparent partition wall and a voltage to repel the toner from the transparent partition wall;
A developer concentration adjustment device comprising means for replenishing toner by detecting a difference between a first value measured by applying a toner attraction voltage and a second value measured by applying a toner repulsion voltage. Device.