JPH02298961A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain a contact electrostatic charging type image forming device which is inexpensive and has high reliability by constituting integrally respective process equipments for exposure, electrostatic charging, and cleaning in one process cartridge and replacing the cartridge a specific period later. CONSTITUTION:The respective process equipments 1, 2, and 7 which are a photosensitive drum 1, a contact electrostatic charging device 2, and a cleaning device 7 are constituted as the process cartridge 10 which is attachable to and detachable from a main body, and a couple of right and left bearing plates 7d are used as a holding part to assemble and support the drum 1 and electrostatic charging roller 2 rotatably between the bearing plates 7a. In this state, the drum 1, roller 2, and device 7 are held while positioned in specific arrangement state with high accuracy and a cleaning blade 7 and the roller 2 are also held in a specific state. The cartridge 10 is detachable and replaced with a new cartridge when the life of the drum 1 expires. Consequently, neither drum replacement nor disposal of waste toner is required and the reliability of the device is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is applicable to electrophotographic photoreceptors, electrostatic recording dielectric materials, etc. of rotating drum type, rotary belt type, running web type, etc. that are driven by surface movement. A transferable image is formed and carried on the surface of the image carrier by an image forming process device including means for charging the surface of the image carrier, the formed and carried image is transferred to the surface of the recording material, and the surface of the image carrier after the transfer is The present invention relates to an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus using a transfer method in which a cleaning device removes residue to make a clean surface and repeatedly uses the surface for image formation.

More specifically, the present invention relates to the above-mentioned transfer type image forming apparatus which uses a contact (direct) charging device as a charging device for the surface of an image carrier.

(Prior art) Conventionally, in electrophotographic devices, electrostatic recording devices, etc., the surface of an image bearing member such as a photoreceptor or dielectric material is uniformly charged (including charge removal).
As a means for this purpose, a corona discharger consisting of a wire electrode and a shield electrode to which a voltage of several kilovolts is applied is generally used.

However, corona dischargers require an expensive high-voltage power supply, require space for themselves and the shield space of the high-voltage power supply, and also generate a large amount of corona products such as ozone and NOx when corona occurs. To deal with this, additional measures such as ozone decomposition filter devices and air channels are required.
These are factors that make the equipment larger and more expensive.
In terms of electric power, only about 5 to 30% of the current flows toward the surface of the image carrier, and most of it flows through the shield electrode, resulting in poor efficiency.

Therefore, in recent years, consideration has been given to adopting a contact charging method instead of a corona discharger, which has many problems. Contact charging is a method of transferring electric charge directly to the surface of a charged object by directly contacting the surface of the charged object with a conductive member (charging member, roller type, brush type, blade type, etc.) to which a voltage is applied by a power source with a predetermined pressing force. Injection) to charge the surface to be charged to a desired potential, and compared to conventional corona discharge devices, this contact charging device has a higher The applied voltage can be lowered,
Since the amount of ozone generated during the charging process is very small,
It has various advantages such as not requiring an ozone removal filter or air passage inside the device.

(Problems to be Solved by the Invention) Although the contact charging device has the above-mentioned advantages, it is not an effective substitute for the corona discharger for charging the image bearing surface in an image forming apparatus. The reason why contact charging has not been fully put into practical use as a method is that due to its structure, the conductive member that is the charging member is in contact with the surface of the image carrier that is the object to be charged, and the image is not transferred from the surface of the conductive member. Charge transfer occurs on the image carrier and the surface of the image carrier is charged. However, if a developer such as toner adheres to the surface of the image carrier, the charged area (between the image carrier and the conductive member) The foreign matter adheres to the surface of the conductive member (contact surface area of There was a drawback that it could be stored away.

In a transfer type image forming apparatus, a cleaning device such as a fur brush rubber plate type cleaning device is disposed at a position upstream in the direction of surface movement of the image bearing member from the position of the charging processing means on the image bearing member surface, and cleans the image bearing member after the transfer process. The cleaning device removes residual adhering toner and other adhering foreign substances from the image carrier surface after transfer, and the cleaned surface of the image carrier moves to the charging processing means position where it is charged. Over the course of 10,000 sheets, a very small amount of foreign matter such as toner leaks from the cleaning device and is carried to the charging device, and when the charging device is a contact charging device, the image carrier of the charging member. The particles adhere to and accumulate on the contact surface, causing dirt and charging failure.

