JPH0973214A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily automatically clean a grid and to obtain an excellent-quality image by retreating a second electrostatic charge means disposed on a downstream side from the actuating position as necessary and enlarging a gap between the electrostatic charge means and the surface of an image carrier faced to it. SOLUTION: This image forming device is constituted so that a grid wire 9 is arranged at the part of the second electrostatic charge means 6, which is disposed on the downstream side, faced to the image carrier 1 so that it can be moved in a direction that it is brought into contact and separated with respect to the surf ace of the carrier 1. Besides, it is provided with a cleaning member 13 abutting on the wire 9 and rubbing and cleaning it when the wire 9 is set at a retreating position and a cleaning signal generation means for actuating the cleaning member 13 when the wire 9 is retreated. Then, when the cleaner 13 is moved in the longitudinal direction of the electrostatic charger 6 through a screw lever 14 by driving a motor 18, an electrostatic charge wire 8, the wire 9 and the inside surface of a shield case 10 are respectively cleaned by a pad.

Description

Detailed Description of the Invention

[0001]

[Object of the invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrostatic copying machine and a printer.

In this kind of well-known image forming apparatus, two different kinds of latent images, for example, a combination of a format frame and character information or black character information and a red mark, a seal imprint, etc. are formed, and these are the same or different colors. Conventionally, there has been proposed a method of developing an image with the above-mentioned developer to obtain an image.

Regarding such an image forming process,
An image forming apparatus shown in FIG. 1, which is an embodiment of the present invention and basically includes the image forming steps as described above,
The two-color image forming process will be briefly described with reference to the explanatory views shown in FIGS.

As shown in FIG. 11, the photosensitive layer on the surface of the image carrier is uniformly translated by the first primary charger 3 +600.
V. Then, the charged surface is irradiated with the image signal L ₁ , and the potential of the site is attenuated to form a latent image as shown in FIG.

To this latent image, a one-component insulating toner T ₁ having a red non-magnetic positive charging polarity is supplied from a first developing device 4 through a developing sleeve 4 ₁ and a toner image is formed by reversal development. (“FIG. 13”). At this time, the distance between the image carrier and the developing sleeve is about 300 μm, the developing bias is DC of 500 V, and 1500 Hz and peak-to-peak voltage of 1500 V _p-p are superposed.

Next, the photosensitive layer on the surface of the image carrier 1 is charged by the second primary charger 6. At this time, the charging bias is +6.0 Kv, and a grid is arranged on the release side of the charger 6 facing the image carrier, and the grid is +600 V.
Grid bias is applied. This second
Is charged to about +600 V both in the developed area and the unexposed area by the red toner T ₁ (see FIG.
4 ").

Then, the image signal L ₂ is projected on the image carrier 1 to attenuate the potential of the relevant portion to form a latent image corresponding to a black image as shown in FIG. One-component magnetic toner T ₂ having positive polarity of magnetism
Is applied by reversal development through the developing sleeve 7 ₁ of the developing device 7 to form a black toner image (see FIG.
6 ”). At this time, the distance between the image carrier 1 and the developing sleeve 7 ₁ is about 300 μm, and the developing bias applied is the same as in the first developing.

At the time of the second development, the surface potential of the image carrier at the red toner developing area and the unexposed area is about +58 due to dark decay.
Although it is 0 V, the potential of the red toner developing portion is black toner T ₂
Since the bias repels the black toner, the black toner is prevented from being mixed with the red toner portion. The toner image thus formed is transferred onto a transfer material at a transfer portion to form a hard copy of a two-color image.

By the way, in this way, in the method of sequentially repeating the charging, latent image formation, and development steps on a single image carrier that travels in one direction, the developing device on the upstream side in the image carrier travel direction. And the charger of the next process must be placed close to each other, the discharge wire and grid wire of the charger of the next process are contaminated by the toner leaked from the developer of the preceding process, which causes the deterioration of the image quality. There is a great risk of

The present invention has been made in order to cope with such a situation, and at least two sets of image forming portions provided with a charging device and a developing device are sequentially arranged in the running direction of the image bearing member. In the image forming apparatus described above, it is possible to prevent the leakage of toner from the developing device in the first image forming portion to contaminate the charging device in the second image forming portion as much as possible. The purpose is to do.

