JPH11272041A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the sticking of toner caused by the long-term use of a blade used for both of cleaning and electrifying. SOLUTION: The blade 2 used for both of cleaning and electrifying is constituted of at least a base material 2a and a conductive coat layer 2b and the surface roughness of the surface abutted on the outer periphery of a photoreceptor drum (electrified body) 10, of the coat layer 2b is set to be smaller than the averaged grain diameter of the toner. Further, it is preferable that electrifying bias supply 5 develops a vibrating voltage and it is applied to the blade 2 used for both of cleaning and electrifying.

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 using an electrophotographic process, such as an electrostatic copying machine or a laser printer, and more particularly, to an outer peripheral surface of a member to be charged (image carrier). The present invention relates to an image forming apparatus including a cleaning / charging blade for removing residual toner on the surface and charging the outer peripheral surface thereof.

[0002]

2. Description of the Related Art FIG. 2 is a schematic structural view of an image forming apparatus using an electrophotographic process. The photoconductor drum (charged body) 101 has a photoconductor 101a on the surface of a conductor 101b, and rotates in the direction of the arrow in FIG. Around the photosensitive drum 101, charging means (charging device) 102,
An exposure unit 103, a development unit 104, a transfer unit 105, and a cleaning unit 106 are provided, and each unit operates as follows.

[0003] That is, the charging means 102 is
The surface (outer peripheral surface) of 1a is charged to a required potential. Subsequently, the exposure unit 103 exposes the surface of the photoconductor 101a to form an electrostatic latent image corresponding to a desired image on the surface of the photoconductor 101a. The developing unit 104 develops the electrostatic latent image formed by the exposing unit 103 with toner, and forms a toner image on the surface of the photoconductor 101a.

[0004] Thereafter, the transfer means 105 is placed on a transfer medium P such as a sheet sent by a transport means (not shown).
The toner image formed on the surface of the photoconductor 101a is transferred. The transfer medium P on which the toner image has been transferred by the transfer unit 105 is transported to a fixing unit (not shown), where the toner image is fixed by heating, and then discharged out of the apparatus.

On the other hand, the cleaning means 106 removes (removes) toner remaining on the surface of the photoconductor 101a after the transfer, and cleans the surface of the photoconductor 101a. Now,
In the conventional image forming apparatus, the cleaning unit 106 and the charging unit 102 are separately provided as described above.

FIG. 3 is a schematic configuration diagram showing an example of a cleaning unit used in a conventional image forming apparatus.
The cleaning means 106 includes the cleaning blade 10
6a. The cleaning blade 106a is made of urethane rubber and has a thickness of 2 [m
m] and a length of 300 [mm].
Supported by Cleaning blade 106a
Of the supporting member 106b protrudes from the front end of the supporting member 106b, and the protruding amount a is adjusted to be, for example, 8 [mm].

The supporting angle θ of the cleaning blade 106a (the inclination angle of the blade with respect to the tangential direction of the photosensitive drum) is 20 °, and the amount b of the residual toner on the photosensitive member 101a is about 1.2 mm. It has been adjusted to be. Cleaning blade 106a having such a configuration
Edge cuts into the residual toner attached to the photoconductor 101a and is chipped off the photoconductor 101a.

On the other hand, as the charging means 102, a so-called contact charging device is widely used in addition to a conventional corona charging device such as a scorotron. The contact charging device charges the surface of the photoconductor 101a by bringing a charging member into contact with (contacting) the surface of the photoconductor 101a and applying a voltage to the charging member.

FIG. 4 is a schematic diagram showing an example of a contact charging device. This contact charging device includes a roller-shaped charging member 107. The charging member 107 includes a conductor 107
b has an elastic layer 107a on its peripheral surface,
0 [mm] and about 300 [mm] in length. The photosensitive drum 101 has a diameter of, for example, 30 to 80 [m
m] and a length of about 300 [mm].

The charging member 107 rotates in accordance with the rotation of the photosensitive drum 101 in contact with the surface of the rotating photosensitive drum 101. Charging member 107
Elastic layer 107a has a resistivity of 10 ⁷ to 10 ⁹ [Ωcm].
It is made of a conductive material of a certain degree. Further, the charging member 10
7 (the surface of the elastic layer 107a) has a film thickness of 10
In some cases, a surface protective layer of about 20 [μm] is formed.

