JPH09212046A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce toner scattering in an image forming device and to restrain the deterioration of a photoreceptor caused by ozone and the unevenness of image density by providing a shutoff means shutting off an air current at a specified distance from the periphery of the photoreceptor. SOLUTION: The shutoff means 12 shutting off the air current is provided nearly in parallel with the surface of the photoreceptor at the specified distance from the periphery of the photoreceptor. Therefore, ozone is enclosed between the photoreceptor 1 and the shutoff plate 12. Ozone enclosed in such a way flows in a turning direction as the photoreceptor is turned, and is prevented from retaining. In such a case, when the photoreceptor 1 is turned counterclockwise, ozone is produced from a charger 2 on a lower side and flows counterclockwise along the photoreceptor 1 to an exposure window, a developing device and a transfer device. By providing an exhauster 15 between them, air is efficiently exhausted. It is good to provide the exhauster 15 between the charger 2 and the developing device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoconductor unit and an exhaust device for an electrophotographic image forming apparatus.

[0002]

2. Description of the Related Art An electrophotographic image forming apparatus exposes the surface of a photoconductor charged by a charger with an exposure device to form an electric latent image on the surface of the photoconductor, and then attaches a charged developer thereto. To form a toner image and transfer it to paper,
It is fixing.

Nowadays, a corona discharge is generally used as a charger for charging the photoreceptor. Ozone is generated in a charger using corona discharge. High concentration of ozone is not only toxic to the human body, but also causes deterioration of the photoconductor. Deterioration of the photoconductor causes unevenness in image density of the printed image and partial fog (background stain).

As a conventional example of ozone exhaust
Japanese Patent Laid-Open No. 3-245163 describes that a fan, which is an exhaust means, is rotated for a certain period of time after completion of transfer.

[0005]

In the exhaust means for removing ozone, if the output is increased and a large amount is exhausted, the developer, especially toner is scattered into the image forming apparatus and each functional component is contaminated. Defects were likely to occur. Further, when the output of the exhaust means is reduced, ozone is likely to remain in the image forming apparatus, so that partial photoconductor deterioration is likely to occur when the photoconductor drum or belt is stopped, causing partial image density unevenness. Was there.

An object of the present invention is to provide an image forming apparatus which reduces toner scattering in the image forming apparatus and reduces deterioration of a photoreceptor due to ozone and uneven image density caused by the deterioration.

[0007]

An electrophotographic image forming apparatus having a charging device, a developing device, and a transfer device has a blocking means for blocking an air flow at a predetermined distance around a photoconductor.

Exhaust means for exhausting ozone is provided at a position in the rotational direction of the photosensitive member from the charger.

A charger arranged on the surface of the photoconductor generates ozone. The generated ozone diffuses around it and moves on the surface of the photoconductor as the photoconductor moves.

By disposing a shut-off means for shutting off the flow of ozone at a predetermined distance outside the photoconductor, the range in which ozone diffuses can be narrowed. Further, by providing the exhaust device and the exhaust member in the rotation direction of the photoconductor, unnecessary substances such as ozone accumulated between the photoconductor and the blocking means can be efficiently removed.

As described above, it is possible to reduce the deterioration of the photoreceptor and obtain a good image without image unevenness.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An electrophotographic image forming apparatus will be described with reference to FIG. The photoconductor 1, which is an image bearing member, is arranged substantially at the center of the image forming apparatus, and a toner image is obtained by arranging a means for performing each process around it. First, the surface of the photoconductor 1 is charged by the charger 2, and the exposure device 3 selectively irradiates the photoconductor with light to erase the charge, thereby obtaining an electric latent image on the photoconductor according to an image signal. Further, a toner image can be formed (development) on the photoconductor by bringing the charged developer in the developing devices 7y, 7m, 7c, and 7k into contact with the photoconductor. The toner image on the photoconductor is electrically moved (transferred) to the intermediate transfer drum 9,
Further, the drum charger 8 makes the charging polarity of the toner uniform, and the toner is transferred onto a printing medium such as paper between the transfer roller 4 which is a transfer device and the intermediate transfer drum 9. The paper on which the toner image is transferred is peeled off from the drum by the static eliminator and fixed by the fixing device 5.

The photosensitive member is charged by a charging device, discharged by an exposure device, charged by a transfer device, electrically charged by an AC charging device and erased by an erase lamp. It is a component that is mechanically loaded by rubbing by the developing device and cleaning means.

While a device using corona discharge, such as a charger, a transfer device, and a static eliminator, is driven, ozone is generated, which deteriorates the photoconductor, so that the photoconductor later obtains a predetermined charging potential. It is known that you cannot do it.

As described above, a charger, a developing device, an exposure device, a transfer device and the like are arranged around the photosensitive belt which is an image carrier, and ozone is generated by the charger, the transfer device and the static eliminator. To do. The amount rises rapidly as shown in FIG. 3, but is saturated later. This is because oxygen existing in the machine becomes ozone, and ozone cannot be generated any more. Therefore, the total amount of ozone generated during printing can be reduced by sealing the inside of the machine and preventing the inflow of air, particularly oxygen. However, if it is left as it is, the entire photoreceptor is deteriorated. Therefore, in order to reduce the ozone deterioration of the photoconductor, it is necessary to remove ozone as soon as possible.

