JPH0333883A - image forming device - Google Patents

Abstract

PURPOSE:To suppress fogging due to triboelectric charge between an erasing member and a recording medium by controlling bias voltage impressed on the erasing member responding to reflected density of the recording medium. CONSTITUTION:A recording electrode 4, a means which feeds developer to a recording electrode 4, the recording medium 5 which travels in the vicinity of the recording electrode 4, the erasing member 8 which is in contact with the recording medium 5, and a detecting means 15 which detects the reflected density of the recording medium 5 are provided. Then, the voltage impressed for eliminating the developer to the erasing member 8 is controlled responding to the reflected density detected by the detecting means 15. That is, the fogging generated due to electrical charge generated at the erasing member 8 is detected, and the bias voltage impressed on the erasing member 8 is controlled responding to that. Thus, a clear recording image with little fogging due to remaining electrical charge generated in the recording medium 5 can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming apparatus that forms an image by depositing a developer on a recording medium.

[Conventional technology]

As an image forming method for attaching a developer to a recording medium, there is a method known from Japanese Patent Publication No. 51-46707 and the like. In this method, as shown in FIG. 2, conductive magnetic toner 1 is transported 1 over a non-magnetic cylinder 3 by a rotating magnet 2 and passed over a recording electrode 4 made of a magnetic material. Then, a voltage is applied between the conductive layer 7 of the recording medium 5 having the insulating layer 6 on the surface thereof and the recording electrode 4 to cause the toner 1 to adhere to the recording medium 5 to form an image.

FIG. 3 shows an overall configuration diagram of a display device using such an image forming method. 1 is a conductive magnetic toner, 4 is a recording electrode, 5 is a recording member formed in the shape of an endless belt (hereinafter referred to as a recording belt), 8 is an erasing member, 10 is a toner container, 11 is a recording belt support roller, and 12 is a main body. The frame 13 is a recording control section.

In the above configuration, an image is formed by toner 1 being attached or not attached to the recording belt 5 depending on the signal voltage from the recording electrode. For example, the signal voltage from the recording control unit l3 is 4
When 0V is applied, the toner 1 adheres to the recording belt 5 due to static electricity, and when OV is applied, it does not adhere, thereby forming an image. After an image is formed with the toner 1, the recording belt support roller 11 is driven by a motor (not shown), and the recording belt 5 is conveyed in the direction of the arrow to display the image, a toner is formed using conductive carbon fiber, conductive resin, conductive rubber, etc. By the erasing member 8, static electricity is removed from the recording belt 5 and the toner 1 is mechanically stripped off, and the toner 1 falls into the toner container 10 by its own weight, and is again prepared for the next recording. still,
A certain voltage V is applied to the erasing member 8 . This voltage is determined by the triboelectric charging characteristics of the materials of the recording member 5 and the erasing member 8. Conventionally, when the recording member 5 was made of titanium oxide and the erasing member was made of carbon fiber, the printing characteristics changed when -3V was applied.
That is, an image with less fog was obtained.

FIG. 4 shows the vicinity of the erasing member 8 mentioned above. In this figure, a recording medium 5 composed of an insulating layer 6 and a conductive layer 7 is conveyed from above to below (indicated by a pronation arrow) by a driving means (not shown). Since the toner 1 electrostatically adhered to the recording medium 5 by the recording electrode 4 is biased from the erasing member 8 to the battery 14, the positive static charge on the insulating layer 6 is eliminated. Toner 1 that is electrostatically attached
The particles tend to fall off and are further removed by the brush 8a made of conductive carbon fiber. However, as is clear from the figure, even if the recording medium 5 passes through the erasing member 8,
Toner often remained behind.

[Problem that the invention is trying to solve]

However, in the above conventional example, in the erasing member 8,
There was a further drawback in that the toner 1 was scraped off and collected by rubbing against the recording member 5'.

(1) When the erasing member and the recording member rub against each other, an electric charge is generated on the recording member due to frictional charging, and when the recording member passes through the toner container, the toner is attracted by this electric charge, and the surface of the recording member becomes dirty, causing fogging. Occur. Since this fog is caused by friction, it has the disadvantage that it is greatly affected by relative humidity. FIG. 5 shows the relationship between the bias voltage and relative humidity at 25° C. that does not cause fogging. However, when the temperature is further changed, fogging occurs again as shown in FIG. 6, which is a drawback.

