JP3862972B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrophotographic image forming apparatus that performs a photostatic discharge process.
[0002]
[Prior art]
Conventionally, in an electrophotographic image forming apparatus, charging, exposure, development, transfer, and cleaning processes are performed around a photoconductor as an image carrier. Before and after the process, there was a work in which static elimination work was performed on the photosensitive member by a photostatic elimination method. In this light neutralization method, a light emitting diode (LED) is often used, and in particular, an LED array 100 in which a large number of LED chips 102 are arrayed on a substrate 101 as shown in FIG. 1 is often used. In this configuration, as shown in FIG. 1B, the LED chips 102 are densely arranged so that the surface of the photosensitive drum 4 to be illuminated is substantially uniform and high. Illuminance was obtained.
[0003]
However, in the above configuration, since many expensive LED chips 102 are used, it is difficult to produce the LED array 100 at low cost, and it is difficult to reduce the cost of the image forming apparatus. On the other hand, if the number of LED chips 102 used is reduced in order to reduce the cost, the distance between the LED chips 102 increases, and the illuminance distribution of the photosensitive drum 104 becomes uneven, so uniform illumination cannot be achieved.
[0004]
Japanese Utility Model Laid-Open No. 55-35584 discloses a light static elimination device that irradiates light on the surface of a photosensitive drum by combining a light source for illumination and a fluorescent light emitter.
[0005]
Moreover, as what can be applied to such a static eliminator, in JP-A-8-43633, a light source is provided at an end portion and provided on a side surface portion along a longitudinal direction of a columnar light guide made of a translucent material. A technique for an illuminating device including a light guide having a light irradiation surface and a light diffusing portion by cutting or roughening provided on a surface facing the light irradiation surface is disclosed.
[0006]
Further, in Japanese Patent Application Laid-Open No. 10-133026, light from an LED light source is incident from an end of a light guide formed of a rod-shaped transparent material, and a light beam incident on a side surface along the rod-shaped longitudinal direction is emitted. An illuminating device including a light guide having a light emitting surface and a sawtooth region for reflecting, diffusing, or reflecting / diffusing a light beam incident on a surface facing the light emitting surface is disclosed. Yes.
[0007]
And according to these structures, it is said that it is effective with respect to size reduction and cost reduction.
[0008]
[Problems to be solved by the invention]
However, in the above-described configuration, it is difficult to solve the problem in actual use that the light amount deviation depending on the distance from the light source portion is generated by the light irradiation from the light guide in the photoconductor. In other words, in the axial direction of the photosensitive member, there are areas that are close to the light source and receive a large amount of static elimination irradiation light, and areas that are far from the light source and relatively not receive the static elimination irradiation light. There is still a light intensity deviation that cannot be obtained. This light amount deviation significantly affects the sensitivity deterioration due to light irradiation among the life characteristics of the photoconductor mounted on the image processing apparatus, and causes the sensitivity deviation in the longitudinal direction of the photoconductor. For example, the density difference of the solid image portion, the halftone It affects the image quality, such as degradation of image uniformity.
[0009]
An object of the present invention is to provide an image forming apparatus capable of forming a highly reproducible image without being affected by a deviation in sensitivity deterioration of the photosensitive member due to light fatigue, and realizing a reduction in size and cost. It is.
[0010]
[Means for Solving the Problems]
The present invention has the following configuration.
[0011]
(1) An image forming apparatus that performs an image forming process of an electrophotographic method including a static eliminating process of a light static eliminating process, and that performs the static eliminating process by a static eliminating apparatus having a point light source and a light guide.
For each position in the axial direction of the photoconductor, the longer the distance from the point light source, the smaller the rate of increase in exposure amount due to sensitivity deterioration due to light fatigue of the photoconductor in the image forming step. A light amount adjusting means for correcting the exposure amount is provided.