[0011]

Configuration of the Invention

In order to achieve the above-mentioned object, the present invention is provided with a first charging means which is disposed in the vicinity of a running image carrier to charge the image carrier and which is charged. An image including first developing means for developing the latent image formed on the surface of the image carrier, second charging means and second developing means arranged on the downstream side in the traveling direction of the image carrier. In the forming apparatus, the grid wire arranged at a portion of the second charging unit facing the image carrier can be moved in a direction toward and away from the surface of the image carrier, and the grid wire is in a retracted position. A cleaning member for abutting against the grid wire and cleaning the same when the grid wire is in position, and a cleaning signal generating means for activating the cleaning member when the grid wire is retracted. In the image forming apparatus (1) characterized by the above, or in the above (1), since the grid wire is brought into contact with or separated from the surface of the image carrier, the second charging means is brought into contact with or separated from the image carrier. In the image forming apparatus (2) or the above-mentioned (1), the grid wire is brought into contact with and separated from the surface of the image carrier, so that the grid wire is attached to the surface of the image carrier by the second charging means. In the image forming apparatus (3) characterized in that it is elastically biased in the direction close to the above, or in any one of the above (1) to (3), An image forming apparatus (4), characterized in that a duct for attracting foreign matter adhering to the charging means is provided, or in the above-mentioned (4), the second charging means is placed inside the duct when it is inactive. Image forming device characterized by evacuation (5), or,
In any one of the above items (1) to (5), the cleaning signal generating means detects that the number of discharges of the second charging means has reached a predetermined number of times, (6) Alternatively, in any one of the above (1) to (5), the cleaning signal generating means detects that the integrated discharge time of the second charging means has reached a predetermined time, and image formation. The device (7).

With such a configuration, even in the image forming apparatus that performs the image forming operation a plurality of times on one image carrier, the charging means in the image forming portion in the latter stage is in the image forming portion in the former stage. It is possible to preferably prevent contamination by the leaked toner of the developing unit and obtain a high quality image.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS "FIG. 1" and "FIG. 2" are side views of an image forming apparatus which is an embodiment of the present invention, and "FIG. 1" shows that the second charger is in an operating position. 2 "indicates that the charger is in the retracted inoperative position. The basic operation of the image forming apparatus has been described above, and therefore the description thereof will be omitted and the cleaning of the second charger 7 will be described below.

FIG. 3 is a partially cutaway perspective view of the charger 6 used in the above apparatus. The charger has a shield case 10 having insulating supporting portions 11 at both ends.
A discharge wire 8 is provided in the inner longitudinal direction, and a grid wire 9 is provided on the release side of the shield case and the side facing the image carrier.

Further, a cleaner 13 having a structure to be described later is arranged so as to substantially surround the shield case 10. The cleaner 13 has a projection on a screw rod 14 extending in the longitudinal direction of the back surface of the shield case. 13-1 (see FIG. 5). The screw rod 14 is connected to a motor 18 capable of rotating in the forward and reverse directions, and the cleaner 13 is moved along the shield case 10 via the screw rod 14 by driving the motor 18.

The discharge wire 8 and the grid 9 are made of tungsten thin wire and stainless thin wire, and reference numeral 12 is for applying a charging bias to the discharge wire 8 from the main body of the apparatus when the charger is mounted at a predetermined position. Is the terminal.

FIG. 4 is a sectional view of the charger showing the structure of the cleaner 13. As shown in the figure, the cleaner 13 that engages with the screw rod 14 extends along the inside and outside of the shield case of the charger, and a part thereof extends along the outside surface of the shield case. And extends to the outside to form an extending portion 13-3.

