JPH0544674B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a developer toner concentration detection device for detecting the toner concentration in a magnetic two-component developer used for developing an electrostatic latent image.

[Prior art]

Conventionally, as a means for detecting toner concentration in developer,
A magnetic two-component developer consisting of carrier and toner,
The electrostatic latent image is developed by being held and conveyed on a developing roller by magnetic force, and the toner concentration (mixing ratio) is determined by detecting the optical reflectance of the developer on the developing roller.
The device designed to measure the
It is publicly known as shown in No. 3830401 and the like.

In addition, in this toner concentration detection means, in order to stabilize the output of the photoelectric sensor, a light transmitting plate is arranged in front of the photoelectric sensor, and the developer is brought into contact with the light transmitting plate. Opening 57
−172464.

By the way, when measuring the optical reflectance of the developer, it is possible to prevent the sensor from becoming dirty if the measurement is performed through a light-transmitting plate and the developer is brought into contact with the light-transmitting plate as in the latter case. However, the drawback is that the photoelectric detection output of the sensor will be a small value.
Further, if the sensor is placed apart from the developer as in the former case, the photoelectric detection output will be increased, but this will have the disadvantage of complicating the structure for preventing the sensor from becoming dirty.

Next, such drawbacks of the conventional device will be explained based on a specific configuration example.

FIG. 1A is a schematic diagram of a toner concentration detection device constructed using a conventional known technique. In the figure, reference numeral 1 denotes a charge retention member, which is constructed by providing a charge retention layer 2 made of a photoconductor, an insulator, etc. on the surface of a conductive support 3. A developing roller 4 is composed of a magnet roller 5 and a non-magnetic sleeve 6, and the non-magnetic sleeve 6 is configured to rotate counterclockwise. 7 is a part of the developing machine housing, and 8 is a doctor blade. 9 is a sensor for detecting toner concentration, and the sensor body 11
A light transmitting plate 10 is provided in the opening. The developer is held and conveyed onto the developing roller 4 by magnetic force, and is developed by coming into contact with the electrostatic latent image formed on the charge retention member 1 in the development spike area X, and then is developed in the toner density detection spike area Y. The toner mixture ratio is detected by facing the toner concentration sensor 9. At this time, since the transparent plate 10 is in contact with the spikes of the developer,
Photoelectric sensing can be performed without toner contamination.

FIG. 1B is a diagram showing one configuration example of a toner concentration sensor used in the apparatus shown in FIG. A light source 14 and a light receiving element 15 are installed. Furthermore, as described above, the transparent plate 10 is provided in the opening portion to prevent toner from entering.

According to the inventor's experiments, as described above, the transparent plate 10 of the toner concentration sensor 9 is placed at a position in contact with the developer, and the surface of the transparent plate 10 is subjected to a conductive treatment, so that the charging of the toner is the same as that of the toner. If you apply a polar bias voltage that is 100V or more higher than the developing bias voltage, the toner concentration sensor will not be contaminated by toner and a stable detection output will be obtained.
It was confirmed that this value was extremely small.

On the other hand, when the toner concentration sensor is moved away from the developer surface, the detection output increases once and then decreases again.The output at the position where the maximum output is obtained is Compared to the detection output when it is in contact with
It was confirmed that the increase was ~10 times. However, if the toner concentration sensor is separated from the developer, the above-mentioned problem arises in that the transparent plate becomes dirty, making it impossible to obtain a stable detection output.

[Purpose of the invention]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a toner concentration detection device that can obtain a large photoelectric detection output, prevent the toner concentration sensor from being contaminated by toner, and provide a stable detection output. .

[Summary of the invention]

The present invention provides means for periodically changing the distance between the developer surface on the developing roller and the toner concentration sensor, and when the developer surface and the toner concentration sensor are close to each other, the transparent plate of the toner concentration sensor and the developer The photoelectric detection signal obtained when the developer surface and the toner concentration sensor are separated from each other is sampled and used as a toner concentration detection signal, and the toner adhering to the surface of the transparent plate is removed and detected. In addition to stabilizing the output, it is possible to obtain a large detection output by separating the developer and the toner concentration sensor.

[Embodiments of the invention]

Examples of the present invention will be described below.

FIGS. 2A and 2B are schematic configuration diagrams of an embodiment of the toner concentration detection device of the present invention. In the figures, parts designated by the same reference numerals as those shown in FIGS. 1A and 1B indicate the same constituent members. Toner density sensor 9
As in the conventional example, a transparent plate 10 is disposed in the opening of the sensor body 11. Preferably, the surface of the transparent plate 10 is treated to be conductive so that it has the same polarity as the toner charge. Apply bias voltage.
Reference numeral 21 denotes a means for changing the height of the developer spikes in the toner concentration detection spike area Y, and is composed of a plate-shaped regulation plate 22 and a shaft 23 that rotatably supports the regulation plate 22. As shown in FIG. 2A, the regulating plate 22 has a position where its tip is inserted into the developer layer on the developing roller 4 to reduce its thickness;
In FIG. 2B, as indicated by reference numeral 22',
It is configured to periodically move between positions spaced apart from the developer layer.

