JPH0193761A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent inversion which arises in a contacting electrification member and to uniform the electrification processing of an image carrier by setting an abutting angle of the contact electrification member with respect to the image carrier smaller than an abutting angle of a cleaning member with respect to the image carrier. CONSTITUTION:The abutting angles are acute, which is made by abutting surfaces of the contacting electrification member 2 and the cleaning member 6A with respect to the image carrier 1 and the tangent of the abutting surface of the image carrier 1. One part of the abutting surface on the image carrier 1 is gradually separated along the moving direction of the surface of the image carrier 1. The abutting angle theta2 of the contacting electrification member 2 with respect to the image carrier 1 is set smaller than the abutting angle theta1 of the cleaning member 6A with respect to the image carrier 1. By such constitution, cleaning of the surface of the image carrier 1 is made efficient and peeling- off can be prevented which arises in the contact electrification member 2 without adhering residues acting as a smoothing agent in the abutting part with respect to the image carrier 1. In addition to that, the surface of the image carrier 1 is uniformly electrified and processed.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an image forming apparatus, and more specifically, a rotary acid is a means for uniformly charging the surface of an image carrier whose surface is moved by rotational driving or the like. The present invention relates to an image forming apparatus in which image formation is performed by applying an image forming process means including the above, and the surface of an image carrier that has been used for one image formation is cleaned by a cleaning means and used for image formation repeatedly.

[Conventional technology]

Specific examples of image forming apparatuses of the above type include transfer type electrophotographic copying apparatuses, transfer type electrostatic recording apparatuses, and the like.

Transfer-type electrophotographic copying devices use a drum-type or endless belt-type electrophotographic photoreceptor in which a rotating acid is rotationally driven as an image carrier, and basically uniformly charge, expose, and develop images on the surface of the photoreceptor. A visual image is formed by applying an image forming process means to form a visual image, the visual image is transferred to the transfer material surface by a transfer device, the transferred visual image is fixed to the transfer material surface by a fixing device, and the transfer material is transferred to the image forming material. Output as . After the image has been transferred, the surface of the photoreceptor is cleaned by a cleaning means and repeatedly used for image formation.

Transfer-type electrostatic recording devices use a rotationally driven drum-type or endless belt-type dielectric material as an image carrier, and basically uniformly charge, selectively eliminate, and develop the surface of the dielectric material. A visual image is formed by applying an image forming process means, and then the visual image is transferred and fixed onto the transfer material surface in the same manner as the electrophotographic copying apparatus described above, and the transfer material is output as an image-formed product, and After the image has been transferred, the dielectric surface is cleaned by a cleaning means and repeatedly used for image formation.

The cleaning means removes transfer residual developer (toner), transfer material paper dust, and other adhered contaminants remaining on the surface of the photoreceptor, dielectric, etc. as an image carrier after image transfer to the transfer material surface. A structure is used in which a rubber elastic member such as urethane rubber is used for aggregation, and the member is brought into contact with the surface of the image carrier to wipe off contaminants adhering to the surface of the image carrier.

Corona dischargers such as corotrons and scorotrons, which have good uniform charging properties, are widely used as means for uniformly charging the surfaces of photoreceptors, dielectric materials, and the like as image carriers. However, corona dischargers require an expensive high-voltage power source, require space for themselves and the shield space for the high-voltage power source, and often generate corona products such as ozone, which requires additional means and mechanisms to deal with them. This poses problems, such as the fact that these factors are factors that increase the size and cost of the device.

Therefore, in recent years, consideration has been given to adopting a contact charging method instead of a corona discharger, which has many problems. In contact charging, a voltage (for example, 1 to 2 K
By contacting a conductive member (contact charging member) to which a DC voltage of about V or a superimposed voltage of a DC voltage and an AC voltage, etc. is applied, charges are directly injected into the image carrier surface. A device that charges to a predetermined potential, such as a roller charging type (Japanese Patent Application Laid-Open No. 58-91253), a blade charging type (Japanese Patent Application Laid-Open Nos. 56-194349 and 80-147758), and a combination charging and cleaning type (JP Showa 5Ei-185
No. 188) etc. have been devised.

[Problem that the invention seeks to solve]

In the contact charging method, it is important to uniformly contact the conductive member, which is the charging member, with the surface of the image carrier, which is the object to be charged, at each part along its length, and to maintain a uniform contact state. If this is not achieved, uneven charging will occur on the surface of the image carrier.