[0012]
In this configuration, the exposure amount on the photoconductor in the image forming process is adjusted according to the deviation of the sensitivity deterioration in the axial direction of the photoconductor generated by the static elimination process. Therefore, the exposure process is performed with the adjusted light quantity taking into account the variation in the image density of the electrostatic latent image formed on the photoconductor, which corresponds to the deviation of the sensitivity degradation of the photoconductor. An electrostatic latent image that is not affected by deviations in sensitivity of the body is formed, and highly reproducible image forming processing is performed.
[0013]
(2) The light amount adjusting means adjusts the intensity of light applied to the photosensitive member.
[0014]
In this configuration, the intensity of light applied to the photoconductor during the image forming process is adjusted according to the deviation in sensitivity deterioration in the axial direction of the photoconductor that occurs in the static elimination process. Therefore, since exposure is performed with a light amount corresponding to a deviation in sensitivity deterioration of the photoconductor due to light fatigue, while maintaining a constant exposure time for each pixel in the main scanning direction of the photoconductor during the exposure process, exposure is simple. The amount is adjusted, and the problem in the image forming process caused by the deviation of the sensitivity deterioration of the photoreceptor due to light fatigue is solved.
[0015]
(3) The light amount adjusting means adjusts an exposure time of light applied to the photosensitive member.
[0016]
In this configuration, during the image forming process, the exposure time of the light applied to the photoconductor is adjusted according to the deviation in sensitivity deterioration in the axial direction of the photoconductor caused by the static elimination process. Therefore, by adjusting the exposure time for each pixel in the main scanning direction of the photosensitive member within a range that does not interfere with the exposure process while keeping the light amount of the exposure device such as a laser scanner unit constant, it is caused by light fatigue. Problems in image formation processing resulting from deviations in sensitivity deterioration of the photoreceptor are eliminated.
[0017]
(4) The light amount adjusting means adjusts the intensity of light applied to the photosensitive member and the exposure time.
[0018]
In this configuration, during the image forming process, the intensity of the light applied to the photoconductor and the exposure time are adjusted according to the deviation in sensitivity deterioration in the axial direction of the photoconductor caused by the static elimination process. Therefore, compared with the case where the exposure amount is adjusted only by either one of the light intensity or the exposure time, the adjustment is performed in a wider range and with higher accuracy.
[0019]
Further, since the adjustable range is expanded, the allowable range of sensitivity deterioration due to light fatigue when using the photoconductor is expanded, so that the lifetime of the photoconductor is extended.
[0020]
(5) The light source for exposure is a semiconductor laser or a light emitting diode.
[0021]
In this configuration, the exposure amount from the semiconductor laser or the light emitting diode to the photosensitive member is adjusted during the image forming process. Therefore, it is easy to adjust the light intensity in the light amount adjusting means. In particular, when a light emitting diode is used, the exposure time can be adjusted more easily.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0023]
FIG. 2 is a diagram showing the configuration of the image forming apparatus of the present invention.
[0024]
In the present embodiment, the image forming apparatus 30 includes an image reading unit 31, an image forming unit 47, a paper feeding unit 50, and a post-processing device 34.
[0025]
The image reading unit 31 is provided as an image input device in the image forming apparatus 30 for reading an image of a document or the like. In addition to the document placing table 35 made of transparent glass, the image reading unit 31 is a double-sided automatic document feeder (hereinafter referred to as a document feeder). RADF) 36, and an optical system unit 40. The image reading unit 31 sequentially reads images of the original document one by one from the original document placed on the document placement table 35. The RADF 36 conveys originals set on a predetermined original tray (not shown) one by one to the original placement table 35, and after the image is read by the optical system unit 40, it is carried out to a predetermined removal position.
[0026]
The optical system unit 40 is configured as a document image reading unit that reads an image of a document conveyed to the document placement table 35 for each predetermined unit in the scanning line direction. The optical system unit 40 includes a first mirror base 40a, a second mirror base 40b, an optical lens 43, and a photoelectric conversion element (hereinafter referred to as a CCD) 44.
[0027]
The first mirror base 40a includes a lamp reflector assembly 41 for irradiating light and a first reflection mirror 42a for guiding reflected light from the document to a second mirror base 40b described later, and a document table. The light is irradiated to the document while moving at a constant speed V from left to right in FIG.
