JPS62144184A - Picture density adjusting device for electrostatic recording device - Google Patents

Abstract

PURPOSE:To obtain a stable density picture without fail by detecting the density of a picture formed on a recording paper after picture development so as to control the makeup of an concentrated solution supplied to liquid toner. CONSTITUTION:A density detector 12 such as an optical sensor is installed the back of a developing unit 5 at a position where a developed detection patch 4 can be detected, and the picture density of the detection patch 4 after development is detected. After a density signal detected by the density detector 12 is A/D-converted by an A/D converter circuit 13, it is inputted to a density control circuit 14, in which a reference value is preset. If the picture density detected by the density detector 12 is lower than the reference value, a signal is transmitted to a drive circuit 15 to open a solenoid valve 9. Thus a pump 6 supplies the concentrated solution in a makeup tank 10 to the developing unit 5 together with the liquid toner in a tank 8.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an image density adjusting device for an electrostatic recording device that adjusts the density of liquid toner by detecting image density from a developed image.

BACKGROUND OF THE INVENTION Conventional wet-type electrostatic recording devices form an electrostatic latent image on recording paper using a recording head into which data is input from a computer, etc., and develop this electrostatic latent image with a developer using liquid toner. are doing.

In addition, in order to stabilize the image density after development, the density of the liquid toner is detected by a transmissive optical sensor, and if the density drops below a preset value, the liquid toner is replenished with concentrated liquid and the liquid toner is constantly maintained. The concentration is adjusted to be constant.

Problems to be Solved by the Invention" However, the conventional image density adjustment device described above detects the concentration of liquid toner, which is easily affected by the environment, especially humidity, temperature, changes over time, etc., and adjusts the concentration of liquid toner according to the obtained value. Since the density of the liquid toner is adjusted, even if the density of the liquid toner is always maintained constant, the image density after development varies and a stable image density cannot be obtained.

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

Means and operation for solving the problem, in which an electrostatic latent image formed on a recording paper by a recording head and a back electrode is developed into a visible image by a developing device using liquid toner, which is formed on the recording paper. By detecting the density of the developed image and controlling the amount of concentrated liquid supplied to the liquid toner based on the detected value,
An image density adjustment device for an electrostatic recording device that allows images with constant density to be obtained at all times.

Embodiment' An embodiment of the present invention will be described in detail with reference to the drawings. In the figure, 1 is a recording paper that is intermittently fed in the direction of the arrow by a drive means such as a drive roll (not shown), and 2 is a recording paper that is inputted from a computer or the like. A recording head 3 records data as an electrostatic latent image on the recording paper 1, and reference numeral 3 indicates a back electrode provided at a position facing the recording head 2 with the recording paper 1 sandwiched therebetween. Further, when an electrostatic latent image is formed on the recording paper 1 by the recording head 2, a detection patch 4 is formed on the non-image area of the recording paper 1, for example, on the side edge of the recording paper 1 as shown in FIG. It looks like this.

The electrostatic latent image and detection patch formed on the recording paper 1 by the recording head 2 are sent to the developing device 5, where they are developed into a visible image using liquid toner.

The surface of the developing device 5 that comes into contact with the recording paper 1 is sloped lower in the feeding direction of the recording paper 1, and between this inclined surface 5α and the recording paper 1, liquid toner is pumped by a pump 6 through a conduit 7. is ejected from the ejection port 5b, so that the electrostatic latent image on the recording paper and the detection patch 4 are simultaneously developed.

A suction side of a pump 6 that supplies liquid toner to the developing device 5 is connected to a tank 8 containing liquid toner and a replenishment tank 10 containing concentrated liquid via a solenoid valve 9, respectively.

Further, the liquid toner that has been developed is dropped into a recess 5C provided at the bottom of the inclined surface 5α, and is then collected into the tank 8 through the conduit 11.

