JP3293021B2 - 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 a copying machine, a printer, an F
An image forming apparatus such as an AX, and charging means around an image forming body;
The present invention relates to an electrophotographic image forming apparatus that forms an image by arranging an image exposing unit and a developing unit, and particularly relates to a method of grounding an image forming body.

[0002]

2. Description of the Related Art Conventionally, as one method of forming a multi-color image, a color image is formed by sequentially charging, exposing, and developing each color within one rotation of a photoreceptor as one image forming body. 2. Description of the Related Art A color image forming apparatus for forming an image is known, in which a base of an image forming body is formed of a transparent material such as resin or glass, and a plurality of image exposure units are accommodated therein, and an image is formed on the base. An apparatus for exposing a photosensitive layer formed on the outer periphery of the device through a light-transmitting device is disclosed in, for example,
No. 307.

As a conventional method of grounding an image forming body, as shown in FIG. 6, the image forming body is exposed to an end of a photosensitive drum 410 which is an image forming body formed by a base 401, a conductive layer 402 and a photosensitive layer 403. A method is used in which a conductive portion 402a is provided, and a conductive brush 408 is brought into contact with the conductive portion 402a and grounded.

As shown in FIG. 7, as a method of maintaining a gap between the developing sleeve 431 of the developing device 413 and the photosensitive drum 410, abutting rollers 438a, which are driven and rotated by the photosensitive drum 410, are provided at both ends of the developing sleeve 431. 438
Those provided with b are conventionally used.

[0005]

However, in the above-mentioned grounding method, the conductive layer is easily peeled off, and there is a possibility that poor grounding may occur. On the other hand, in an image forming apparatus in which the gap between the developing device and the photosensitive drum is maintained by the abutting roller, the photosensitive layer of the photosensitive drum is abraded by the abutting roller as the image forming apparatus is used, and the abutting roller and the conductive roller are electrically conductive. There is a problem in that the conductive layer is in contact with the layer or the abutting roller further cuts the conductive layer, resulting in poor grounding. In any case, there is a problem in how to ground the image forming body from the conductive layer. In particular, in the above-described color image forming apparatus, since a plurality of developing units are used, the photosensitive layer and the conductive layer are abraded by the abutting rollers, which is a cause of occurrence of remarkable grounding failure.

SUMMARY OF THE INVENTION The present invention has been achieved by solving the above problems, and as a result, in an image forming apparatus using an abutting roller,
It is an object of the present invention to provide a method of grounding an image forming body without occurrence of a grounding failure, and particularly to provide a grounding method suitable for a color image forming apparatus in which abutting rollers are frequently used.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus having a base made of a high-resistance member, a conductive layer and a photosensitive layer provided on an outer peripheral surface of the base, and a latent image formed on the image forming body. Developing means for developing the image forming body, and an abutting roller provided in the developing means for maintaining a gap between the image forming body and the developing means at a predetermined value, and the abutting roller is used to image the image forming body. In the image forming apparatus, which is in contact with both ends of the image forming body outside the area, the base of the image forming body is pierced between the image area of the image forming body and the abutting roller. This is achieved by an image forming apparatus characterized by providing a conductive path for a conductive layer.

[0008]

1 to 4 show an embodiment of a grounding method according to the present invention and an image forming process and mechanisms of a color image forming apparatus which is an embodiment of an image forming apparatus suitable for carrying out the present invention. It will be described using FIG. FIG. 1 is a cross-sectional configuration diagram of a color image forming apparatus according to an embodiment of an image forming apparatus suitable for carrying out the present invention, and FIG. 2 is a diagram illustrating a cross section taken along line AOA in FIG. FIG. 3 is a schematic configuration diagram of the photosensitive drum, and FIG. 4 is a diagram showing an embodiment of a method of grounding the photosensitive drum.

