JPH10282741A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of always obtaining a high-quality image by preventing image flowing from occurring. SOLUTION: In this image forming device, one-component toner 6 is held on the surface of the developing sleeve (developer carrier) of a developing device 5 so as to develop a latent image on a photoreceptor drum (image carrier) 3. In such a case, by providing a fogging mode for setting such a developing condition that fogging easily occurs and line width is not changed, a mode is automatically or manually shifted from an ordinary mode to the fogging mode in circumstances that the image flowing easily occurs. Since the mode is automatically or manually shifted from the ordinary mode to the fogging mode (mode for setting the developing condition that the fogging easily occurs) in the circumstances that the image flowing easily occurs, the image flowing is prevented from occurring even in the case of using paper containing a large amount of talc under high humidity environment. Even if the image flowing occurs, it is quickly prevented and the high-quality image is always and stably obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a laser beam printer and a copying machine.

[0002]

2. Description of the Related Art In an image forming apparatus such as a laser beam printer or a copying machine, an organic photoconductor (OP) is used as a photoconductor.
C) and amorphous silicon (A-Si) are often used, and organic photoconductors (OPCs) are mostly used recently. In addition, as a developing method, a one-component developing method is often used because of its simple configuration and good image quality.

[0003]

However, in the one-component developing method, the power for cleaning the surface of the photosensitive drum is weaker than in the two-component developing method, so that a phenomenon called "image deletion" is likely to occur. It has been known that this phenomenon of "image deletion" occurs when a low-resistance substance adheres to the surface of the photoreceptor, causing the latent image to collapse.

Accordingly, there are two conditions under which this "image deletion" is likely to occur, and it is likely to occur when these two conditions overlap. The two conditions are that one is a humid environment and the other is the use of talc-rich paper.

In a high-humidity environment, moisture in the air tends to adhere to dirt on the photoreceptor, so that image deletion easily occurs in a high-humidity environment. Also, when a paper containing a large amount of talc is used, talc in the paper adheres to the photoconductor. Talc has deliquescence, easily absorbs moisture in the air, and tends to cause image deletion due to low resistance. It should be noted that talc has a flat crystal structure, and does not easily peel off when attached to the photoreceptor surface.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus which can always obtain a high quality image while preventing occurrence of image deletion.

[0007]

In order to achieve the above object, the present invention is directed to an image forming apparatus for developing a latent image on an image carrier by holding a one-component toner on a surface of a developer carrier. The apparatus is provided with a fogging mode for setting development conditions in which fogging is likely to occur and the line width is not changed, and the mode is automatically or manually shifted from the normal mode to the fogging mode in a situation where image deletion is likely to occur. It is characterized by the following.

According to a second aspect of the present invention, in the first aspect of the present invention, (primary charging potential)-(development bias voltage) is set to be small as a developing condition in which fog is likely to occur.
(Development bias voltage)-(exposure potential) is reduced.

According to a third aspect of the present invention, in the first aspect of the present invention, as a developing condition in which fog is likely to occur, the voltage of the developing bias voltage is increased, and (developing bias voltage)-(exposure potential) is set. It is characterized in that it is made smaller.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the frequency of the developing bias voltage is reduced as a developing condition in which fogging is likely to occur.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the duty ratio of the developing bias voltage is changed as a developing condition in which fogging is likely to occur.

According to a sixth aspect of the present invention, in the first to fourth or fifth aspects of the present invention, a means for adjusting a line width is provided for each of the normal mode and the fog mode.

According to a seventh aspect of the present invention, in the first to fifth or sixth aspects of the present invention, the fog mode is set by an input from the host side or a direct input to the image forming apparatus. Features.

According to an eighth aspect of the present invention, in the first to fifth or sixth aspects of the present invention, the fog mode is set by a process cartridge.

According to a ninth aspect of the present invention, in the first to seventh or eighth aspects, after the image forming apparatus is set to the fog mode, the image forming apparatus judges the environment and actually shifts to the fog mode. It is characterized by the following.