In addition, in the case of the charging/cleaning type, uneven charging may occur due to residual developer, transfer material paper dust, and other foreign matter that are wiped from the surface of the image carrier after image transfer and accumulate in the charging section. In particular, in the case of an image forming apparatus in which a process cartridge is removable, foreign matter may get mixed into the charged area due to vibrations caused when the process cartridge is installed or removed or carried around.

Furthermore, when the contact charging member or the cleaning member comes into pressure contact with the image carrier, wear and tear on the surface of the image carrier or inversion of the member may occur, and uniform charging may not be obtained.

The present invention employs a contact charging method in which a charging member is brought into contact with the surface of the image carrier as a charging means for the image carrier.
In this case, the contact setting of the contact charging member with respect to the image carrier surface is made highly accurate, that is, the state in which the contact charging member is uniformly and stably contacted with the image carrier surface at each part along its length is always ensured. The purpose of this method is to uniformly charge the surface of the image carrier.

[Means for solving problems]

The present invention is.

Image formation is performed by applying an image forming process means including a means for uniformly charging the surface of the image bearing member to the surface of the image bearing member that moves, and the surface of the image bearing member used for image formation is cleaned by a cleaning means and the image forming process is repeated. In the image forming apparatus, the charging means is a blade-shaped contact charging member brought into contact with the surface of the image carrier and applied with a voltage.

The cleaning means is a blade-shaped cleaning member brought into contact with the surface of the image carrier, and the contact charging member and the cleaning member each have a contact surface with respect to the image carrier and a tangent line of the contact portion of the image carrier. The contact charging member has an acute contact angle, and at least a part of the contact surface with respect to the image carrier is gradually separated from the image carrier surface along the surface movement direction of the image carrier, and the image carrier of the contact charging member The image forming apparatus is characterized in that the contact angle between the cleaning member and the image carrier is smaller than the contact angle between the cleaning member and the image carrier.

[For production]

After being subjected to image formation (after image transfer), the surface of the image carrier passes through a blade-shaped cleaning member that is brought into contact with it to wipe away residual deposits and make it a clean surface. The surface of the image bearing member that has been stained is uniformly subjected to contact charging treatment by a blade-shaped contact charging member that is in contact with the image bearing member surface at a position downstream in the direction of surface movement of the image bearing member surface than the cleaning member position, and the next image is formed. served.

In this case, if the contact angle of the blade-shaped cleaning member with respect to the image carrier is increased in order to improve the cleaning effect of the image carrier surface, the cleaning member may turn over (turn over) due to the coefficient of friction with the image carrier. However, in the case of the cleaning member, even if the contact angle with the image carrier is set to be quite large within an acute angle range, in reality, the residual deposits wiped from the surface of the image carrier will be removed by the cleaning member. exists at the contact area between the cleaning member and the image carrier, and acts like a lubricant to reduce the dynamic coefficient of friction, preventing the cleaning member from turning over and effectively cleaning the surface of the image carrier. The surface is cleaned.

However, since the contact charging member contacts the surface of the image carrier after the surface has been cleaned by the cleaning member, there is no effect of reducing the dynamic coefficient of friction due to the lubricant action of the residual deposits as in the case of the cleaning member. This tends to lead to a state in which the member is likely to be inverted.

Therefore, the contact angle of the contact charging member with respect to the image carrier is set smaller than that of the cleaning member. As a result, the friction coefficient between the contact charging member and the image carrier is reduced, so that the member does not turn over, and the contact charging member is uniformly and stably abutted against the image carrier surface at each longitudinal portion, so that the image carrier surface It becomes possible to charge the material uniformly.

〔Example〕

FIG. 1 is a schematic diagram of the structure of an embodiment of the apparatus. This embodiment is a transfer type electrophotographic copying apparatus with a removable process cartridge.

