JP2786365B2 - Electrophotographic equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic device provided with a cleaning blade for removing and recovering residual toner adhering to the surface of a photoreceptor after a transfer process and for equalizing the potential on the surface of the photoreceptor. It relates to a photographic device.

[0002]

2. Description of the Related Art A conventional electrostatic transfer type copying machine such as an OP
In a reversal process type electrophotographic apparatus using a C photoconductor, as shown in FIG. 7, a charging roller 32 which is a charging member made of conductive rubber or the like is disposed in contact with the photoconductor 31. By applying a voltage from a DC power supply 33 to the charging roller 32, the surface of the photoconductor 31 is negatively charged, and the negatively charged photoconductor 31 is
Exposure is performed by using the reflected light 34 from the original to make only the exposed portion positive, and a negative toner is supplied to the positively charged portion from a developing tank (not shown) to develop and develop. The obtained toner image is transferred to transfer paper using a positive transfer device (not shown).

After the transfer of the toner image is completed, a cleaning blade 36, which is a cleaning member made of insulating rubber, is used.
Then, the residual toner on the surface of the photoreceptor 31 is scraped off and collected, and is exposed by a neutralization lamp 35, so that the positively-charged partly charged during transfer of the toner image is neutralized.

On the other hand, in Japanese Patent Publication No. 44-2036, instead of the charging method using the charging device having the charging roller 32 as described above, as shown in FIG. A method is disclosed in which the formed cleaning blade 36 is formed of conductive rubber, and a voltage is applied from a DC power supply 33 to the cleaning blade 36 ′ to charge the photosensitive drum 31.

[0005]

In the above-mentioned conventional construction, the surface of the photoreceptor 31 is partially provided with a charge having a polarity opposite to the charge at the time of transfer, resulting in an uneven state. The static elimination lamp 35 is used to eliminate the static electricity. However, in the exposure or the like by the static elimination lamp 35, sufficient static elimination cannot be performed, and the photosensitive member 31 is not uniformly charged.
Alternatively, it is charged by the cleaning blade 36 '. In order to charge the photosensitive member 31 in such a non-uniform state partially positively charged to only about −600 to −700 V using only the charging roller 32 and the cleaning blade 36 ′, it is necessary to use the conductive material which is a constituent member. Rubber having a resistivity of 10 ⁶ to 10 ⁸ Ω · cm and an applied voltage of -1500 to-
About 2000 V is required.

However, a conductive rubber having a resistivity of 10 ⁶ to 10 ⁸ Ω · cm has a drawback that stable production is difficult to be performed, and that the resistivity is easily influenced by environmental conditions and the resistivity tends to fluctuate. Therefore, the photosensitive member 31 cannot be stably and uniformly charged, and there is a problem that charging stability cannot be improved.

The conductive rubber is made by mixing a rubber material with an organic polymer conductive material such as carbon. The resistivity of the conductive rubber is as shown in FIGS. 3 and 4 which are explanatory diagrams of the present invention. It does not change linearly with the mixing ratio of the rubber material and the organic polymer conductive material but has an S-shaped characteristic. In addition, the charging roller 32 and the cleaning blade 3
The resistivity of 10 ⁶ to 10 ⁸ Ω · cm required for 6 ′ is S
Since it is located at the steepest point of the character characteristic, the resistivity varies due to the variation of the mixing ratio, and stable production cannot be performed. Furthermore, the resistivity is liable to fluctuate greatly due to environmental changes due to the moisture absorption characteristics of the material itself, a change in the number of carriers of the organic polymer conductive material, and the like.
The conductive rubber of ⁶ to 10 ⁸ Ω · cm is more significantly affected by environmental changes. Therefore, as described above, the photoconductor 31 cannot be stably charged.

In view of the above, the present invention reduces the resistivity and applied voltage required for the charging member from the conventional values, reduces the influence of changes in environmental conditions, and improves the charging stability of the photoconductor. Still another object of the present invention is to reduce the cost of the charging member by forming the charging member from a conductive rubber capable of being stably produced.

[0009]

Means for Solving the Problems] electrophotographic apparatus of the present invention, along the surface of the photosensitive member, a charging roller for charging the photosensitive member in contact with the photosensitive member, sensitive at a position before the charging roller
A cleaning blade is provided which removes residual toner adhering to the surface of the photoreceptor in contact with the photoreceptor and applies a voltage so that an electric field in the charging direction is generated at the contact portion.