Therefore, according to the present invention, the mode is automatically or manually shifted from the normal mode to the fogging mode (mode for setting development conditions in which fogging is likely to occur) in a situation where image deletion is likely to occur. Even when using paper that contains a lot of talc in a high humidity environment, it is possible to prevent the occurrence of image deletion, and even if image deletion occurs, this image deletion can be quickly erased. As a result, a high-quality image can always be stably obtained.

[0017]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a sectional view showing a schematic configuration of a laser beam printer (LBP) according to the present invention.
Is a scanner unit having an optical unit for irradiating and scanning a laser beam emitted according to image information and a scanning unit;
Reference numeral 0 denotes a process cartridge containing main image forming means. The process cartridge includes a photosensitive drum 3 serving as an image carrier, a roller charger 4 made of semiconductive rubber, and a one-component toner 6 on the photosensitive drum 3. And a cleaner 8 for removing waste toner from the photosensitive drum 3.

The photosensitive drum 3 in the process cartridge 10 rotates in the direction of the arrow shown in the figure. After the surface of the photosensitive drum 3 is uniformly charged by the roller charger 4, the laser beam emitted from the scanner unit 1 is emitted. Irradiation via the mirror 2 forms an electrostatic latent image on the surface.
Then, the electrostatic latent image is developed by the developing device 5 and is visualized as a toner image.

On the other hand, the transfer material 14 in the paper cassette 12
Are separated and fed one by one by a paper feed roller 13 and a separation pad (not shown) provided opposite to the paper feed roller 13. Then, the fed transfer material 14 is conveyed to a pair of registration rollers 15 along upper and lower guides 19. The registration roller 15 is stopped until the transfer material 14 arrives, and the skew of the transfer material 14 is corrected by abutting the leading end of the transfer material 14 on the transfer roller 14. Next, the registration roller 15 conveys the transfer material 14 to the transfer unit in synchronization with the leading end of the toner image formed on the photosensitive drum 3. A paper feed sensor (not shown) is provided near the registration roller 15, and the paper feed sensor can detect a paper passing state, a jam, and the length of the transfer material 14.

Reference numeral 7 denotes a transfer roller, which applies a charge having a polarity opposite to that of the toner 6 from the back side of the transfer material 14,
The toner image formed on the photosensitive drum 3 is transferred to a transfer material 14.
Transfer to The transfer material 14 to which the toner image has been transferred is
The toner image is conveyed to the fixing device 17 by the conveyance roller 16a and the conveyance guide 16b, and after the toner image is fixed by heat and pressure by the fixing device 17, is discharged to the discharge tray 18 through each conveyance path selected by a flapper (not shown). Is done.

As described above, the process cartridge 10 includes a photosensitive drum 3 as an image carrier, a roller charger 4, a developing device 5 for developing a latent image on the photosensitive drum 3 using toner 6, and a waste toner. The image forming apparatus comprises a cleaner 8 and the like which are removed from the photosensitive drum 3, and is detachably mounted on the image forming apparatus main body. Note that the entire process cartridge 10 is covered with a K cover 9, and the process cartridge 10 is supported by a guide (not shown) on the main body side and is loaded into the image forming apparatus.

Here, the photosensitive drum 3 is an organic photosensitive member (OP)
C), the developing unit 5 employs a one-component reversal developing method (so-called jumping developing method) using an insulating toner 6, and a developing bias applied with a direct current and an alternating voltage applied thereto is applied.

By the way, in the one-component developing method, particularly in the jumping developing method, the force of rubbing the photosensitive drum surface during development is weaker than that in the two-component developing method or the one-component contact developing method, and the toner adheres to the photosensitive drum surface. It is considered that dirt is difficult to remove.

FIG. 2 shows the primary charging voltage (dark potential Vd) and the developing bias voltage V of the laser beam printer according to the present invention.
FIG. 6 is a diagram showing the relationship between dc and the potential of an exposed portion (bright portion potential Vl).

