JPS6245551B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a development amount detection method for detecting the development ability of a developer used in electrophotographic copying machines, electrostatic recording devices, and the like.

As is well known, in electrophotographic copying machines and electrostatic recording devices, an electrostatic latent image formed on a carrier is visualized using a developer. The developer used here is a wet type developer in which colored charged powder is dispersed in an insulating liquid, a one-component system consisting only of toner particles, or a two-component system consisting of both carrier and toner particles. There is a dry developer. In development performed using these developers, toner is electrostatically attracted to an electrostatic latent image of opposite polarity, and a visible image of the toner is formed on the latent image carrier. Usually, after this developing step, a step of transferring the toner image onto a transfer paper, a fixing step, etc. are performed to obtain a copy or the like. In this way, the density of the toner-developed image on the latent image carrier or transfer paper is affected by the developing ability of the developer.

Incidentally, the developing ability of a developer can be defined as the ability of the developer used to develop an electrostatic latent image to a specific density. In other words, it is the ratio of the amount of toner that the developer used can impart to the electrostatic latent image bearing surface per unit electric field strength and unit area. The developing ability of such a developer cannot be kept constant simply by maintaining an appropriate toner concentration. For example, developer fatigue may occur due to various factors during use, and changes in environmental conditions such as temperature, especially humidity may cause changes in the amount of charge on the toner and the frequency distribution of the amount of charge, resulting in electrostatic potential. This results in a change in the amount of toner used to develop the image, ie, a change in the density of the developed image. Therefore, by detecting the developing ability of the developer and maintaining it appropriately, it is possible to perform true density control of the developed image.

As a conventional method for detecting developing ability, for example, an electrostatic latent image with a constant electric field strength is formed on the surface of a photoreceptor, this is then visualized, and the area where the toner is attached is irradiated with light, and the amount of reflected light is determined. There is a method for detecting the amount of toner attached. In this case, if the layer thickness of the toner adhesion area becomes thick, detection becomes impossible (optically saturated), and if there is dirt or scratches on the toner adhesion surface, such as the photoconductor surface, accurate detection cannot be performed. There is this inconvenience. Furthermore, Japanese Patent Application Publication No. 1973-
As disclosed in No. 118064, the toner concentration in the two-component developer is detected by applying a magnetic field to the two-component developer, applying an electric field in the same direction as the magnetic field, and measuring the current flowing there. There is a way to do it. In this case, the toner concentration of the two-component developer used as the magnetic brush is measured before it is actually used for development. Therefore, due to the above-mentioned factors, the toner concentration may not correspond correctly to the developing ability of the developer, and this method has the disadvantage that a developed image with uniform density cannot be obtained.

SUMMARY OF THE INVENTION An object of the present invention is to provide a developed amount detection method that can easily detect the attached amount of magnetic toner actually used for developing an electrostatic latent image.

In the developed amount detection method according to the present invention, when detecting the amount of magnetic toner used for developing an electrostatic latent image, a recording signal is magnetically recorded on the magnetic toner adhesion area, and then this magnetic recording area is electrically By regenerating a signal and using this regenerated electric signal, the layer thickness of the magnetic toner-attached portion is detected.

According to such a method of detecting the amount of development, a magnetic recording portion that is magnetically recorded on a portion to which magnetic toner is attached is regenerated. At this time, since the value of the regenerated electric signal changes depending on the thickness of the toner layer, the thickness of the toner layer, that is, the developing ability of the developer can be detected using the regenerated electric signal.

This invention will be explained below with reference to the drawings.

FIG. 1 is an explanatory diagram showing a method for detecting the amount of development as an embodiment of the present invention. In FIG. 1a, the toner image bearing member is a transfer paper 1, on the surface of which a toner adhering portion 2 of magnetic toner is formed. The transfer paper 1 moves in the direction of arrow a and faces the recording head 4 one after another. This recording head 4 sends a recording signal I1 of a set frequency to the toner adhesion section 2.
A magnetic recording section S is formed by performing magnetic recording. Next, as shown in FIG.
direction, and sequentially face the reproducing head 5. This reproducing head 5 is a magnetic recording section S of the toner adhesion section 2.
is detected and converted into a reproduced electrical signal I2.
At this time, as shown in FIG. 2, the value of the reproduced electric signal I2 changes monotonically in response to the thickness of the magnetic toner layer of the toner adhering portion 2. The magnetic toner used here has an average particle size of 0.3μ as a magnetic material.
Magnetite 6 with a residual magnetism of 100 oersted is dispersed in resin 7 at a weight ratio of 50% (see Figure 3). When this magnetic toner is used, a frequency-electrical signal magnitude characteristic as shown in FIG. 4 can be obtained. That is, the recording signal I that can be used here
1 and the reproduced electric signal I2 based thereon have their low and high frequency limits regulated by the magnetic properties and density of magnetite 6 in the magnetic toner. Therefore, if the magnetic toner described above is used and the recording signal I1 of a predetermined frequency is used, the value of the reproduced electric signal I2 corresponds to the thickness of the toner layer (in FIG. 4, the layer thicknesses A, B, and C are In other words, the larger the layer thickness, the larger the layer thickness. By detecting the reproduced electric signal I2 in this manner, the reproduced electric signal I2 can be used as a signal indicating the thickness of the toner layer, that is, the developing ability.

