JPH0734138B2 - Image forming device - Google Patents

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 of the type in which an electrostatic latent image is formed by exposing it to an image bearing member, developing it with colored powder, and transferring it to a recording medium, and more particularly, a scorotron type transfer means. The present invention relates to an image forming apparatus having.

[0002]

2. Description of the Related Art FIG. 3 is a schematic diagram of the periphery of an image carrier in a conventional example of an image forming apparatus of the above type. In the figure, 1 is a photosensitive drum, 2 is a charging device, 3 is an exposing means, 4 is a developing device, 5 is a bias power source for the developing device, 8 is a recording paper, and 15 is a recording paper.
Is a transfer device, and 16 is a cleaner. As the image bearing member, a drum-shaped photosensitive member is usually used as in this example. The photosensitive drum 1 rotates in the direction of the arrow.

The image forming process is started by uniformly charging the photosensitive drum 1 with the charger 2, and then the exposing means 3 forms an electrostatic latent image. The exposure is performed by slit exposure using an optical system, a laser beam modulated by an image signal, or the like. Then, the latent image is developed with the toner, which is colored powder, by the developing device 4, and the latent image is transferred to the recording paper 8 by the transfer device 15 to form an image.

The toner remaining on the photosensitive drum after transfer is
It is cleaned by the cleaner 16. Cleaner 16
In this case, the blade 16a is used to scrape off the residual toner, and the conveying screw 16b sends it out to an external toner recovery box (not shown).

Such a blade-type scraping-type cleaner requires a space for the recovery box and must monitor the fullness of the toner recovery box. Further, there is a problem that the surface of the photosensitive drum 1 is easily scratched by the blade 16a and the life of the photosensitive drum is shortened.

A memory removing member is used in the image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 64-20587, in which a cleaning method using no scraping blade has been proposed. FIG. 4 is a schematic configuration diagram around the image carrier. In the figure, the same parts as those in FIG. 6 is a scorotron type transfer device,
7 is a high voltage power supply, 9 is a varistor, 14 is a memory removing member,
Reference numeral 17 is a high-voltage power supply. In this image forming apparatus,
It can be used for an external output device such as an electronic computer or a word processor.

To perform recording, a print start signal
The photosensitive drum 1 rotates and is charged by the charger 2. The charging potential is V ₀ shown in FIG. 6, for example, −700V. The exposure unit 3 scans and exposes the photosensitive drum 1 with a laser beam modulated by dot image data from an electronic computer or a word processor to form an electrostatic latent image.

FIG. 5A is an explanatory diagram of a charged state when the residual toner remains on the photosensitive drum 1.
Since the photosensitive drum 1 is charged to the charging potential V ₀ , the residual toners a and b are also charged to the same potential V ₀ . The photoconductors under the residual toners a and b are also charged to the same potential V ₀ .

FIG. 5B is an explanatory diagram of an exposure state.
Since the exposed portion forms an electrostatic latent image having the exposure potential V _c in FIG. 6, the residual toner b in that portion also has the exposure potential V c.
_c . When the residual toner in the exposed portion is dispersed in a small area, for example, one by one, the photoconductor under the residual toner is also exposed. When the photoconductors under a large area are aggregated and present, underexposure occurs. However, when the underexposed portion is filled with the toner adhering to the surrounding exposed portion, the residual toner is not a problem. Therefore, as will be described later, by the memory removal member,
If the residual toner is dispersed to the extent that exposure does not matter, the residual toner will be substantially negligible.

The developing device 4 has a developing potential V _b1 , for example, -4.
Develop the latent image at 50V. As shown in FIG. 5C, the toner in the developing device is developed and attached to the exposed portion. The residual toner b in the exposed portion remains,
No problem. The residual toner a in the non-exposed portion returns to the developing device 4 and cleaning can be achieved. Charging potential V ₀
And the development potential V _b1 , V _CL = V _b1 −V ₀ is called a cleaning potential.

The transfer is performed using a scorotron type charger. By using the scorotron type, it is possible to apply a voltage of 5 kV or more from the high voltage power source 7 to the corona wire 6a and stabilize the discharge. A varistor 9 is connected to the grid 6b, and a constant voltage, for example, 560V is generated by a part of the corona current. Therefore, the grid potential is 560V. The toner developed by the transfer potential is transferred to the recording paper 8, the transferred toner is fixed by a fixing device (not shown), and the recording paper is ejected. The transfer causes the photosensitive drum to have a post-transfer potential V _T , for example, 1 at the exposed portion.
It becomes 00V. In addition, the non-exposed portion is about 0 to -80V.

Next, the memory removal potential V _b2 is applied to the photosensitive drum 1 by the memory removal member 14 connected to the high voltage power supply 17. The memory removal potential V _b2 is 100 to
700V is suitable. As the memory removing member 14,
A brush is used. The memory removal member 14 temporarily electrostatically adsorbs the residual toner, and then spontaneously ejects the residual toner to the photosensitive drum 1 to change the adhesion position on the photosensitive drum 1. As a result, the residual toner pattern is diffused. Is brought.

