JP5137689B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus using an electrophotographic method, such as a copying machine, a printer, a facsimile.

  Conventionally, in an electrophotographic image forming apparatus, when a photosensitive drum is charged by a charging unit, the occurrence of image defects may become a problem. This is mainly an image detrimental effect called “horizontal streaks generated in a halftone image or the like” caused by disturbance of the potential on the photosensitive drum before the charging step or “drum positive ghost” caused by a charged potential difference on the photosensitive drum.

  In order to suppress such image damage, it is generally known that a static elimination exposure means that neutralizes the residual potential by irradiating the photosensitive drum with light before the charging step is effective.

As the static elimination exposure means, as disclosed in Patent Document 1, an LED as a light source is arranged on one end side in the rotation axis direction of the photosensitive drum to irradiate the photosensitive drum. In addition, as disclosed in Patent Document 2, the amount of light on the surface of the photosensitive drum is increased and controlled by disposing a reflective member on the other end side opposite to the one end side where the light source is disposed in the rotation axis direction of the photosensitive drum. Means to do this have been proposed. Further, in Patent Document 1 and Patent Document 2, space saving and cost reduction are realized by adopting a configuration in which light from an LED is irradiated to a photoconductor without using a light guide.
JP 2006-030856 A JP2007-094203

  However, the image forming apparatus according to the conventional example has the following unsolved problems.

  In recent years, with the demand for higher speed image forming apparatuses, the rotational speed of the photosensitive drum has increased, and in order to perform stable static elimination exposure by irradiating a sufficient amount of light on the image forming area of the photosensitive drum, static elimination exposure is required. It is desirable to increase the light intensity of the light source of the means. In order to prevent the light from losing its light intensity in the process until it enters the photosensitive drum, it is desirable to irradiate the photosensitive member with direct light or primary reflected light as much as possible without passing through the reflecting means. Therefore, it is conceivable to increase the light intensity of the light source of the static elimination exposure means by narrowing the directivity angle of the light source.

  However, in a configuration in which an LED having a narrow directivity angle is arranged on one end side in the rotation axis direction of the photosensitive drum without using a light guide, if an attempt is made to irradiate the entire image forming area of the photosensitive drum, the distance between the photosensitive drum and the LED is reduced. It is necessary to take enough. As a result, the device becomes large. Therefore, Patent Document 1 proposes a method of using two LEDs in order to reduce the size of the apparatus by bringing the LEDs closer to the photosensitive drum. Patent Document 2 proposes a method in which a reflecting member is disposed on the opposite side of the photosensitive drum that faces the LED outside the image forming area.

  Here, in order to further reduce the size of the apparatus, the LED must be disposed closer to the image forming area of the photosensitive drum. However, if the LED is arranged closer to the image forming area, the exposure area of the LED with respect to the photosensitive drum becomes narrower. As a result, we have found that there may be a region where a sufficient amount of light cannot be irradiated to the image forming region near the LED light emission position of the photosensitive drum. On the other hand, as shown in Patent Document 1, if two LEDs are used, an exposure region with a sufficient amount of light can be obtained, but the cost increases. Also, as shown in Patent Document 2, in the method of disposing the reflecting member on the opposite side opposite to the LED, if the reflected light from the reflecting member disposed on the opposite side is radiated more on the photosensitive drum, the LED Must be directed to the reflecting member side (side approaching parallel to the axis of the photosensitive drum). For this reason, the amount of direct light irradiated in the direction of the photosensitive drum is reduced. Accordingly, there is a possibility that an area where light cannot be sufficiently irradiated to the image forming area near the LED light emission position of the photosensitive drum may be formed.

  Further, even if the photosensitive drum cannot be irradiated with a sufficient amount of light by direct light from the LED, there is a possibility that the static elimination exposure amount may be compensated by irradiating diffusely reflected light from peripheral components. However, since irregularly reflected light largely depends on the shape, arrangement, reflectance, and the like of peripheral components, it is difficult to positively control the direction and amount of light by the irregularly reflected light.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus having a discharge exposure unit that can perform a stable discharge exposure with a compact and low-cost configuration.

Typical configuration of an image forming apparatus according to the present invention in order to solve the aforementioned problem, a rotatable photosensitive member, the charging means for the photosensitive member to a static-, by exposing the charged the photosensitive member an exposure means for forming a latent image, a developing means for visualizing the latent image on the photosensitive member as a toner image, a transfer unit that transfers the toner image on the photosensitive member, related to the rotational direction of the photosensitive member a downstream side of the transfer unit Te, and is disposed upstream of said charging means, an image forming apparatus and a discharging exposure means for exposing to neutralizing the photoconductor,
The static elimination exposure means is disposed on one end side in the rotation axis direction of the photoconductor, and irradiates light toward an image forming area of the photoconductor, and light emitted from the light source provided in the vicinity of the light source anda reflection means for reflecting the image formation region of the photosensitive member includes a first region in which the direct light primary light reflected is emitted from the light source without irradiating the reflecting means is irradiated , and having a, a second region to be irradiated primary light reflected by the closer to the light source than the first region in the rotation axis direction of the photosensitive member, the reflecting means.

