JPH08262840A - Electrifier - Google Patents

Abstract

PURPOSE: To provide an electrifier capable of easily exchanging an electrode part, for a new one and protecting the top end of the electrode part at the time of exchanging, in an electrifier provided with a sawtooth-shaped electrode. CONSTITUTION: An electrode supporting member 120A supporting the sawtooth shaped electrode 111A is provided with electrode protective members 121A for surrounding/protecting an inner electrode with elasticity, on both sides and an exchange part 110A provided with guide pins 123A for regulating a position and electrically connecting on the front and the rear is inserted and fitted into an exchange part attaching opening part 117A on the rear of the electrifier, in a state where the electrode protective members 121A are opening on both sides and the top end of the electrode is exposed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a corona discharge type charging device used in an electrophotographic image forming apparatus,
In particular, the present invention relates to a corona discharge type charging device using a non-contact type sawtooth electrode.

[0002]

2. Description of the Related Art Conventionally, a corona discharge type charging device used in an electrophotographic image forming apparatus is a wire discharge type (corotron, scorotron, dicorotron, etc.).
And the pin discharge method (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 a sawtooth electrode in which a plurality of sawtooth electrode portions are provided on one thin plate member is disclosed in Japanese Patent Laid-Open No. 63-15272.
It is disclosed in Japanese Patent Laid-Open No. 5-45999 and the like.

[0003]

In the above-mentioned wire discharge type charging device, when the bias voltage applied to the discharge electrode is increased in order to increase the discharge capacity, the charge becomes non-uniform, but a plurality of sawtooth electrodes are formed. A charging device having a structure using a sawtooth electrode having a portion has a higher discharge capacity than the wire discharge method, which is advantageous. However, in corona discharge from a charging device using a sawtooth electrode, if toner or the like adheres to the sawtooth electrode portion and stains occur, this causes uneven charging and uneven charging. Become. A metal thin plate of about 0.1 mm is used for the sawtooth electrode portion, and the cleaning is not easy as compared with the wire discharge type wire cleaning. The serrated electrode has a sharp tip and is dangerous to handle.
Easy to bend. If the tip of the electrode portion is bent during cleaning, the charging uniformity will be impaired.

According to the present invention, when the sawtoothed electrode portion loses its uniformity of charging characteristics due to dirt or the like, the electrode portion can be easily replaced with a new one, and the tip of the electrode portion is protected during the replacement. It is an object of the present invention to provide a charging device in which good charging characteristics can be obtained by replacing the charging device.

[0005]

SUMMARY OF THE INVENTION The above object is to provide a charging device for corona charging a body to be charged with a sawtooth electrode supported by a support, wherein the sawtooth electrode supported by the support is the electrode tip. The charging device is characterized in that it can be mounted and removed as a replacement member together with a protection member that protects the electrode, and that the protection member is moved at the time of mounting to expose the tip of the electrode.

The replacement member is mounted by inserting it from the back surface, side surface or end of the charger, and the tip of the electrode is exposed when the replacement member is mounted by opening the protective member to the electrode. It is a preferred embodiment that the protection member is configured to cover and protect the tip of the electrode when the replacement member is taken out.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to the description of the present invention, the general structure of a charging device having a sawtooth electrode will be described. 4 is a front view showing the configuration of a charging device having a sawtooth electrode, and FIG. 5 is a sectional view taken along line AA of the charging device of FIG. In the figure 111
Is a sawtooth electrode for corona discharge, which has a plurality of equal-length sawtooth-shaped tips 111a protruding toward the photosensitive drum 10, which is a member to be charged, and has a thickness of, for example, 0.
It is made by etching a 1 mm stainless steel plate, and the pointed portions 111a are processed with a pitch of 2 mm and a radius R of the tip thereof of 30 μm or less. Reference numeral 113 is a side plate which is a stainless steel shield plate having an opening having a U-shaped cross section. After attaching the sawtooth electrode 111 to the supporting member 120 made of an insulating resin and pressing it with the pressing member 121 made of the insulating resin, both ends are made of an insulating resin, for example, ABS resin. Side members 112a, 11
Side plate 1 sandwiched by 2b (not shown)
13, the side plate 113 is screwed to the side members 112a and 112b by a fixing means such as a resin screw to support the sawtooth electrode 111 in the center, and a holding member 121 and a pressing member 121.
And the side members 112a and 112b are integrally formed into the side plate 113.
Fixed to. On the side of the opening of the side plate 113, for example, a stainless steel plate having a thickness of 0.1 mm is etched to form a control grid 115 having a mesh width of 1 mm, and a side member 112 is fixed by a fixing means such as a resin screw for grid attachment.
Attached to a and 112b, a scorotron type charging device 11 is assembled. Reference numeral 114 denotes a guide pin that is integrally provided on the side member 112a on the insertion side when the charging device 11 is inserted into the main body of the image forming apparatus. Reference numeral 116 denotes a spacer member provided on the side members 112a and 112b, provided with a predetermined gap between the photosensitive drum 10 and the charging device 11, and sliding in line contact with the rotationally moving photosensitive drum 10. The sliding surface is coated with a material having a good sliding property such as fluororesin.

