JPS61232473A - Automatic controlling method for image density of copying machine - Google Patents

Abstract

PURPOSE:To perform precise image density control by the upper limit and lower limit of the quantity of toner to be supplied in a memory previously, calculating the operation time of an auger for toner supply from a current value on the basis of the upper and lower limit values, and taking a copy with invariably stable image density. CONSTITUTION:When a switch is turned on while an original having an optional image occupation rate is placed on an original platen, a current value originating from the transfer of toner from a developing roll 10 to a photosensitive body 1 during developing is detected by a current detecting circuit 17 and inputted to an arithmetic circuit 18 to calculate the operation time of the auger 13 for toner supply from a binary current value detected during self-diagnostic operation. The calculated operation time is outputted to a driving motor 13a and the auger 13 for toner supply rotates to supply toner which is as much as toner consumed during development to a developing device 4 newly. When a factor of variation in detected current value is generated, the current value originating from the transfer of toner from the developing roll 10 to the photosensitive body 1 during the development is detected and stored in the memory and then the self-diagnostic mode is reset automatically. Consequently, a copy with stable image density is obtained.

Description

[Detailed Description of the Invention] Industrial Application Field This invention detects the current value generated when toner particles are transferred to a photoreceptor (from the developing roll) during development, and controls the amount of toner replenishment according to the obtained current value. The present invention relates to an automatic video control method for a copying machine.

Conventional technology In conventional electronic copying machines that use a dry two-component developer, the toner in the developer is consumed during copying, so the amount of toner in the developer is detected in order to maintain the density of the copied image. If the amount exceeds the specified amount, it must be replenished.

Various methods have been proposed for detecting the amount of toner in a developer.

For example, a batch-like development area that forms another latent image is provided close to the photoconductor or development roll, and this development area is developed and the reflection density of that area is optically detected. (2) A method of controlling the amount of toner replenishment so that the reflection density is always a constant value, and a method of installing a detector that detects the magnetic permeability of the developer in the developing device, and detecting the magnetic permeability of the developer, and using the obtained detector to detect the permeability. Generally, a method is adopted in which the amount of toner replenishment is controlled so that the magnetic force is constant.

Another method is to detect changes in the surface potential of the photoreceptor, changes in the amount of light in the optical system, and the background density of copied paper, and control the amount of toner replenishment using the detected values in combination with the discharge current. It is used in high-end copying machines in the department.

Problems to be Solved by the Invention However, since the method described above does not detect the amount of toner actually consumed during the process, the amount of toner replenishment may be excessive or insufficient relative to the amount of toner consumed. However, there have been disadvantages in that highly accurate image density control cannot be obtained, and one detection means is complicated and expensive.

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

How to solve the problem: When the self-diagnosis mode is turned on, the latent image formed on the surface of the photoconductor is developed by a developing roll to which a developing bias is applied. The current generated when the toner is transferred is detected by a current detection circuit installed in the developing bias application circuit, and the upper and lower limits of the toner replenishment amount are stored in the memory in advance. Based on the lower limit value, the operation time of the toner supply auger is calculated from the newly detected current value, and the amount of toner commensurate with the amount of toner consumed during development is delivered to the developing device by the toner supply auger. An automatic image density control method for a copying machine in which copies with stable image density can be obtained at all times even if external factors affecting a detected current value change.

Embodiment One embodiment of the present invention will be described in detail with reference to the drawings.
The figure shows a copying machine that implements the method of the present invention, in which 1 is a photoreceptor, 2 is a charger that charges the surface of the photoreceptor 10, and 3 is a self-hock lens that forms an electrostatic latent image on the surface of the photoreceptor 10. An electrostatic latent image formed on the surface of the photoreceptor 1 showing an optical system such as the above is developed by the developing device 4 and transferred to the paper 6 fed by the paper feeding device (not shown) in the transfer device 50 section, The transferred paper 6 is sent to a fixing device (not shown) by a conveying means 7, and the toner image on the paper 6 is fixed on the surface of the paper 60, and the untransferred toner remaining on the surface of the photoreceptor 1 is removed by a cleaning device g. It is removed from the surface of the photoreceptor 1.

On the other hand, in the developing device 4, a developing roll 10 is provided in a housing 4cL close to the photoreceptor 1.

As shown in FIG. 2, the developing roll 10 has a sleeve job that rotates in the direction of the arrow around a magnetic roll 10α having magnetic poles arranged thereon. After the agent is trimmed by a trimmer 11 so that the spike height is constant, the agent reaches the photoreceptor 1 and develops an electrostatic latent image on the surface of the photoreceptor 1. Also, the housing 4α
Inside, the developer scraped off from the sleeve 10b is mixed with the developer stored in the housing 4α, and the developer is mixed with the newly replenished toner from the toner bottle 12 via the toner supply auger (3t). A mixing roll 14 for mixing the developer in the housing 4α is provided, and a pivot motor 1311 such as a stepping motor is connected to a toner supply auger 13 for replenishing the toner in the toner bottle 12 to the housing 4α. has been done.

Next, to explain the automatic image density control method using the developing device 4, when copying, when the main switch (not shown) on the main body of the copying machine is turned on, power is supplied to each part and at the same time the self-diagnosis mode is turned on. The self-diagnosis circuit starts operating.

