JPH0895346A - Image forming device provided with electrifying device - Google Patents

Abstract

PURPOSE: To improve the positional accuracy of an electrifying device with respect to a photoreceptor drum and to eliminate set ballast between equipments without using a complicated mechanism by providing a stopper means for positioning the electrifying device with respect to an image forming body when the image forming body is rotated and moved. CONSTITUTION: In a state where a scorotron electrifier is inserted in a device main body, a guide pin 114 does not interfere with the tapered part 40d of a guide rail 40, and front and rear spacer members 116 depress and is brought into contact with the photoreceptor drum 10. The stopper member 160 for positioning the scorotron electrifier is constituted of a dowel caulked to the guide rail 40 fixed in the device main body. Then, the scorotron electrifier is positionally fixed with respect to the drum 10 rotating and moving counterclockwise by the stopper member 160 provided on the guide rail 40 on a downstream side from a contact part between the spacer member 116 and the drum 10, and a depressing member 150.

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 having a corona discharge type charging device which is used for the purpose of charging a photosensitive member in electrophotographic image formation. In particular, it relates to an image forming apparatus having a corona discharge type charging device using a sawtooth electrode.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus, a corona discharge type charging device is positioned with respect to a rotating photosensitive drum, with respect to a photosensitive drum attached to the main body of the apparatus, and a guide attached to the main body of the apparatus. In most cases, the charging device is attached based on rails, etc., and it is positioned and fixed in a non-contact state with the photoconductor drum. There is disclosed a structure in which the rollers are provided and abutted against the non-image portions on both ends of the rotating photosensitive drum to maintain a gap between them. Conventionally, corona discharge type charging devices of this type are roughly classified into a wire discharge type (corotron, scorotron, dicorotron, etc.) and a pin discharge type (pin electrode type, sawtooth electrode type, etc.). The latter has come to be used in electrophotographic copying machines, printers, etc. in recent years because of low ozone generation. In particular, a charging device having a structure using an electrode plate in which a plurality of sawtooth electrode parts are provided on one thin plate member is disclosed in JP-A-63-15272 and JP-A-5-45999.
It is disclosed in Japanese Patent Publication No.

[0003]

However, in such non-contact positioning with the photoconductor drum, the gap changes due to the runout of the rotating photoconductor drum, and if the abutting roller is used, the mechanism becomes complicated. Accuracy becomes difficult to obtain. As described above, unless the positional accuracy of the charging device with respect to the photosensitive drum is constant, the charging potential is nonuniform and unstable. In particular, the parallelism with respect to the axial direction of the photoconductor drum and the setting variation of the distance between the grid and the surface of the photoconductor drum in the scorotron charger, which is a charging device, are significant causes of the setting variation of the charging potential.

The present invention solves such a problem and improves the positional accuracy of the charging device with respect to the photosensitive drum without using a complicated mechanism, and also has an image having a charging device having no setting variation among devices. An object is to provide a forming device.

[0005]

The above object is to provide an electrophotographic image forming apparatus for forming a latent image on a moving image forming body by charging by a charging device and exposure by an exposing device. A spacer member provided at an end portion in the longitudinal direction, pressing means for pressing the charging device to bring the spacer member into contact with the image forming body, and the charging device for forming the image when the image forming body is rotationally moved. It is achieved by an image forming apparatus having a charging device characterized by having stopper means for positioning with respect to a body. Also,
An image forming apparatus having a charging device is a preferred embodiment, wherein the charging device is a charging device having a saw-toothed electrode, and the image of the spacer member is brought into contact with the image forming body and slid. Coefficient of friction against formed body is 0.70
An image forming apparatus having a charging device characterized by the following, and an image forming apparatus having a charging device characterized in that the pressing force of the pressing means is a linear pressure of 10 to 100 g / cm are also preferable embodiments. is there.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of an image forming apparatus having a charging device according to the present invention is shown in FIG. 1 using a color image forming apparatus having a scorotron charger, which is a charging device. explain. FIG. 1 is a sectional configuration diagram of a color image forming apparatus showing an example of an image forming apparatus having a charging device of the present invention.

