JPH0425548B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a toner replenishment method for an electrostatic recording device that performs development using a developer consisting of toner and carrier.

When developing an electrostatic image using a developer consisting of toner and carrier in an electrostatic recording device such as an electrophotographic copying machine, the toner concentration in the developer does not have a significant effect on image quality, especially image density. As such, various toner replenishment methods have been proposed and implemented for replenishing toner in a developer material at a controlled rate.

The first example of such conventional toner replenishment methods is the method described in Japanese Patent Publication No. 16199/1983, which measures the density of a developed image and controls toner replenishment based on that information. . Since such a method controls toner replenishment so that the image density of the reference density piece is constant, it is advantageous in that it is direct in guaranteeing the recorded image density. However, the developed density does not depend only on the toner concentration of the developer, but is also influenced by the charging strength of the electrostatic image and fluctuations in the charging strength of the toner due to friction between the toner and the carrier. Therefore, for example, if the developing density decreases due to weak toner charge strength,
When toner is replenished by the toner replenishment method described above, toner is replenished excessively, increasing the toner concentration in the developer, and as a result, the toner is further charged due to friction between the toner and the carrier. As the toner becomes weaker, excessive toner replenishment continues, resulting in an abnormal increase in toner density, causing toner scattering from the developing device and resulting toner adhesion contamination, resulting in a decrease in the clarity of recorded images. Such problems tend to occur when zinc stearate or the like is used as an additive in the toner.

On the other hand, a method is also known in which the toner concentration in the developer is determined by measuring the magnetic permeability and color density of the developer, and the toner is replenished so that the toner concentration is constant. However, although such a method is a direct method for maintaining toner concentration,
It is only an indirect guarantee that the developed density and the recorded image density, which is closely related to it, will be constant, and measuring the toner density is not only troublesome but also difficult to obtain stable and accurate information. There are also the problems mentioned above.

The present invention has been made in order to provide a toner replenishment method that prevents the toner concentration of the developer from increasing abnormally by a simple means. Toner replenishment for an electrostatic recording device that performs development using a developer, measures the developed density of a reference piece for each recording process, and replenishes a predetermined amount of toner to the developer when the density is light. In the method, if the light continues for a predetermined number of times or more of recording processes, toner replenishment is suppressed or stopped for the number of recording processes exceeding the predetermined number of times, and when the suppression or stop reaches another predetermined number of times of recording processes, the subsequent operation is performed. In the recording process, the predetermined amount of toner is replenished until the predetermined number of times is reached again, and this feature prevents abnormal increases and decreases in the toner concentration in the developer.

Hereinafter, the present invention will be explained based on the drawings.

FIG. 1 is a block circuit diagram of an apparatus implementing the method of the present invention, and FIG. 2 is a flowchart showing a toner replenishment control routine in which one cycle is performed by the CPU of FIG. 1 in one recording process. .

In FIG. 1, 1 is a photoreceptor, and 2 is a developing device. On the surface of the photoreceptor 1, an electrostatic image of an original image and a patch, that is, an image of a reference piece, is formed. The toner is then developed. The developed density of the patch, that is, the patch density, is detected by a toner density sensor made of a photocoupler.
This is input to the CPU as patch density information. The CPU then stops or drives the toner replenishment unit depending on whether the patch density is dark or light. The above is the same as the conventional method of controlling toner replenishment according to the developer density. In addition, the CPU also performs control to prevent the toner density from becoming abnormally high when the toner replenishment unit is driven in response to information about low patch density. Control is also performed to prevent the toner concentration from becoming too low. The above control operation of the CPU will be explained with reference to FIG.

In FIG. 2, the state in which the CPU performs control based on patch density information is the state in which FLAG is 0.
When the recording process is performed in this state, the patch density is detected by the toner density sensor, and when the patch density is high, the toner replenishment unit is not driven.
The counter is reset to i=0 and the toner image of the original image is recorded on the transfer paper. Similarly, in the next repeated printing process, if the patch density is high, printing is repeated without driving the toner replenishment unit, so the toner density of the developer gradually decreases, and eventually the patch density becomes light. It becomes like this. When the patch density becomes light, the counter will display i+1 or i+2 depending on whether the transfer paper size is A4 or 3.
The toner replenishment unit is then driven to perform recording. If the patch density is similarly light in the next repeated recording process,
Add i+1 or i+2 to the counter each time,
Recording is performed by driving the toner supply unit. During recording while driving the toner replenishment unit, the toner concentration of the developer gradually increases. Therefore, when electrostatic image formation and toner development are performed with the recording device in a normal state, the patch density will increase until the counter reaches i = 24, thereby increasing the patch density. Toner supply control is performed according to the normal patch density.

However, an abnormal state in which the patch density does not increase even if the toner density of the developer increases may occur due to deterioration of the photoreceptor 1, changes in atmospheric conditions, or the like. In this case, if toner replenishment control is continued in accordance with the patch density, the toner density of the developer will abnormally increase, causing problems such as toner scattering. In order to prevent this, even if the patch density is light, when the counter reaches i = 24, the toner replenishment unit is not driven, the counter is reset to i = 0, FLAG is set to 1, and from then on FLAG is 0
Until then, recording is performed without driving the toner supply unit.

That is, when the recording process is performed with FLAG set to 1, either i+1 or i+2 is added to the counter depending on whether the transfer paper size is A4 or A3, and recording is performed without driving the toner supply unit. The recording process in this state is repeated until the counter i
=96, then FLAG is set to 0 and the counter is reset to i=0. Therefore, in the subsequent recording process, toner replenishment control will be performed again with FLAG set to 0. In addition, i of the count to change FLAG from 1 to 0
=96 is determined based on the relationship between the amount of toner replenishment and the amount of toner consumed in one recording process, and in the example where i = 24 is set as a count that is determined within a range where the toner concentration of the developer does not become abnormally high, the amount of toner replenishment is This shows that the ratio of toner consumption and toner consumption is close to 4:1. If the conditions for returning FLAG to 0 are determined in this way, there is no risk that the development density will decrease due to a decrease in the toner concentration of the developer. Furthermore, the contents of FLAG, counter contents, etc. are stored in the memory shown in Figure 1, and the memory is retained by the memory backup power supply even if the recording device is stopped, so intermittent operation of the recording device is not possible. Also, the above-described toner supply control is performed without any problem.

As described above, according to the method of the present invention, even if the relationship between the toner concentration of the developer and the developer concentration becomes abnormal, the toner concentration of the developer can be easily prevented from increasing abnormally, and An excellent effect can be obtained in that an abnormal decrease in concentration can also be prevented. In the present invention, the toner replenishment ratio may be changed.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram of an apparatus implementing the method of the present invention, and FIG. 2 is a flowchart showing a toner replenishment control routine in which one cycle is performed by the CPU of FIG. 1 in one recording process. . 1...Photoreceptor, 2...Developing device.

Claims (1)

[Claims] 1. Developing using a developer consisting of toner and carrier, measuring the developed density of the reference piece for each recording process, and replenishing the developer with a predetermined amount of toner when the density is low. In the toner replenishment method for an electrostatic recording device, when the light color continues for a predetermined number of recording processes or more, toner replenishment is suppressed or stopped in the recording process for the predetermined number of times or more, and the suppression or stop is applied to other predetermined recordings. 1. A toner replenishment method for an electrostatic recording apparatus, characterized in that, when the number of processes is reached, the toner replenishment of the predetermined amount is repeated in subsequent recording processes until the predetermined number of times is reached again.