  According to the present invention, it is possible to provide an image forming apparatus having a static elimination exposure unit capable of performing stable static elimination exposure with a compact and low-cost configuration.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. .

(First embodiment)
[Entire configuration of image forming apparatus]
An image forming apparatus according to a first embodiment to which the present invention is applicable will be described with reference to FIGS.

  An image forming apparatus 101 shown in FIG. 1 is an electrophotographic color laser printer. Reference numeral 102 denotes a process cartridge. The process cartridge 102 includes a photosensitive drum 1021 as a rotatable photosensitive member, a charging unit, a developing device, and the like. The latent image formed on the photosensitive member by the laser beam emitted from the exposure device 103 based on the image information is developed on the photosensitive drum 1021 by a known process. In a color laser printer, process cartridges of a total of four colors of black, yellow, magenta, and cyan are generally arranged. Further, the developed toner image is transferred to the intermediate transfer member 104 by the primary transfer unit 105, and the toner image is formed on the surface of the intermediate transfer member 104 by continuously transferring each color.

  On the other hand, a paper feed cassette 107 that can store the recording material 106 is disposed below the image forming apparatus 101. The recording material 106 is separated and fed one by one by the rotation of the paper feed roller 108 disposed in the vicinity of the leading end of the recording material 106. Thereafter, the sheet is conveyed downstream by the conveying roller pair 109. Subsequently, in the secondary transfer unit 110, the toner image on the surface of the intermediate transfer member 104 is transferred onto the recording material 106. The recording material 106 onto which the unfixed toner image has been transferred is further conveyed downstream, is pressurized and heated by the fixing device 111, and the toner is melted to fix the toner image on the recording material 106. Thereafter, the recording material 106 is discharged to the paper discharge tray 112. Through the series of operations described above, image formation on the surface of the recording material 106 is performed.

[Configuration of image forming unit]
Next, FIG. 2 is a schematic view of the vicinity of the image forming unit. In the process cartridge 102, a photosensitive drum 1021, a cleaning blade 201, a charging roller 202, and a developing roller 203 are arranged and held by a frame body 204. The photosensitive drum 1021 is in contact with a transfer belt 205 which is an image conveying unit of the intermediate transfer member 104 and is pressed by a primary transfer roller 206.

  Here, a general image forming process in the image forming unit will be described. First, the photosensitive drum 1021 is uniformly charged to a predetermined polarity by a charging roller 202 as a charging unit. Next, the charged photosensitive drum 1021 is exposed by an exposure device 103 as an exposure unit to form an electrostatic latent image. Next, when toner is attached to the electrostatic latent image on the photosensitive drum 1021 by the developing roller 203 as a developing unit, the toner image is visualized. Next, the toner image on the photosensitive drum 1021 is transferred to the transfer belt 205 by the primary transfer roller 206 as transfer means. Next, the residual potential is discharged by irradiating the transferred photosensitive drum 1021 with light from the LED 207 serving as a light source of the discharging exposure means. Finally, the transfer residual toner on the photosensitive drum 1021 that has not been transferred is scraped off by the cleaning blade 201 and stored in a waste toner container (not shown). The image forming process from charging to cleaning described above is repeated.

[Configurations of static elimination exposure means and reflection means]
The LED 207 is disposed downstream of the primary transfer roller 206 and upstream of the charging roller 202 in the rotation direction of the photosensitive drum 1021. The LED 207 is installed at a predetermined angle in the process cartridge 102 so that a portion surrounded by the photosensitive drum 1021, the transfer belt 205, and the frame 204 of the process cartridge 102 can be irradiated from one end side of the photosensitive drum 1021. Yes. Further, in the vicinity of the LED 207, a reflecting surface 208 is disposed as reflecting means for reflecting the light beam emitted from the LED 207 in a predetermined direction.

  FIG. 3 is a diagram of the vicinity of the image forming unit in FIG. 2 viewed from the lateral direction. The optical axis of the LED 207 is tilted so as to illuminate the image forming area of the photosensitive drum 1021. The first area α of the image forming area of the photosensitive drum 1021 is irradiated with the direct light emitted from the LED without being irradiated with the primary reflected light reflected by the reflecting surface 208 of a part of the light emitted from the LED 207. doing. On the other hand, the image forming area of the photosensitive drum 1021 includes a second area β closer to the LED 207 than the first area α. The second region β is irradiated with primary reflected light reflected by the reflecting surface 208. In other words, there is a possibility that the image forming area near the LED light emission position of the photosensitive drum may not be sufficiently irradiated with only the direct light from the LED 207, so that the light from the LED is reflected by the reflection surface 208. The primary reflected light is irradiated.