Reference numeral 10 denotes a photosensitive drum, which is a drum-shaped image forming body, and has a transparent conductive layer, an a-Si layer or an organic photosensitive layer on the outer periphery of a cylindrical substrate formed of a transparent member such as optical glass or transparent acrylic resin. A photoreceptor layer such as a layer (OPC) is formed. 110Y, 110M, 110C and 110K
Is a scorotron charger, which is a charging device used in the image forming process of each color of yellow (Y), magenta (M), cyan (C), and black (K), with respect to the above-mentioned organic photoreceptor layer of the photoreceptor drum 10. A charging operation is performed by a grid held at a predetermined potential and corona discharge by a discharge wire, and a uniform potential is given to the photosensitive drum 10.

12Y, 12M, 12C, and 12K are FL, EL, PL, and LED in which light emitting elements arranged in the axial direction of the photosensitive drum 10 are arranged in a line in an array, and elements having an optical shutter function in a row. Lined up LISA, PLZT, LCS,
An exposure optical system which is an exposure device composed of a self-occ lens as a unity-magnification imaging element, in which the image signals of respective colors read by a separate image reading device are sequentially taken out from a memory and the exposure optical system is used. It is inputted to 12Y, 12M, 12C and 12K as an electric signal, respectively. The exposure optical systems 12Y, 12M, 12C and 12K are all mounted on a cylindrical holding member 20 and housed inside the base of the photosensitive drum 10.

13Y, 13M, 13C and 13K are yellow (Y), magenta (M), cyan (C) and black (K).
In a developing device which is a developing device using a non-contact developing method for accommodating the respective developers, a developing sleeve 130 that rotates in the same direction while maintaining a predetermined gap with respect to the peripheral surface of the photoconductor drum 10.
It is equipped with Y, 130M, 130C and 130K.

The developing devices 13Y, 13M, 13C and 13K
Is the scorotron charger 110Y, 110M, 110C described above.
And 110K, and photoconductor drum 10 formed by image exposure by exposure optical systems 12Y, 12M, 12C, and 12K
The above electrostatic latent image is reversely developed in a non-contact state by applying a developing bias voltage.

The original image is temporarily read as an image signal for each color of Y, M, C and K from an image read by an image pickup device or an image edited by a computer in an image reading apparatus separate from this apparatus. Stored and stored in memory.

By the start of the image recording, the photoconductor driving motor is started to rotate the photoconductor drum 10 clockwise.
At the same time, application of electric potential to the photoconductor drum 10 is started by the charging action of the scorotron charger 110Y.

After the photosensitive drum 10 is applied with an electric potential,
In the exposure optical system 12Y, the exposure by the electric signal corresponding to the first color signal, that is, the yellow (Y) image signal is started, and the yellow (Y) image of the original image is formed on the photosensitive layer on the surface by the rotational scanning of the drum. To form an electrostatic latent image corresponding to.

The latent image is reversal-developed by the developing device 13Y with the developer on the developing sleeve in a non-contact state, and a yellow (Y) toner image is formed according to the rotation of the photosensitive drum 10.

Next, the photosensitive drum 10 is further provided with a scorotron charger 110M on the yellow (Y) toner image.
An electric signal corresponding to the second color signal of the exposure optical system 12M, that is, an image signal of magenta (M) is applied by the charging action of the exposure optical system 12M to perform the exposure, and the non-contact reversal development is performed by the developing device 13M. A magenta (M) toner image is sequentially formed on the yellow (Y) toner image.

A scorotron charger by the same process
Further, a cyan (C) toner image corresponding to the third color signal is generated by 110C, the exposure optical system 12C, and the developing device 13C, and a scorotron charger 110K, the exposure optical system 12K, and the developing device 1 are also provided.
By 3K, a black (K) toner image corresponding to the fourth color signal is sequentially superimposed and formed, and a color toner image is formed on the peripheral surface of the photosensitive drum 10 within one rotation.

These exposure optical systems 12Y, 12M, 12C and 12
The exposure of the organic photosensitive layer of the photosensitive drum 10 by K is performed from the inside of the drum through the transparent substrate.
Therefore, the exposure of the image corresponding to the second, third, and fourth color signals is performed without any influence of the toner image previously formed, and is equivalent to that of the image corresponding to the first color signal. It is possible to form an electrostatic latent image. Exposure optical system
Photoreceptor drum 10 by heat generation of 12Y, 12M, 12C and 12K
The internal temperature is stabilized and the temperature rise is prevented by the holding member.
A material with good thermal conductivity is used for 20, a heater is used when the temperature is low, and heat is radiated to the outside through a heat pipe when the temperature is high. . Further, the developing devices 13Y, 13M, 13C and 13
When developing with K, the developing sleeve 13
0Y, 130M, 130C, and 130K are applied with a developing bias in which direct current or further alternating current is applied, and jumping development is performed by the one-component or two-component developer accommodated in the developing device to ground the transparent conductive layer. A DC bias having the same polarity as the toner is applied to the photoconductor drum 10 to perform non-contact reversal development in which the toner is attached to the exposed portion.