The charging device 11 is pushed down toward the photosensitive drum 10 of the main body of the image forming apparatus by a pressing member having a pressing spring (not shown), but a guide pin 114 and a guide rail (not shown) provided on the side member 112a. ), The spacer member 116 abuts on the base material having no photosensitive layer in the non-image area at both ends of the photosensitive drum 10, and the control grid 115 is accurately spaced at a constant distance from the photosensitive layer of the photosensitive drum 10. It is supposed to be maintained. The charging device having the saw-toothed electrode 111 has a higher discharge directivity toward the photoconductor than the charging device having the wire discharge electrode, and has an advantage that corona ions do not easily flow into the side plate 113.

Next, an example of an image forming apparatus using the charging device having the sawtooth electrode will be described. FIG. 6 is a configuration cross-sectional view showing the configuration of the color image forming apparatus.

First, the configuration and operation will be described. In the figure, reference numeral 10 is a photosensitive drum which is an image bearing member, which is formed by coating an OPC photosensitive layer on the drum and is grounded and driven and rotated clockwise. Reference numeral 11 denotes a charging device having a sawtooth electrode, and uniform charging of V _H is applied to the peripheral surface of the photosensitive drum 10 by corona discharge by a grid and a sawtooth electrode whose potential is held at V _G. Prior to the charging by the charging device 11, the peripheral surface of the photoconductor is neutralized by exposure by the PCL 12 using a light emitting diode or the like in order to eliminate the history of the photoconductor until the previous printing.

After uniformly charging the photosensitive member, the image exposing means 13 performs image exposure based on the image signal. Image exposure means
Reference numeral 13 is a reflection mirror 1 via a polygon mirror 131 that rotates using a laser diode (not shown) as a light emitting source, an fθ lens
The optical path is bent by 32 and scanning is performed, and a latent image is formed by the rotation (sub-scanning) of the photosensitive drum 10.
In this embodiment, the character portion is exposed to form an inverted latent image in which the character portion has a lower potential V _L.

Yellow (Y) on the periphery of the photosensitive drum 10,
Developers each containing a developer composed of toner such as magenta (M), cyan (C), black (K), and a carrier.
14 is provided, and first, the development of the first color is performed by the developing sleeve 141 which contains a magnet and holds the developer and rotates. The developer is a carrier in which a ferrite core is coated with an insulating resin around it, a polyester as a main material, a pigment according to the color, and a charge control agent,
It consists of toner to which silica, titanium oxide, etc. have been added.
The layer is regulated to a layer thickness of ~ 600 μm and conveyed to the developing zone.

The gap between the developing sleeve 141 and the photosensitive drum 10 in the developing area is 0.4 to larger than the layer thickness (developer).
As 1.0mm, V _AC AC ice and V _DC D
The C bias is superimposed and applied. Since V _DC and V _H and the toner are charged with the same polarity, the toner given the opportunity to be separated from the carrier by V _AC does not adhere to the V _H portion, which has a higher potential than V _{DC, and} has a potential higher than V _DC. attached to a lower V _L portion of visualized (reversal development) is carried out.

After the visualization of the first color is completed, the process proceeds to the image forming process for the second color, the charging is performed again by the charger 11, and the latent image is formed by the image exposing means 13 by the image data of the second color. It At this time, the charge elimination by the PCL 12 performed in the image forming process of the first color is not performed because the toner attached to the image portion of the first color scatters due to the sudden decrease in the potential around the image.