In the figure, reference numeral 1 designates a drum-type electrophotographic photoreceptor as an image carrier, which is rotated at a predetermined circumferential speed in the direction of the arrow around a support shaft 1a, and has a resin layer on its surface, such as OPC ( (hereinafter abbreviated as photoreceptor), 2 is a contact charging member as a means for uniformly charging the circumferential surface of the photoreceptor, and in this embodiment, a conductive elastic blade made of conductive rubber or the like or an appropriate resistance on the outer surface thereof is used. value (e.g. volume resistivity 108~1012
A resistive layer having a resistance of ΩφC■) is provided and is in contact with the counter direction with respect to the plane movement direction of the photoreceptor. 3 is a short focus lens array as a light image exposure means, 4 is a developing device, 5 is a transfer device, and 51 is a device that synchronizes the transfer material P conveyed one sheet at a time from a paper feed section (not shown) with the rotation of the photoreceptor L. a timing roller 5 which is fed between the photoreceptor 1 and the transfer device 5;
2 is a transfer material guide member disposed between the timing roller 51 and the transfer device 5, and 52 is a transfer material guide member (not shown) that fixes the transfer material P that has passed between the photoreceptor 1 and the transfer device 5 and has received the image transfer. A conveyance device 6 introduced into the apparatus is a cleaning device that cleans the surface of the photoreceptor after image transfer.

The apparatus of this example includes a photoreceptor 1, a contact charging member 2, and a developing device 4e.
The four process devices of the cleaning device 6 are collectively assembled into a process cartridge 7 in a predetermined arrangement relationship with each other. It can be inserted and installed, and conversely, it can be removed and removed from the main body of the copying machine. .

By fully inserting and mounting the process cartridge 7 into the copying apparatus main body, the copying apparatus main body side and the process cartridge 7 side are mechanically and electrically coupled to each other, and the copying apparatus becomes operable.

During the rotation process of the photoreceptor l, its peripheral surface is sequentially and uniformly charged by the blade 2, which is a contact charging member, to which a voltage (for example, a superimposed voltage of a DC voltage and an alternating voltage) is applied from a high-voltage power source E, and then By passing through the position of the light image exposure means 3 and sequentially receiving light image exposure L (slit exposure of the original image), electrostatic latent images corresponding to the exposure light image pattern are sequentially formed. The optical image exposure can also be performed by laser beam scanning, which shows a light transmission window opening in the cartridge housing wall portion corresponding to the image exposure means 3. In the case of an electrostatic recording device, latent images are sequentially formed on the photoreceptor surface by means such as an electrode array that selectively removes static electricity from the photoreceptor surface.

The latent image formed on the surface of the photoreceptor 1 is then sequentially developed (developed) as a toner image by the developing device 4, and the toner image on the surface of the photoreceptor is transferred by the transfer device 5 between the transfer device 5 and the photoreceptor l. One sheet is conveyed from a paper feeding section (not shown), and is transferred onto the surface of the transfer material P fed by a timing roller 51 in synchronization with the rotation of the photoreceptor 1.

The transfer material P that has passed through the transfer device 5 and has received the image transfer is sequentially separated from the surface of the photoreceptor, is introduced into a fixing device (not shown) by the conveyance device 53, undergoes image fixation, and is output as an image formed product. Ru.

On the other hand, the first surface of the photoreceptor after image transfer is cleaned by cleaning equipment f! The cleaning member 6A of No. 16 removes residual toner, transfer material paper powder, and other residual deposits to form a clean surface, which is repeatedly used for image formation.

The cleaning member 6A is a blade-shaped rubber elastic member (hereinafter referred to as a cleaning blade) made of urethane rubber-EPDM, NBR, etc., which is oriented counter to the rotational direction of the photoreceptor and whose tip edge is in contact with one surface of the photoreceptor. ), and the photoreceptor 1 is cleaned by the cleaning blade 6A.
Any residual deposits on the surface are scraped off and wiped clean.

The cleaning blade 6A applies the pressure necessary to remove the residual deposits t (FIG. 2) from the surface of the photoreceptor 1, and also maintains contact between the contact surface of the cleaning blade 6A to the photoreceptor and the tangent of the contact portion. Angle θ! is an acute angle, and at least a part of the contact angle forming this angle θ□ is spaced apart from the photoreceptor 1. The angle θ1 is set at such an angle that the contact surface does not contact the photoreceptor.

The cleaning blade 6A tends to reverse (turn over) in the direction of surface movement of the photoreceptor 1 due to the coefficient of friction with the photoreceptor 1, and this phenomenon tends to occur as the angle θ increases, but in reality, the angle θ is Even if the setting is relatively large, residual deposits t wiped off from the surface of the photoconductor 1 remain in the contact area between the cleaning blade 6A and the photoconductor 1, and this acts like a lubricant and causes dynamic Although the friction coefficient is reduced, the reversal of the cleaning blade 6A does not occur, that is, the permissible setting range of the contact angle θ1 is widened.