Thus, the color toner image formed on the peripheral surface of the photosensitive drum 10 is sent from the paper feeding cassette 15 by the sending roller 15a in the transfer device 14a.
The sheet is conveyed to the timing roller 16 by the pair of conveying rollers 15b and 15c, and is driven by the timing roller 16 to be transferred onto the transfer sheet P which is a transfer material that is fed in synchronization with the toner image on the photosensitive drum 10.

The transfer paper P on which the toner image has been transferred is separated from the drum peripheral surface by being removed of the charge in the static eliminator 14b, and then the transfer belt stretched between the transfer drive roller 14c and the driven roller 14d. In the fixing device 17, the fixing roller 17a and the pressure roller 17 are conveyed to the fixing device 17 by 14e.
After being heated and pressure-bonded between b to fuse and fix the toner on the transfer paper P, the toner is ejected from the fixing device 17 by the fixing exit roller pair 17d and is conveyed by the paper ejection conveying roller pair 18a and is ejected via the paper ejection roller 18. The paper is discharged onto the paper discharge tray 200 at the top of the device.

On the other hand, the photosensitive drum 10 from which the transfer paper has been separated is cleaned by the cleaning blade 19a in the cleaning device 19.
The surface of the photoconductor drum 10 is rubbed to remove and clean residual toner, and the toner image of the original image is continuously formed or is temporarily stopped to form a new toner image of the original image. The waste toner scraped off by the cleaning blade 19a is discharged to a waste toner container (not shown) by the toner transport screw 19b.

The photosensitive drum 10 has a plurality of scorotron chargers on its outer peripheral surface even if the diameter of the drum is relatively small because the exposure optical system is housed therein.
110Y, 110M, 110C and 110K, developing units 13Y, 13M, 13
It is possible to arrange C and 13K, and the outer diameter is 60
The device volume can be made compact by using a drum with a small diameter of mm to 150 mm.

A scorotron charger, which is an embodiment of the charging device of the present invention, will be described with reference to FIGS. The scorotron chargers 110Y, 110M, 110C, and 110K have the same function and structure, and therefore will be described as a representative of 110Y. FIG. 2 is a schematic view showing the structure of a scorotron charger showing an embodiment of the charging device.
FIG. 3 is a sectional view of the scorotron charger shown in FIG. 2.

Reference numeral 111 is a saw-tooth electrode plate for corona discharge, which has a plurality of saw-tooth electrodes 111a, which are electrode portions of equal length, extending toward the photosensitive drum 10 as an image forming body at a constant pitch. It is made by etching a stainless steel plate of mm. Reference numeral 113 is a stainless steel shield having an opening having a U-shaped cross section. After attaching the sawtooth electrode plate 111 to the supporting member 120 made of an insulating resin and pressing it with the pressing member 121 also made of an insulating resin, both ends are made of an insulating resin, for example, ABS resin. It is sandwiched between the side members 112a and 112b (not shown), dropped into the shield 113, and the shield 113 is screwed to the side members 112a and 112b with the resin screw 117, and the supporting member 120 having the sawtooth electrode plate 111 is attached. , Holding member 12
The 1 and side members 112a and 112b are integrally fixed to the shield 113. On the opening side of the shield 113, for example, a plate thickness of 0.1
A grid 115 made by etching a stainless steel plate of mm is attached to the side members 112a and 112b with a resin screw 118 for attaching the grid to form a scorotron charger 110Y as a charging device. 114 is a scorotron charger
When inserting 110Y into the apparatus body, the side member 112 on the insertion side
It is a guide pin provided integrally with a.
Reference numeral 116 is a spacer provided on the side members 112a and 112b, which is provided with a predetermined gap between the photoconductor drum 10 and the scorotron charger 110Y, and slides in line contact with the photoconductor drum 10 which rotates and moves. It is a member.

The insertion of the scorotron charger, which is a charging device, into the main body of the device will be described with reference to FIGS.
Hereinafter, similarly to the above, the scorotron charger 110Y will be described as a representative. FIG. 4 is a diagram showing the relationship between the charging device and the photoconductor drum, FIG. 5 is a diagram showing the insertion state of the charging device, and FIG. 6 is a diagram showing the rotation of the photoconductor drum after mounting the charging device. It is a figure which shows a state.