The setting indicated by A in FIG. 2 is the potential setting in the normal mode, and the setting indicated by B is the potential setting in the fog mode. F1 is a setting for increasing the line width, F9 is a setting for decreasing the line width, and F5 is a setting for the center.

Thus, in the present embodiment, by lowering the primary charging voltage (dark portion potential Vd) in the fog mode B, the latent image contrast potential (Vd) is lower than in the normal mode A.
−Vdc) is reduced. This corresponds to V- in FIG.
D diagram (latent image contrast potential (V-Vdc) and development density D
When the contrast potential (V-Vdc) shifts from the position A to the position B, the position of the developing density D also shifts from P to Q, and the developing density D increases. , Which means that fog increases.

FIG. 3B shows the contrast potential (V-Vdc) on the horizontal axis and the reflectance on the vertical axis. The reason for using the reflectance is that the fog can be measured more accurately than the image density.

However, when the primary charging voltage Vd is reduced, the potential Vl of the exposed portion is slightly reduced accordingly. In addition, when (Vd-Vdc) decreases, the development density D increases, so it is necessary to adjust the line width, and (Vdc-Vdc)
l) also needs to be slightly smaller. There are two methods for this. One is a method for reducing the exposure amount as shown in FIG. 2, and the other is a method for reducing the developing bias voltage Vdc as shown in FIG.

In this embodiment, in order to change the primary charging voltage Vd, the voltage applied to the grid may be changed in corona charging. In a system using contact charging such as a C roller, the DC voltage applied to the C roller may be changed.

FIG. 5 is a graph showing the relationship between the primary charging voltage (dark portion potential Vd), the developing bias voltage Vdc, and the exposure portion potential (bright portion potential Vl) of a laser beam printer according to another embodiment of the present invention.

In FIG. 5, the setting indicated by A is the potential setting in the normal mode, and the setting indicated by B is the potential setting in the fog mode.

In this embodiment, the developing bias voltage Vdc in the fog mode B is higher than that in the normal mode A (V
d-Vdc). In this case, FIG.
(The diagram showing the relationship between the latent image contrast potential (V-Vdc) and the development density D), the latent image contrast potential (V-Vdc) shifts from the position A to the position B. ,
The development density D also shifts from P to Q, and the development density D increases. This is due to an increase in fog.

However, when the developing bias voltage Vdc is moved, the latent image contrast potential (V-Vdc) greatly increases, so that the line width increases. For this reason, it is necessary to adjust the line width, and (Vdc-Vl) is reduced. Specifically, it can be implemented by lowering the laser exposure.

FIG. 6 is a block diagram showing the configuration of the control system of the laser beam printer according to the present invention.

When the fog mode B is selected from the display panel 21 of the laser beam printer, this signal is transmitted to the controller 20, and after the CPU of the controller 20 performs an operation, the semiconductor laser 22, the fixing device 23, and the high-voltage power supply 24 Control. The fog mode B may be selected from the keyboard or the screen of the host computer 25.

As described above, when fog mode B is selected, the amount of toner in the white background on the photosensitive drum 3 increases. The toner 6 in the white background portion transfers the transfer material 1 in the transfer portion.
4, but most of the toner 6 is collected by the cleaner 8. When the toner 6 remaining on the photosensitive drum 3 is scraped off by a rubber C blade, the toner 6 serves as an abrasive, and the dirt attached to the photosensitive drum 3 is collected by the cleaner 8 together with the toner 6. Will be. Incidentally, the dirt attached to the photosensitive drum 3 is, as described above, paper dust,
In particular, it refers to deliquescent substances such as talc.

Therefore, when the fog mode B is selected, even if a paper containing a deliquescent substance such as talc is passed under a high temperature and a high humidity of a temperature of 32 ° C. and a humidity of 80% or more, an image flow such as an image deletion occurs. The occurrence of image defects was prevented.

Next, another method for selecting the fog mode B will be described as an example of another laser beam printer embodying the present invention.