In addition, when the image bearing member is attached/detached or the cleaning device is released during maintenance and inspection of the image forming device, foreign matter such as developer may leak out from the cleaning device and the contact charging device may become dirty during the next machine operation. , there was a risk that charging defects would occur.

The present invention uses a contact charging device as a means for charging the surface of an image carrier in a transfer type image forming apparatus, and in this case, it is devised to effectively eliminate the problem of charging failure caused by foreign matter contamination of the contact charging device as described above. This makes it possible to stably output high-quality images over a long period of time.This makes it possible to make full use of the various advantages of the contact charging device, making it more economical in terms of device configuration than conventional image forming devices using corona dischargers. It is an object of the present invention to realize a highly reliable image forming apparatus that is also advantageous in terms of performance.

(Means for Solving the Problems) The present invention forms and carries a transferable image on the surface of an image carrier driven by surface movement using an image forming process device including means for concurrently processing the surface of the image carrier. The formed image is transferred onto the surface of a recording material, and the surface of the image carrier after the transfer is cleaned by cleaning means to remove residue, and is repeatedly used for image formation.The image carrier surface is electrically charged. The charging device to be processed is a contact charging device, and among the image forming process devices, at least the image carrier and the cleaning device are collectively configured as a process cartridge that is detachable from the main body of the image forming apparatus. In the process cartridge, the image carrier is supported by a holding portion integrally provided on the side of the cleaning means while maintaining a predetermined mutual arrangement relationship with the cleaning means.

The image forming apparatus is characterized in that the contact charging device is disposed downstream in the moving direction of the image carrier surface from the position of the cleaning member that acts on the image carrier surface of the cleaning device.

(Function) (1) As described above, a process cartridge configured to include at least an image bearing member and a cleaning device (hereinafter referred to as a cleaning device) is used when the image bearing member reaches its end of repeated use or after cleaning. When waste toner accumulates in the device to a predetermined upper limit, it is assumed that the process cartridge has reached its lifespan and is replaced with a new process cartridge in the image forming device. It is a maintenance-free device that does not require maintenance or inspection such as replacing the image carrier or disposing of waste toner accumulated in the cleaning device.

Therefore, in terms of the lifespan of the image carrier and the storage capacity of waste toner in the cleaning device, it is difficult to print tens of thousands of sheets or 600 sheets as compared to conventional devices.
It is not necessary to have a service life of 100,000 sheets, and as a process cartridge that is used disposable by replacing the new one with the old one in the main body of the image forming apparatus, it is designed to have a relatively short service life of, for example, only a few dozen sheets. It is possible to do so.

However, during the usage life of the process cartridge, even if a very small amount of foreign matter such as toner leaks from the cleaning device and is carried to the contact charging device and stains the contact charging member, The degree of contamination of the area of the charging member in contact with the image carrier does not reach such a level as to cause a charging failure until the end of the service life of the process cartridge and the process cartridge must be replaced with a new one.

(2) Since the process cartridge is maintenance-free, it does not require maintenance or inspection such as replacing the image carrier or disposing of waste toner in the cleaning device during its lifespan, so it is possible to remove the image carrier or cleaning device and reinstall it. When the image carrier surface and the cleaning member of the cleaning device are separated from each other during assembly, etc., foreign matter such as developer may leak out of the cleaning device due to scattering, and the contact charging member may be contaminated during the next machine operation. A situation that would cause charging failure is also avoided.

(3) The image carrier is supported by a holding part integrally provided on the cleaning device side while maintaining a predetermined mutual arrangement relationship with the cleaning device, so that the cleaning member on the cleaning device side is always kept in contact with the surface of the image carrier. The charging member of the contact charging device, which is located downstream of the cleaning member in the direction of movement of the image carrier surface, is maintained in a stable operating state in which an effective leaning action is maintained to prevent contamination due to insufficient cleaning of the image carrier surface. Uniformity of charging treatment can be maintained.

