JPH0322626B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a toner density detector, particularly a toner density detector used in a high-speed electronic printing device used in a facsimile machine, etc., for detecting the density of a toner mark exposed on a photosensitive drum. The present invention relates to a toner concentration detector in which a transparent electrode to which a voltage is applied is arranged in front of an optical reflection densitometer to eliminate toner that scatters and adheres to the optical reflection densitometer.

High speed electronic printing equipment generally employs charge removal configurations and uses two-component developers. In order to control the print density, for example, a toner mark is exposed on the photosensitive drum for each page of printing paper, and the density of the toner mark is detected by an optical reflection densitometer. There is. That is, a selenium plate, for example, is used as the photosensitive drum, and the concentration of toner components in the developer deposited on the silver layer is measured, and based on the detection results, the concentration of toner components contained in the two-component developer is determined. The yield of toner components is controlled.

However, since the above-mentioned optical reflection densitometer is opposed to the photosensitive drum surface at a distance of, for example, 2 to 3 mm, toner components scattered on the front wall of the optical reflection densitometer may be undesired. This causes a measurement error in concentration detection by the optical reflection densitometer. For this reason, conventionally, it has been necessary for the operator to clean the dirt adhering to the front wall of the optical reflection densitometer after extracting the optical reflection densitometer from the apparatus.

The present invention aims to solve this problem, and the toner density detector of the present invention includes a latent image forming member and a latent image forming means for forming a latent image corresponding to image information on the latent image forming member. , a developing section that supplies developer to the latent image; a paper feed supply section; and a paper feed section that supplies the developer deposited on the latent image forming body to the paper supplied from the paper feed supply section. the toner mark formed on the latent image forming body in correspondence with a predetermined unit of the paper, and irradiating the toner mark on the latent image forming body with light. An optical reflection densitometer is provided to detect the density of the toner mark by detecting the reflected light as a result of irradiation, and the developer is supplied to the developing section based on the density detected by the optical reflection densitometer. In a toner density detector used in an electronic printing device that controls a toner concentration sensor, a transparent electrode plate through which the irradiated light and the reflected light pass is disposed on a surface of the optical reflection densitometer that faces the latent image forming body. The present invention is characterized in that a voltage having the same polarity as the potential of the developer deposited on the latent image forming body is applied to the surface of the transparent electrode plate. This will be explained below with reference to the drawings.

FIG. 1 shows the configuration of an embodiment of an electronic printing device to which the present invention is applied, FIG. 2 shows the configuration of an embodiment of the toner concentration detector of the present invention, and FIG. 3 shows an optical type used in the toner concentration detector. An example of a reflection densitometer is shown in each case.

In FIG. 1, reference numeral 1 is a photosensitive drum that rotates in the direction of the arrow, 2 is a charger that charges the photosensitive drum 1, and 3 is an optical system that rotates on the photosensitive drum 1. 4 is a developing machine that applies a two-component developer to the electrostatic latent image to form a visible image; 5 is a sheet of paper; 6 is a paper feed supply section; 7 is a transfer section which transfers the toner component in the two-component developer deposited on the photosensitive drum 1 as the visible image to the paper 5 side; 8;
9 represents a cleaning brush, and 9 represents a toner concentration detector of the present invention.

The photosensitive drum 1 is uniformly charged by a charger 2, and then image information is exposed by an optical system 3. Since the surface voltage of the photosensitive drum 1 decreases in the exposed area, image information due to light is transferred to the photosensitive drum 1.
An electrostatic latent image pattern is left on the surface. The electrostatic latent image pattern is then developed by a developing device 4, and a two-component developer is applied to form a visible image.

On the other hand, the paper 5 is fed by the paper feed supply section 6 at a speed commensurate with the surface speed of the photosensitive drum 1. Then, the toner components in the two-component developer deposited as the visible image in the transfer section 7 are transferred to the paper 5.
The toner components transferred to the paper 5 are fixed on the paper 5 in a fixing section (not shown). The toner remaining on the photosensitive drum 1 that has not been transferred is completely removed by the cleaning brush 8.

The developing device 4 is of a type that uses a two-component developer having a carrier component and a toner component, and the optimum range of the ratio of toner components (toner concentration) in the developer is relatively narrow. If the toner concentration is too high, toner components will adhere to areas that should not be printed, while if the toner concentration is too low, the print density will drop and the image quality will be significantly degraded.

For this purpose, the optical system 3 exposes a pattern called a toner mark outside the print area on the photosensitive drum 1 every time the page of the paper 5 changes, and this area is exposed in the developing machine 4 in the same manner as described above. A visual image is created, and the density of the visible image corresponding to this toner mark on the photosensitive drum 1 is measured by an optical reflection densitometer 10. When the measured value falls below the reference value, a predetermined amount of toner components is supplied to the developing device 4 to bring the toner concentration within the optimum range.