FIG. 7 is a block diagram showing the configuration of a control system of another laser beam printer. As shown in FIG. 7, the switch SW 26 connected to the controller 20 is set for each country or region, and Built-in year
It is also possible to automatically select the fog mode B at a hot time in a hot area by the clock 27 indicating the month and day.

FIG. 8 shows that after inputting a country-specific instruction from the display panel 21, the environment temperature where the laser beam printer is placed is detected by the environment detection thermistor 28, and the room temperature becomes 3 degrees.
FIG. 4 is a block diagram showing a configuration of a control system that automatically selects fog mode B when the temperature becomes 0 ° C. or higher. The thermistor 28 for detecting the environment is installed, for example, at a location close to room temperature that is open to the outside air on the back of the display unit or the laser beam printer. The reason why the room temperature of 30 ° C. is set as the temperature for entering the fog mode B is that the room where the air conditioner works is the room temperature of 30 ° C.
This is because it is possible to judge that the outside temperature is high and the humidity is high at the place where the room temperature is 30 ° C. or higher, without exceeding the temperature of 30 ° C. In particular, if a country or region is entered, it can be entered almost exactly.

In the above embodiment, the display panel 21 of the laser beam printer and the computer 2 on the host side are used.
Although the input is made from the keyboard 5 or the screen, the setting on the main body side may be changed by a protrusion attached to the process cartridge 10. Further, in the above-described embodiment, the jumping development method has been described as an example. However, when image deletion is likely to occur, a one-component contact development method can be used.

Next, another embodiment of the present invention will be described.

In the above embodiment, the fog mode B is performed by changing the latent image setting and the DC voltage of the developing bias. However, in the present embodiment, the fog is changed by changing the AC voltage of the developing bias. I try to increase it.

FIG. 9 shows the frequency f (H
z), and the vertical axis indicates image density and fog reflectance.
The development density increases as the frequency of the rectangular wave is lower in the range of 500 Hz to 2.5 KHz, but the reflectance of fog also increases. However, since image quality deteriorates, 1200H
z is the limit. In this case, since the image density is also high,
If there is any inconvenience, it is necessary to reduce the amount of laser light in order to adjust the image density.

Although the frequency of the rectangular wave is reduced in the example shown in FIG. 9, the duty ratio of the rectangular wave may be changed.

FIG. 10 shows another embodiment for executing the fog mode B.

FIG. 10A shows a rectangular waveform of the conventional developing bias, and FIG. 10B shows a waveform of the developing bias in the fog mode B, in which the developing bias on the side for moving the toner to the photosensitive drum is shown. This is intended to increase the fog by increasing the duty and decreasing the duty of the developing bias on the side where the fog toner is peeled off from the photosensitive drum.
When this method is used, the image density is increased. Therefore, if there is any inconvenience, it is necessary to reduce the amount of laser light in order to adjust the image density.

FIG. 11 is a sectional view of a developing unit of an image forming apparatus according to still another embodiment.

In the image forming apparatus shown in FIG. 11, a developing sleeve 30 is provided to face the photosensitive drum 3, and a magnet 31 is provided in the developing sleeve 30. An interval (SD interval) of about 300 μm is formed between the photosensitive drum 3 and the developing sleeve 30.

FIG. 12 is a graph showing changes in reflectance and image density when the SD interval is changed. The standard value of the SD interval is 300 μm. The toner 6 on the developing sleeve 30 stands like a spike, and its height is about 100 to 200 μm.
Therefore, when the thickness exceeds 200 μm, fog increases rapidly. For this reason, the fog mode is-
It is appropriate that the width is narrowed by 10 to -25%. In this case, since the fog mode can be set by the process cartridge, it is not necessary to change the setting on the image forming apparatus main body side.

A protruding portion is formed on the process cartridge so that it can be seen that the process cartridge set to the fog mode is used, and the protruding portion is configured to press a switch of the apparatus main body. The switch signal indicates that the fog mode is being used on the display unit of the apparatus main body or the screen of the host computer, and the laser intensity is reduced to adjust the line width.