Due to this action, as described above, the residual toner does not hinder the next exposure,
In addition, the residual toner in the non-exposed area is not removed at the same time as the development.
It was collected and was eventually cleaned.

Further, if such a residual toner collecting system is adopted, charging of the photosensitive member by the transfer device 6 becomes a problem.
The potential of the photoconductor that has passed through the transfer device 6 is affected by the presence or absence of recording paper. The potential V _T0 after transfer when there is recording paper is 10
If it is 0 V, the post-transfer potential V _T1 is obtained when there is no recording paper.
Is about 400V. The photoconductor is V _T1 , 40
If it is charged to about 0 V, the toner attached to the memory removing member 14 will be developed on the photoconductor.
The toner produced by this development does not form a dispersed pattern and thus becomes an obstacle in the next exposure step.

Therefore, in the cleaning method described in the above publication, the voltage applied to the corona wire 6a of the transfer device 6 is turned on only when the recording paper 8 is passing under the transfer device 6. The exposed portions of the photosensitive member before and after the recording paper 8 are prevented from being positively charged.

However, it is difficult to accurately synchronize the conveyance position of the recording paper 8 and the power-on of the high-voltage power supply 7, and there is also a problem of start-up time and fall-time when the power is turned on and off. It is difficult to avoid charging the exposed portion of the photoconductor.

There is also a problem that the high voltage power supply 17 to the memory removing member 14 is required as compared with the case of using the conventional blade type scraping type cleaner.

As a photosensitive drum, an OPC for negative charging is used.
However, the same applies to positively charged OPC.

[0019]

The present invention has been made in view of the above-mentioned circumstances, and does not require the high-voltage power supply 17 to the memory removing member 14, and does not require the high-voltage power supply 7 and the conveyance position of the recording paper 8. It is an object of the present invention to provide an image forming apparatus capable of adopting a residual toner collecting method that does not require accurate synchronization with power-on.

[0020]

According to a first aspect of the present invention, there is provided an image forming apparatus according to the present invention, wherein a charging means for charging an image carrier and an exposing means for forming an electrostatic latent image on the image carrier. A developing means for developing the electrostatic latent image with colored powder, a scorotron type transfer means for transferring the developed colored powder to a recording medium, and a memory removing member which is in contact with the image carrier and disturbs the residual colored powder. In the image forming apparatus having the above, the grid potential of the scorotron type transfer means is used as a power supply applied to the memory removing member. In claim 2, the storage means is added to the power supply applied in claim 1. According to a third aspect of the present invention, the capacitor is used as the storage means in the second aspect, and the directional element is interposed in the charging circuit. Than it is.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic diagram of the periphery of an image carrier of an embodiment of the image forming apparatus of the present invention. In the figure, 1 is a photosensitive drum, 2 is a charging device, 3 is an exposing means, 4 is a developing device, 5 is a bias power supply for the developing device, 6 is a scorotron type transfer device, 7 is a high voltage power supply, 8 is a recording paper, 9 Is a varistor, 10 is a resistance, 1
1 is a condenser, 12 is a variable resistor, 13 is a resistor, 14
Is a memory removing member. As the memory removing member 14, a fixed brush, a rotating brush, a roller, a blade or the like can be used. Similar to the case described with reference to FIG. 4, the case of using it in an external output device such as an electronic computer or a word processor will be described.

The charging, exposure, development, transfer and memory removal are the same as described with reference to FIG. The high voltage power supply to the memory removing member 14 utilizes the grid potential of the scorotron type transfer device 6. That is, the varistor 9 is connected to the grid 6b, and part of the corona current causes
A constant voltage, for example 560V, is generated. Therefore, the grid potential becomes 560 V, as in FIG. This voltage is divided by the variable resistor 12 via the resistor 10 and applied to the memory removal member 14 via the resistor 13.

When the grid potential of the scorotron type transfer device 6 is used as the power supply to the memory removing member 14, as described above, only when the recording paper 8 is passing under the transfer device 6, the transfer device 6 of the transfer device 6 is transferred. When the voltage applied to the corona wire 6a is turned on and the exposed portions of the photoconductor in the front and rear of the recording paper 8 are not positively charged, the memory is removed when the rear end of the recording paper 8 passes the transfer device 6. The voltage applied to the member 14 is 0V. Then, when the voltage of the transfer device 6 is turned off, when the photosensitive member portion of the photosensitive drum 1 between the memory removing member 14 and the transfer device 6 reaches the position of the memory removing member 14, Since the electric potential of the memory removing member 14 is 0V, the residual toner cannot be dispersed. Not only that,
Since the photoconductor portion between the memory removing member 14 and the transfer unit 6 is charged to the potential after transfer, the toner attached to the memory removing member 14 moves to the photoconductor and is developed. Become. When the voltage of the transfer device 6 is turned off after the recording paper has passed, the potential after transfer becomes high, and therefore development of residual toner on the photosensitive drum is unavoidable.

