JPS61232475A - Automatic image density controller for copying machine - Google Patents

Abstract

PURPOSE:To supply toner accurately by measuring the stop time of a developing motor and correcting a current value detected in next development when the measured time exceeds a preset time. CONSTITUTION:The stop time of the developing motor which drives a developing roll 10 is measured by a controller 15 and when the stop time of the developing motor exceeds the preset time, a decision on copying is made for the 1st time after a stop and an automatic zero reference level B is corrected, so that the condition of the current value detected in development is the same as the condition of copying of the 2nd and succeeding copies. Toner consumption calculated by the controller 15, on the other hand, is outputted as a control signal to a toner supply motor 16, whose control is controlled. Tone is supplied from a toner bottle 18 to a developing device as the toner supply motor rotates to supply an amount of toner suitable to the toner consumption during the development. Consequently, even the 1st copy image has stable density.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention detects a weak current generated by the transfer of toner from a developing roll to a photoreceptor during development, and adjusts the amount of toner replenishment according to this detected current. The present invention relates to an automatic image density control device for a copying machine to be controlled.

2. Description of the Related Art In conventional electronic copying machines, an electrostatic latent image formed on the surface of a photoreceptor during an exposure process is developed into a toner image in a development process, and this toner image is transferred to paper in a transfer process. In addition, in the developing process, a developing bias is applied to develop the surface of the photoreceptor between the developing roll and the photoreceptor, but when the toner is transferred from the developing roll to the photoreceptor during development, a weak current is generated in the developing bias application circuit. do. The weak electric current is proportional to the amount of toner transferred from the developing roll to the photoreceptor, that is, the amount of toner consumed during development, so this current value is detected and new toner corresponding to this current value is sent to the developing device. By replenishing the toner, the toner concentration of the developer in the developing device is always kept constant, thereby making it possible to obtain a copied image with a stable density.

In addition, an automatic image density control method for a copying machine using the above method has already been published in Japanese Patent Application No. 59-274175.
-274176, Japanese Patent Application No. 1) 1!59-274177, Japanese Patent Application No. 59-274178, etc.

Problems to be Solved by the Invention In the automatic image density control method for a copying machine disclosed in the above application, the developing motor is controlled on and off for each copying process as shown in FIG. 3 for development. Note that the person in the figure indicates the copying pause time.

Furthermore, in the above-mentioned conventional automatic image density control method, the amount of toner consumed is calculated based on the traveling current value detected during development, and toner is replenished according to the amount consumed. However, when copying is performed for the first time after a pause, Since the photoconductor has not undergone the charging, exposure, and static elimination processes, the automatic zero reference level B is high for the second and subsequent copies that have undergone these processes, as shown in Figure 4. If the toner is replenished according to the traveling current value detected at the current time, there is a problem that the toner is oversupplied and it becomes impossible to obtain copies with stable density.

This invention was made for the purpose of improving the above-mentioned problems.

Means and Effects for Solving the Problems The toner consumed during development, t, is detected by a current detector provided in the development bias application circuit, and the rotation time of the toner supply motor is controlled in accordance with this current value. In a copying machine that supplies toner in an amount commensurate with the amount of toner consumed during development to the developing device, the stop time of the developing motor that drives the developing roll is measured, and the stop time is set to a preset time. If the amount exceeds the amount of toner consumed during development from the first copy, the next copy is determined to be the first copy and the current value detected during development is corrected. An automatic image density control device for copying machines that enables accurate toner replenishment.

Embodiment An embodiment of the present invention will be described in detail with reference to the drawings. In the figure, 1 is a photoconductor of a copying machine, 2 is a charger that charges the surface of the photoconductor 1, and 3 is a charger that guides the original image to the surface of the photoconductor 1 to form an electrostatic latent image on the surface of the photoconductor 1. The electrostatic latent image formed on the surface of the photoreceptor 10 by the exposure process, which represents an optical system such as a cell-hoc lens, is developed into a toner image by a developing device 4, and then transferred to a paper feeding device (not shown) by a transfer device 5. The toner image is transferred onto the fed paper 6, and further sent to a fixing device (not shown) by the conveyance means 7, where the toner on the paper 6 is fixed on the surface of the paper 6. Further, untransferred toner remaining on the surface of the photoreceptor 1 without being transferred to the paper 6 is removed by the cleaning device g.

