JPH0511630B2 - - Google Patents

Description

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

Conventional technology In electronic copying machines that conventionally 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 keep the density of the copied image constant. If the amount is less than the specified amount, it will be necessary to replenish it.

Furthermore, various methods have been proposed for detecting the amount of toner in the developer.

For example, a patch-like development area that forms another latent image is provided close to the photoreceptor or development roll, and this development area is developed and the reflection density of that area is optically detected. There is a method of controlling the amount of toner replenishment so that the reflection density is always a constant value, and a method of detecting the magnetic permeability of the developer by installing a detector inside the developer to detect the magnetic permeability. Generally, a method is adopted in which the amount of toner replenishment is controlled to be 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 none of the above methods detects the amount of toner actually consumed during development, the amount of toner replenishment may be excessive or insufficient relative to the amount of toner consumed, resulting in poor accuracy. In addition, there were problems in that high image density control could not be obtained, and the detection means was complicated and expensive.

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

Method for solving the problem In self-diagnosis mode, a chart with a known image occupancy is placed on the document table, and the electrostatic latent image on the surface of the photoreceptor based on this chart is generated by applying a bias power supply. Development is carried out by the developing roll with applied voltage, and at this time, the current generated when the toner in the developer is transferred from the developing roll to the electrostatic latent image on the photoreceptor is detected by a current detection circuit provided in the developing bias application circuit. Therefore, when copying a chart with a high image occupancy rate and a chart with a low image occupancy rate, the values of the current flowing through the current detection circuit are obtained, these values are stored in memory, and the electrostatic potential is When an image is developed with a developing roll to which a developing bias power is applied, the current generated when the toner in the developer is transferred from the developing roll to the electrostatic latent image on the photoreceptor is
Detected by a current detection circuit provided in the developing bias application circuit, the detected current value and the toner supply auger 13 set in advance for both charts are calculated.
An automatic image density control method for a copying machine in which the operation time of a toner supply auger is calculated from the operation time of the toner supply auger, and an amount of toner commensurate with the amount of toner consumed during development is supplied to a developing device by the toner supply auger. .

Embodiment An embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a copying machine in which the method of the present invention is implemented. Reference numeral 3 indicates an optical system such as a self-cleaning lens that forms an electrostatic latent image on the surface of the photoreceptor 1. The electrostatic latent image formed on the surface of the photoreceptor 1 is developed by the developing device 4, and then transferred to a paper 6 fed by a paper feeding device (not shown) in the transfer device 5, and the transferred paper 6 is The toner image on the paper 6 is sent to a fixing device (not shown) by the conveying means 7 and fixed on the surface of the paper 6, and the untransferred toner remaining on the surface of the photoreceptor 1 is removed by the cleaning device 8. removed.

On the other hand, the developing device 4 has a photoreceptor 1 inside the housing 4a.
A developing roll 10 is provided adjacent to. As shown in FIG. 2, the developing roll 10 has a structure in which a sleeve 10b that rotates in the direction of the arrow is provided around a magnetic roll 10a in which magnetic poles are arranged. The agent is trimmed by a trimming bar 11 so that the spike height is constant, and then the photoreceptor 1
, and the electrostatic latent image on the surface of the photoreceptor 1 is developed. Further, the developer scraped off from the sleeve 10b is mixed with the developer stored in the housing 4a, and the housing 4a is newly replenished from the toner bottle 12 via the toner supply auger 13. A mixing roll 14 is provided for mixing the toner and the developer in the housing 4a, and a toner bottle 12 is provided.
A drive motor 13a such as a stepping motor is connected to a toner supply auger 13 for replenishing the toner inside the housing 4a.

Next, to explain the automatic image density control method using the developing device 4, when copying, when the main switch (not shown) 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. Then the self-diagnosis circuit starts operating.

In conjunction with the operation of the self-diagnosis circuit, first, the copying start switch is turned on with the toner supply auger 13 not operating to start the copying operation. At this time, a chart with an image occupancy rate of 0% is placed on the document table in advance, and this chart is copied, and the current value at this time is stored in the memory.