The condenser 11 is provided to avoid development on the photosensitive drum 1. The discharge time constant of the condenser 11 is set so that the condenser 11 can store the voltage of the memory removing member 14 until the portion of the photosensitive drum located when the voltage of the transfer device 6 is turned off reaches the memory removing member 14. This prevents the above-mentioned problem of residual toner and the development from the memory removing member 14 to the photosensitive drum 1.

However, since the variable resistor 12 is provided for discharging the capacitor 11 when not in use and for adjusting the voltage applied to the memory removing member 14, it may be replaced with a fixed resistor. , Not necessarily required. Further, the resistor 13 is inserted as a protective resistor for preventing electric shock from the residual voltage of the capacitor 11 at the time of inspection, and may be omitted.

FIG. 2 is a schematic configuration diagram of the periphery of an image carrier of another embodiment of the image forming apparatus of the present invention. In the figure, the same parts as those in FIG. In this embodiment, diode D is connected in parallel with resistor 10 of FIG.
Connected.

If the recording paper 8 is not present when the high-voltage power supply 7 of the transfer device 6 is turned on, the photosensitive drum 1
The portion of the photoconductor that receives the electric field of the transfer device 6 is charged to a high potential. If the potential of the memory removing member 14 is not higher than the potential of the charged portion of the photosensitive drum 1 by the time this portion reaches the position of the memory removing member 14, the toner adhered to the memory removing member 14 Is developed and adheres to the photosensitive drum side, which adversely affects printing.

If the charging time constant of the capacitor 11 by the resistor 10 is large, even if the voltage of the transfer device 6 rises,
The rising of the voltage applied to the memory removal member 14 is delayed.

In the embodiment shown in FIG. 2, the power source applied to the memory removing member 14 is started up quickly to prevent development from the memory removing member 14 to the photosensitive drum side. Resistance 10
Since the diode D is connected in parallel with the capacitor D, the forward resistance of the diode D reduces the charging time constant of the capacitor 11, and the terminal voltage of the capacitor 11 becomes
It can be raised almost simultaneously with the grid potential of the transfer unit 6. Therefore, when the charged portion of the photosensitive drum reaches the position of the memory removal member 14 when the voltage of the transfer device 6 is applied, it means that the predetermined voltage has already been applied to the memory removal member 14. Member 14
The toner adhered to is not developed on the photosensitive drum side.

The diode D is not limited to being connected to the resistor 10 in parallel, and the diode D may be used instead of the resistor 10. Further, not only the diode but also another directional element can be used. Of course, it may be an active element.

The above voltage values are examples, and
An appropriate voltage value is set according to the characteristics of the toner. Also, the varistor is not limited to this,
Other elements such as Zener diodes can be used.

[0032]

As is apparent from the above description, according to the present invention, the voltage applied to the memory removing member is transferred to the photosensitive member by using the grid potential of the scorotron type transfer means as the power source of the memory removing member. It can be related to the after-potential, and development on the photoreceptor can be prevented regardless of variations in the transfer potential.

Further, by giving a memory effect to the power supply applied to the memory removing member, there is an effect that development of the memory removing member can be completely avoided.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram around an image carrier of an embodiment of an image forming apparatus of the present invention.

FIG. 2 is a schematic configuration diagram around an image carrier of another embodiment of the image forming apparatus of the invention.

FIG. 3 is a schematic configuration diagram around an image carrier of a conventional image forming apparatus.

FIG. 4 is a schematic configuration diagram around an image carrier of a conventional image forming apparatus using a memory removing member.

FIG. 5 is an explanatory diagram of a cleaning action of the memory removing member.

FIG. 6 is an explanatory diagram of potential distribution.

[Explanation of symbols]

 1 Photosensitive Drum 2 Charging Device 3 Exposure Means 4 Developing Device 6 Scorotron Type Transfer Device 7 High Voltage Power Supply 8 Recording Paper 9 Varistor 10, 12, 13 Resistance 11 Condenser 14 Memory Removal Member

Claims (3)

[Claims] 1. A charging means for charging an image carrier, an exposing means for forming an electrostatic latent image on the image carrier, a developing means for developing the electrostatic latent image with colored powder, and a developing means. In an image forming apparatus having a scorotron type transfer means for transferring colored powder to a recording medium and a memory removing member for disturbing residual colored powder in contact with the image carrier, the grid potential of the scorotron type transferring means is changed to the memory removing member. An image forming apparatus characterized by being used as a power source applied to the image forming apparatus. 2. The image forming apparatus according to claim 1, wherein a storage unit is provided in the applied power source. 3. The image forming apparatus according to claim 2, wherein a condenser is used as the storage means, and a directional element is interposed in a charging circuit of the condenser.