The photosensitive drum 10 is supported on the front and rear side plates 21a and 21b of the apparatus main body through the drum shaft 10a, and the guide rail 40 serves as a guide when the scorotron charger 110Y is inserted into the main body. , And Scorotron charger 11
A pressing member 150, which is a pressing unit in the mounted state of 0Y, is attached. The pressing member 150 drops the inner cylinder 155 into the outer cylinder 154, fixes the pressing plate 153 that presses the scorotron charger 110Y against the photoconductor drum 10 to the inner cylinder 155, for example, by caulking, and then presses the pressing springs 152 into both cylinders. The inner cylinder fixing plate 151 is pressed and the outer cylinder 154 is fixed to the fixing plate 151, and the fixing plate 151 is fixed to the side plates 21a and 21b by screws 156.

When the scorotron charger 110Y is inserted through the charger insertion opening 41 of the side plate 21a on the front side of the apparatus main body, the pressing plate 153 comes into contact with the upper part of the side member 112a on the insertion side of the scorotron charger 110Y, The scorotron charger 110Y is pushed down. When the guide pin 114 provided on the side member 112a hits the tapered portion 40a of the guide rail 40,
The scorotron charger 110Y has a guide rail 40 taper 4
It is lifted up along 0a and pushes up the pressing plate 153, so that the spacer member 116 provided on the side member 112a and the end portion of the photosensitive drum 10 are inserted without contact.

Then, when it reaches the valley portion 40b of the guide rail 40, the side member 112a is pushed down by the pressing plate 153, and the guide rail 40 and the guide pin 114 are in a state in which there is play that does not interfere, but the spacer The member 116 is in a state of being pressed by the photosensitive drum 10 (dotted line in FIG. 5). The spacer member 116 slightly slides on the end surface portion of the photosensitive drum 10 in the drum axial direction, and the guide pin 114 causes the guide rail 40 to form the tapered portion 4 of the guide rail 40.
When 0c is reached, the scorotron charger 110Y is lifted again, and is pushed to the rear position of the apparatus main body in a state where the spacer member 116 and the photosensitive drum 10 are not in contact with each other. In the inserted state, the guide pin 114 does not interfere with the tapered portion 40d of the guide rail 40 and the front and rear spacer members 11
Reference numeral 6 presses the photosensitive drum 10 to bring it into contact with it (dotted line in FIG. 5). Reference numeral 160 denotes a stopper member (stopper means) for positioning the scorotron charger 110Y with respect to the photoconductor drum 10 rotating in the direction of the arrow. For example, as shown in FIG. 6, the stopper member 160 is caulked by the guide rail 40 fixed to the apparatus main body. It consists of dowels. 6 arrow direction (counterclockwise direction)
Spacer member for the photosensitive drum 10
The position of the scorotron charger 110Y is fixed by the stopper member 160 provided on the guide rail 40 on the downstream side of the contact portion between the 116 and the photosensitive drum 10 and the pressing member 150.

The portions of the photosensitive drum that come into contact with the spacer members are the non-image portions at both ends, have no photosensitive layer, and are the surface of the aluminum layer which is the base material. Preferably, the maximum height Rmax is 3S or less. It is a mirror surface. Further, the spacer member that abuts on the photosensitive drum is formed by coating, for example, a fluororesin on the contact portion of the side member with the drum,
Alternatively, a resin having good slipperiness, for example, another member having a fluororesin surface may be attached to the side member to be formed.
The friction coefficient of the spacer member sliding on the photosensitive drum with respect to the photosensitive drum is preferably 0.70 or less in terms of static friction coefficient,
If it exceeds 0.70, smooth sliding cannot be obtained. Also,
The pressing force of the pressing member is preferably 10 to 100 g / cm in linear pressure. If it is 10 g / cm or less, the pressing force will fluctuate due to small dust and the like, and bouncing tends to occur, the positioning and fixing of the charging device will not be stable, and a uniform charging potential cannot be obtained. The wear on the contact surface with the photoconductor drum, for example, the wear of the fluororesin becomes more severe. In addition, the problem that the driving torque of the photosensitive drum becomes large also occurs.