A part of the cleaner 13 is branched from a slit 10a formed in the longitudinal direction of the back surface of the shield case to extend into the inside thereof, and one branch portion 13-2 is divided into two tips. The discharge wire 8 is sandwiched between them. The other branch 13-4 extends along the inner surface of the shield case 10.

On the inside of the extending portion 13-3, on the side facing the grid 9, the pad 16 is pressed against the grid wire, and at the portion of the branch portion 13-2 where the discharge wire 8 is sandwiched. Pads 15 are respectively arranged so as to be in pressure contact with the wires 8, and pads 17 are arranged on the outer surfaces of the branch portions 13-4 so as to rub against the inner surface of the shield case 10.

With such a structure, when the cleaner 13 is moved in the longitudinal direction of the charger through the screw rod 14 by driving the motor 18, the pads 15, 16 and 17 charge the respective charges. The wires 8, the grid wires 9, and the inner surface of the shield case can be cleaned.

As described above, the extending portion 13-3 for cleaning the grid wire 9 of the cleaner 13 projects to the outside of the charger on the grid side. However, when the charger is mounted like an image forming apparatus, the grid Since the distance between the wire and the surface of the image carrier is usually as small as about 1 mm, one end of the charger is formed so as to project outside the end of the image carrier facing the charger. Then, this portion is set as the home position of the cleaner 13 so that the cleaner is located at this position during non-cleaning so that the cleaner does not interfere with the operation of the apparatus.

As can be seen from FIG. 1, the second charger 6 is mounted on the guide rail 21 so as to be movable in the contacting / separating direction with respect to the image carrier 1 and the solenoid 20.
Connected to. Further, the charger 6 is biased by a spring 22 to a position where it is always in contact with the stopper 23, and this offset position is the operating position of the charger 6.

As described above, the cleaner 13 is always in the home position, and the charger 6 is in the operating position shown in FIG. In this state, image formation is performed and the number of copy operations is counted.
At a preset cleaning time such as 0th, 1000th, 2000th, etc., the solenoid 20 is energized by a signal from a control circuit (not shown), and the charger 6 moves backward against the action of the spring 22. And take the position shown in FIG.

Next, the motor is activated, and the cleaner 13 is moved in the longitudinal direction of the charger by the action of the screw rod 14, so that the pads 15, 16 and 17 perform the cleaning action as described above. At this time, since the charger 6 has already retracted to the position shown in FIG. 2, the extending portion 13-3 of the cleaner 13 does not collide with the image carrier 1.

When the cleaner 13 arrives at the opposite end of the charger, it is detected by a sensor (not shown), the motor 18 rotates in the reverse direction, and when the cleaner 13 reaches the home position, it is detected and the motor is stopped. Shall be allowed. Then, the solenoid 20 is deenergized and the cleaning is completed.

The timing for cleaning is as follows.
Needless to say, it can be performed at the time of discharging, when the main switch is turned on, etc., in addition to depending on the number of copies as described above.

FIG. 6 and FIG. 7 are side sectional views of the essential part showing another embodiment. The first charging device 3, the first developing device 4, the second charging device 6, and the second developing device 7 are arranged in proximity to the image carrier 1 from the upstream side to the downstream side when viewed in the traveling direction of the image carrier 1. It is arranged over the side. The method of performing the image forming work twice on the image bearing member by using the toners of the same color or different colors is basically the same as that of the apparatus shown in "FIG. 1" and "FIG. 2".

In the above apparatus, the fan 32 is provided in the vicinity of the second charger 6, and at the time of image formation, the air is blown toward the image carrier 1 through the duct 33 and the first developing device 4 is supplied.
This prevents the toner leaked from the toner from adhering to the second charger 6. The fan 32 is stopped during non-image formation.

The charger 6, the fan 32, and the guide rail 21 are integrally formed, and are slidable in the duct 33 in a direction of approaching and separating from the image carrier 1.
As shown in FIG. 6, an arm 35 is provided on the charger 6, and a spring 34 acts on the arm 35 to bias the charger 6 toward the image carrier 1. The arm 35 is positioned by abutting on an arm 36 provided on the second developing device 7.

