JPH05341624A - Image forming device with contact electrifying device - Google Patents

Abstract

PURPOSE:To prevent the deterioration of the effect of cleaning contact electrifying rotary bodies, over a long period of time even in the simple structure without decreasing image forming speed and making an image forming sequence complex. CONSTITUTION:An electrifying roller 12 and a transfer roller 17 as the contact electrifying rotary bodies are provided so as to rotate normally and reversely, and they are made to rotate following a photosensitive drum 11. When image formation is carried out, the photosensitive drum 11 is normally rotated to rotate the contact electrifying rotary bodies normally, and when image formation is not carried out, they are rotated reversely, so that the reverse rotation causes the fall of sticking objects such as toner and dust accumulating at the front ends of cleaning blades 13 and 18 as cleaners sliding against the contact surfaces of the contact electrifying rotary bodies. By cleaning the front ends of the blades, the satisfactory effect of cleaning is maintained over a long period of time.

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 such as a copying machine, a printer or a fax machine equipped with a contact charging device for rotating a contact charging rotating member such as a charging roller or a transfer roller in contact with the surface of an image carrier.

[0002]

2. Description of the Related Art Conventionally, as a contact charging device provided in an image forming apparatus such as a copying machine, there is, for example, Japanese Patent Laid-Open No. 58-1.
As described in Japanese Patent Laid-Open No. 94061, as shown in FIG. 4, a charging roller 3 which is a contact charging rotator in which a conductive elastic body 2 made of rubber is formed on the surface of a metal substrate can be rotated in contact with the photosensitive drum 1. And a blade 4 having a knife edge at the tip thereof is arranged at a constant angle so as to resist the rotation direction of the charging roller 3, There is a device in which an adhered matter such as toner or paper powder adhered to the surface of the charging roller 3 is scraped off by the tip of the blade 4 and collected on the tray 5.

Further, instead of the blade, a cleaning element made of a tungsten wire is provided close to the charging roller in the longitudinal direction, and an alternating current is applied to the cleaning element to attach the cleaning element to the surface of the charging roller. There is also one in which the present toner is attracted to the cleaning element to be peeled off, and the toner is collected on a tray to be electrically cleaned. Further, as described in Japanese Patent Application Laid-Open No. 3-101768, there is also one in which a sponge material is brought into contact with the surface of the charging roller as a cleaner to thereby clean the surface of the charging roller.

[0004]

However, in the case of the contact charging device using such a conventional blade type cleaner, the charging roller is always rotated in the same direction. Adhered substances such as scraped toner and paper dust tend to adhere to and remain on the blade tip portion, so that the cleaning effect is likely to decrease with time.

Further, in the case of a contact charging device in which the surface of the charging roller is electrically cleaned by electrostatic attraction by a non-contact proximity electrode formed by a cleaning element, it is mechanically pressed against the surface of the charging roller. It is difficult to remove the adhered toner and dust, or the paper dust that is difficult to be charged, and the device that collects the dust and the like adhered to the electrodes was also required, which made the configuration complicated and made the entire device expensive. There was a problem that it would become.

Further, in the case of a contact charging device using a sponge material as a cleaner, since the surface of the sponge material is uneven, streaky cleaning marks remain on the surface of the charging roller wiped off. , I couldn't clean it well. In addition, since toner and dust easily enter the air bubbles of the sponge material to cause clogging, the cleaning effect is poor and the life is relatively short.

The present invention has been made in view of the above problems, and has a simple structure and a contact charging rotary member for a long period of time without lowering the image forming speed or complicating the image forming sequence. The purpose is to prevent the cleaning effect from being lowered.

[0008]

To achieve the above object, the present invention provides an image forming apparatus having a contact charging device as described above, wherein a contact charging rotary member is provided so as to be rotatable in both forward and reverse directions. The image carrier is driven to rotate, the image carrier is normally rotated during the image forming operation to normally rotate the contact charging rotor, and the image carrier is reversed during the non-image forming operation to reverse the contact charged rotor. It was done like this.

The contact charging rotary member is a charging roller that charges the surface of the image bearing member during image formation, and the application of the charging voltage to the roller may be stopped during the reverse rotation of the roller, or It is effective to apply a bias voltage for static elimination to the roller. Further, in the image forming apparatus including the contact charging device, the contact position of the cleaner of the cleaning unit with the contact charging rotary member may be displaced depending on the rotation direction of the contact charging rotary member.

[0010]

According to the image forming apparatus having the contact charging device constructed as described above, when the image bearing member is rotated in the reverse direction, the contact charging rotating member in contact therewith is driven to rotate and reversely rotate. Adhesives such as toner and dust that have accumulated on the cleaner part of the cleaning means that is rubbing against the contact surface fall away from the cleaner due to its reversal, so a good cleaning effect can be obtained by removing the adhered substances. Can last for a long time.