On the other hand, a developing roll 1o is provided in the housing 4α of the developing device 4Fi in close proximity to the photoreceptor 1. The developing roll 1o has a structure in which, as shown in FIG. While the developing bias power supply 12 is being applied, the developer in the housing 4α is attracted to the surface of the sleeve 10b in the form of a brush due to the magnetic action of the magnet roll 1QcL. Further, the developer adsorbed on the surface of the sleeve IOb is trimmed by the trimming bar #3 so that its height is constant, and then reaches the photoreceptor 1.
When the electrostatic latent image formed on the surface of the photoreceptor 10 is developed and the toner is transferred from the developing roll 10 to the photoreceptor 1, a weak current flows through the development bias circuit 11 as follows.

That is, as shown in FIG. 2, there is usually a gap of about 1.0 to 1*5M8 between the photoreceptor 1 and the developing roll 1o. The triboelectric charge caused by the toner is filled with sufficiently insulating toner that is electrostatically attracted to the carrier. At this time, the toner and carrier, which have a certain charge due to triboelectric charging, are electrically balanced, but they come into contact with the surface of the photoreceptor 1 on which the electrostatic latent image is formed, and a nine-dimensional electrostatic latent image is formed. Toner in the developer is transferred to the photoreceptor 1 side in an amount corresponding to the amount of charge. As a result, the stain 1° above the developing roll disappears by the amount of charge that the toner particles had, and a weak current flows to the developing roll 10 to compensate for this.

This weak current is proportional to the amount of toner transferred from the developing roll 1o to the photoconductor 1 during development, that is, the amount of toner consumed for development. ] is detected and taken into the control device 15 consisting of a microcomputer.

The control device 15 calculates the amount of toner consumption from the current value taken in, but in the case of copying for the first time after a pause, the photoreceptor t
2 because it has not been subjected to ilt charging, exposure and static elimination processes.
The automatic zero reference level is higher than when copying from the first sheet onwards, as shown in FIG. 4.

Therefore, in the present invention, the control device 15 measures the stop time of the developing motor (not shown) that drives the developing roll IoT.
When the stop time of the developing motor exceeds a preset time, it is determined that this is the first copying after the stop, and the automatic zero reference level B is corrected. As a result, the conditions for the current value detected during development become the same as those for the second and subsequent copies.

On the other hand, the amount of toner consumption calculated by the control device 15 is output as a control signal to the toner supply motor 16, and the rotation of the toner supply motor 16 is controlled.

The toner supply motor 16 is connected to a toner supply auger 17, and as the toner supply motor rotates, it supplies the toner in the toner bottle 18 to the developing device 1lt4, and supplies an amount of toner corresponding to the amount of toner consumed during development. The fish start to replenish.

Effects of the Invention As described in detail above, the amount of toner consumed during development gII is detected by the current detection means provided in the development bias application circuit, and the toner supply motor is controlled in accordance with this current value. In a copying machine that supplies an amount of toner commensurate with the amount of toner consumed during development to the developing device by controlling the rotation time, the stopping time of the developing motor that drives the developing roll is measured and the stopping time is calculated. If the current value exceeds a preset time, the next original to be copied is determined to be the first copy and the current value detected during development is corrected. Since more toner than the consumed amount of toner is not supplied to the developing device, a stable copy image of a degree can be obtained from the first copy.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; FIG. 1 is an overall configuration diagram, FIG. 2 is an explanatory diagram of the developing device and control system, FIG. 3 is a diagram showing the operation of the developing motor, and FIG. 4 is a diagram showing the operation of the developing motor. It is a diagram obtained by converting a detected current into a voltage. 4 is a developing device i, to is a developing roll, 11 is a developing bias application circuit, and 16 is a toner supply motor.

Claims (1)

[Claims] The amount of toner consumed during development is calculated by the development bias application circuit 1.
The current value is detected by the current detection means provided in 1, and the rotation of the toner supply motor 16 is controlled according to this current value, so that an amount of toner commensurate with the toner consumed during development is supplied to the developing device 4. In the copying machine, the stop time of the developing motor that drives the developing roll 10 is measured,
Automatic image density of a copying machine characterized in that when the stop time exceeds a preset time, the document to be copied next is determined to be the first copy, and the current value detected during development is corrected. Control device.