  If the material of the reflective surface 208 is a mirror surface, there will be no restriction | limiting in particular. Since the reflection surface 208 is disposed immediately after the light beam is emitted from the LED 207, the reflection surface 208 can reflect the high-density light before the light beam is reflected by other components. Therefore, even if the reflecting surface 208 is formed on a mold member having a low reflectance, it is possible to obtain a sufficient reflected light amount for static elimination exposure. In addition, since no special processing is required for reflection, the cost is not increased.

  With the above configuration, the following effects can be obtained.

  Of the light beams emitted from the LED 207, the center of the optical axis of the light beam directly irradiated on the photosensitive drum 1021 can be shifted to the image forming region farther from the LED 207 in the rotation axis direction of the photosensitive drum 1021. Thereby, the attachment position of the LED 207 can be brought close to the photosensitive drum 1021. Therefore, it is possible to reduce the size of the image forming apparatus.

  Further, by irradiating the photosensitive drum 1021 with the direct light from the LED and the primary reflected light from the reflecting surface 208 without depending on the irregular reflection by the LED 207 and the peripheral parts of the photosensitive drum 1021, a stable static elimination effect without reducing the light intensity. Is obtained. Further, when the light intensity of the LED is controlled by changing the voltage, the relationship between the light intensity and the change in the charge removal effect does not become complicated, so that the light intensity can be easily controlled.

  Therefore, by adopting the configuration of this embodiment, an inexpensive and space-saving image forming apparatus having good image performance can be provided.

(Second embodiment)
An image forming apparatus according to a second embodiment to which the present invention is applicable will be described with reference to FIG.

  Reference numeral 401 denotes a holding member that holds the LED 207. A part of the holding member 401 is extended, and a part of the light beam emitted from the LED 207 is reflected by the reflection surface 4011.

  With the above configuration, the following effects can be obtained in addition to the effects of the first embodiment.

  By integrating the holding member 401 and the reflecting surface 4011, the accuracy of the relative position between the LED 207 and the reflecting surface 4011 can be easily ensured. Therefore, the accuracy of the path of the light beam emitted from the LED 207 can be improved. Further, by integrating the members, the configuration of the first embodiment can be realized without increasing the cost.

  As mentioned above, although typical embodiment which can apply this invention was described, this invention is not limited to the structure of the said embodiment at all, and various deformation | transformation are possible within the technical thought of this invention. Any configuration may be used as long as the photosensitive member is subjected to the static elimination exposure by the static elimination exposure means. For example, in the above embodiment, the apparatus using the photosensitive drum has been described. However, the present invention can also be applied to an apparatus using the photosensitive belt. Further, the apparatus for transferring to the intermediate transfer belt has been described, but the present invention can also be applied to an apparatus for transferring to the recording material.

1 is a schematic diagram of an image forming apparatus according to a first embodiment. FIG. 2 is a schematic view of the vicinity of an image forming unit according to the first embodiment. FIG. 2 is a schematic view of the vicinity of an image forming unit according to the first embodiment. FIG. 10 is a schematic view of the vicinity of an image forming unit according to a second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Image forming apparatus 1021 Photosensitive drum 103 Exposure apparatus (exposure means)
202 Charging roller (charging means)
203 Developing roller (developing means)
206 Primary transfer roller (transfer means)
207 LED (light source)
208, 4011 Reflection surface (reflection means)
401 Holding member

Claims (2)

A rotatable photoreceptor,
A charging unit that a static-the photoreceptor,
Exposure means for exposing the charged photoreceptor to form a latent image;
Developing means for visualizing the latent image on the photoreceptor as a toner image;
Transfer means for transferring a toner image on the photoreceptor;
Wherein regarding the rotation direction of the photosensitive member to a downstream side of the transfer unit, and is disposed upstream of said charging means, a charge removing exposure means for exposing to neutralizing the photoconductor,
In an image forming apparatus comprising:
The static elimination exposure means is disposed on one end side in the rotation axis direction of the photoconductor, and irradiates light toward an image forming area of the photoconductor, and light emitted from the light source provided in the vicinity of the light source anda reflection means for reflecting,
The image forming area of the photoconductor includes a first area that is irradiated with direct light emitted from the light source without being irradiated with primary reflected light reflected by the reflecting means, and the first area in the rotation axis direction of the photoconductor. an image forming apparatus characterized by having close to the light source than one region, and a second region to be irradiated primary reflected light reflected by said reflecting means. A holding member for holding the light source;
The image forming apparatus according to claim 1, wherein the reflection unit is provided integrally with the holding member.

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