A cam 37 is provided in the second developing device 7, and the cam 37 is in the position shown in FIG. 6 when the second charger 6 shown in FIG. 6 is in operation. Charger 6,
All the second developing devices 7 are in the operating position.

When cleaning the second charger 6, the cam 37 is moved to "FIG. 7" by a cleaning signal.
It shall be rotated as shown in. As a result, the arm 36 of the developing device 7 presses the arm 35 of the charging device 6 against the action of the spring 34, and the charging device 6, the Rero 21, and the fan 3
2 is integrally drawn into the duct 33, and a gap is formed between the charger 6 and the surface of the image carrier 1 through which a portion of the cleaner for cleaning the grid wire can pass.

In this device, when the charger 6 is retracted, the unused space in the duct can be utilized, so that no space for retracting is particularly required. As the cleaning member at this time, it is possible to use the cleaning members as shown in the above-mentioned "FIG. 3" and "FIG. 4" or the cleaning means as described below in "FIG. 8".

FIG. 8, FIG. 9, and FIG. 10 are side sectional views of only the charger, showing another embodiment, respectively, a sectional view when the charger is operating, and a line BB shown in the drawing. 2 is a cross-sectional view taken along the line and a cross-sectional view at the time of non-operation.

FIG. 9 is a sectional view of the image forming apparatus as shown in FIG. 1 taken along the longitudinal direction of the second charger, and a shield case 10 having support members 11 at both ends.
The discharge wire 8 is stretched inside. As the cleaning means (not shown) for this discharge wire 8, the same one as in the above-mentioned embodiment can be used.

In the charger having the above-described structure, the one shown in the figure has grid wire support members 24 and 25 on the outside of the support member 11 on the shield case opening side.
Are arranged, and the grid wire 9 is stretched between them.

Each grid wire support member 24, 25
As shown in "FIG. 10" (the drawing shows one support member 24, the other support member 25 is also the same), both sides of the portion where the grid wire 9 is extended are shielded by the shield case 10.
It extends to the inner side of the inner side of the
The projecting portion 2 protruding outward from the long holes 10a and 10b provided in the
8, 29 are formed.

Further, leaf springs 26 and 27 are provided between the outer side surface of the support member 11 and the inner side surfaces of the grid wire support members 24 and 25 where the grid is extended, respectively. The members 24 and 25 are biased so as to be separated from the opening side of the shield case, whereby the ends of the elongated holes 10a and 10b serve as stoppers and the supporting members 24 and 25 are restricted by the elongated holes. It is biased outward to the position. In this state, the charger is incorporated into the main body of the apparatus and operates.

Cams 30 and 31 are disposed in contact with the protrusions 28 and 29 of the grid wire support members 24 and 25, and when the charger is in the operating position, these cams take the positions shown in the drawing. Be present.

At the time of cleaning, the cam 30 is rotated clockwise by 90 degrees and the cam 31 is rotated counterclockwise by 90 degrees by a driving means (not shown). As a result, the support members 24 and 25 and the grid wire 9 supported by these support members move toward the shield case 10 against the springs 26 and 27 to be in the state shown in FIG.

A movable cleaner member 13 having the same structure as the cleaner 13 in the apparatus of the above-mentioned embodiment is arranged along the longitudinal direction of the charger, and a cleaning pad is provided on the surface facing the grid wire 9. The extended part is provided. The positions of the extended portions are the same as the support members 24, 2
5. The cleaning pad is set so as to rub against the grid wire 9 when the grid wire 9 is retracted to a position close to the shield case 10 and is in the position shown in FIG. Cleaning can be accomplished in a manner similar to that of the apparatus of the previous embodiment.

It will be easily understood that the grid wire cleaning means described above can perform the cleaning of the grid wires in the same manner as the apparatus of the above-mentioned embodiment. With such a configuration, it is possible to perform cleaning by moving only the grid wire portion without retracting the entire charger.