(2) As explained above, since toner is collected and reused, foreign matter other than toner may get mixed in with the toner during repeated use, or foreign matter may get mixed into the toner when the recording member reaches the end of its lifespan. However, there was a problem in that the characteristics of the toner changed and the state of fogging changed.

[Means to solve the problem]

The present invention controls the optimum bias voltage to be applied to the erasing member according to the reflection density of the recording medium, thereby suppressing fogging due to frictional charges caused by rubbing between the erasing member and the recording medium. I can do it. Furthermore, fogging is eliminated even when the recording member and the erasing member deteriorate due to their lifetimes, and the characteristics deteriorate due to the contamination of toner with foreign matter, and clear recorded images can be obtained.

〔Example〕

Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1-a shows a sectional view of an image display device to which the present invention can be applied. Numbers of parts previously described in the drawings have the same number. 15 is a concentration sensor which is a main component of the present invention, 16 is a bias control circuit, and 17 is a cable connecting the output of the bias control circuit F and the erasing means 8. A cable 18 connects the concentration sensor 15 and the bias control circuit 16. Reference numeral 19 denotes a control line that transmits a signal generated by a timing generation circuit (not shown).

The concentration sensor 15 is explained in detail in FIG. 1-b. 1
5-1 is a light emitting source, and an LED is used. 15
-2 is the power supply for lighting the LED 15-1, and 15-3 is the power supply for lighting the LED 15-1 so that the LED 15-1 is in the optimal lighting state.
This is a resistor that limits the current flowing through 1. 15-4 is 15
The amount of light emitted from the LED -1 reaches the recording medium 5. Reference numeral 15-5 indicates the amount of light reflected from the recording medium 5, which is the amount of emitted light 15-4.

15-6 is a phototransistor for converting the amount of reflected light 15-5 into electricity, and 15-7 is a resistor for converting the current flowing through the phototransistor 15-5 into voltage. 15-8 is an operational amplifier that amplifies the voltage generated by the resistor 15-7. 18 is a cable that connects the output voltage of the density sensor 15 to the bias control circuit 16; when there is a lot of fog on the recording medium 5, the bias control circuit 16
The output voltage is low, and when there is little fog, the voltage output is high.

A detailed block diagram of the bias control circuit 16 is shown in FIG. 1-c. 16-1 in the figure is an analog-to-digital converter (hereinafter referred to as A/D converter), and the concentration sensor 15
It converts the output voltage from the converter into a digital value. 16
-2 is a control circuit (CPC), which is a computer that performs operations according to the flowchart described in the next section. 16
-3 is a memory, which stores calculations performed on the flowchart. 16-4 is a digital-to-analog converter (hereinafter referred to as a D/A converter), which converts the hexadecimal value calculated by the CPU 16-2 into an analog voltage.

FIG. 11-d shows an operation flowchart of the microcomputer 16-2. According to this chart, 1-c
The operation of the bias control circuit 16 shown in the figure will be explained.

This operation is started when a recording medium drive device (not shown) is operating, that is, when a signal indicating that the recording medium 5 is moving is input from the control line 19. From the control line 19,
When the signal is input, the microcomputer 16-2 issues a command to the D/A converter 16-4 to lower the bias voltage below the voltage -3V mentioned in the conventional example. After a certain period of time, that is, when the recording medium 5 to which the above voltage has been applied to the erasing member 8 reaches the density sensor 15, the microcomputer 16-2 outputs the density voltage through the A/D converter 16-1. take in. Here, the microcomputer 16-2 operates to lower the bias potential to a certain value, that is, until fogging by the erasing member 8 occurs.

The microcomputer 16-2 stores in the memory 16-3 the bias potential at the time when fog reaches a certain value, that is, the voltage Vl applied to the erasing member 8.

Next, the microcomputer 16-2 increases the bias voltage through the D/A converter 16-4. Then, the same operation is repeated until the above-mentioned certain fog density is reached. Then, the bias potential at the time when the fog density becomes the same is stored in the memory 16-3 as 2. After that, the microcomputer 16-2 performs ■,
and V.

is read from the memory 16-3 and the following calculation is performed.