In the color image forming apparatus of this embodiment, a photosensitive drum as an image forming body is formed of a transparent material, and a conductive layer and a photosensitive layer are provided on the outer peripheral surface of the transparent substrate. It has a structure in which a body drum is used, and image exposure means is arranged inside the photosensitive drum, and image forming process means such as a charger, a developing unit, a transfer unit, a static eliminator, and a cleaning device are arranged outside.

The photosensitive drum 10 as an image forming body is provided with a cylindrical substrate 1 having a high resistance of 10 ¹⁴ Ωcm or more and formed of a transparent member such as an optical glass or a transparent acrylic resin. A transparent conductive layer 2, an a-Si layer or a photosensitive layer 3 such as an organic photosensitive layer (OPC) is formed on a drum on the outer periphery of the drum. Is driven to rotate.

In this embodiment, in the photoconductor layer of the photoconductor drum, which is the image forming point of the exposure beam for image exposure, an appropriate contrast with respect to the light attenuation characteristic (photocarrier generation) of the photoconductor layer. What is necessary is that it has an exposure light amount of a wavelength that can be provided. Therefore, the light transmittance of the transparent substrate of the photosensitive drum in the present embodiment does not need to be 100%, and may have a characteristic such that a certain amount of light is absorbed when the exposure beam is transmitted. As a material of the translucent substrate, soda glass, Pyrex glass, acryl used for borosilicate glass and general optical members, fluorine, polyester, polycarbonate, polyethylene terephthalate,
Various translucent resins, such as, for example, can be used. Further, as the light-transmitting conductive layer, indium tin oxide (IT
O), tin oxide, lead oxide, indium oxide, copper iodide,
A light-transmissive metal thin film made of Au, Ag, Ni, Al, or the like is used. As a film forming method, a vacuum deposition method, an active reaction deposition method, various sputtering methods, various CVD methods,
A dip coating method, a spray coating method, or the like is used. Also,
As the photoconductor layer, amorphous silicon (a-S
i) An alloy photosensitive layer, an amorphous selenium alloy photosensitive layer, or various organic photosensitive layers (OPC) can be used.

The scorotron charger 11 serving as a charging means is used in image forming processes of yellow (Y), magenta (M), cyan (C) and black (K). A charging operation is performed on the body layer by a control grid maintained at a predetermined potential and corona discharge by a discharge wire, and a uniform potential is applied to the photosensitive drum 10.

An exposure optical system 12 serving as an image exposure means for each color.
Are linear FL (phosphor emission), EL (electroluminescence), PL (plasma discharge), and LE in which light emitting elements arranged in the axial direction of the photosensitive drum 10 are arranged in an array.
D (light emitting diode), linear LISA (magneto-magnetic effect optical shutter array), PLZT (transmissive piezoelectric element shutter array), L
It is configured as a unit by an exposure element such as a CS (liquid crystal shutter) and a selfoc lens as an equal-magnification image-forming element, and is attached to a support member 20 provided inside the photosensitive drum 10 and separated from each other. The image signal of each color read by the image reading device is sequentially taken out of the memory and input to the exposure optical system 12 for each color as an electric signal. The emission wavelength of the light emitting element used in this embodiment is in the range of 600 to 900 nm.

Developing means which is a developing means for each color using a non-contact developing method in which a one-component or two-component developer containing yellow (Y), magenta (M), cyan (C) and black (K) is accommodated respectively. Each of the photoconductor drums 10
The developing sleeve 131 rotates in the same direction while maintaining a predetermined gap with respect to the peripheral surface of the developing sleeve 131.

The developing unit 13 for each color described above applies the developing bias voltage to the electrostatic latent image on the photosensitive drum 10 formed by the charging by the scorotron charger 11 and the image exposure by the exposure optical system 12. Reversal development is performed in a non-contact state.

An original image is read by an image reading apparatus separate from the present apparatus, and an image read by an image pickup element or an image edited by a computer is temporarily converted into image signals for respective colors of Y, M, C and K. Stored and stored in memory.

At the start of image recording, the photoconductor driving motor rotates to rotate the photoconductor drum 10 clockwise,
At the same time, application of a potential to the photosensitive drum 10 is started by the charging action of the Y scorotron charger 11.