A charging voltage is applied to the charging member 107 by a power supply 108, and the surface of the photoreceptor 101a is charged. The applied voltage is a DC voltage of about -1.0 to -1.5 [kV]. As described above, the cleaning means 10
The conventional image forming apparatus including the charging device 102 and the charging device 102 separately has the following problems.

(1) Since both a cleaning space and a charging space are required around the photosensitive drum 101, this is a bottleneck in miniaturizing the entire apparatus. (2) The cleaning unit 106 and the charging unit 102
Since it is a separate component, the number of parts is large and the cost is increased. In order to solve such a problem, for example, as disclosed in Japanese Patent Application Laid-Open No. 7-92767, an image forming apparatus provided with a cleaning / charging apparatus that combines the functions of both a cleaning unit and a charging unit. Has also been proposed.

FIG. 5 is a schematic diagram showing an example of a cleaning and charging device. The cleaning / charging device includes a cleaning / charging blade (hereinafter, also simply referred to as a “blade”) 110. The blade 110 is formed of a conductive elastic body, is supported by a support member 111, and has a tip at the photosensitive drum 10.
1 is in contact with the surface.

The shape and contact conditions of the blade 110 are as follows. That is, the blade 110 is formed to have a thickness of 2 [mm] and a length of 300 [mm], for example, and has a tip protruding from the tip of the support member 111. It has been adjusted as follows.

The support angle θ of the blade 110 (the angle of inclination of the blade with respect to the tangential direction of the photosensitive drum) is 20.
And the amount b of penetration into the residual toner on the photoreceptor 101a is adjusted to be approximately 1.2 [mm]. The blade 110 having such a configuration has an edge portion of the photoconductor 101a.
The photoconductor 101 penetrates the residual toner attached to the
Remove from a.

The blade 110 has a resistivity adjusted to about 10 ⁶ to 10 ⁹ [Ωcm] by dispersing carbon or an ion conductive material based on urethane rubber. The charging voltage is applied to the blade 110 from the power supply 112 in the same manner as the charging member 107 described above.
To charge the surface. The applied voltage is -1.5 to -2.0.
DC voltage of about [kV].

[0017]

In an image forming apparatus provided with the conventional cleaning and charging apparatus as described above, the residual toner adhering to the outer peripheral surface of the photoreceptor 101a after transfer is originally cleaned and charged. Combined blade 1
10 should be removed.

However, in actuality, there is toner that passes through the blade 110 (a small amount as compared with the amount of untransferred toner). Conversely, if no toner passes through the blade 110, the blade 110 and the photoconductor 1
No toner exists in the contact portion (nip portion) with the photoconductor 101a (the blade 110 directly contacts the photoconductor 101a).
The frictional force between the blade 110 and the blade 110 becomes large, causing the blade 110 to be caught and the blade 110 to be worn.

That is, the toner passing through the blade 110 plays a role of improving the slip between the blade 110 and the photosensitive member 101a, thereby preventing the blade 110 from being caught and the blade 110 from being worn.

In the conventional blade charging (normal blade charging instead of blade charging by a cleaning / charging device), residual toner adhering to the surface of the photoreceptor after transfer is removed by a normal cleaning blade, and then charged. (Charged blade) is pressed against the surface of the photoreceptor to charge the surface. For this reason,
In conventional blade charging, there is almost no toner between the charging blade and the photoconductor, and there is a problem that the influence of blade wear due to contact between the charging blade and the photoconductor is reduced.

On the other hand, for example, Japanese Patent Application Laid-Open No.
As disclosed in Japanese Unexamined Patent Publication No. 53-53, there has been proposed a method of coating the blade surface with a low friction resin or the like. According to this, damage due to wear of the blade surface is eliminated, and abnormal charging does not occur. Alternatively, in the case of a cleaning / charging apparatus that simultaneously charges the surface of the photoconductor while removing the residual toner attached to the surface of the photoconductor using the cleaning / charging blade described above, the distance between the blade and the photoconductor is reduced. , The wear of the blade is not a significant problem.

Rather, the cleaning / charging device has another problem as follows. That is, a part of the toner passing through the blade adheres to the contact surface of the blade with the surface of the photoconductor. Therefore, as the number of durable sheets (for example, the number of copies) increases, the blade (the contact surface)
Are stained by the adhesion of the toner, and the stain accumulates. This contamination may hinder the potential convergence of the blade due to voltage application, cause charging unevenness, and cause image defects such as vertical stripes on an output image.