Conventionally, an optical reflection densitometer 10 as conceptually shown in FIG. 3 has been used. In the optical reflection densitometer 10, a light emitting element 10 is placed in an opaque container.
-1, a photoelectric conversion element 10-2, and a lens 10-3 are housed, and holes 10-4 and 1 correspond to the optical path.
0-5 is formed. And light emitting element 10-
The light from the densitometer 10 exits the densitometer 10 through the hole 10-4 and is irradiated onto the visible image of the toner mark on the photosensitive drum 1. The reflected light from the visible image passes through the hole 10-5, is focused by the lens 10-3, and enters the photoelectric conversion element 10-2.

It can be considered that conventionally only the optical reflection densitometer 10 as shown in FIG. 3 has been used as the toner concentration detector 9 shown in FIG. A transparent cover 10 - 6 is provided on the front surface of the optical reflection densitometer 10 , but toner components merely adhering to the photosensitive drum 1 and toner components scattered from the developing device 4 can be removed from the densitometer 10 . Because of this, it is detected that the ratio of toner components in the developer is apparently sufficient, and even if the toner concentration actually decreases, the toner components are not replenished.
As a result, the operator has had to occasionally extract the optical reflection densitometer 10 from the apparatus and clean the cover 10-6 on the front of the densitometer 10.

In the case of the present invention, a toner concentration detector 9 as shown in FIG. 2 is used. That is, the optical reflection densitometer 10 is housed in a case 14, a transparent plate 13 is placed in front of the densitometer 10, and it is held down by a conductive holding plate 11. A transparent conductor such as indium oxide is deposited on the surface of the transparent plate 13 facing the photosensitive drum 1 to form an electrode, and a voltage is applied to the electrode by the power source 12. The toner concentration detector 9 thus constructed is fixed to the apparatus such that it passes through a position facing the toner mark forming portion on the photosensitive drum 1 at a distance of, for example, 2 to 3 mm.

The polarity of the voltage applied to the electrode is the same as the potential of the toner component on the photosensitive drum 1, so that the toner component scattered to the front of the toner concentration detector 9 is electrostatically moved away from the transparent plate 13. Make it.

Note that the toner concentration detector 9 of the present invention includes:
The cover 10-6 shown in FIG. 3 is not limited to the one that houses the existing optical reflection densitometer 10
It is not excluded that the above-mentioned electrodes are provided on the device itself and a voltage is applied thereto.

As described above, according to the present invention, it is possible to prevent toner components from undesirably adhering to the front surface of the toner concentration detector 9, to correctly detect the density of toner marks, and to replenish toner components correctly. It becomes possible.

In the above embodiments, the present invention was applied to an electrophotographic apparatus, but the present invention is not limited thereto, and is applicable to electrostatic recording using, for example, a dielectric drum as a latent image forming body. A similar effect can be obtained when applied to a device.

Further, the latent image forming body does not have to be drum-shaped, and may be an endless belt-shaped one or a wind-up belt-shaped one without any problem.

Further, the developer is not limited to a so-called two-component developer consisting of toner and carrier, but a one-component developer can be applied in the same manner.

[Brief explanation of the drawing]

FIG. 1 shows the configuration of an embodiment of an electronic printing device to which the present invention is applied, FIG. 2 shows the configuration of an embodiment of the toner concentration detector of the present invention, and FIG. 3 shows an optical type used in the toner concentration detector. An example of a reflection densitometer is shown. In the figure, 1 is a photosensitive drum, 2 is a charger, 3 is an optical system, 4 is a developing device, 5 is paper, 6 is a paper feed supply unit,
7 is a transfer unit, 8 is a cleaning brush, 9 is a toner concentration detector, 10 is an optical reflection densitometer, 12
13 represents a power source, 13 represents a transparent plate, and 14 represents a case.

Claims (1)

[Scope of Claims] 1. A latent image forming member, a latent image forming means for forming a latent image corresponding to image information on the latent image forming member, and a developing section that supplies a developer to the latent image. , comprising at least a paper feed supply section and a transfer section that transfers the developer deposited on the latent image forming body to the paper supplied from the paper feed supply section, and a predetermined unit of the paper. The toner mark formed on the latent image forming body is made to face the toner mark formed on the latent image forming body, and the reflected light as a result of irradiating the toner mark on the latent image forming body is detected and the toner mark is detected. A toner concentration detector used in an electronic printing device, which is equipped with an optical reflection densitometer for detecting density, and controls developer supplied to the developing section based on the density detected by the optical reflection densitometer, A transparent electrode plate through which the irradiated light and the reflected light are transmitted is disposed on a surface of the optical reflection densitometer that faces the latent image forming body, and a transparent electrode plate through which the irradiated light and the reflected light are transmitted is disposed, and the surface of the latent image forming body is A toner concentration detector characterized in that it is configured to apply a voltage of the same polarity as the potential of a developer deposited on the toner concentration detector.