After a potential is applied to the photosensitive drum 10, the Y exposure optical system 12 starts exposure with the first color signal, that is, an electric signal corresponding to the Y image signal, and the rotation is performed by rotating the drum. An electrostatic latent image corresponding to the Y image of the original image is formed on the photosensitive layer on the surface.

The latent image is reversal-developed by the Y developing device 13 in a state where the developer on the developing sleeve is not in contact with the developer, and a yellow (Y) toner image is formed in accordance with the rotation of the photosensitive drum 10.

Next, a potential is applied to the photosensitive drum 10 by the charging action of the magenta (M) scorotron charger 11 on the yellow (Y) toner image.
Exposure is performed by an electrical signal corresponding to the second color signal of the exposure optical system 12, that is, the M image signal, and the M developing device 1
The magenta (M) toner image is sequentially superimposed on the yellow (Y) toner image by the non-contact reversal development by No. 3.

According to the same process, the cyan (C) toner image corresponding to the third color signal is further formed by the cyan (C) scorotron charger 11, the exposure optical system 12 of C and the developing device 13 of C. A black (K) toner image corresponding to the fourth color signal is sequentially formed by the scorotron charger 11, the exposure optical system 12, and the developing device 13 of (K), within one rotation of the photosensitive drum 10. A color toner image is formed on the peripheral surface.

These Y, M, C and K exposure optical systems 12
Exposure to the organic photosensitive layer of the photosensitive drum 10 is performed from the inside of the drum through the transparent substrate described above.
Therefore, the exposure of the images corresponding to the second, third, and fourth color signals is performed without any influence from the previously formed toner image, and the same exposure as the image corresponding to the first color signal is performed. It is possible to form an electrostatic latent image. To stabilize the temperature in the photosensitive drum 10 and prevent the temperature from rising due to the heat generated by the exposure optical system 12, a material having good thermal conductivity is used for the support member 20, a heater is used at a low temperature, and a heater is used at a high temperature. By taking measures such as radiating heat to the outside through a heat pipe, the temperature can be suppressed to a level that does not cause a problem.

The developer for replenishment of each color is supplied to the replenishing tank 21.
The toner is further supplied to the developing device 13 of the corresponding color, and is stirred by the two stirring rollers 136 and 137. Then, the developing sleeve 131 is moved by the toner supply roller 135 and the thin layer forming rod 133.
Supplied to At both ends of the developing sleeve 131 outside the image area S, abutting rollers 138a and 138b which are driven and rotated by the photosensitive drum 10 are provided.

The developing device 13 is pressed by a pressing member (not shown), for example, a pressing spring, and the abutting rollers 138a and 138b serving as gap holding members press the photosensitive drum 10 in pressure. The developing sleeve 131 is brought into contact with the photosensitive drum 10 by abutting rollers 138a and 138b, and the developing sleeve 131 is brought into contact with the photosensitive drum 10 by a predetermined value, for example, 0.03 mm, 0.05 m
m, 0.3 mm, 0.5 mm, 1 mm, etc., are kept in a non-contact state with a gap of a certain value, and when developing by the developing unit 13 for each color, a developing sleeve in which a fixed magnet 132 is disposed inside is used. A developing bias to which a direct current or an alternating current is applied to 131 is applied, a jumping development is performed by a one-component or two-component developer contained in the developing device, and the toner is applied to the photosensitive drum 10 grounding the transparent conductive layer. A non-contact reversal development is performed in which a DC bias having the same polarity as that described above is applied to attach the toner to the exposed portion. The developer on the developing sleeve 131 after the development is scraped off by the scraping plate 134.