Therefore, in order to solve such a problem,
The following have also been proposed: For example, Japanese Patent Application Laid-Open
In the image forming apparatus described in JP-A-134521, a superimposed voltage of a DC voltage and a vibration voltage having a peak-to-peak voltage smaller than twice the so-called charging start voltage is applied to the blade during non-image formation. This is because the toner applied and fixed to the blade is reduced when the voltage applied to the blade is only the DC voltage, rather than the superimposed voltage of the vibration voltage and the DC voltage.

However, even in this image forming apparatus, when an image is formed, a superimposed voltage of an oscillating voltage having a peak-to-peak voltage larger than twice the charging start voltage and a DC voltage is applied to the blade. As a result, image defects occur as described above, and the durability over a long period of use is not sufficient. In addition, since different voltages are applied to the blade during non-image formation and during image formation, there is a disadvantage that a more complicated mechanism is required.

The present invention has been made in view of the above points, and has a cleaning / charging apparatus (cleaning / charging apparatus).
The purpose of the present invention is to prevent the toner from adhering to the blade due to the long-term use of the charging blade.

[0026]

SUMMARY OF THE INVENTION The present invention provides a cleaning / charging blade for contacting an outer peripheral surface of a member to be charged to remove residual toner on the outer peripheral surface and to charge the outer peripheral surface. In order to achieve the above object, an image forming apparatus provided with a power supply for applying a charging voltage to a cleaning / charging blade is characterized as follows.

According to a first aspect of the present invention, a cleaning / charging blade is formed of at least a substrate and a conductive coating layer, and the surface roughness of the contact surface of the coating layer with the outer peripheral surface of the member to be charged is reduced. It is smaller than the average particle size of the toner. According to a second aspect of the present invention, the power supply is a power supply for generating an oscillating voltage and applying the oscillating voltage to the cleaning / charging blade.

[0028]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a configuration diagram showing an example of a main part of an image forming apparatus embodying the present invention. In this image forming apparatus, reference numeral 1 denotes a cleaning / charging apparatus, which includes a blade 2.

The blade 2 is formed by providing a conductive coating layer (eg, carbon-dispersed polyvinyl butyral) 2b on at least the surface of a non-conductive substrate (eg, urethane rubber) 2a. The blade 2 is adhered to a conductive support member 3, and an edge portion of the blade 2 is in contact with an outer peripheral surface of a photosensitive drum 10, which is a member to be charged, via a coat layer 2 b.

The surface roughness Rmax of the contact surface of the coat layer 2b with the outer peripheral surface of the photosensitive drum 10 is smaller than the average particle diameter of the toner, and the contact surface is a smooth surface. Since the edge of the blade 2 is pressed against the outer peripheral surface of the photosensitive drum 10, the actual gap between the blade 2 and the photosensitive drum 10 is smaller than the value of Rmax.

A charging bias power supply 5 is connected to the coat layer 2b of the blade 2 via a conductive support member 3, and the charging bias power supply 5 generates a high charging voltage (charging bias). Then, the high voltage is applied to the coat layer 2b of the blade 2.

On the other hand, the photosensitive drum 10 is rotatably supported by the apparatus main body, and is rotated by driving means (not shown). Around the photosensitive drum 10, the exposing means 103, the developing means 104, and the transferring means 10 as shown in FIG.
5 and the like are arranged so that a toner image is formed on the outer peripheral surface of the photosensitive drum 10.

Next, the operation of this embodiment will be described. Now, when a predetermined switch (not shown) is pressed by the operator, the charging bias power supply 5 is activated, and the charging bias is applied between the coat layer 2 b of the blade 2 and the photosensitive drum 10. Based on the applied charging bias, the vicinity of the contact portion is charged to a constant potential by discharge in a minute space near the contact portion (contact portion) between the coat layer 2b of the blade 2 and the photosensitive drum 10. You.

Since the photosensitive drum 10 is rotated in response to a predetermined signal, the coating layer 2b of the blade 2 slides on the surface (outer peripheral surface) of the photosensitive drum 10 to make the entire surface uniform. It is charged to a potential. The contact surface of the coat layer 2b with the surface of the photoconductor drum 10 is smooth, the contact state with the photoconductor drum 10 is good, and there are almost no gaps microscopically. Even when the toner is conveyed to the photosensitive drum 10, the toner does not enter between the coat layer 2b and the photosensitive drum 10.