Next, the method will be explained. A developing bias power source 15 applies a developing bias to the developing roll 10 that develops the electrostatic latent image formed on the surface of the photoreceptor 1. There is a power supply detection circuit 1 in the middle of the line 16 to be connected.
7 is provided to detect the current value generated when toner is transferred from the developing roll 10 to the photoreceptor 1 during development. That is, the photoreceptor 1 and the developing roll 10
As shown in Figure 2, there is usually a gap of about 1.0 to 1.5 mm between the carriers, and during development, this gap is caused by electrostatic charge on the carrier due to frictional electrification between the carrier and the carrier, which has sufficient insulation. The area is filled with a developer consisting of toner which has been adsorbed and has sufficient insulating properties. At this time, the toner and the carrier, which have a certain charge due to frictional charging, are electrically balanced, but when they come into contact with the surface of the photoreceptor 1 on which the electrostatic latent image is formed, the electrostatic latent image has Toner in the developer is transferred to the photoreceptor 1 side in an amount corresponding to the amount of charge. As a result, the charge that the toner particles had,
The charge disappears from the top of the developing roll 10, and in order to replenish it, the developing roll 1 is supplied from the developing bias power supply 15.
0, and this current is detected by the current detection circuit 17.

Usually, a developing bias of 200 to 500 V is applied to the developing roll 10, and the contact between the photoreceptor 1 and the developing roll 10 is made by a developer having sufficient electrical resistance (usually ^{109 to} 10 Ω or more). Therefore, the leakage current when the developing bias is applied is about 0.2 to 0.05 μA, and the value exceeding this is the phenomenon roll 10 during development.
It is detected as a current value generated when toner is transferred to the photoreceptor 1. This value is stored in the memory as the current value when the image occupancy rate is 0%.

Next, a chart with an occupancy rate of 15% is placed on the document table, this chart is copied, and the current value at this time is stored in the memory.

The current values detected by these self-diagnosis are held in the memory until the next self-diagnosis is performed, regardless of whether the main switch of the copying machine 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 is started and the photoreceptor is moved from the developing roll 10 during development. The current value generated by the transfer of the toner to the toner 1 is detected by the current detection circuit 17. 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.

In other words, when the image occupancy rate of the original is 0%, the toner supply auger 13 is in a stopped state, and the image occupancy rate is 0%.
15% (normally, the image occupancy rate of a document with a large image area is about 15%), the toner supply auger 13 is assumed to rotate at full speed, and the respective current values are stored, so based on these current values, The operation time of the toner supply auger 13 is calculated.

The operating time calculated by the arithmetic circuit 18 is output to the drive motor 13a, and the toner supply auger 1
3 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, the setting mode can be changed accordingly to achieve a chart with an image occupancy of 15%. 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 10 to the photoreceptor 1 during development is detected by the current detection circuit 17. Detected and stored in memory.

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

The above action is shown in a flowchart as shown in range A in FIG.

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 18.

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, the present invention uses a self-diagnosis function to memorize the current flowing through the current detection circuit when copying a chart with a high image occupancy rate and a chart with a low image occupancy rate, and subsequently stores these values. Since the operation time of the toner supply auger is controlled accordingly, even if the photoconductor or developer deteriorates or is replaced, toner is always consumed during development without being affected. An amount of toner commensurate with the amount of toner is supplied to the developing device, and copies with stable image density can be obtained.

[Brief explanation of the drawing]

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] 1. In the self-diagnosis mode, a chart with a known image occupancy rate is placed on the document table, and an electrostatic latent image on the surface of the photoreceptor 1 based on this chart is developed by the developing roll 10 to which a bias power is applied. By detecting the current generated when the toner in the developer is transferred from the developing roll 10 to the electrostatic latent image on the photoconductor during development using a current detection circuit provided in the development bias application circuit, a high When copying a chart with a high image occupancy rate and a chart with a low image occupancy rate, the values of the current flowing through the current detection circuit are obtained, and these values are stored in the memory, and the electrostatic latent image is developed in subsequent normal copying. When developing with a developing roll to which bias power is applied, a current detection circuit provided in the developing bias application circuit detects the current generated when the toner in the developer is transferred from the developing roll to the electrostatic latent image on the photoreceptor. Then, the operation time of the toner supply auger 13 is calculated from this detected current value and the operation time of the toner supply auger 13 set in advance for both charts, and the operation time is calculated to match the amount of toner consumed during development. An automatic image density control method for a copying machine, characterized in that the amount of toner is supplied to the developing device 4 by the toner supplying auger 13.