Subsequently, the color toner image formed on the peripheral surface of the photosensitive drum 10 is once transferred onto the intermediate transfer roller 41 by the action of the intermediate transfer roller 41. The color toner image formed on the peripheral surface of the intermediate transfer roller 41 is sent upward from a paper feed cassette 15 which is a transfer material storage means provided below the photosensitive drum 10 at a transfer section, and is horizontally transferred. Upper and lower guide plates 1 of the placed paper feed unit
A transfer material, which is a transfer material fed horizontally to the timing roller 16 through the space between 5a and 15b and fed in synchronization with the toner image on the intermediate transfer roller 41 rotating in the counterclockwise direction by the driving of the timing roller 16 The paper P is re-transferred to the paper P by a transfer roller 45 as a transfer device.

The transfer roller 45 is synchronized with the transfer sheet P fed to the transfer section by the timing roller 16, and the transfer of the length of the transfer sheet P is performed in the circumferential direction of the intermediate transfer roller 41. A control unit and a transfer roller provided in an image forming apparatus (not shown) so that the intermediate transfer roller 41 is pressed against the intermediate transfer roller 41 only when the transfer process is not performed. And the pressure release mechanism.

The transfer paper P to which the toner image has been transferred is separated from the peripheral surface of the intermediate transfer roller by the curvature of the intermediate transfer roller 41, and is then horizontally conveyed to the fixing device 17 via a conveyance belt 14e as a conveyance means. After the toner is heated and pressed by the heating roller 17a and the pressure roller 17b in the fixing device 17 to fuse and fix the toner on the transfer paper P, the toner is transferred onto the tray on the side of the color image forming apparatus via the discharge roller 18. The toner is discharged with the toner image surface facing down.

On the other hand, the photosensitive drum 10 from which the transfer paper is separated
In the cleaning device 19, the surface of the photosensitive drum 10 is rubbed by a cleaning blade 19a to remove residual toner, and is cleaned and continued to form a toner image of a document image, or temporarily stopped to form a toner image of a new document image. It takes formation. The waste toner scraped off by the cleaning blade 19a and the cleaning roller 19b is discharged to the waste toner container 22 through the toner conveying screw 19c and the toner conveying pipe 19d. After the cleaning, the cleaning blade 19a and the cleaning roller 19b are kept separated from the photosensitive drum 10 in order to prevent the photosensitive drum 10 from being damaged.

The photosensitive drum 10 includes an exposure optical system 1
As a result of the transfer area being improved and the transfer area being improved, even if the diameter of the drum is relatively small, the above-mentioned plurality of scorotron chargers 11, the developing device 13, the cleaning device 19, and the intermediate transfer roller 41 are provided on the outer peripheral surface thereof. And the like, and a small-diameter drum having an outer diameter of 60 mm to 200 mm can be used, and the volume of the apparatus can be made compact.

The horizontal line Q passing through the center of the photosensitive drum 10
Y, M, C, and K developing sleeves 13 on a diagonal line provided at an angle α and bisected by 1-O-Q2
1 is located at the center, and abutting rollers 1 provided in each developing device
Y, M, Y, M, and Y are preferably symmetrical vertically and symmetrically with respect to the center of the photosensitive drum 10 so that the 38a and 138b are pressed against the photosensitive drum 10 with uniform pressing force.
Four developing units 13 of C and K are provided. Developing device 13
Is pressed by, for example, a pressing spring, which is a pressing member (not shown), and the abutting rollers 138a and 138b press the photosensitive drum 10 in pressure. Developing devices 1 above and below Y, M and C, K
3 is preferably 60 ° or more and 90 ° or less, and if it is less than 60 °, the rotation of the image forming body is likely to be unstable. Is not stable.

With the arrangement of the developing devices 13 as described above, the abutting rollers of a plurality of developing devices disposed outside of the image forming body with respect to the cylindrical image forming body which rotates while the image forming apparatus is driven. A stable rotation of the photosensitive drum is obtained by the balanced pressing force, and the abrasion of the photosensitive layer by the abutting roller is small.