[0010]

According to the above construction, cleaning is performed.blade
Is charged when the residual toner is collected.rollerBefore charging by
Run to give the same charge to the photoreceptor surface
It has become. As a result, the conventional copying process
The non-uniform potential of the photoreceptor surface becomes uniform
Can be approached. Therefore, the surface voltage of the photoconductor
High voltage is required to charge from uneven position
ChargedrollerVoltage and the resistivity
Can be chargedrollerEnvironment of resistivity
Small fluctuation due to change, stable charge on photoconductor
It is possible to improve the performance. Furthermore, electrificationLow
LaFormed of conductive material with resistivity that enables stable production
Can reduce member costs.
You.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

An electrophotographic apparatus such as an electrostatic copying machine of the present embodiment is an inversion process type electrophotographic apparatus using an OPC photosensitive member (organic photosensitive member). As shown in FIG. 2, the present electrophotographic apparatus has a photosensitive drum 1 as a photosensitive member rotatably provided. The photosensitive drum 1 is made of a P-type semiconductor, has a negative charging ability, and is driven by a drive motor (not shown) so as to rotate in the direction of the arrow in the figure.

Around the photosensitive drum 1, the main charger 2 is disposed in contact with the surface of the photosensitive drum 1 and charges the surface to a predetermined potential, and is guided by an optical system (not shown). A developing device 6 for developing an electrostatic latent image formed on the photosensitive drum 1 by reflected light 5 from a document, and transferring a toner image formed on the surface of the photosensitive drum 1 to transfer paper by a developing operation of the developing device 6 Charger 7 for peeling off, transfer charger 8 for peeling off transfer paper from photoreceptor drum 1, and peeling claw 9
And a cleaning device 3 for collecting the toner remaining on the surface of the photosensitive drum 1 after the transfer operation is completed.

As shown in FIG. 1, the main charger 2 is provided with a charging roller 2a at a position facing the grounded photosensitive member 1. The charging roller 2a has a roller shape and is made of a rubber such as polyurethane or silicon which has been subjected to a conductive treatment, and can be set to a predetermined resistivity by changing the material. Further, a constant voltage power supply 4 as voltage applying means is connected in series to the charging roller 2a, so that a high DC voltage having a predetermined voltage value is applied to the charging roller 2a.

The cleaning device 3 includes a peeling roller 3b for peeling off the toner remaining on the surface of the photosensitive drum 1 after the end of the transfer operation, and scraping off the residual toner not peeled off by the peeling roller 3b. 1
Is provided with a cleaning blade 3a for pre-charging, and the peeling roller 3b and the cleaning blade 3a are arranged in contact with the surface of the photosensitive drum 1, respectively.

The cleaning blade 3a is made of a conductive rubber having a resistivity of 10 ³ to 10 ⁴ Ω · cm.
As shown in FIG. 1, it is connected to the constant voltage power supply 4 via a resistor R. By appropriately setting the resistance value of the resistor R, the voltage applied to the cleaning blade 3a can be adjusted. In this embodiment, for example, a voltage of about -1000 V is applied. Has become.

In the above-described configuration, when performing a copying operation, an original placed on an original mounting table (not shown) is scanned by being irradiated with an exposure lamp of an optical system.
As a result, the reflected light 5 from the original is, as shown in FIG.
The light is guided to the photosensitive drum 1 by the optical system. At this time, the surface of the photoconductor drum 1 is charged to a potential of about −600 to −700 V in advance by the charging roller 2 a of the main charger 2, and the surface of the photoconductor drum 1 is exposed by the reflected light 5, The exposed portion receives a positive charge, and an electrostatic latent image corresponding to the original image is formed. This electrostatic latent image is developed with the negative polarity toner supplied from the developing device 6 to become a toner image.

Next, when the photosensitive drum 1 further rotates and the toner image reaches the transfer charger 7 having a positive polarity, transfer paper is supplied from a supply device (not shown) in synchronization with the rotation of the photosensitive drum 1, and The negative toner image on the surface of the photosensitive drum 1 is electrically transferred by the positive transfer charger 7. At this time, a positive charge is partially applied to the surface of the photoreceptor drum 1 by the transfer charger 7, and the surface becomes non-uniform.

After the completion of the transfer step, the transfer paper is peeled off from the photosensitive drum 1 by a peeling charger 8 and a peeling claw 9,
The toner is discharged outside the apparatus through a fixing process by a fixing device (not shown).

On the other hand, on the photosensitive drum 1 after the transfer paper has been peeled off, residual toner adhering to the surface of the photosensitive drum 1 is collected by the cleaning roller 3b of the cleaning device 3. Further, the toner not collected by the cleaning roller 3b is scraped off by the cleaning blade 3a and collected. At this time, the cleaning blade 3 a to which a voltage of −1000 V is applied from the constant-voltage power supply 4 applies preliminary charge to the surface of the contacting photosensitive drum 1, that is, the same negative charge as the charge by the main charger 2. Give. As a result, the surface of the photosensitive drum 1, which has been given a non-uniform state due to the transfer of the positive charge having a polarity opposite to that of the charging by the transfer charger 7, becomes a uniform state.

Thereafter, the photosensitive drum 1 comes into contact with the charging roller 2a of the main charger 2, and the main charging is performed.
It is charged to about 0 to -700 and stands by for the next copying operation.

As described above, in the electrophotographic apparatus of this embodiment, before the photosensitive drum 1 is charged by the main charger 2, the same negative charge as that of the charge is given by the cleaning blade 3a to perform the preliminary charge. Is performed to bring the surface potential of the photosensitive drum 1 closer to a uniform state.