(4) The process cartridge may include other desired process means such as a contact charging device and a developing device. In the case where the contact charging device is also included and the device is also supported by the holding section on the cleaning device side. When the waste toner container and holding part of the cleaning device are integrally molded, the contact charging device and the image carrier can be positioned with high precision, so that the contact charging device can reliably contact the image carrier in the longitudinal direction. can be guaranteed, and the uniformity of charging can be significantly improved.

(Embodiment) FIG. 1 is a schematic diagram of an image forming apparatus according to an embodiment of the present invention, and FIG. 2 is a plan view of a process cartridge. This example is a drum-type electrophotographic device using the Carlson process.

1 is a rotating drum type electrophotographic photoreceptor (
The photosensitive drum (hereinafter referred to as a photosensitive drum) is rotated around a support shaft 1a in a clockwise direction as indicated by an arrow at a predetermined circumferential speed (process speed).

2 is a charging member of a contact charging device, and the one in this example uses a roller-shaped member (hereinafter referred to as charging roller).
Brush-shaped, blade-shaped, etc. can also be used. The charging roller 2 was formed by covering the outer periphery of a metal core 2a with a conductive elastic layer 2b made of EPDM/urethane rubber or the like in which conductive particles such as carbon were dispersed. The charging roller 2 is freely rotatable around a metal core 2a, and is kept in pressure contact with the surface of the photosensitive drum 1 with a predetermined pressing force. For example, the circumferential surface of the rotating photosensitive drum l is uniformly charged to a predetermined surface potential by applying a DC voltage or a combination of DC and AC voltage to the metal core 2a by an external power source 20. When a DC voltage of -1.3 KV was applied, the circumferential surface of the photosensitive drum 1 was charged to -700 V.

The surface of the photosensitive drum that has been subjected to the charging process is subjected to exposure L (analog exposure processing such as imaging exposure of the original image, laser scanning exposure, LED array, liquid crystal shutter array, etc.) of the target image information by an exposure means (not shown) at the exposure position 3. digital exposure processing such as scanning exposure). Through this exposure, a static i! pattern corresponding to the exposure pattern is printed on one surface of the photosensitive drum. A latent image is formed. The latent image is developed as a toner image by the developing device 4 and reaches the position of a transfer charger 6 as a transfer means.

On the other hand, a transfer material P passes through a guide 5 from a paper feed section (not shown) to a transfer site between the photosensitive drum l and the transfer charger 6, and is synchronized with the rotation of the photosensitive drum l (image registration).
The toner image on the first side of the photosensitive drum is sequentially transferred to the surface of the fed transfer material at a transfer site.

The transfer material on which the image has been transferred is separated from the first surface of the photosensitive drum and introduced into a fixing means (not shown) to undergo image fixing and processing.The first surface of the photosensitive drum after the image transfer is transferred to a cleaning device 7
At this step, residual adhesion contaminants such as residual toner and transfer material paper dust are removed and the surface is cleaned, which is repeatedly used for image formation.

The cleaning device 7 of this example is of a blade type, and a cleaning blade 7a made of rubber or the like is kept in constant contact with the surface of the photosensitive drum at a predetermined pressure angle, thereby removing the residue on the surface of the photosensitive drum. Adhering foreign matter such as toner is scraped off and wiped away by this abutting blade, resulting in a clean surface. Foreign matter such as residual toner scraped off from the surface of the photosensitive drum 1 is stored and accumulated in the cleaning container 7b. 7c is a flexible and elastic pick sheet.

In the image forming apparatus of this example, a photosensitive drum l is used as an image carrier.
The three process devices 2117, ie, the contact charging device 2 and the cleaning device 17 are collectively configured as a process cartridge 10 that can be attached to and detached from the main body of the image forming apparatus.

In this process cartridge 10, a pair of bearing plates 7d-7d are provided on both left and right end sides of the cleaning device 7, projecting forward together with the cleaning container 7b, and holding the pair of left and right bearing plates 7d-7d. The photosensitive drum 1 and charging roller 2 are mounted on left and right bearing plates 7, respectively.
It is supported by assembling a bearing between d and 7d so that it can rotate freely.