When the regulation plate 22 is in the position shown in FIG. 2A, the height of the developer spikes in the concentration detection spike area Y is reduced due to the tip of the regulation plate biting in, and the developer particles are separated from the toner concentration sensor 9. Therefore, a high detection output can be obtained from the toner concentration sensor 9. However, since it is away from the developer, some toner adheres to the surface of the transparent plate 10.

On the other hand, in FIG. 2B, as indicated by 22',
When the regulating plate is positioned away from the developer layer, the developer spikes in the detection spike area Y come into contact with the transparent plate 10 to remove stains caused by toner adhesion. However, the detection output of the toner concentration sensor 9 is significantly lower than in the state shown in FIG. 2A. Therefore, the regulation plate 22 is driven back and forth periodically, and the high detection output from the toner concentration sensor 9 is sampled based on the timing when it takes the position A in FIG. 2, and is used as a detection signal of the toner concentration. It is.

As a result, a high detection output of toner concentration can be obtained, and a stable detection output can be obtained by preventing the sensor from becoming dirty.

FIG. 3 is a schematic diagram of another embodiment of the present invention. In this embodiment, instead of the regulating plate 22 in the embodiment shown in FIG. The thickness of the developer layer is changed periodically. Eccentric cam 2
4 is configured to rotate around an axis 25,
When in the position shown in FIG. 3, the thickness of the developer layer is regulated and a high detection output can be obtained as in the state shown in FIG. 2A. When the cam 24 assumes a position rotated by 180 degrees, the developer and the cam 24 are in a non-contact state, and the spikes of the developer come into contact with the transparent plate 10, similar to the state shown in FIG. Acts to remove dirt.

When a cam is used as in this embodiment to regulate the thickness of the developer layer, the cam can be rotated continuously in one direction, so the second
Unlike the embodiments shown in FIGS. A and B, a mechanism for performing reciprocating motion is not required, and therefore a highly reliable detection device with a simplified configuration can be provided.

In each of the embodiments shown in FIGS. 2A and 2B and FIG. 3, an example is shown in which the present invention is applied to a developing device in which the magnetic roller 5 is fixed and the non-magnetic sleeve 6 is rotated. The present invention can also be applied to a device in which a sleeve is fixed by rotating a magnetic roller, or a device in which both a magnetic roller and a sleeve are rotated.

FIG. 4 is a diagram showing an embodiment in which the present invention is applied to a magnetic roller rotating type developing device, in which the developer is moved counterclockwise by rotating the magnetic roller 5' in the direction of the arrow. transported. In this embodiment, the eccentric cam 24 is applied to regulate the developer layer as in the embodiment shown in FIG. 3, but the regulation plate 22 shown in FIGS. 2A and B is applied. You may.

In the embodiments shown in FIGS. 2A and B to FIG. 4, when the means for regulating the thickness of the developer on the developer roller takes a retracted position with respect to the developer roller, the developer In the above example, the toner concentration sensor is arranged so that the toner concentration sensor is in constant contact with the transparent plate, but even if the developer is in contact with the transparent plate for a short time, the purpose can be achieved. It is also possible to adopt a structure in which the agent temporarily contacts the agent. Further, although the area where the developer contacts the transparent plate is the ridged portion, it is not necessarily necessary to make contact with the ridged portion.

FIG. 5 is a diagram showing still another embodiment of the present invention. In this embodiment, like the embodiment shown in FIGS. 2A and 2B, the regulating plate 26 is supported by a shaft 27, but as shown in FIG. The tip portion 26' sinks into the developer layer,
The scraped amount by the tip 26' of the regulating plate 26 is set so that the thickness is reduced and at the same time the scraped developer forms a large lump as shown by Z. When the regulating plate 26 is moved away from the developing roller 4 at high speed, for example by driving with a solenoid, the accumulation Z is conveyed in the direction of the toner concentration sensor 9 while maintaining its height, and the transparent plate 10 to remove the dirt. Once the accumulation Z passes through, the developer no longer acts on the transparent plate 10.

In this embodiment, the toner concentration sensor 9 can be placed either in the developer spike formation area or in the non-spike area, but when the toner concentration sensor 9 is placed opposite the developer spike formation area, , Tamari Z
does not have to be so large that it directly contacts the light-transmitting plate; it is sufficient that the height is within the range where it contacts the light-transmitting plate when the panicle is formed.