For this reason, the photosensitive drum 1 is moved from -600 to-
In order to charge to about 700 V, in the charging roller 32 (see FIG. 7) of the main charger in the conventional electrophotographic apparatus, the resistivity is 10 ⁶ to 10 ⁸ Ω · cm, and the applied voltage is −15.
Although about 100 to -2000 V was required, in the electrophotographic apparatus of this embodiment, the cleaning blade 3a
Performs pre-charging on the surface of the photosensitive drum 1 before charging by the main charger 2, so that the resistivity of the charging roller 2a is 1
0 ⁴ to 10 ⁸ Ω · cm, applied voltage -800 to -120
It can be reduced to 0V.

As described above, the charging characteristics due to the environmental change of the photosensitive drum 1 in the electrophotographic apparatus of the present embodiment in which the resistivity and the applied voltage required for the charging roller 2a are lower than those of the prior art are shown. It is shown in FIG. As a reference example, the charging characteristics of the photosensitive drum 31 in an electrophotographic apparatus employing a conventional cleaning blade 36 made of insulating rubber (see FIG. 7) are also shown in FIG . As is clear from this figure, the potential drop at low temperature and low humidity is smaller than that of the conventional one. In other words, by performing the preliminary charging by the cleaning blade 3a, the resistivity and the applied voltage of the charging roller 2a can be reduced, and accordingly, the influence of the environmental change is reduced, and as a result, the charging stability of the photosensitive drum 1 is stabilized. Performance can be improved.

The resistivity of the charging roller 2a is 10 ⁴
~10 ⁸ Ω · cm, as shown in FIGS. 3 and 4, stable for inclusion in producible area enables stable production, also when applied voltage of the OPC photosensitive member leak hazardous voltage areas - Since the voltage is out of the range of 1500 to -2000 V, the risk of photoconductor leakage is also avoided.

Further, the required resistivity of the conductive rubber of the cleaning blade 3a is 10 ³ -10
⁴ Ω · cm and the applied voltage is 1000 V or less,
Stable production is possible, and the danger of photoconductor leakage is excluded.

Since the cleaning blade 3a brings the surface of the photosensitive drum 1 closer to a uniform state, the load on the conventional static elimination lamp 35 (see FIG. 7) can be reduced. It is also possible to eliminate 35 and reduce the size of the electrophotographic apparatus.

[0028]

According to the electrophotographic apparatus of the present invention, there is provided a charging device for charging a photoconductor by contacting the photoconductor along the surface of the photoconductor .
And over La, to remove the residual toner in contact with the photoreceptor adhere to the sensitive <br/> optical surface at the front position of the charging roller, a voltage is applied to the electric field in the charging direction is generated on the contact portion Cleaning blade is provided.

Therefore, conventionally, the voltage and resistivity of the charging roller , which required a high voltage to charge the surface of the photosensitive member from an uneven state, can be reduced. Variations in the resistivity of the roller due to environmental changes are reduced, and the effect is obtained that the charging stability of the photoconductor can be improved. Furthermore, since the charging roller can be formed of a conductive member having a resistivity that enables stable production, the effect of reducing member costs can be achieved.

[Brief description of the drawings]

FIG. 1 illustrates one embodiment of the present invention, and is a schematic diagram illustrating a mutual relationship among a photosensitive drum, a charging roller, and a cleaning blade in an electrophotographic apparatus.

FIG. 2 is an explanatory diagram showing a configuration around a photosensitive drum of the electrophotographic apparatus.

FIG. 3 shows the amount of the organic polymer conductive material relative to the rubber material,
It is a graph which shows a relationship with a volume specific resistance value.

FIG. 4 shows the amount of the organic polymer conductive material relative to the rubber material,
It is a graph which shows a relationship with a volume specific resistance value.

FIG. 5 is a graph showing a relationship between a charged potential on a photosensitive drum surface and an environmental change in the electrophotographic apparatus.

FIG. 6 is a graph showing a relationship between a charging potential on a photosensitive drum surface and an environmental change in a conventional electrophotographic apparatus.

FIG. 7 is a schematic diagram showing a mutual relationship among a photosensitive drum, a charging roller, and a cleaning blade in the conventional electrophotographic apparatus.

FIG. 8 is a schematic diagram showing a mutual relationship between a photosensitive drum and a cleaning blade in another conventional electrophotographic apparatus.

[Explanation of symbols]

 Reference Signs List 1 photoconductor drum (photoconductor) 2a charging roller 3a cleaning blade 4 constant voltage power supply

Claims (1)

(57) [Claims] A charging roller that contacts the photoconductor along the surface of the photoconductor and charges the photoconductor; and a charging roller that contacts the photoconductor at a position in front of the charging roller and adheres to the surface of the photoconductor. And a cleaning blade to which a voltage is applied such that an electric field in a charging direction is generated at the contact portion while removing the residual toner.