JPH063930A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent an electrostatic charging member from being deteriorated and to use a cleaning member for a long period by bringing the cleaning member into contact with the electrostatic charging member at least at some time during electrostatic charging for forming an image on an image carrier by the electrostatic charging member is not performed. CONSTITUTION:By depressing a start button, a main motor is rotated, a photosensitive drum 2 coupled and driven by the main motor is rotated, and an electrostatic charging roller 3 pressed to the drum 2 is rotated by following the drum 2 in an electronic copying machine. The cleaning member 1 is pressed to the roller 3 by solenoid 10 only at the time of cleaning, and it is separated from the roller 3 except at the time of cleaning. The time when the member 1 is pressed is set to the time when the roller 3 is rotated three times, for example. In a contact electrostatic charging system in which the member 3 is directly brought into contact with the image carrier 2, fine powder and dust, etc., adhering to the member 3 are removed, and the potential drop and the local faulty electrostatic charging of the image carrier 2 are prevented, and the members 1 and 3 are prevented from excessively being rubbed each other.

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 or a printer which uses an electrophotographic system, and more particularly to an image forming apparatus having a charging member that contacts an image carrier to charge the image carrier.

2. Description of the Related Art Conventionally, as a charging device used for pre-image exposure charging of a copying machine or the like, a device utilizing a discharge phenomenon such as a scorotron charger has been widely used, but recently, a conductive charging member. There is also used a contact charging method in which the charging member is directly contacted with the photosensitive member and a charging voltage is applied to the charging member.

For example, in a structure in which a conductive rubber roller is brought into contact with the photosensitive drum and is driven to rotate together with the rotation of the photosensitive drum, the photosensitive drum is uniformly charged by supplying a voltage to a core metal that is the shaft of the rubber roller.

In this contact charging system, the charging member is liable to be soiled with toner or the like, and this soiling may cause uneven charging, so that the surface of the roller is rubbed and scraped off by pressing a cleaning pad. In some cases, a cleaning mechanism is added.

[0005]

When a copying machine or the like using the above-mentioned contact charging system is used for a long period of time, if the cleaning mechanism for the charging member is not provided, the dirt naturally obstructs the charging.

[0006] Contamination due to fine powder does not cause uneven charging, but the fine powder is stacked and the overall electric resistance increases, so that the potential applied to the photosensitive drum decreases.

Further, in the case where toner lumps or other foreign matter adheres, charging failure of the adhered portion occurs.

For that purpose, a mechanism for removing a deposit by installing a cleaning member for scraping the charging member is implemented. However, since the cleaning member is pressed against the charging member, the charging member is damaged or worn due to long-term use. In this case as well, charging failure may occur.

As described above, even an image forming apparatus having a cleaning mechanism may result in defective charging.

(Object of the Invention) An object of the present invention is to avoid excessive rubbing of the cleaning member and the charging member, and to achieve deterioration of the charging member and long-term use of the cleaning member.

In order to achieve the above object, according to the present invention, an image carrier, a charging member that contacts the image carrier to charge the image carrier, and a contact member that contacts the charging member. In the image forming apparatus having a cleaning member for cleaning the charging member and an image forming unit for forming an image on the image carrier, the cleaning member can be brought into contact with and separated from the charging member. The cleaning member is brought into contact with the charging member only at least partly when the charging for image formation on the image carrier is not performed.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic side view of an image forming apparatus having a charging member cleaning mechanism according to an embodiment of the present invention.

A charging roller 3 as a charging member is arranged in contact with the photosensitive drum 2. A charging voltage is applied to the charging roller 3 from a high voltage power source 4. A is image exposure according to image information of a document or the like, 5 is a developing device, 6 is a transfer device, 7 is a cleaning device, and 8 is a fixing device. P is a transfer sheet, which is fed from a sheet feeding device (not shown), passes through the transfer area, and is conveyed to the fixing device 8.

A cleaning member 1 is configured to be pressed against the charging roller 3. FIG. 2 shows a cleaning state of the cleaning member.

In the electronic copying machine to which the present invention is applied, when the start button is pressed, the main motor rotates to rotate the photosensitive drum 2 which is connected and driven, and the charging roller 3 which is pressed against the photosensitive drum is It rotates following the photosensitive drum 2. The photosensitive drum 2 includes a photosensitive layer 2a and a photosensitive layer 2a.
Conductive substrate 2b made of aluminum or the like that supports and is grounded
And are equipped with.

First, in order to charge the surface of the photoconductor drum 2 to a uniform potential during the charging process, an applied voltage is applied by the charging roller 3 to set a predetermined potential. In this embodiment, in order to obtain a more uniform potential, the residual charge on the photoconductor is reset by a pre-exposure device (not shown) before charging, and then a voltage of -1500V is applied to the charging roller 3 from the high voltage power source 4. The photosensitive drum 2 is uniformly charged to -750V.

Next, a developing step is carried out in which the charged photosensitive drum 2 is imagewise exposed to form an electrostatic latent image and then developed with toner in a developing device.

Further, the photosensitive member 2 formed through the developing process
The upper toner image is transferred by the transfer device 6 to the transfer paper P fed in synchronism with the transfer device 6, and the transfer paper P that has undergone this transfer process is conveyed to a fixing device by a conveyor belt, and the toner on the transfer paper is transferred to the transfer paper P. It is fixed by the fixing device 8.

On the other hand, the residual toner on the photoconductor is removed by the cleaning device 7.

FIG. 3 shows a timing chart showing the timing of applying the voltage of the charging roller 3 and the timing of pressurizing and non-contacting the cleaning member 1 in all these steps.