Again, V is applied over the entire peripheral surface of the photosensitive drum 10.
A latent image similar to that of the first color is formed on the portion of the photoconductor having the _H potential and the image of the first color is not developed, but development is performed again on the portion having the image of the first color. In the portion to be performed, the latent image of V _M ′ is formed due to the light shielding by the toner of the first color and the electric charge of the toner itself, and V _DC
And development is performed according to the potential difference between V _M ′ and V _M ′. In the overlapping portion of the images of the first color and the second color, the development of the first color is V _L
When the latent image of is formed, the balance between the first color and the second color is lost, so the exposure amount of the first color is reduced and V _H > V _M > V
_It may be an intermediate potential that becomes _L.

An image forming process similar to that for the second color is performed for the third and fourth colors, and a visible image of four colors is formed on the peripheral surface of the photosensitive drum 10.

On the other hand, the recording paper P fed from the paper feed cassette 21 by the paper feed mechanism 22 is fed to the transfer area by the transfer belt device 30 in which the transfer belt 31 is stretched, and the peripheral surface of the photosensitive drum 10 is fed. The above multicolor image is collectively transferred onto the recording paper P. That is, the recording paper P that has been fed enters between the brush 34 and the transfer belt 31, the electric charge is injected into the recording paper P from the brush 34, and the suction force is exerted between the recording paper P and the transfer belt 31. Occurs. After that, the recording paper P enters a nip portion (transfer area) 35 formed by the photosensitive drum 10 and the transfer belt 31, and a transfer electric field is generated from the back surface of the transfer belt 31 by the corona discharger 36 or a bias roller instead. Attached, recording paper P
A multicolor image is transferred on top.

The recording paper P separated from the photosensitive drum 10 is
The shaft 33a of the holding roller 33 on the downstream side which stretches the transfer belt 31.
Transfer belt 31 after receiving static electricity by AC corona discharge with the counter electrode as the counter electrode, or while receiving AC corona discharge.
Separate from. The transfer belt 31 of the transfer belt device 30 is separated from the photosensitive drum 10 about the axis of the holding roller 33 on the downstream side as a rotation center during the formation of the multicolor image.

The recording paper P holding the multicolor image separated from the transfer belt device 30 is conveyed to a fixing device 23 composed of two pressure bonding rollers having a heater inside at least one of the rollers, and is heated between the pressure bonding rollers. The applied toner is melted by being applied with pressure and fixed on the recording paper P.
It is discharged to the outside of the device.

After the transfer, the residual toner remaining on the peripheral surface of the photosensitive drum 10 is subjected to static elimination by a static eliminator 15 using an AC corona discharger, and then is removed from a rubber material that is in contact with the cleaning device 16 or the photosensitive member. It is scraped off into the cleaning device 16 by the cleaning blade 16a, discharged by a screw or the like, and then stored in the recovery box. Depending on the arrangement of the static eliminator 15, the static eliminator 15 can also serve as static eliminator for the recording paper as shown in FIG.

The photosensitive drum 10 from which the residual toner has been removed by the cleaning device 16 is exposed by the PCL 12 and then uniformly charged by the charging device 11, and enters the next image forming cycle. During the formation of the multicolor image, the cleaning blade 16a is separated from the surface of the photoconductor and
C static elimination is maintained in the OFF state.

The present invention relates to a charging device using a sawtooth electrode used in such an image forming apparatus, although it is difficult to replace the sawtooth electrode plate alone, but the sawtooth electrode plate is attached to a support. Is relatively easy to replace with
In addition, it was done paying attention to the fact that it is necessary to protect the tip of the electrode when handling, and the sawtooth electrode supported by the support is attached and taken out as a replacement member together with a protection member for protecting the electrode tip. In addition, the protective member is moved to expose the tip of the electrode at the time of mounting so that corona charging is performed.

(Embodiment 1) FIG. 1 shows a first embodiment, in which a replacement member having a serrated electrode can be attached and removed from the back surface of the charger. FIG.
1A shows a fixed portion to the image forming apparatus in a state where the replacement unit 110A is removed from the charger 11A, FIG. 1B shows the replacement unit 110A having a sawtooth electrode 111A, and FIG. The state where the exchange part 110A is attached from the back of the charger to enable corona charging is shown.

As shown in the YY section, the exchange section 110A encloses the sawtooth electrode 111A inside with an insulating electrode support member 120A molded from a resin material that supports the sawtooth electrode 111A and elastically from both sides thereof. There is a plate-shaped electrode protection member 121A made of a resin material or the like for protection by
Guide pins 123A for electrically connecting the electrodes are provided in the front and rear of the charger when the replacement unit 110A is attached to the charger 11A.