As an example, the process speed is 150 mm
/ Sec, when the SD interval was set to 300 μm as standard, the SD interval was set to 250 μm as the fog mode. On the other hand, the laser light amount was set to be reduced by 20%. By doing so, without changing the line width,
It was possible to minimize the occurrence of image deletion.

[0054]

As is apparent from the above description, according to the present invention, the fogging mode (the developing condition in which fogging is likely to occur is set automatically or manually from the normal mode in a situation where image deletion is likely to occur. Mode), it is possible to prevent the occurrence of image deletion even when using paper containing a large amount of talc in a high-humidity environment. This image deletion can be eliminated quickly, and a high-quality image can always be obtained stably.

[Brief description of the drawings]

FIG. 1 is a laser beam printer (LBP) according to the present invention.
FIG.

FIG. 2 shows a primary charging voltage Vd, a developing bias Vdc, and an exposure portion potential Vl in the laser beam printer according to the present invention.
FIG.

FIG. 3 is a diagram showing a relationship between a latent image contrast potential (V-Vdc), a development density, and a reflectance in a laser beam printer according to the present invention.

FIG. 4 shows a primary charging voltage Vd, a developing bias Vdc, and an exposure portion potential Vl in the laser beam printer according to the present invention.
FIG.

FIG. 5 is a diagram showing a relationship between a primary charging voltage Vd, a developing bias Vdc, and an exposure portion potential Vl in another laser beam printer according to the present invention.

FIG. 6 is a block diagram illustrating a configuration example of a control system of the laser beam printer according to the present invention.

FIG. 7 is a block diagram illustrating a configuration example of a control system of the laser beam printer according to the present invention.

FIG. 8 is a block diagram illustrating a configuration example of a control system of the laser beam printer according to the present invention.

FIG. 9 is a diagram illustrating a relationship between a frequency f of a developing bias voltage, an image density, and a reflectance.

FIG. 10 is a diagram showing a developing bias waveform.

FIG. 11 is a sectional view of a main part of an image forming apparatus according to another embodiment of the present invention.

FIG. 12 is a diagram illustrating a relationship between an SD interval, an image density, and a reflectance.

[Explanation of symbols]

 Reference Signs List 3 photosensitive drum (image carrier) 4 roller charger 5 developing device 6 one-component toner 10 process cartridge 30 developing sleeve (developer carrier) f frequency of developing bias voltage Vd primary charging potential Vdc developing bias voltage Vl exposure potential

Claims (9)

[Claims] In an image forming apparatus for developing a latent image on an image carrier by holding a one-component toner on a surface of a developer carrier, development conditions in which fogging is likely to occur and a line width is not changed are set. An image forming apparatus provided with a fog mode to be set, and automatically or manually shifting from a normal mode to a fog mode in a situation where image deletion is likely to occur. 2. The developing conditions under which fogging easily occurs are as follows:
2. The image forming apparatus according to claim 1, wherein (primary charging potential)-(developing bias voltage) is reduced, and (developing bias voltage)-(exposure potential) is reduced. 3. The image forming apparatus according to claim 1, wherein the developing condition in which fogging easily occurs is to increase the developing bias voltage and to decrease (developing bias voltage)-(exposure potential). apparatus. 4. The image forming apparatus according to claim 1, wherein the frequency of the developing bias voltage is reduced as a developing condition under which fogging easily occurs. 5. The image forming apparatus according to claim 1, wherein a duty ratio of a developing bias voltage is changed as a developing condition under which fogging easily occurs. 6. An image forming apparatus according to claim 1, further comprising means for adjusting a line width between the normal mode and the fog mode. 7. The image forming apparatus according to claim 1, wherein the setting of the fog mode is performed by input from the host side or direct input to the image forming apparatus. 8. The image forming apparatus according to claim 1, wherein the fog mode is set by a process cartridge. 9. The image forming apparatus according to claim 1, wherein after setting the fog mode, the image forming apparatus judges an environment and actually shifts to the fog mode.