In the assembled state, the photosensitive drum, the charging roller 2, and the cleaning device 7 are held in a state where they are positioned with high precision in a predetermined relationship with each other, and the cleaning blade 7a of the cleaning device 7 is held in a predetermined position on the surface of the photosensitive drum. The state of contact is maintained at a pressure and angle of , and the charging roller 2
is maintained in a securely pressed state with a predetermined pressing force over the entire longitudinal length of the photosensitive drum.

The process cartridge 1G is removable from a predetermined position in the main body of the image forming apparatus in a predetermined manner (such as by opening and closing the front door of the apparatus or by opening and closing the upper half of the apparatus). 10 is mechanically and electrically coupled to the main body of the image forming apparatus to drive the rotation of the photosensitive drum 1, apply voltage to the charging roller 2, and drive the waste toner gathering member if there is one in the cleaning container 7b. etc. becomes possible.

When the usage life of the photosensitive drum 1 is exhausted or a predetermined upper limit amount of waste toner has accumulated in the cleaning container 7b, the process cartridge 10 is removed.
Assuming that the life of the process cartridge 0 has expired, a new process cartridge is replaced and used in the image forming apparatus main body.

During the use of the process cartridge 10, the photosensitive drum 1 in the cartridge is not removed or replaced, the cleaning device 7 is not released, and the waste toner is not disposed of.

Therefore, it has the effects (1) to (3) described in the (effect) section above.

The photosensitive drum 1 as an image carrier is a cleaning container 7b.
In the case where the contact charging device 2 is rotatably attached to the holding parts 7d, which are integral with the cleaning container 7b, and the contact charging device 2 is also fixed to the holding parts 7d, which are integral with the cleaning container 7b, the container 7b and the holding parts 7d-7d are molded. When the contact charging device 2 and the image carrier 1 are integrally molded with a mold, the positions of the contact charging device 2 and the image carrier 1 are determined with high precision, so that reliable contact of the contact charging device M2 with the image carrier 1 in the longitudinal direction can be guaranteed, and the charging It is possible to significantly improve the uniformity of

(Effects of the Invention) As described above, according to the present invention, a contact charging device is used as a means for charging the surface of an image carrier in a transfer type image forming apparatus, and in this case, charging failure due to foreign matter contamination of the contact charging member occurs. By effectively solving the problem, we have made it possible to stably output high-quality images over a long period of time.This makes it possible to take full advantage of the various advantages of contact charging devices and replace conventional image formation using a corona discharger. It is possible to realize a highly reliable image forming apparatus that is more advantageous in terms of structure and economy than the conventional image forming apparatus, and the intended purpose is well achieved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an image forming apparatus according to an embodiment of the present invention, and FIG. 2 is a plan view of a process cartridge. 1 is a rotating drum-type electrophotographic photoreceptor as an image carrier;
2 is a contact charging roller, 20 is a voltage application source, 4 is a developing device, 6 is a transfer charger, 7 is a cleaning device, and 7a is a cleaning blade. 7b is a cleaning container, 7d-7d is a barrier part (bearing plate) integral with the cleaning container, which holds a photosensitive drum and a charging roller by bearings, and 1O is a process cartridge.

Claims (1)

[Claims] (1) A transferable image is formed and carried on the surface of the image carrier driven by surface movement using an image forming process device including means for charging the surface of the image carrier, and the formed and carried image is transferred to the surface of the recording material, and the image is transferred. The image forming apparatus uses a cleaning device to remove residue from the subsequent image carrier surface to make it a clean surface and repeatedly uses it for image formation, and the charging device for charging the image carrier surface is a contact charging device. Among the image forming process means, at least the image carrier and the cleaning means are collectively configured as a process cartridge that can be attached to and detached from the main body of the image forming apparatus, and in the process cartridge, the image carrier is The contact charging device is supported in a predetermined mutual arrangement relationship with the cleaning means by a holding part integrally provided on the cleaning means, and the contact charging device is located at a position lower than the position of the cleaning member that acts on the image carrier surface of the cleaning means. An image forming apparatus characterized in that the image forming apparatus is disposed on a downstream side in a direction of movement of an image carrier surface.