According to the developed amount detection method as shown in FIG. 1, a recording signal I1 is once magnetically recorded on the magnetic toner adhering portion 2, and then the magnetic recording portion S is reproduced to obtain a reproduced electric signal I2. Therefore, even if an excessive amount of toner adheres to the toner adhering area 2, the layer thickness of the magnetic toner can be accurately detected from the surface side, and the amount of development, that is, the developing ability can be determined regardless of the state of the toner adhering area 2. Can be detected. Moreover, since it is possible to detect the layer thickness of the part where the magnetic toner is attached after being developed, it is also possible to detect the layer thickness of the part where the magnetic toner is attached before it is fixed on the transfer paper. teeth,
It is also possible to develop the electrostatic latent image with magnetic toner before transfer and detect the layer thickness of the area to which the magnetic toner is attached at the time when it becomes a visible image.

FIG. 5 shows an electrophotographic copying machine 8 equipped with a device for carrying out a method for detecting the amount of developed material according to an embodiment of the present invention. This electrophotographic copying machine 8 rotates a photoreceptor drum 9 in the direction of the arrow b, and surrounding the photoreceptor drum 9 along this rotation direction is a developing device that forms a charging device 10, an exposure device 11, and a magnetic brush 121. A device 12, a paper feed device 13 that feeds the transfer paper 1 at a set timing, a transfer device 14, and a separation device 1
5. The cleaning device 16 and the static eliminator 17 are arranged in this order. Further, the transfer paper 1 separated from the photosensitive drum 9 by the separating device 15 passes through the conveying device 18 and reaches the fixing roller 19 . The transfer paper 1 that has undergone the fixing process advances along a paper discharge path 20 and is delivered to a paper discharge tray 21. In the paper discharge path 20 of such an apparatus, a recording head 22 and a reproducing head 23 are sequentially disposed facing each other toward the downstream side, that is, toward the paper discharge tray 21 side. The recording head 22 is connected to a recording control unit 24 for recording a recording signal I1, which includes an AC signal generator. On the other hand, the reproducing head 23 converts the magnetic recording section S into the reproducing electric signal I2.
It is connected to a playback control section 25 that converts the data into .

The electrophotographic copying machine 8 shown in FIG. 5 makes copies by the rotation of the photosensitive drum 9 and the actions of surrounding devices that operate in conjunction with the rotation of the photosensitive drum 9. In this case, the electrostatic latent image formed on the photoreceptor drum 9 and corresponding to the pattern for detecting the amount of development is developed by the developing device 12 .
Then, a visible image is formed by the toner, and this toner image is transferred to the transfer paper 1 and, after being fixed, reaches the paper discharge path 20. Then, the recording head 22 uses the recording signal I1 of the set frequency to magnetically record on the toner image for detecting the amount of development on the transfer paper. Subsequently, the toner image with the magnetic recording portion S formed thereon faces the reproduction head 23, at which time the magnetic recording portion S is reproduced, converted into a reproduction electric signal I2, and output.
This reproduced electric signal I2 corresponds to the layer thickness of the toner image portion, and its signal value has a monotonous relationship (see FIG. 2).
If this reproduced electric signal I2 is fed back to each control system of the charging device 10, the exposure device 11, and the developing device 12, a copy with a stable toner adhesion amount, that is, toner density can be obtained.

For example, when the amount of toner adhesion is too large, control can be performed such as lowering the charging potential or bringing the developing bias voltage closer to the latent image potential.

The recording head 22 and the reproducing head 23 shown in FIG. 4 may be located at other positions, for example, at a position facing the transfer paper 1 on the conveying device 18 side, or at a position facing the photosensitive drum 9, and It is also possible to install it at a predetermined position within the space between the developing device 12 and the cleaning device 16.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating a method for detecting the amount of development as an embodiment of the present invention, FIG. 2 is a characteristic diagram of the magnetic toner layer thickness versus electric signal magnitude, and FIG. 3 is an enlarged diagram of the magnetic toner layer. Fig. 4 is a frequency-electric signal magnitude characteristic diagram with the layer thickness of the magnetic toner as a parameter, and Fig. 5 is an electrophotograph of an apparatus for carrying out a method for detecting the amount of development, which is an embodiment of the present invention. Each shows a schematic diagram of a copying machine. 2... Toner adhesion part, I1... Recording signal, I2... Reproduction electric signal, S... Magnetic recording part.

Claims (1)

[Claims] 1. In a development amount detection method for detecting the amount of magnetic toner used to develop an electrostatic latent image, a recording signal is magnetically recorded on the magnetic toner adhesion area, and then this magnetic recording area is reproduced into an electric signal. . A method for detecting the amount of development, characterized in that the layer thickness of the magnetic toner adhesion area is detected by using the reproduced electric signal.