Using the apparatus shown in FIG. 1, a φ100 mm photosensitive drum having an OPC photosensitive layer has a peripheral speed of 80 mm / sec, a voltage applied to a sawtooth electrode plate of −5 kV, and a voltage applied to a shield of −700 V.
As a result of an experiment in which the voltage applied to the grid was -700 V and the pressing force of the spring of the pressing member was 50 g / cm of linear pressure, a stable and uniform charging potential was obtained, and a good image could be obtained.
As the electrode of the charging device of the present invention, the saw-tooth electrode plate is used in the above-described embodiments, but a wire electrode is also included in the present invention. In the present invention in which the accuracy of the distance between the grid and the photoconductor drum is important, the sawtooth electrode has a higher discharge directivity in the photoconductor direction than the wire electrode, and is affected by the distance between the grid and the photoconductor drum. The present invention is more effective because of its large degree.

[0030]

The charging device is pressed against the photosensitive drum by the pressing member via the simple spacer member without using a complicated mechanism, and is prevented from rotating by the stopper member and the pressing member as the positioning member. Therefore, the charging device is attached to the photoconductor drum that is attached to the main body of the device as in the past, with the guide rail and the like attached to the main body of the device as a reference, and the photoconductor drum is positioned in a non-contact state. The change in the gap caused by the runout of the rotating photosensitive drum, which is caused by the fixed configuration,
Further, when using the abutting roller, there is no problem such as complexity of the mechanism, and the positional accuracy of the charging device with respect to the photosensitive drum is constant, and the charging potential is uniform and stable.

Particularly, there is no variation in the setting of the charging potential due to the parallelism with respect to the axial direction of the photosensitive drum, variation in the distance between the grid and the surface of the photosensitive drum in the scorotron charger, and the setting between the devices does not occur. It has become possible to provide an image forming apparatus which has a stable charging potential and which has a stable charging potential.

Particularly, the charging device using the sawtooth electrode has a high discharge directivity in the direction of the photosensitive member and is greatly affected by the distance between the grid and the photosensitive drum, so that the charging device is more effective and uniform. An electric potential can be obtained, and the frictional coefficient of the spacer member with respect to the photosensitive drum is set to 0.70 or less.
/ Cm, it is possible to stably and highly accurately position the charging device with respect to the rotating photosensitive drum, and it is possible to provide an image forming apparatus having a charging device with no setting variations among devices. became.

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram of a color image forming apparatus showing an example of an image forming apparatus having a charging device of the present invention.

FIG. 2 is a schematic diagram showing a structure of a scorotron charger showing an embodiment of a charging device.

3 is a cross-sectional view of the scorotron charger of FIG.

FIG. 4 is a diagram showing a relationship between a charging device and a photosensitive drum.

FIG. 5 is a view showing an inserted state of the charging device.

FIG. 6 is a diagram showing a state when the photosensitive drum is rotated after the charging device is attached.

[Explanation of symbols]

 10 Photosensitive drum 12Y, 12M, 12C, 12K Exposure optical system 13Y, 13M, 13C, 13K Developing device 14a Transfer device 14b Static eliminator 15 Paper feed cassette 16 Timing roller 17 Fixing device 18 Paper discharging roller 19 Cleaning device 20 Holding member 40 Guide rail 110Y, 110M, 110C, 110K Scorotron charger 111 Sawtooth electrode plate 111a Sawtooth electrode 112a, 112b Side member 113 Shield 114 Guide pin 115 Grid 116 Spacer member 120 Support member 121 Press member 150 Press member 160 Stopper member P Transfer paper

Claims (4)

[Claims] 1. An electrophotographic image forming apparatus in which a latent image is formed on a moving image forming body by charging by a charging device and exposure by an exposing device, and the latent image is provided at a longitudinal end of the charging device. Spacer member, pressing means for pressing the charging device to bring the spacer member into contact with the image forming body, and stopper means for positioning the charging device with respect to the image forming body when the image forming body is rotationally moved. And an image forming apparatus having a charging device. 2. The image forming apparatus having a charging device according to claim 1, wherein the charging device is a charging device having a sawtooth electrode. 3. An image having a charging device according to claim 1, wherein a coefficient of friction of the spacer member, which comes into contact with and slides on the image forming body, with respect to the image forming body is 0.70 or less. Forming equipment. 4. The pressing force of the pressing means is a linear pressure of 10 to 100 g.
The image forming apparatus having the charging device according to claim 3, wherein the image forming apparatus has a charging device.