The front and rear flanges 111, 1 which are flange portions
The photoreceptor drum 10 mounted on the bearing 12 is fitted into a bearing 141 and a front flange 111 which are bearing members provided on a rear side plate 103 of the apparatus main body of the color image forming apparatus, and a bearing mounted on the front side plate 102 of the apparatus main body. It is supported by a bearing 143 as a member and is rotatably attached to the apparatus main body. In a state where the support member 20 to which the exposure optical system 12 is attached is included in the photosensitive drum 10, the support member 20 is fitted into a bearing 142 provided on the rear side plate 103 and a bearing 143 provided on the front side plate 102 and is attached to the front side plate 102. It is fixed with screws. A cleaning device 19, a scorotron charger 11 for each color, a developing device 13 for each color, and a replenishing tank 21 for each color developer are attached to the outer periphery of the photoconductor drum 10.

A gear 10g provided on the rear flange 112 of the photosensitive drum and a gear G1 provided on the apparatus main body and connected to a drive motor for the photosensitive drum (not shown) are connected to drive the photosensitive drum 10.

Outside the image area S where the toner image is formed by the developing sleeve 131, the photosensitive drum 10 is located closer to the developing sleeve (inner side) than the developing sleeve side end of the abutting roller 138a as a gap holding member. A through hole is provided from the outer peripheral surface to the inner peripheral surface through the base 1 to connect the conductive layer 2 and the conductive end portion 7 provided inside the base 1 with a conductive member such as a metal pin or a conductive paste. Build passage 6,
For example, a front flange 111 made of a metal such as Al, iron, and SUS and a bearing 1 fitted to the front flange 111
The conductive layer 2 of the photoreceptor drum 10 is grounded in a state of being electrically connected to the apparatus main body through 43.

Outside the image area S where the toner image is formed, a conductive path is provided through the base on the developing sleeve side (inside) of the end of the abutting roller on the developing sleeve side to form a conductive layer. By grounding, even if the photosensitive layer or the conductive layer of the photosensitive drum is worn by the rotation of the abutting roller, the grounding is performed without causing a poor grounding. In particular, a grounding method suitable for a color image forming apparatus in which abutting rollers are frequently used is provided.

The method of forming the conductive path 6 is as follows.
The conductive layer 2 is applied by placing a through-hole in the base 1 in advance, and the conductive path 6 is formed in the through-hole of the photosensitive drum 10 by a metal pin or a conductive paste before the conductive layer 2 is applied as described above. Alternatively, after applying the conductive layer 2 or the photosensitive layer 3, a method of forming a conduction path 6 with a metal pin or a conductive paste by making a through hole in the photosensitive drum 10 is used. The resistance value of the ground path formed by the conductive layer 2 including the conductive path 6 and the conductive end 7 is 10 ⁴ Ωcm or less.

FIG. 5 shows a color image forming apparatus according to another embodiment of the image forming apparatus suitable for carrying out the present invention. FIG.
FIG. 6 is a sectional configuration diagram of a color image forming apparatus according to another embodiment of the image forming apparatus suitable for carrying out the present invention. Members having the same functions and structures as the members described in FIG. 1 are denoted by the same reference numerals. In this embodiment, the superimposed toner image formed on the photosensitive drum is directly transferred onto the transfer paper directly by the transfer device without using the intermediate transfer roller used in FIG.

The Y, M, C and K toner images are formed on the peripheral surface within one rotation of the photosensitive drum 10 by the same image forming process as that described with reference to FIG.

The color toner image formed on the peripheral surface of the photosensitive drum 10 is sent out from a paper feed cassette 15 as a transfer material storage means in a transfer unit 14a, and is conveyed to a timing roller 16 where the timing roller 16 Is transferred onto a transfer sheet P, which is a transfer material fed in synchronization with the toner image on the photosensitive drum 10.

The transfer paper P to which the toner image has been transferred is separated from the peripheral surface of the drum by the removal of the charge in the static eliminator 14b, and then is conveyed to the fixing device 17 by the conveyer belt 14e as a convey means. Heating in the fixing device 17
After the toner is pressed and fused and fixed onto the transfer paper P, the toner is discharged from the fixing device 17, conveyed by a pair of discharge conveyance rollers 18 a, and the toner image surface is placed on a tray at the upper portion of the apparatus via the discharge roller 18. And discharged.