On the other hand, a density detector 12 such as an optical sensor is provided behind the developing device 5 at a position where the developed detection patch 4 can be detected, and is configured to detect the image density of the detection patch 4 after development. ing. The concentration signal detected by the concentration detector] 2 is A/D converted by an A/D conversion circuit 13 and then input to a concentration control circuit 14. A reference value is set in advance in the density side #circuit 14, and when the image density detected by the density detector 12 is lower than the reference value,
A signal is sent to the drive circuit 15, and the drive circuit 15 opens the solenoid valve 9.

As a result, the pump 6 supplies the liquid toner in the tank 8 and the concentrated liquid in the supply tank 10 to the developing device 5, and the electromagnetic valve 9 is opened for a preset time and then closed. Further, as shown in FIG. 2, the detection patch 4 is formed every one or several images formed on the recording paper 1, and the density detector 12 detects the density of the detection patch 4 each time. The above operation is repeated until the concentration reaches the reference value.

This allows the concentration of the liquid toner to be adjusted so that the image quality obtained after development is constant.

On the other hand, FIGS. 3 and 4 show another embodiment, which will be explained next.

FIG. 3 shows a configuration in which a means for notifying the time to replace the liquid toner is added to the above embodiment, and a transmission type optical sensor 1B is installed in the middle of the circulation path connecting between the pump 6 and the electromagnetic valve 9.
is provided to detect the concentration of liquid toner flowing within the circulation path 17. The detection value detected by the optical sensor 18 is subjected to Φ conversion by the A/D conversion circuit +9v-, and then inputted to the density control circuit 14 as a density signal VJ, and the reference density V set in advance in the density control circuit 14 is inputted to the density control circuit 14.
It is compared with o. When the detected concentration signal N'J becomes equal to or exceeds the reference concentration signal Vo, a signal is output to the display 21 provided on the operation panel 20 to warn that the liquid toner should be replaced. It looks like this.

This makes it easy to know when to replace liquid toner, which is easily affected by environmental changes and changes over time, so you can avoid using liquid toner that has reached the end of its lifespan by incorrectly replacing it, or replacing liquid toner that has reached the end of its lifespan. Problems such as problems that occur can be resolved.

On the other hand, FIG. 4 shows the first embodiment, in which the concentration of liquid toner is detected and when this concentration exceeds a set value, a solenoid valve 9
Another embodiment is provided with means for closing the circulation circuit 1 and means for controlling the voltage applied to the recording head 2 and the back electrode 3.
The density signal detected by the transmission type optical sensor 23 provided at 7 is A/D converted by an A/D conversion circuit 24, and then inputted to the density control circuit 14 and compared with a reference density. When the reference concentration is reached, a signal is output to the drive circuit 15 of the solenoid valve 9 to close the solenoid valve 9, and the voltage applied to the recording head 2 and the back electrode 3 is controlled via the IIX control circuits 26 and 27. A control signal is output to the device 25 to control it so that the applied voltage becomes high.

As a result, if the liquid toner deteriorates due to environmental changes or changes over time, and the concentration of the liquid toner does not increase even after replenishing the concentrated liquid, increase the voltage applied to the recording head 2 and the back electrode 3 to increase the image density. This prevents a decrease in the density of the image, allowing images with stable density to be obtained. Furthermore, by increasing the applied voltage, it is possible to extend the life of liquid toner that has already reached the end of its life, which is economical.

Effects of the Invention As detailed above, the present invention detects the density of the image formed on the recording paper after development and controls the amount of concentrated liquid supplied to the liquid toner. Compared to devices that detect the density of liquid toner, this method is not affected by the product term of liquid toner or changes over time, so images with stable density can always be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of the present invention, FIG. 2 is an explanatory diagram of an image formed on recording paper, and FIGS. 3 and 4 are explanatory diagrams showing other embodiments. 1 is recording paper, 2 is a recording head, 3 is a back electrode, and 5 is a developing device.

Claims (1)

[Claims] An image formed on the recording paper 1 in which an electrostatic latent image formed on the recording paper 1 by the recording head 2 and the back electrode 3 is developed into a visible image by the developer 5 using liquid toner. An image density adjustment device for an electrostatic recording device, which detects the density after development and controls the amount of concentrated liquid supplied to the liquid toner based on the detected value.