V='A (V'+ +Vs) Using V obtained by this calculation as a bias potential, the D/A converter 1
6-4 is applied by the erasing means 8.

Figures 1-e and 1-b show the relationship between bias voltage and time when the flowchart shown in Figure 1-d is operated.

In Fig. 1-e, the bias voltage is concentrated around ○V. This indicates that less charge is generated in the recording member 5 and the erasing member 8.

In FIG. ib, the initial bias potential is lower than -3V. This indicates that a lower bias potential is required because there are many positive charges generated in the erasing member 8.

[Other Examples]

As a second embodiment, FIG. 1-g shows a flowchart using the bias control section 16 shown in FIG. 1-c.

This will be explained using diagrams.

The operation of this flowchart is based on the premise that the recording medium 5 is being moved by a drive circuit (not shown).

When the recording medium 5 is moving, this flowchart is activated. When activated, the bias potential of the erasing member 8 is set to -3.
Set to v. Here, the fog density is detected through the density sensor 15, and if the degree of fog is within the standard, the operation is the same as in the conventional example. If it is outside the standard, it waits for a signal to come from a control line 19 (not shown). This signal is a timing signal for absorbing the positional error between the erasing member 8 and the density sensor 15. When a control signal is input,
The microcomputer 16-2 checks a flag to be described later, and if there is no flag, lowers the bias potential by a certain value. Then, the fog is sampled again and it is determined whether the fog is within the standard. If it is within the standard, the flag is reset and this flowchart ends. If it is outside the standard, a flag is set if it is larger than the previous fog, and if it is smaller, the flag is not set and a control command is waited for. When a control command is input, the flag is checked again. If there is a flag, reverse the bias change direction, that is, increase the bias and check for fog. Repeat the steps mentioned above. Adjust the bias to within the Capri standard.

FIG. 1-b shows the relationship between fog density and time when this flowchart is operated.

〔Effect of the invention〕

As described above, according to the present invention, the residual charge generated on the recording medium is detected by using the erasing member to detect fog caused by the generated charge, and to control the bias voltage to be applied to the erasing member accordingly. A clear recorded image with less fog can be obtained.

The present invention is not limited to the display device described above, but is also applicable to image forming devices such as printers and copying machines that use image forming and developing as shown in FIG. 2 above.

[Brief explanation of drawings]

Fig. 1-a is a cross-sectional view of the image forming apparatus according to the present invention, Fig. 1-b is a detailed view of the density sensor, Fig. 1-c is a detailed view of the control section, and Fig. 1-d is a first embodiment. Flowchart of 1-e
The figure is a relationship diagram between bias voltage and time, Figure 1-f is a relationship diagram between other biases and time, Figure 1-g is a flowchart of the second embodiment, and Figure 1-h is a diagram of the second embodiment. Figure 2 is a diagram explaining the recording principle, Figure 3 is a cross-sectional view of a conventional image forming apparatus, and Figure 4 is a diagram of the charge distribution when fog occurs. Figure 5 shows the relationship between bias voltage and relative humidity to reduce fog, and Figure 6 shows the relationship between fog and temperature when the bias characteristics shown in Figure 5 are given. In the figure, 1 is toner, 2 is a rotating magnet, 3 is a non-magnetic cylinder, 4 is a recording electrode, 5 is a recording medium, 6 is an insulating layer, 7 is a conductive layer, 8 is an erasing member, 13 is a recording control unit, 15 1 is a concentration sensor, and 16 is a bar bias control section.

Claims (2)

[Claims] (1) a large number of recording electrodes, means for supplying developer to the recording electrodes, a recording medium that moves relatively close to the recording electrodes, and an erasing member made of a soft material that comes into contact with the recording medium; An image forming apparatus having a detection means for detecting a reflection density of a recording medium, the image forming apparatus comprising: controlling a voltage applied to the erasing member for developer removal according to the reflection density detected by the detection means; Features of the image forming device. (2) The image forming apparatus according to claim 1, wherein the detection means detects the reflection density of a non-printing area of the recording medium.