On the other hand, the photosensitive drum 10 from which the transfer paper is separated
In the cleaning device 19, the surface of the photosensitive drum 10 is rubbed by a cleaning blade 19a to remove residual toner, and is cleaned and continued to form a toner image of a document image, or temporarily stopped to form a toner image of a new document image. It takes formation. The waste toner scraped off by the cleaning blade 19a and the cleaning roller 19b is discharged to the waste toner container 22 through the toner conveying screw 19c and the toner conveying pipe 19d. After the cleaning, the cleaning blade 19a and the cleaning roller 19b are kept separated from the photosensitive drum 10 in order to prevent the photosensitive drum 10 from being damaged.

In the above color image forming apparatus, FIG.
The grounding method of the present invention described with reference to FIG.

[0043]

According to the first or second aspect, the conductive material penetrates through the base outside the image area S where the toner image is formed, closer to the developing sleeve than the end of the abutting roller on the developing sleeve side. And the conductive layer is grounded, so that even if the photosensitive layer or the conductive layer of the photosensitive drum is worn by the rotation of the abutting roller, the grounding is reliably performed without causing a grounding failure. In particular, a grounding method suitable for a color image forming apparatus in which abutting rollers are frequently used is provided.

According to the third or fourth aspect, even if the conductive layer is peeled off by the abutting roller, the grounding is reliably performed without causing a grounding failure. In particular, the photosensitive drum, which is an image forming body, is made of a transparent material, and a conductive drum and a photosensitive layer are provided on the outer peripheral surface of the transparent substrate. And a grounding method suitable for an image forming apparatus having a structure in which image forming means such as a charger, a developing unit, a transfer unit, a static eliminator, and a cleaning device are disposed outside.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of a color image forming apparatus according to one embodiment of an image forming apparatus suitable for carrying out the present invention.

FIG. 2 is a diagram showing a cross section taken along the line AOA of FIG. 1;

FIG. 3 is a schematic configuration diagram of a photosensitive drum.

FIG. 4 is a diagram showing an embodiment of a method of grounding a photosensitive drum.

FIG. 5 is a sectional view of a color image forming apparatus according to another embodiment of the present invention, which is suitable for carrying out the present invention.

FIG. 6 is a diagram showing a conventional method of grounding a photosensitive drum.

FIG. 7 is a diagram illustrating a method for maintaining a gap between a developing sleeve and a photosensitive drum.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 base 2 conductive layer 3 photosensitive layer 6 conduction path 10 photosensitive drum 13 developing device 131 developing sleeve 138a, 138b abutting roller S image area

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-66704 (JP, A) JP-A 55-95161 (JP, U) JP-A 63-78972 (JP, U) JP-A 62- 188776 (JP, U) Japanese Utility Model 63-137378 (JP, U) Japanese Utility Model Application Hei 5-15068 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/08 G03G 21 / 00

Claims (4)

(57) [Claims] An image forming body provided with a base made of a high-resistance member, a conductive layer and a photosensitive layer provided on an outer peripheral surface of the base, a developing means for developing a latent image formed on the image forming body; An abutting roller provided in a developing means for keeping a gap between the image forming body and the developing means at a predetermined value, and the abutting roller is used for forming the image outside the image area of the image forming body. In the image forming apparatus in contact with both ends of the body, a conductive path for the conductive layer is provided between the image area of the image body and the abutting roller, penetrating the base of the image body. An image forming apparatus comprising: 2. The image forming apparatus according to claim 1, wherein the conductive layer of the image forming body is grounded through the conductive path, a conductive end provided inside a base of the image forming body, and a flange of the image forming body. The image forming apparatus according to claim 1, wherein: 3. The image forming apparatus according to claim 1, wherein the base of the image forming body is made of a transparent member. 4. An image forming apparatus according to claim 3, characterized in that arranged the image exposure means for performing image exposure to the image forming body along the inner periphery of said image forming body.