The main motor starts rotating as soon as the start button is pressed, and stops after the entire process is completed. During this time, a voltage is applied to the charging member in the charging process for forming an image on the photosensitive drum 2.

The charging roller 3 is cleaned at least partly when the charging roller 3 is not charged for image formation on the drum 2. In this embodiment, the voltage from the high voltage power source 4 is applied to the charging roller 3. Not after being applied but after charging is complete. As shown in FIG. 2, the cleaning member 1 is pressed against the charging roller 3 by the solenoid 10 or the like only at the cleaning time, and otherwise the cleaning member 1 is separated from the roller 3. Here, the time when the cleaning member is pressed is three rotations of the charging roller 3.

In this embodiment, a machine having a copy speed of 10 sheets / minute can copy about 50 to 100 sheets per day.

The cleaning sequence can be operated only every plural steps of the image forming process (every predetermined number of copies) by introducing software control, but in the present embodiment, the life of the drum cartridge including the charging roller 3 is shortened. Since it is about 10,000 sheets, the adverse effect of rubbing can be ignored even after cleaning every time, so no special software control was put in.

In a machine with a copy speed of 30 sheets / minute, the number of copies per day is about 200 to 500 sheets.
In this case, the cleaning sequence of the charging roller 3 is not required to be carried out every time the image forming process is carried out, but may be decided to be multi-headed, once in ten times, once in 100 times, etc. depending on the scale and specifications of the image forming apparatus.

The cleaning member used in this embodiment has a two-layer structure and its structure is shown in FIG. 11 is a fine fiber surface, which directly contacts the charging roller 3 and rubs against it. Reference numeral 12 is an intermediate elastic member, and 13 is a support for the cleaning member.

As a fine fiber, 1 mm thick trade name EXCENE (manufactured by Toray) was used, and it was attached to an intermediate elastic member 12 made of maltoprene on a 2 mm thick sponge and AB
It was attached to the support 13 of S.

An endurance test was carried out with the above-mentioned structure. As a result, the number of times of cleaning was about one in 300 sheets, which was a sufficient practical level for ordinary fine powder stains.

However, if the cleaning sequence is performed once for every 300 sheets, a slight density difference will occur before and after cleaning, so in this embodiment, the cleaning sequence is inserted at one start-up in the morning, rather than entering the sequence in a fixed number of times. I decided. As a matter of course, the timing of the cleaning sequence does not start after charging as shown in FIG. 3, but the main motor is driven during warm-up operation after the main switch is turned on, that is, when the temperature of the fixing device is detected to be below a predetermined value. Enter in time. At this time, one cleaning sequence is performed between approximately 200 and 500 sheets.

Further, the number of copies per day is about 500 to 1000 on a machine having a copy speed of 40 sheets / min. In this case, if there is only one sequence in the morning, the cleaning may not be able to catch up a little. Since the difference in density before and after cleaning appears as described above when the number of cleanings is one, the cleaning sequence was performed once for every 50 sheets in this embodiment.

It was confirmed by a durability test that cleaning once every 50 sheets is at a practical level.

Further, by performing the cleaning relatively frequently in this way, it is more effective against accidental dust adhesion and local contamination.

The cleaning time of the charging member may be a part or all of the non-image forming time in the charging process.

A charging device including a charging member and a photosensitive drum as an image carrier may be provided in the process cartridge so that the process cartridge can be attached to and detached from the image forming apparatus.

[0036]

As described above, by carrying out the present invention, it is possible to remove fine powder, dust and the like adhering to the charging member by the contact charging system in which the charging member is brought into direct contact with the image bearing member, and thereby the image carrier. It is possible to prevent the potential drop and local electrification failure, and to prevent excessive rubbing between the cleaning member and the charging member to withstand long-term use.

[Brief description of drawings]

FIG. 1 is a partial side view of an image forming apparatus embodying the present invention.

FIG. 2 is a schematic side view illustrating a cleaning operation of the cleaning member of the present invention.

FIG. 3 is an operation sequence diagram of the present invention.

FIG. 4 is a perspective view of a cleaning member.

[Explanation of symbols]

 1 Cleaning Member 2 Photoreceptor Drum 3 Charging Roller 4 High Voltage Power Supply 11 Fine Fiber Layer of Cleaning Member 12 Intermediate Elastic Body 13 Cleaning Member Support

Claims (5)

[Claims] 1. An image carrier, a charging member that contacts the image carrier to charge the image carrier, a cleaning member that contacts the charging member to clean the charging member, and the image carrier. In the image forming apparatus having an image forming unit for forming an image on the image forming member, the cleaning member can be brought into contact with and separated from the charging member, and charging for image formation on the image carrier by the charging member is not performed. The image forming apparatus is characterized in that the cleaning member is brought into contact with the charging member only at least partially. 2. The apparatus is capable of forming a toner image on a recording material and has a fixing device for thermally fixing the toner image on the recording material, and the cleaning member is provided only when the temperature of the fixing device is below a predetermined value. The image forming apparatus according to claim 1, wherein the image forming apparatus is brought into contact with the charging member. 3. The image forming apparatus according to claim 1, wherein the cleaning member has fine fibers on its cleaning surface. 4. The cleaning member includes at least a surface layer that contacts the charging member, and an elastic layer that is adjacent to a support of the cleaning member. Image forming apparatus. 5. The amount of penetration of the cleaning member into the charging member when the cleaning member cleans the charging member is less than 0.5.
The image forming apparatus according to claim 1, wherein the image forming apparatus has a length of 1 mm to 3.0 mm.