As described above, this embodiment is characterized in that a large accumulation Z of developer is formed by the regulating plate 26, thereby making it easier for the developer to come into contact with the transparent plate 10. As a result, a sufficient distance can be maintained between the toner concentration sensor and the developer when detecting the toner concentration, so that even higher photoelectric detection output can be obtained.

Another feature of this embodiment is that the toner concentration sensor 9 can be placed opposite the developer on the developing roller 4 that does not form spikes. When the toner concentration sensor 9 is placed opposite the developer portion other than the stand-up portion, the detection output is further increased.
It will be about 10 times larger than when facing the panicle.

In each of the embodiments described above, the thickness of the developer layer on the developing roller is periodically changed to alternately clean the transparent plate of the toner concentration sensor and obtain a high photoelectric detection output. However, without making any changes to the developer on the developing roller,
The present invention can also be practiced by periodically moving the toner concentration sensor.

FIG. 6 is a schematic diagram of an embodiment constructed based on the above principle. The toner concentration sensor 28 is
The configuration is such that a state a, in which the developer is located away from the developer on the developing roller 4, and a state b, in which the developer is in contact with the transparent plate 29, are periodically generated. In state a, a high photoelectric detection output is obtained, so the photoelectric detection output in this state is sampled and used as a toner concentration detection signal,
In the state b, toner adhering to the transparent plate 29 is cleaned. This embodiment can be implemented even when the thickness of the developer layer on the developing roller 4 is small and it is difficult to apply the embodiments of the system shown in FIGS. 2A, B to 5. , a has the advantage that the position of the toner concentration sensor in the state of state a can be set to any position where the maximum output can be obtained.

〔Effect of the invention〕

In the present invention, the developer toner concentration detection device is provided with a means for periodically changing the distance between the developer surface on the developing roller and the toner concentration sensor, and the toner is detected in a state where the developer surface and the toner concentration sensor are close to each other. The light-transmitting plate of the density sensor is in contact with the developer, and the photoelectric detection signal obtained when the developer surface and the toner density sensor are separated is sampled and used as the toner density detection signal, so the toner density sensor Since contamination by toner can be prevented and high photoelectric detection output can be obtained, detection accuracy and reliability can be improved.

Furthermore, by configuring the means for periodically changing the distance between the developer surface and the toner concentration sensor as a means for periodically changing the thickness of the developer layer,
The present invention can be implemented with a simple configuration.

Furthermore, by configuring the means for periodically changing the distance between the developer surface and the toner concentration sensor as means for periodically moving the toner concentration sensor toward and away from the developing roller, the developer on the developing roller can be It can be applied even when the layer thickness is small, and since there are no restrictions on setting the distance between the toner concentration sensor and the developer, the optimal conditions can be set for cleaning the transparent plate and detecting the toner concentration. Effects such as being able to place the toner concentration sensor at the position can be obtained.

[Brief explanation of the drawing]

FIG. 1A is a schematic diagram of a configuration example of a conventional developer toner concentration detection device, FIG. 1B is a schematic diagram of an example of a toner concentration sensor, and FIG. FIG. 2B is a schematic diagram showing one operating mode of an embodiment of the concentration detection device, and FIGS. 3 to 6 are schematic diagrams showing other operating modes of the above embodiment, respectively. FIG. 6 is a schematic diagram of another embodiment. In the figure, 1 is a charge retention member, 4 is a developing roller, 5 is a magnetic roller, 6 is a non-magnetic sleeve, 8 is a doctor blade, 9 is a toner concentration sensor, 10 is a transparent plate, and 21 is a change in spike height. 22 is a regulating plate, 24 is an eccentric cam, 26 is a regulating plate, and 28 is a toner concentration sensor.

Claims (1)

[Scope of Claims] 1. In a developer toner concentration detection device for a developing device using a magnetic two-component developer, the device is supported opposite to the developer held and conveyed on a developing roller, and detects the developer through a transparent plate. a photoelectric toner concentration sensor that measures optically reflected light; a distance changing means that changes the distance between the developer surface and the transparent plate of the toner concentration sensor so that they come into contact with each other or are separated; and the developer surface and the transparent plate of the toner concentration sensor. 1. A developer toner concentration detection device comprising: sampling means for sampling a photoelectric detection signal obtained by the toner concentration sensor in a state where the toner concentration sensor is separated from the toner concentration sensor. 2. The developer toner concentration detection device according to claim 1, wherein the distance changing means is a layer thickness control means for changing the thickness of the developer layer on the developing roller. 3. The developer toner concentration detection device according to claim 1, wherein the distance changing means is a sensor moving means for moving the toner concentration sensor.