As a result, the toner on the photosensitive drum 10 is blocked by the blade 2 and the photosensitive drum 1
Since the toner does not enter the contact portion between the coating layer 2 and the coating layer 2b, toner does not accumulate in the contact portion and the blade 2 is not stained, so that charging unevenness does not occur. Therefore, image defects such as vertical stripes do not occur in the output image, and a good image can be obtained over a long period of time.

Furthermore, this embodiment is characterized in that the charging bias applied by the charging bias power supply 5 to the coat layer 2b of the blade 2 is a vibration (AC) voltage only or a voltage obtained by superimposing a vibration voltage on a DC voltage. Join. In general, in a cleaning / charging device, when only a DC voltage is applied to the blade, the contact between the blade and the photoconductor is strictly limited, and the influence of toner near the contact portion between the blade and the photoconductor is strictly limited. There are problems such as susceptibility.

For this reason, considering the difficulty in obtaining uniform charging, it is not practical to apply only a DC voltage to the blade, and only an oscillating voltage or an oscillating voltage superimposed on a DC voltage is impractical. A method of applying a voltage is required. However, when the voltage applied to the blade is a vibration voltage alone or a voltage obtained by superimposing a vibration voltage on a DC voltage, the adhesion and fixation of the toner to the surface of the blade that comes into contact with the photosensitive member tends to be promoted.

On the other hand, in the embodiment of the present invention,
The surface roughness Rmax of the contact surface of the coating layer 2b with the surface of the photoconductor drum 10 is made smaller than the average particle diameter of the toner to prevent the toner from entering the contact portion between the coating layer 2b and the photoconductor drum 10. Therefore, even when the voltage applied to the coating layer 2b is a vibration voltage alone or a voltage obtained by superimposing a vibration voltage on a DC voltage, the adhesion and fixation of the toner to the surface of the coating layer 2b in contact with the photosensitive drum 10 does not occur. Absent. For this reason, even when the blade 2 is used for a long period of time, uneven charging due to toner contamination does not occur.

[0039]

As described above, according to the image forming apparatus of the first and second aspects of the present invention, the cleaning / charging blade is formed by at least the base material and the conductive coating layer, and the coating layer is formed. By making the surface roughness of the surface in contact with the outer peripheral surface of the member to be charged smaller than the average particle size of the toner, it is possible to prevent the toner from entering the contact portion between the coat layer and the member to be charged, and the blade It is possible to prevent toner contamination. Therefore, even when the cleaning / charging blade is used for a long time, charging unevenness does not occur, and a good image can be obtained for a long time.

Furthermore, according to the second aspect of the present invention, since the power supply generates an oscillating voltage and applies the oscillating voltage to the cleaning / charging blade, contact between the blade and the member to be charged is strictly limited. Also, there is no problem that the blade is easily affected by toner near the contact portion between the blade and the member to be charged, and uniform charging can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an example of a main part of an image forming apparatus embodying the present invention.

FIG. 2 is a schematic configuration diagram of an image forming apparatus using an electrophotographic process.

FIG. 3 is a schematic configuration diagram illustrating an example of a cleaning unit used in a conventional image forming apparatus.

FIG. 4 is a schematic configuration diagram illustrating an example of a conventional contact charging device.

FIG. 5 is a schematic configuration diagram showing an example of a conventional cleaning and charging device.

[Explanation of symbols]

 1: Device for both cleaning and charging 2: Blade for both cleaning and charging 2a: Base material 2b: Coating layer 3: Support member 5: Power supply for charging bias 10: Photoconductor drum

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kei Yasutomi Ricoh Co., Ltd. 1-3-6 Nakamagome, Ota-ku, Tokyo

Claims (2)

[Claims] 1. A cleaning / charging blade for contacting an outer peripheral surface of a member to be charged to remove residual toner on the outer peripheral surface and to charge the outer peripheral surface, and a charging / charging blade for the cleaning / charging blade. An image forming apparatus comprising a power supply for applying a voltage of at least one of the following: wherein the cleaning / charging blade is formed by at least a substrate and a conductive coating layer, and the coating layer is applied to the outer peripheral surface of the member to be charged. An image forming apparatus wherein the surface roughness of the contact surface is smaller than the average particle size of the toner. 2. The image forming apparatus according to claim 1, wherein the power supply is a power supply that generates an oscillating voltage and applies the oscillating voltage to the cleaning / charging blade.