JPS6027022B2 - Toner concentration detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting toner concentration of a powder developer comprising a magnetic carrier and a non-magnetic toner used for developing a static latent image.

An electrostatic latent image formed on a recording medium through a predetermined process using electrophotography or static fin recording is visualized using colored resin powder called toner.

Generally speaking, a developer made of toner alone is called a one-component developer, and a developer made of toner and a carrier is called a two-component developer. The carrier in the two-component developer plays the role of triboelectrically charging the toner to a polarity opposite to the polarity of the charge forming the electrostatic latent image, as well as adsorbing the toner and transporting it to a development position.

The carrier is usually magnetic powder such as iron powder, and is attracted together with the toner onto a magnetic developing roller immediately inside the developing bag and transported to the developing position.

As described above, since direct development is performed using toner, in the case of a two-component developer, the amount of toner in the developer gradually decreases due to development, and the toner concentration decreases.
If this continues, the density of the developed image will naturally decrease. Therefore, in order to keep the density of the developed image constant and obtain a high-quality image, the toner density in the developer must be detected, and the required amount of toner should be supplied to the developer as needed to adjust the toner density. Must be kept in optimal condition. As a method for detecting the toner concentration in the developer, a coil is installed in the developer, and the inductance of the coil changes as the toner concentration changes.This change is detected to detect the toner concentration. There are known ways to control it.

Similarly, a method of detecting reactance fluctuations of a coil in a developer using a resonant circuit is also known. However, all of these methods require a separate standard signal generator, a comparison circuit with the standard signal generator, a circuit for determining the result, and an amplification and operation circuit, making them extremely complicated and expensive. Not only that, but there is also the drawback of lack of reliability due to noise and the like.

In the toner concentration detection method according to the present invention, a double coil constituting an oscillation circuit is provided in the developer flow path, and a change in magnetic permeability due to a change in the bulk density of the developer is detected by changing the magnetic axis interlinked with the coil. At the same time, a slight change in magnetic permeability is treated as a large change in mutual inductance, and the feedback point is set near the amount of positive feedback required for oscillation, causing a sudden change in the oscillation output voltage, and this is detected. Control toner density as a signal.

According to this invention, it is possible to easily detect toner concentration, and moreover, it is possible to detect toner concentration as small as 4.

Furthermore, since the circuit configuration is simple, the device used is inexpensive and can be provided with high reliability. Therefore, an object of the present invention is to provide an improved toner concentration detection method that utilizes changes in coil inductance.

A further object of the present invention is to provide the above-mentioned method that can sensitively detect slight changes in toner concentration.

A further object of the present invention is to provide the above-mentioned method, which uses inexpensive equipment and has a simple circuit configuration.

Hereinafter, the present invention will be described with reference to the attached drawings.

FIG. 1 is a schematic perspective view showing an example of a coil unit used in carrying out the present invention. A first coil 2 is wound around the parallel portion of a funnel-shaped guide slope member 1 which is open at the top, parallel at the middle, and constricted at the bottom. At the center of the first coil 2, a second coil 3 having a smaller diameter is wound around a magnetic core 4 having a conical top. supported (see Figure 3). The developer flows down into the space between the guide member 1 and the second coil 3 from above. The first coil 2 and the second coil 3 constitute a part of an oscillation circuit (not shown). FIG. 2 is a schematic perspective view showing another example of the coil unit.

A cylindrical magnetic core 4 is provided around the parallel part of the guide village 1 having a similar shape.
A coil unit in which the first coil 2 is wound on the outside and the second coil 3 is wound on the inside is inserted through the coil. The developer flows down inside the guide member 1. Next, the operation when the coil unit shown in FIG. 1 is used will be explained with reference to FIGS. 3 and 4.

The developer used in this invention is a mixture of magnetic carrier and non-magnetic toner.

Therefore, as the toner concentration decreases, the magnetic permeability of the developer increases. As the toner concentration increases, the magnetic permeability of the developer decreases by 4. When the toner concentration is low, as shown in FIG. 3, the magnetic flux 5 in the magnetic field generated in the first coil 2 passes through the developer 6 having high magnetic permeability. On the other hand, when the toner concentration is high, the magnetic flux 5 has a magnetic permeability of 4.
The developer passes through the magnetic core 4, which has a higher magnetic permeability than the developer 6, which has become thinner. In other words, the magnetic permeability of the magnetic core 4 is determined so that the magnetic flux 5 passes through the magnetic core 4. This is determined by the set standard value of toner density, that is, the magnetic permeability of the standard developer. When the magnetic flux of the first coil 2 changes depending on the toner concentration, the electromotive force induced in the second coil 3 changes, and the mutual inductance changes.

This change is detected as a change in the output voltage of the oscillation circuit. The oscillation circuit used in this invention is a feedback type L
This is a C oscillation circuit.

FIG. 5 shows an example of a collector-tuned oscillation circuit. When a collector current flows through the LC circuit formed by the first coil 2 and capacitor 8 by the DC power supply 7, a fraction of the terminal voltage is applied to the base of the transistor 9 through the second coil 3, resulting in a base current. flows and amplifies the collector current. FIG. 6 shows an example of a base-tuned oscillation circuit used in the present invention.

The center tap of coils 20 and 22 is connected to the base of transistor 30 via capacitor 24. A tuned circuit is formed by the capacitor 23, the coils 20 and 22, and the coil 21 having mutual inductance, and the oscillation frequency is determined. The resonant current 27 shown by the solid line causes the resonant voltage to be divided to the center tap, and the transistor 30
A resonant signal stream 28 shown by a dotted line passes through the oscilloscope, and an output is obtained. The capacitor 24 is for passing only the alternating current component and blocking the direct current bias current component. Resistors 25 and 26 are DC bias dividing resistors for operating the transistor 30. In this way, toner concentration can be measured by intentionally changing the mutual inductance of the oscillation circuit and varying the oscillation frequency or oscillation voltage.

In addition, several modified oscillation circuits can be applied based on the idea of the present invention. As described above, since the oscillation circuit used in the present invention includes a feedback circuit, if the feedback point is set near the limit feedback amount necessary for oscillation, the magnetic permeability of the developer flowing in the coil can be reduced. The oscillation output voltage fluctuates rapidly even with a slight change, and by detecting this, changes in toner concentration can be ascertained.

[Brief explanation of drawings]

1 and 2 are schematic perspective views showing different examples of coil units used in carrying out the present invention, and FIG.
5 and 4 are explanatory views of the operation inside the coil unit shown in FIG. 1, and FIGS. 5 and 6 are circuit diagrams showing different examples of oscillation circuits used in carrying out the present invention. 1... Guide member, 2... First coil,
3... Second coil, 4... Shishin, 5...
・Magnetic flux, 6...Developer. Camellia, rare 2 figures, 8 figures, 4 figures, rare 5 figures, 6 figures

Claims (1)

[Claims] 1. A method for detecting the toner concentration of a powder developer consisting of a magnetic carrier and a non-magnetic toner, in which a plurality of coils are provided in a concentric cylindrical shape, a feedback oscillation circuit using the coils as a reactance is used, and the inside of at least one of the coils is The mutual inductance changes according to the change in the concentration of the passing developer,
This changes the amount of feedback required for oscillation, and the resulting variation in output is used as a detection signal.