Since no unique driving means or command control for reversing the contact charging rotary member is required, the structure can be simplified and the cost can be reduced. Further, since the contact charging rotary member is reversed only during the non-image forming operation, the image forming speed is not reduced and the image forming sequence is not complicated.

Further, the contact charging rotary member is a charging roller, and the application of the charging voltage to the roller may be stopped during the reverse rotation of the charging roller, or a bias voltage for removing the charge may be applied to the charging roller. By doing so, the toner is not adsorbed on the charging roller, so that the cleaning effect is further improved.

Further, if the contact position of the cleaner of the cleaning means with respect to the contact charging rotary member is displaced according to the rotation direction of the contact charging rotary member, the contact position of the cleaner is changed from during cleaning to during non-cleaning. Since the toner is displaced when it changes, the toner and the like accumulated at the contact position of the cleaner is more likely to drop at that time.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing the periphery of a photosensitive drum of an image forming apparatus including a contact charging device according to an embodiment of the present invention. This image forming apparatus rubs against a charging roller 12 which is a contact charging rotator that rotates in contact with an image carrier surface 11a of a photosensitive drum 11 which is an image carrier, and contacts the charging roller 12 with the photosensitive drum 11. A contact charging device 10 having a cleaning blade 13 as a cleaning means for cleaning the surface 12a is provided.

The photosensitive drum 11 is composed of OPC, A-Si,
The image carrier has a photoconductive layer such as A-Se, and rotates in the direction of arrow A during an image forming operation while being held by a rotation shaft (not shown). In addition, the charging roller 12 is for uniformly applying an electric charge to the surface of the image bearing member 11a on the surface of the photoconductor drum 11 to charge it.

Reference numeral 19 denotes a light source including a semiconductor laser, an LED, etc., which irradiates the uniformly charged image carrier surface 11a of the photosensitive drum 11 with image light based on a predetermined electric signal, and electrostatically irradiates the image carrier surface 11a. Form a latent image. 14 is a developing device,
Toner is stored in the inside thereof, and the developing sleeve 1
The toner is attached to the image carrier surface 11a of the photosensitive drum 11 by the rotation of 4a, and the electrostatic latent image formed there is visualized. Then, the image formed on the image carrier surface 11a is moved to the transfer portion 23 by the rotation of the photosensitive drum 11 in the arrow A direction.

On the other hand, the photosensitive drum 11 is provided in the conveying path 16.
The transfer paper P is supplied by a paper feeding device (not shown) in synchronism with the rotation of, and is conveyed to the transfer portion 23 provided with the contact charging device 15 at the timing when it matches the image on the photosensitive drum 11.

The transfer section 23 is provided with a transfer roller 17 which is a contact charging rotary member which comes into direct contact with the photosensitive drum 11. The transfer roller 17 is attached to the transfer paper P conveyed to the transfer section 23. By applying an electric charge to the surface, the toner image formed on the surface of the photosensitive drum 11 is transferred onto the transfer paper P. Further, the cleaning blade 18 rubs against the surface of the transfer roller 17,
A saucer 26 is disposed below it.

The transfer paper P on which the image is transferred in this way
Is conveyed to a fixing device (not shown) to fix the image, and then discharged to a discharge tray or the like outside the machine. Then, the residual toner remaining on the image carrier surface 11 a of the photosensitive drum 11 after the image transfer is scraped off and collected by the cleaning blade 21 of the cleaning device 20.

In this embodiment, the charging roller 12
Further, the transfer roller 17 is rotatably provided in both forward and reverse directions so that the photosensitive drum 11 is driven to rotate, and during the image forming operation, the photosensitive drum 11 is normally rotated in the direction of arrow A so as to rotate the charging roller 12 and the transfer roller 17. 1 are normally rotated in the directions indicated by arrows in FIG. 1, and during non-image forming operation, the photosensitive drum 11 is rotated in the reverse direction so that those rollers are rotated in the reverse direction.

Further, during the reverse rotation of the charging roller 12, a control means 25 which is a microcomputer for controlling the application of the charging voltage to the charging roller 12 by the power source 22 is provided. In FIG. 1, reference numeral 24 denotes a power supply for applying a predetermined voltage to the transfer roller 17,
Is a control means which is a microcomputer for controlling the application of the voltage.

In this image forming apparatus, since the photosensitive drum 11 rotates in the direction of arrow A during the image forming operation as described above, the charging roller 12 and the transfer roller 17 which are in contact with the photosensitive drum 11 are rotated.
Rotate in the direction indicated by the arrow in FIG.

Since the cleaning blade 13 and the transfer roller 17 are rubbed against the charging roller 12 and the transfer roller 17, respectively, toner and toner adhering to the surface of the roller when the rollers are normally rotated. The cleaning blades 13 and 18 are attached by paper dust or the like.
Part of the deposits scraped off at that time is collected at the tip portions of the blades.