The image forming apparatus is provided with a charger 11A in a state as shown in FIG. That is, the charger 1
1A side plate 113A and control grid 115
A is an insulating side plate support member 11 made of resin or the like
2A is attached and supported, and is electrically connected to the main body of the image forming apparatus. To newly attach the replacement portion 110A, the electrode protection member 121A is opened to the left and right to expose the tip of the sawtooth electrode 111A, and the replacement portion mounting opening 117A provided in the side plate support member 112 on the back of the charger. Inserted from the rear side into the guide pin hole 118
The guide pin 123A of the exchange unit 110A is inserted and fixed to A. This ensures that the sawtooth electrode 111A has a regular positional relationship with the photoconductor drum 10. Figure 1 (c)
Shows a state in which the exchange unit 110A is mounted and the charger 11A is enabled to perform corona charging for the body to be charged.

When toner adheres to the tip of the electrode of the charger 11A and the performance of the charger is deteriorated, the replacement portion 110A is lifted from the back of the charger to electrically connect the electrodes. Exchange section 11 in the cut off form
0A is taken out. When taking out the exchange part 110A, the electrode protection member 121A biased inwardly surrounds the serrated electrode 111A to protect the electrode tip part. The removed replacement part 110A may be replaced with a new replacement part and mounted, or the electrode part may be cleaned with the removed part and then mounted again.

(Embodiment 2) FIG. 2 shows a second embodiment. This embodiment makes it possible to mount and remove an exchange member having a serrated electrode from the side surface of the charger. Figure 2
FIG. 2A shows a portion fixed to the image forming apparatus with the exchange unit 110B removed from the charger 11B, FIG. 2B shows the exchange unit 110B having a sawtooth electrode 111B, and FIG. The state where the exchange part 110B is attached from the side surface of the charger to enable corona charging is shown.

As shown in the YY section, the exchange part 110B has an insulating electrode supporting member 120B molded of a resin material for supporting the sawtooth electrode 111B, a side plate 113B fixed to one side thereof, and an opposite side thereof. There is a plate-shaped electrode protection member 121B made of a resin material or the like that elastically protects the tip of the inner serrated electrode 111B, and its position is regulated before and after the replacement part 110B is attached to the charger 11B. In addition, guide pins 123 for respectively electrically connecting the electrode and the side plate to the main body side.
B is provided.

In the state shown in FIG. 2A, the charger 11B is fixed to the image forming apparatus. That is, the side plate 113B and the control grid 115 on one side of the charger 11B.
Both B are mounted and supported on an insulating side plate support member 112B made of resin or the like, and are electrically connected to the image forming apparatus main body.

To install the replacement section 110B newly,
The tip of the saw-toothed electrode 111B is exposed by pushing up the electrode protection member 121B, and is inserted laterally into the replacement portion mounting opening 117B on the side surface of the charger, and the replacement portion is inserted into guide pin holes 118B provided in the front and rear. The guide pin 123B of 110B is inserted and fixed. This allows the sawtooth electrode 1
11B ensures a regular positional relationship with the photoconductor drum 10. FIG. 2C shows a state in which the exchange section 110B is attached to enable the corona charging operation.

When toner adheres to the tip of the electrode of the charger 11B and deterioration of the performance of the charger is recognized, the replacement section 110B is taken out by an operation of pulling it out from the side surface of the charger. Exchange part 1 taken out
10B is an electrode protection member 121B biased inward.
The electrode tip is protected by being surrounded by. The removed replacement section 110B can be replaced with a new replacement section or can be reused after cleaning or the like.

(Embodiment 3) FIG. 3 shows a third embodiment. This embodiment makes it possible to mount and remove an exchange member having a serrated electrode from the end of the charger. FIG.
FIG. 3A shows a portion fixed to the image forming apparatus in a state where the replacement unit 110C is removed from the charger 11C, FIG. 3B shows the replacement unit 110C having a sawtooth electrode 111C, and FIG. The state in which the exchange section 110C is inserted and attached from the end of the charger to enable corona charging is shown.

As shown in the YY section, the exchange section 110C encloses the saw-toothed electrode 111C inside with an insulative electrode support member 120C molded from a resin material that supports the saw-toothed electrode 111C and elastically from both sides. There is a plate-shaped electrode protection member 121C made of a resin material or the like for protection by
The charging unit 1 is provided with a replacement unit 110C at the tip end when inserting and mounting.
A guide pin 123C is provided which, when attached to 1C, regulates the position and makes an electrical connection.