In the structure of the conventional photoconductor unit, ozone is likely to stay at the front and rear of the charger and at the position where there is a step in the bent portion of the photoconductor. As shown in FIG. 4, when there is the toner drop prevention member 11 for preventing toner drop, the air flow in the A section is small,
The toner can be stored, but at the same time, ozone also stays. Even if the conventional exhaust system is powerful, it is difficult to remove ozone.

An embodiment of the present invention will be described below with reference to FIG.

Deterioration of the photosensitive member due to ozone generated by a charger or the like is extremely rapid, especially when high-concentration ozone is kept in a constant range for a long time. Further, if the total amount of ozone is large, not only the entire photoconductor is deteriorated, but also exhausting takes time.

First, as a method for reducing the total amount of ozone generated, blocking means 12 and 13 for blocking the air flow are provided at a predetermined distance around the photoconductor substantially parallel to the photoconductor surface. Thereby, ozone can be trapped between the photoconductor 1 and the blocking plates 12 and 13. The ozone that has been trapped flows in the rotation direction (the direction of the arrow) with the rotation of the photoconductor, and the ozone does not stay.

The blocking means is preferably provided in the photoconductor unit that supports the photoconductor. When the unit is not provided, the housing may be provided with a blocking means.

The blocking means is as follows. The shape is preferably a plate shape (hereinafter referred to as a blocking plate), and is installed along the flat surface and the curved surface of the photoreceptor. Desirably, it is arranged parallel to the surface of the photoconductor.

The distance between the photosensitive member and the blocking means is 2 mm to 20
mm is good. 2-5 mm is preferable. The distance is not limited depending on the moving speed of the photoconductor. Since the toner scattering is small when the moving speed is slow, the distance may be set to 2 mm or less. On the contrary, when the moving speed is fast, the toner is scattered when the distance is narrow, so the distance is increased.

The blocking means is not provided on the entire surface around the photoconductor. This is because it is necessary to prepare a window for each of the charger, the exposure device, the developing device, the transfer device, and the cleaning device. As shown in FIG. 5, the upper side must be opened wide for the developing device and the left side for the transfer device. The lower side must be partially open for cleaning devices, chargers and exposure devices.

Further, as shown in FIG. 5, it is preferable to install the charger at a position protruding outward so that the blocking plate 13 facing the photoconductor is not uneven. This is because ozone and the like can be prevented from staying by making the flow path resistances on the surface of the photoconductor equal. As you can see in the figure, the charger is protruding outward, so it is easy to create a wasted space by attaching the charger to the cartridge. Therefore, it is better to provide a charger separately from the photoconductor cartridge, provide a mechanism such that when the photoconductor cartridge is mounted, the charger approaches and comes into contact with the photoconductor at a certain distance, and a drive device such as a spring is provided. .

As another embodiment, there is a method in which a blocking means is also provided inside the photoreceptor as shown in FIG. As a result, the total amount of ozone inside and outside the photoconductor unit can be reduced, and the exhaust effect can be enhanced. The blocking means preferably has a box shape without a mouth, but may have a box shape with an opening on the top. This is because ozone is heavier than air and sinks downward.

The above embodiment is an embodiment using a conventional exhaust device. As it is, it takes a very long time from the generation of ozone to the exhaust and disappearance. Therefore, by attaching an exhaust device to the photoconductor cartridge,
The time until exhaustion and extinction can be shortened. As shown in FIG. 7, when the photoconductor 1 is rotated counterclockwise, ozone is generated from the lower charger 2 and rotates counterclockwise along the photoconductor.
It flows toward the exposure window, developing device, and transfer device. Therefore, by providing the exhaust device 15 in the middle of them, efficient exhaust can be performed. The position of the exhaust device is preferably provided in the section from the charger to the developing device. This is because when developing is performed between the developing device and the photoconductor, ozone is diffused at that portion. It is desirable to exhaust and extinguish ozone before the developing device.

At the position of the exhaust device as shown in FIG. 7, the air flow from the exposure window is large and the air from the charger may not be sufficiently discarded. Therefore, it is necessary to make the exposure window as narrow as possible. The width is preferably about 2-4 mm. When the width of the exposure window cannot be narrowed, there is a method of stopping the air flow by placing a film or plate made of transparent plastic or glass on the exposure window. By exhausting the air around the charger using these methods, deterioration due to ozone can be prevented.

The exhaust device is preferably used not only for exhausting ozone but also for collecting scattered toner generated around the developing device. By disposing the toner near the developing device as shown in FIG. 7, the scattered and floating toner can be collected inside the exhaust device. In addition, it is preferable to make a space for the toner reservoir 16 inside the apparatus.