In the non-image forming operation, the photosensitive drum 11
1 reverses in the direction opposite to the arrow A in FIG. 1, so that the adhered substances (dust) accumulated at the tip portions of the cleaning blades 13 and 18 are charged by the charging roller 12 and the transfer roller 1.
As the blades reverse with 7, they fall away from the blade tips, and the blade tips are cleaned. Therefore, good charging performance without uneven charging can be maintained for a long period of time, and the surface of the transfer roller 17 can be kept in a clean state, so that the backside of the transfer paper can be prevented. The toner dropped from the charging roller 12 is collected in the developing device 14, and the toner dropped from the transfer roller 17 is collected by the tray 26 provided below the toner.

Similarly, in the cleaning blade 21 of the cleaning device 20, adhered substances such as toner and dust accumulate on the tip portion of the cleaning blade 21 when the photoconductor drum 11 rotates in the normal direction, but when the image forming operation is not performed, the photoconductor is used. When the drum 11 is rotated in the reverse direction, the deposits accumulated at the tip end of the drum 11 fall apart from the tip end of the cleaning blade 21. Therefore, the adhering substances due to the toner and the like are removed to obtain a good cleaning effect for a long time. Can last over.

Further, in this embodiment, as shown in FIG. 2A, while the photosensitive drum 11 is rotated in the reverse direction and the charging roller 12 is driven to rotate (reverse), the charging roller 12 is moved to the charging roller 12. Since the application of the charging voltage by the power source 22 (FIG. 1) is stopped, the toner is not adsorbed to the charging roller 12 during the reverse rotation of the charging roller 12, so that a large cleaning effect can be obtained.

Further, as shown in FIG. 2B, during the reverse rotation of the charging roller 12, a bias voltage for static elimination having the opposite polarity (same polarity as the toner) to that during the image forming operation is applied to the roller. Even if the AC bias voltage is applied, the toner is not adsorbed to the charging roller 12, so the cleaning effect is further improved.

FIG. 3 is a schematic view showing an embodiment in which the contact position of the cleaner with respect to the contact charging rotary member is displaced according to the rotating direction of the contact charging rotary member. Charging roller 12
When the surface of the transfer roller 17 (see FIG. 1) is made of a smooth material having excellent lubricity, the cleaning blades 13 and 18 are normally rotated as shown in FIG. It may be arranged so as to make an acute-angled contact with the direction opposite to the direction (reverse blade cleaning method). However, since such a smooth material with excellent lubricity is expensive, it can be installed in a small machine or a low-priced machine. It cannot be used as a charging roller or transfer roller.

Therefore, in the case of such a small-sized machine or a low-priced machine, the surface portion of the roller is formed of, for example, an inexpensive resin-rubber copolymer, but in the case of such a material, a frictional force is generated. Because of its large size, when the above-mentioned reverse blade cleaning method is used, the tip portion of the blade bites into the surface of the roller, or the tip portion of the blade is curled up and cannot be used.

Therefore, in this embodiment, the contact position of the cleaning blade 33, which is the cleaner of the cleaning means for cleaning the surface of the charging roller 12, with the charging roller 12 is displaced by the rotating direction of the charging roller 12. ing. That is, the arrow B of the charging roller 12
The contact position is the portion a in FIG. 3 (forward blade cleaning method) during normal rotation of the blade, and the tip of the blade is displaced to the position indicated by an imaginary line by the frictional force in the rotation direction during reverse rotation. Is part b.

Similarly, as for the cleaning blade 18 (see FIG. 1) for cleaning the surface of the transfer roller 17, the contact position of the tip of the blade with the transfer roller 17 is the same as the cleaning blade 33 of FIG. Transfer roller 1
It is arranged to be displaced depending on the rotation direction of 7.

According to this contact charging device, when the photosensitive drum 11 and the charging roller 12 are positively rotated in the directions C and B shown in FIG. 3 during the image forming operation, the cleaning blade 33 is bent at the tip side as shown in the drawing. Then, since the tip end contacts the contact surface 12a of the charging roller 12 at the point a to start the cleaning action, the adhering substances such as toner and dust adhered to the surface of the charging roller 12 scraped by the contact surface 12a are started. Almost all of them fall, but some of them become non-falling deposits 35 and remain attached to the lower side of the tip of the cleaning blade 33. Then, the non-falling adhering matter 35 becomes defective in cleaning when it is accumulated too much.

However, in this embodiment, the charging roller 12 is rotated in the opposite direction to the arrow B by rotating the photosensitive drum 11 in the opposite direction to the arrow C for a predetermined time during the non-image forming operation. The cleaning blade 3 whose tip is in contact with the contact surface 12a of the charging roller 12
The tip portion of 3 is bent and displaced by the frictional force in the direction opposite to the normal rotation direction as indicated by the imaginary line.