The contact charging member 2 is a blade-shaped conductive rubber elastic member (hereinafter referred to as a contact charging blade) whose base material is a rubber elastic body such as urethane, PEDM, NBR, etc., and whose resistance value is controlled to a value necessary for carrying out contact charging. The photoreceptor is disposed in contact with the counter direction with respect to the rotational direction of the photoreceptor.

This contact charging blade 2 also applies a predetermined pressure, and the contact angle θ2 (Fig. 2) formed by the contact surface of the blade 2 with respect to the photoreceptor l and the tangent of the contact portion is an acute angle. At least a part of the contact surface to be formed is arranged so as to be spaced apart from the photoreceptor l. Then, as described above, a voltage capable of charging one surface of the photoreceptor is applied from the power source E to the contact charging blade 2, whereby the surface of the photoreceptor that has been cleaned by the cleaning blade 6A is subjected to contact charging processing. .

This contact charging blade 2 differs from the cleaning blade 6A described above, in that the contact charging blade 2 and the photoreceptor 1
Since there is no residue attached to the photoreceptor surface acting as a lubricant at the contact portion with the surface, reversal is likely to occur, and the reversal depends on the contact angle θ2 of the blade 2 with respect to the photoreceptor 1.

That is, as shown in FIG. 3, the force received by the blade 2 in contact with the surface of the rotating photoreceptor 1 is the resultant force F3 of the acting force F1 of the pressing force and the frictional force F2 between the blade 2 and the photoreceptor 1 due to F1. Figure 3 (
When the direction of the force F3 is within the contact angle of 0 as shown in A), the rotational external force as shown by the arrow in the figure tends to cause the blade to turn over, and as shown in Fig. 3B, <F3 is outside the angle θ2, that is When directed toward the inside of the blade, the force F3 is in a direction that compresses the blade, and is not in the direction of rotation indicated by the arrow, making it difficult to cause reversal.

Therefore, the contact charging blade 2 has a contact angle θ with respect to the photoreceptor 1.
It is desirable to make 2 as small as possible, and making the corresponding lateral direction θ2 small is also effective for uniform charging properties.

That is, when a DC voltage DC is applied to the blade 2 from the power source E, a charge is applied to the photoreceptor (image carrier) near the portion d according to Paschen's law as shown in Figure 4, and in this case, as shown in Figure 4 ( Even if the contact angle θ is as shown in A), the same figure (B
), but applying a DC voltage itself tends to cause uneven charging.
A bias voltage obtained by superimposing an AC (alternating) voltage on the voltage is applied to the blade 2. In particular, when an alternating electric field having a peak value that is twice or more than the charging start voltage is superimposed on the AC voltage, uniform charging without uneven charging can be achieved. I found out that I can get it.

At this time, it is thought that an effect similar to that in which the Paschen region expands and the charged region increases due to the AC effect is obtained, and this region is the range of d1 and d2 in FIGS. 4('A) and 4(B). Here, the angles θ2 and θ' in Fig. 4 (A) and (B) are
2 difference occurs, more uniform charging property is obtained, and (
A) In the case of the angle θ2 of @, the area view is This is undesirable because leakage occurs, and it is advantageous to make the angle θ2 as small as θ'2.

In this way, the contact charging blade 2, which is a contact charging member, and the cleaning blade 6A, which is a cleaning member, are brought into contact with the photoreceptor l, which is an image carrier, and the contact surface formed by the contact surface with respect to the photoreceptor and the tangent of the contact portion of the photoreceptor are brought into contact with each other. The angle is acute angle θ
2・C1, and at least a part of the contact surface with respect to the photoreceptor is gradually separated from the image carrier surface, and the contact angle θ2 of the contact charging blade 2 with respect to the photoreceptor is equal to the contact angle of the cleaning blade with respect to the photoreceptor. smaller than the angle θ1 (C
2C1) By establishing the following relationship, the cleaning blade 6A can achieve good cleaning performance without hitting the photoreceptor l, and the contact charging blade 2 can be cleaned without causing any reversal in the contact charging blade 2. It was found that these are the conditions under which uniform charging properties can be stably obtained.

In addition, conversely, the contact angle θ2 of the contact charging blade 2 with respect to the photoreceptor is changed to the contact angle θ2 of the cleaning blade with respect to the photoreceptor.
1 or more (C2≧θl), the larger the contact angle θ2 is than the contact angle θ1, the more likely the contact charging blade 2 will be reversed, and uniform charging will not be obtained, making it impractical. Understood.