Along with the operation of the self-diagnosis circuit, first the toner supply auger 1
3, turn on the copy start switch and start the copying operation. At this time, a chart with an image occupancy rate of Oqb is placed on the document table in advance, and this chart is subjected to duplication, and the current value at this time is stored in the memory.

Next, the method will be explained. A developing bias power supply 15 applies a developing bias to the developing roll 10 that develops the electrostatic latent image formed on the surface of the photoreceptor 1. A current detection circuit 17 is provided in the middle of the connecting line wr16, and detects the current value generated when toner is transferred from the developing roll 10 to the photoreceptor 1 during development. That is, photoreceptor 1 and developing roll 1
As shown in FIG. The toner is electrostatically attracted to the carrier and is filled with a developer consisting of toner and a material having a sufficiently insulating property. At this time, the toner and carrier, which have a certain charge due to triboelectric charging, are electrically balanced, but when they come into contact with the surface of the photoreceptor 10 on which the electrostatic latent image is formed, the 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 toner particles carry a charge corresponding to the developing roll 1
In order to replenish this waste, a current flows from the developing bias power supply 15 to the developing roll 10, and this current is detected by the current detection circuit 17.

Normally, the developing roll is OK when a 200'-500VID developing bias is applied, and there is sufficient electrical resistance between the optical path light body 1 and the developing roll 100 (usually Ho'10ρ or more).
The leakage current when a developing bias is applied is about 0.2 to 0.
Beyond this, the next value during development is g10-le JO, less photoreceptor I.
It is detected as the current value generated when the hetoner transfers.

This value is stored in the memory as the current value when the image occupancy rate is os.

Next, the chart on the document table is checked at tC.The current value detected by the above self-diagnosis is held in the memory until the next self-diagnosis vfr is performed, regardless of whether the main switch of the multi-zero is turned on or off.

Next, to explain the normal copying operation, when a document with an arbitrary image occupancy is placed on the document table and the copy start switch is turned on, the copying operation starts and the developing roll 1o is exposed to light during development. The current value generated by the transfer of body 1 hetoner is detected by the current detection circuit f7. This value is input to the arithmetic circuit 18, and the operating time of the toner supply auger 13 is calculated from the binary current value detected during the self-diagnosis.

That is, when the image occupancy rate of the original is 0 inches, the toner supply auger 13 is in a stopped state, and when the image occupancy rate is 15% (normally, the image occupancy rate of a document with a large image area is about 15 inches), the toner supply auger 13 is in a stopped state. Since the supplying auger 13 is stored with each current value as a full rotation, the operating time of the toner supplying auger 13 is calculated based on these current values.

The operating time calculated by the arithmetic circuit 1g is the driving motor 13.
The toner is output to α, the toner supply auger 13 is rotated, and the toner consumed during development is newly supplied to the developing device 4.

In addition, if there are factors that change the detected current value, such as deterioration of the photoreceptor 1 or developer, or if these are replaced with new ones, it is necessary to change the setting mode accordingly. and then turn on the copy start switch again. At this time, the toner supply auger 13 is fully rotated to supply toner to the developing device 4, and the current value generated when the toner is transferred from the developing roll 1° to the photoreceptor 1 during development is detected by the current detection circuit 17.
Nyo] is detected and stored in memory.

After that, self-diagnosis mode is automatically turned off.

In addition, when the above-mentioned effect is made into a t-70 chart, it is as shown in the range of FIG. 3.

It is also possible to increase or decrease the operating time of the toner supply auger 13 by inserting a coefficient into the relational expression of the arithmetic circuit 1g.

It should be noted that if the copying operation of the above-mentioned normal original is made into a flowchart, it will be in the range B in FIG.

Effects of the Invention As described in detail above, this invention stores the upper and lower limits of the toner replenisher using the self-diagnosis function, and thereafter controls the operation time of the toner supply auger according to these values. Even if the photoreceptor, developer, etc. deteriorate or are replaced, the amount of toner commensurate with the amount of toner consumed during development is always supplied to the developing device without being affected by these factors. This makes it possible to obtain copies with stable image density.

[Brief explanation of drawings]

(The drawings show one embodiment of the present invention) FIG. 1 is an overall configuration diagram, FIG. 2 is an explanatory diagram of a developing device and a control system for controlling it, and FIG. 3 is a flowchart showing the operation. 1 is a photoreceptor, 4 is a developing device, 10 is a developing roll, 13 is an auger for toner supply, 15 is a bias power source, and 17 is a current detection circuit.

Claims (1)

[Claims] When the self-diagnosis mode is turned on, the electrostatic latent image formed on the surface of the photoreceptor 1 is developed by the developing device 4 to which the bias power supply 15 is applied, and at this time, toner is transferred from the developing roll 10 to the photoreceptor 1. The current generated at this time is detected by the current detection circuit 17 provided in the developing bias application circuit, and the upper and lower limits of the amount of toner replenishment are stored in the memory in advance, and subsequent copies are based on the upper and lower limit values. The automatic copying machine is characterized in that the operating time of the toner supply auger 13 is calculated at the time of development, and the toner supply auger 13 supplies an amount of toner commensurate with the amount of toner consumed during development to the developing device 4. Image density control method.