Therefore, the contact position of the cleaning blade 33 with the charging roller 12 is thus set to the charging roller 1.
By displacing in the rotation direction of 2, the non-falling adhered matter 35 adhered to the tip portion thereof drops as shown in the figure, so that the blade tip is cleaned and a good cleaning effect can be maintained for a long time. ..

As for the cleaning blade 18 (see FIG. 1) for cleaning the surface of the transfer roller 17, the tip of the blade is moved by similarly displacing the contact position of the blade tip with the transfer roller 17. Since it becomes clean, a good cleaning effect can be maintained for a long period of time.

If the contact position of the cleaning blade with respect to the contact charging rotary member such as the charging roller is displaced in accordance with the rotating direction of the contact charging rotary member, the surface of the contact charging rotary member is enlarged. Even if it is formed of an inexpensive material having frictional resistance, it is possible to prevent the tip of the blade from biting into the contact charging rotating body and the blade from curling, so that good cleaning properties can be obtained.

[0037]

As described above, according to the present invention, when the image carrier is rotated in the reverse direction, the contact charging rotary member which is in contact therewith is driven to rotate and rubs against the contact surface of the contact charging rotary member. Since the deposits such as toner accumulated in the cleaner portion of the cleaning unit drop away from the cleaner, a good cleaning effect can be maintained for a long time by removing the deposits.

Since no unique driving means or command control for reversing the contact charging rotary member is required, the structure is simplified and the cost is reduced. Further, since the contact charging rotary member is reversed only during the non-image forming operation, the image forming speed is not reduced and the image forming sequence is not complicated.

Further, the contact charging rotary member is a charging roller, and during the reverse rotation of the charging roller, the application of the charging voltage for image formation to the roller may be stopped, or the bias voltage for removing the charge may be applied to the charging roller. If is applied, the toner will not be adsorbed on the charging roller, so that the cleaning effect is enhanced.

Further, the contact position of the cleaner of the cleaning means which rubs against the contact charging rotary member against the contact charging rotary member is displaced when the contact charging rotary member is rotated in the forward direction and the reverse direction. If so, the contact position of the cleaner is displaced when it changes from during cleaning to during non-cleaning, and at that time, toner and dust accumulated at the contact position of the cleaner are more likely to drop, so that the cleaning effect is enhanced.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing the periphery of a photosensitive drum of an image forming apparatus including a contact charging device according to an embodiment of the present invention.

FIG. 2 is a timing diagram showing a timing of applying a charging voltage to a charging roller of the contact charging device of FIG. 1 and a polarity of the applied voltage.

FIG. 3 is a schematic view showing only a main part of the embodiment in which the contact position of the cleaner with respect to the contact charging rotary member is displaced according to the rotation direction of the contact charging rotary member.

FIG. 4 is a schematic diagram showing an example of a contact charging device provided in a conventional image forming apparatus.

[Explanation of symbols]

10, 15 Contact charging device 11 Photoreceptor drum (image carrier) 11a Image carrier surface 12 Charging roller (contact charging rotor) 12a Contact surface 13, 18, 21, 33 Cleaning blade (cleaner) 17 Transfer roller (contact charging rotation) Body) 20 cleaning device 25, 30 control means

Claims (4)

[Claims] 1. An image forming apparatus provided with a contact charging device having a cleaning means for rubbing against a contact charging rotating member that rotates in contact with the surface of the image bearing member and cleaning the contact surface of the contact charging rotating member with the image bearing member. In the above, the contact charging rotator is rotatably provided in both forward and reverse directions so as to be driven and rotated by the image carrier, and during the image forming operation, the image carrier is normally rotated to normally rotate the contact charging rotator. An image forming apparatus equipped with a contact charging device, wherein the image carrier is reversed during non-image forming operation to reverse the contact charging rotator. 2. The image forming apparatus provided with the contact charging device according to claim 1, wherein the contact charging rotary member is a charging roller that charges the surface of the image bearing member during image formation, and the roller is rotating in the reverse direction. Is an image forming apparatus equipped with a contact charging device, characterized in that the application of a charging voltage to the roller is stopped. 3. The image forming apparatus provided with the contact charging device according to claim 1, wherein the contact charging rotating member is a charging roller that charges the surface of the image bearing member during image formation, and the roller is rotating in the reverse direction. Is an image forming apparatus equipped with a contact charging device, characterized in that a bias voltage for discharging is applied to the roller. 4. An image forming apparatus provided with the contact charging device according to claim 1, wherein a contact position of a cleaner of the cleaning unit with the contact charging rotary member is the contact charging unit. An image forming apparatus provided with a contact charging device, wherein the image forming device is configured to be displaced according to a rotation direction of a rotating body.