[0042]

As described above, according to the present invention,
A first charging device and a first developing device are provided in this order along the traveling image carrier, and a second charging device and a second charging device are provided downstream of the first developing device when viewed in the image carrier traveling direction. In the image forming apparatus including the second developing unit in this order, the second charging unit is retracted from its operating position as necessary to increase the gap between the charging unit and the surface of the image carrier facing it. By doing so, the cleaning of the grid can be easily performed automatically, which is a remarkable effect in obtaining a good quality image.

[Brief description of drawings]

FIG. 1 is a side sectional view of a main part of an image forming apparatus as an embodiment of the present invention.

FIG. 2 is a side sectional view showing the same second charger as the retracted position.

FIG. 3 is a perspective view showing a configuration of a second charger.

FIG. 4 is a sectional view showing the structure of the cleaning member.

FIG. 5 is a side view showing an engagement mode with a screw rod for moving the cleaning member.

FIG. 6 is a side sectional view of a main part of an image forming apparatus showing another embodiment of the present invention.

FIG. 7 is a side sectional view showing the second charger in the retracted position.

FIG. 8 is a longitudinal sectional view of a second charger showing still another embodiment.

FIG. 9 is a sectional view for explaining the structure of the cleaning member of the above.

FIG. 10 is a longitudinal sectional view showing a state during cleaning of the same.

FIG. 11 is an explanatory view showing a state where the surface of the image carrier is uniformly charged.

FIG. 12 is an explanatory diagram showing formation of a first latent image on the photosensitive surface of the image carrier.

FIG. 13 is an explanatory diagram showing that toner is applied to a latent image portion of the same as above.

FIG. 14 is an explanatory diagram showing that the image carrier is uniformly charged again.

FIG. 15 is an explanatory diagram showing the formation of a second latent image on the photosensitive surface.

FIG. 16 is an explanatory diagram showing that a second toner image is formed on the latent image portion of the same.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image carrier 3 1st charging device 4 1st developing device 6 2nd charging device 7 2nd developing device 8 Discharge wire 9 Grid wire 10 Shield case 11 End support member 12 Terminal 13 Cleaner 14 Screw rod 15 , 16, 17 Cleaning pad 20 Solenoid 21 Guide rail 23 Stopper 32 Fan 33 Duct 34 Spring 35 Arm 37 Cam

Claims (7)

[Claims] 1. A first charging device which is disposed in the vicinity of a running image carrier to charge the image carrier, and a first developing device which develops a latent image formed on the surface of the charged image carrier. An image forming apparatus including a second charging unit and a second developing unit disposed on the downstream side in the running direction of the image carrier, the second charging unit facing the image carrier. Cleaning in which a grid wire disposed in a part is movable in a direction of moving toward and away from the surface of the image bearing member, and abuts on the grid wire when the grid wire is in the retracted position to perform rubbing cleaning. And a cleaning signal generating means for operating the cleaning member when the grid wire is retracted. 2. The image forming apparatus according to claim 1, wherein the second charging means is brought into contact with or separated from the image carrier so that the grid wire is brought into contact with or separated from the surface of the image carrier. . 3. The grid wire is elastically biased toward the surface of the image carrier by the second charging means in order to bring the grid wire into and out of contact with the surface of the image carrier. The image forming apparatus according to claim 1. 4. A duct according to claim 1, further comprising a duct for sucking a foreign substance adhering to the charging means when the second charging means is activated. Image forming device. 5. The image forming apparatus according to claim 4, wherein the second charging means retracts into the duct when the second charging means is not operating. 6. The cleaning signal generating means detects that the number of discharges of the second charging means has reached a predetermined number of times, and the cleaning signal generating means detects the number of discharges of the second charging means reaches a predetermined number of times. Image forming apparatus. 7. The cleaning signal generating means detects that the integrated discharge time of the second charging means has reached a predetermined time, as claimed in any one of claims 1 to 5. Image forming device.