In the image forming apparatus shown in FIG. 1, a urethane rubber blade with a hardness of 65° is used as the cleaning blade 6A, the contact angle OI is set to 24±1'', and the free length, thickness, and cross-sectional shape of the blade 2 are varied. When the appropriate contact pressure was investigated, it was found that setting the contact pressure in the range of about 11 to 38 g/c was good in each case.

Also, as the contact charging blade 2, urethane rubber and EPDM are used.
Using a conductive blade with a hardness of 85°, the resistance value of which was controlled by adding a conductive material so that each resistance value was 10'Ω・C, the contact angle θ2 = 24 ± 1° to 16 ± 1°. , contact pressure 5
~24g/cm, applied voltage = 700V DC, exchange meeting 1
An durability test was conducted under the conditions of 500V PP life and 800Hz, in which the OPC photoconductor was subjected to contact charging treatment, and the formed latent image was developed and transferred using positive toner.The image formation cycle was repeated, and good image output was achieved even after 3000 sheets. was maintained.

The contact charging blade 2 and cleaning blade 6A may be appropriately set, but the best contact angle is C1>C2. Further, the resistance value of the contact charging blade 2 also varies depending on the characteristics of the photoreceptor, the shape of the blade, etc., and the above-mentioned value of 10 7 Ω 11C is not necessarily optimal, but it is generally set appropriately in the range of about 10 3 to 10 10 Ω·C11.

The contact charging blade 2 is disposed in contact with the photoreceptor in a counter direction with respect to the surface movement direction of the photoreceptor, so that the cleaning blade 6A is positioned upstream of the contact charging blade 2 in the surface movement direction of the photoreceptor. Even if the cleaning of the photoconductor surface is not performed properly for some reason and the remaining adhering residue reaches the position of the contact charging blade 2, the contact charging blade 2 disposed in the counter direction will not be able to carry out the second cleaning. It also works as a blade, preventing foreign matter from entering the surface of the charging area of the photoreceptor by the contact charging blade 2, maintaining good charging performance, and further cleaning the surface of the photoreceptor.

Figures 5 (A), (B), and (C) show the support 1 of the contact charging blade 2 (or cleaning blade 6A).
00 is shown, in which (A) is a sandwiched support type, (B) is an adhesive support type, and (C) is a support type example.
) indicates a support type that is integrally formed into a mold or metal.

〔Effect of the invention〕

As described above, according to the present invention, the surface of the image bearing member is efficiently leaned, and the surface of the image bearing member is always and stably charged uniformly by the contact charging member. It becomes possible to configure an image forming apparatus that takes full advantage of the advantages.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the configuration of an image forming apparatus according to an embodiment, Fig. 2 is an enlarged view of the cleaning blade portion and the contact charging blade portion, and Figs. 3 (A) and (B) are blade reversal.
Figure 4 (A) and (B) are explanatory diagrams of the force relationship; Figures 4 (A) and (B) are model diagrams that explain the charging area according to Paschen's law; Figure 5 (A) and
(B) and (G) are diagrams showing examples of how the blade is supported. 1 is a rotating photoreceptor as an image carrier, 2 is a conductive blade as a contact charging member, 6A is a blade as a cleaning member, etc., and θ1 and θ2 are contact angles.

Claims (1)

[Claims] 1. Image formation is performed by applying an image forming process means including a means for uniformly charging the surface of the image carrier to the surface of the image carrier that moves, and the surface of the image carrier used for image formation is cleaned. The image forming apparatus is of a type in which the image forming apparatus is repeatedly cleaned by means of a cleaning means and subjected to image formation, wherein the charging means is a blade-shaped contact charging member that is brought into contact with the surface of the image carrier and a voltage is applied thereto, and the cleaning means is a blade-shaped cleaning member that is brought into contact with the surface of the image carrier, and the contact charging member and the cleaning member are in contact with each other between the contact surface with respect to the image carrier and the tangent of the contact portion of the image carrier. The angle is an acute angle, and at least a part of the contact surface with respect to the image carrier is gradually separated from the surface of the image carrier along the surface movement direction of the image carrier, and the contact charging member contacts the image carrier. An image forming apparatus characterized in that a tangent angle is smaller than the contact angle of the cleaning member with respect to the image carrier.