The image forming apparatus is provided with a charger 11C in a state as shown in FIG. That is, the side plate 113C having a U-shaped cross section and the control grid 11
5C, the cross section has a square shape, the side plate support member 112C is attached to one end, and the other end is opened to form an exchange portion attachment opening 117C. Further, a long groove for inserting the exchange section 110C is provided on the upper side of the charger 11C.

To install the replacement section 110C newly,
The electrode protection member 121C is opened to the left and right to open the sawtooth electrode 111.
The tip portion of C is exposed, and insertion and attachment are performed through the exchange portion attachment opening 117C on the end surface of the charger. Exchange part 110
When C is inserted up to a fixed position, the guide pin 123C is inserted into the guide pin hole 1 provided in the side plate support member 112C.
18C is fitted, and the electrical connection of the electrode part is also performed. FIG. 3C shows a state in which the replacement unit 110C is attached and the charger 11C is enabled to perform corona charging on the body to be charged.

When toner adheres to the tip of the electrode of the charger 11C and the performance as the charger is deteriorated, the replacement section 110C is pulled out from the end of the charger and taken out. When the exchange part 110C is taken out from the charger, the electrode protection member 121C biased inwardly surrounds the sawtooth electrode 111C to protect the electrode tip. The removed replacement section 110C may be replaced with a new replacement section and mounted, or the electrode section may be cleaned with the removed section and reattached for use.

In the embodiment described above, the exchange section 110A
(B, C) has a structure in which its position is restricted and is attached to the charger 11A (B, C). However, a lock member is further provided to lock the charger at a proper mounting position, and the lock member is unlocked. It is also possible to have a structure that enables detachment. Further, the electrode protection member 121A (B, C) is fixed to the replacement section 110A (B, C) and cannot be removed even when it is attached to the charger, but the replacement section 1
It is also possible to remove the electrode protection member 121A (B, C) from the exchange section 110A (B, C) while the 10A (B, C) is attached to the charger portion of the image forming apparatus. Further, the electrical connection of the electrodes of the exchange part 110A (B, C) has been described with reference to the embodiment in which the guide pin 123A (B, C) has the function of the connection terminal, but the invention is not limited to this. Exchange part 110A with connection terminal
It is also possible to adopt a configuration in which electrical connection is made with the attachment of (B, C) or separately therefrom.

[0038]

According to the present invention, a sharp-edged tip is dangerous to handle, and the tip is easily bent, and if the tip is bent, performance is impaired. Since the replacement is possible without accompanying it, by applying the present invention as the charging device of the image forming apparatus described in the embodiment, when the electrode part of the sawtooth electrode is contaminated and the performance is deteriorated, the replacement part is replaced. By replacing or cleaning by removing the replacement part, good corona charging is always performed.

[Brief description of drawings]

FIG. 1 shows a charging device according to a first embodiment of the present invention.

FIG. 2 shows a charging device according to a second embodiment of the present invention.

FIG. 3 shows a charging device according to a third embodiment of the present invention.

FIG. 4 is a front view of a charging device having a sawtooth electrode.

5 shows a cross-sectional view of the charging device shown in FIG.

FIG. 6 is a sectional view showing an example of an image forming apparatus in which the charging device of the present invention is used.

[Explanation of symbols]

11A, 11B, 11C Charger 110A, 110B, 110C Exchange part (charging device) 111A, 111B, 111C Sawtooth electrode 112A, 112B, 112C Side plate support member 113A, 113B, 113C Side plate 115A, 115B, 115C Control grid 117A , 117B, 117C Replacement part mounting opening 118A, 118B, 118C Guide pin hole 120A, 120B, 120C Electrode support member 121A, 121B, 121C Electrode protection member 123A, 123B, 123C Guide pin

Claims (5)

[Claims] 1. A charging device for corona charging a body to be charged with a sawtooth electrode supported by a support, wherein the sawtooth electrode supported by the support is a replacement member together with a protection member for protecting the tip of the electrode. The charging device is characterized in that it can be mounted and taken out as described above, and the protective member is moved at the time of mounting to expose the tip of the electrode. 2. The charging device according to claim 1, wherein the electrode tip is exposed by opening the electrode of the protection member. 3. The charging device according to claim 1, wherein the replacement member is mounted by inserting the charging device from a back surface or a side surface. 4. The charging device according to claim 1, wherein the replacement member is mounted by being inserted from an end portion of the charging device. 5. The charging device according to claim 1, wherein the protective member protects the tip of the electrode when the replacement member is taken out.