The fan of the exhaust device may be of various shapes other than a fan-shaped fan. In particular, linear exhaust such as a sirocco fan is more preferable because it can be exhausted without being biased left and right.

The drive source of the fan may be placed outside the photoconductor cartridge. If you put the fan blades and motor in the photoconductor cartridge, it will become heavy and require power supply wiring, which increases the unit price of the cartridge. The fan blades may be placed in the cartridge, and the drive source such as the fan motor may be placed outside the cartridge, and the fan blades may be rotated by transmission by a gear or a belt.

There is also a method in which the drive source is connected to a gear that rotates the photoconductor, the developing device, and the like. This can reduce the number of drive sources such as motors.

The exhaust port 17 may be slit-like or mesh-like, and may be provided with a filter such as an activated carbon filter using a substance that extinguishes ozone. As a result, ozone can be exhausted after being extinguished by the filter, and the toner becomes difficult to be ejected because it is caught in the mesh of the filter.

The embodiment shown in FIG. 8 is an example using the exhaust guide 18. The exhaust guide is generally in the shape of a triangular prism, and the following is recommended.

The surface on the side of the photoconductor is preferably parallel so as not to contact the photoconductor.

The surface on the exhaust means side has a wedge shape with the surface on the side of the photoconductor in order to collect ozone that has moved along the photoconductor.

The surface on the developing device side is made substantially parallel to the plane of the photoconductor so that the toner does not fall on the curved surface of the photoconductor.

The fan of the exhaust device must be driven for a few minutes after the charger is stopped from when the charger is being driven. The standard of the stopping time is when the ozone concentration is 1/20 or less of the saturated ozone concentration, but there is no problem in order to change the ozone concentration after seeing the image defect. Further, the fan may be driven while the developing device is being driven for the purpose of collecting the floating toner.

As the image forming apparatus, the multicolor image forming apparatus having a plurality of developing devices has been described as an example, but the invention can be applied to the case where there is only one developing device.

Further, in the embodiment, the image forming apparatus of the intermediate transfer system using the intermediate transfer drum is used, but the present invention can be applied to other intermediate transfer systems and those other than the intermediate transfer system.

The developing device has been described as a developing device of the type which develops downward using a two-component type developer, but the developing direction may be either upward or sideward, regardless of the developing system such as the one-component developing system. It can be applied without.

[0041]

According to the present invention, since the charging device and the developing device evacuate while driving, partial deterioration of the photosensitive member is small and scattered toner can be collected, so that good printing with less uneven image density can be obtained. Images can be obtained.

[Brief description of drawings]

FIG. 1 is a side view of an embodiment of the present invention.

FIG. 2 is a side view of a conventional image forming apparatus.

FIG. 3 is an ozone concentration-time characteristic diagram when ozone is generated.

FIG. 4 is an explanatory view of a conventional photoconductor cartridge.

FIG. 5 is an explanatory diagram of a photoconductor cartridge in which a blocking unit is provided outside the cartridge.

FIG. 6 is an explanatory view of a photoconductor cartridge in which a blocking unit is provided inside the cartridge.

FIG. 7 is an explanatory diagram of a photoconductor cartridge provided with an evacuation unit together with a blocking unit.

FIG. 8 is an explanatory view of a photoconductor cartridge provided with an exhaust guide.

[Explanation of symbols]

1 ... Photosensitive member (belt), 2 ... Charging device, 3 ... Exposure device, 4
... transfer device, 5 ... fixing device, 6u, 6l, 15 ... exhaust means, 7y, 7m, 7c, 7k ... developing device, 8 ... drum charger, 9 ... intermediate transfer drum, 10 ... cleaning device,
12 ... Blocking plate.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuaki Fukasawa 1-1-1, Higashitaga-cho, Hitachi-shi, Ibaraki Prefectural Electric Appliances Division, Hitachi, Ltd. 1-1-1 Machi Incorporated company Hitachi Ltd. Electric Appliances Division Taga Headquarters

Claims (4)

[Claims] 1. An electrophotographic system comprising a charging device, an image carrier for forming an electric latent image by exposing a surface charged by the charging device, and a developing device for adhering the charged developer to the image carrier. An image forming apparatus, comprising: a blocking unit that blocks an air flow at a predetermined distance around a photoconductor. 2. The image according to claim 1, wherein the exposure slit for passing the light from the exposure device is provided with a light transmitting means for transmitting the light and insulating the flow of air, and is arranged at a predetermined distance outside the photoconductor. Forming equipment. 3. A charging device, an image carrier for forming an electric latent image by exposing a surface charged by the charging device, a developing device for adhering the charged developer to the image carrier, and the image carrier. An image forming apparatus of an electrophotographic system having a transfer device for transferring the developer to a transfer target such as paper, characterized in that an exhaust means is provided downstream from the charger in the rotation direction of the photosensitive member. Image forming apparatus. 4. The image forming apparatus according to claim 3, further comprising a guide member for exhausting air on the surface of the photosensitive member, which is provided at a front portion of the developing device.