[0028]
The second mirror base 40 b includes a second reflection mirror 42 b and a third reflection mirror 42 c that guide light from the first mirror base 40 a in the direction of the optical lens 43 and the CCD 44, and the first mirror Following the operation of the base 40a, it moves at a speed of V / 2.
[0029]
The optical lens 43 forms an image of the reflected light from the second mirror base 42 b on the CCD 44. The CCD 44 converts the light imaged by the optical lens 43 into an electrical signal. The analog electrical signal obtained by the CCD 44 is converted into image data of a digital signal, subjected to various image processing, and then transferred to the image forming unit 47 through a buffer memory or the like as appropriate.
[0030]
The image forming unit 47 includes an image forming unit 32 and an exposure unit 46. The exposure unit 46 exposes the photoconductor in accordance with image data read from the buffer memory or image data transferred from an external device. In this embodiment, the exposure unit 46 is a semiconductor laser light source that emits laser light, a laser. A polygon mirror that polarizes light at a constant angular velocity, and an f-θ lens that further polarizes light from the polygon mirror and moves it at a constant speed on the photosensitive drum 10 are provided.
[0031]
FIG. 3A shows the configuration of the image forming unit 32. As shown in the figure, toner is applied to the electrostatic latent image formed by the exposure unit 46 and the charging device 11 that charges the surface of the photosensitive drum 10 to a predetermined potential around the photosensitive drum 10 that carries the image. A developing device 13 that supplies and visualizes, a transfer device 14 that transfers a toner image formed on the surface of the photosensitive drum 10 to a sheet, a cleaning device 12 that cleans the surface of the photosensitive drum 10, and the photosensitive drum 10. The static eliminator 15 for eliminating the static electricity is disposed respectively.
[0032]
In this configuration, charging, exposure, development, transfer, cleaning, and charge removal processes are performed on the surface of the photosensitive drum 10. The sheet on which a predetermined image forming process has been performed in the image forming unit 32 is heated and fixed by a fixing device 49 provided downstream of the image forming unit 32 and is discharged from a discharge roller 57.
[0033]
On the downstream side of the image forming unit 32 and the fixing device 49, a switchback conveyance path 56 that reverses the sheet to form an image on both sides of the sheet, an elevating tray 60, and stapling processing for the sheet on which the image is fixed A post-processing device 34 for performing the above and the like is arranged.
[0034]
The sheet feeding unit 50 is disposed below the image forming unit 32, and includes a multi-stage sheet feeding unit including a manual feed tray 54, a duplex unit 55, sheet cassettes 51, 52, and 53, and a storage unit for these sheets. (51-54) is provided with a conveying means for conveying the sheet to the image forming unit 32. Note that the duplex unit 55 communicates with the switchback conveyance path 56 and is used when image formation is performed on both sides of the sheet.
[0035]
FIG. 3B is a perspective view of the static eliminator 15 in the image forming unit 32. FIG. 4 is a front view of the static eliminator 15 of FIG. As shown in these drawings, the static eliminator 15 includes an LED lamp 15a, which is a point light source, and a light guide plate 15b.
[0036]
Further, FIG. 5 shows a configuration in the vicinity of the static eliminator 15 of the invention. Here, as shown in the drawing, the light guide plate 15b is mounted on a process cartridge 20 on which a device for discharging is mounted. As shown in FIGS. 5A and 5B, the process cartridge 20 is detachable by sliding on a cartridge guide member 23 attached to frames 21 and 22 of the apparatus main body.
[0037]
On the apparatus main body side, the LED lamp 15a is disposed to face the end portion 20a on the front end side in the mounting direction indicated by the arrow 24 of the process cartridge 20 serving as a non-image forming area of the photosensitive drum 10.
[0038]
The light guide plate 15 b is formed in a longitudinal shape parallel to the photosensitive drum 10, and light incident from the incident surface 25 facing the LED lamp 15 a is evenly transmitted from the emitting surface 26 orthogonal to the incident surface 25 to the photosensitive drum 10. Irradiated.
[0039]
In this embodiment, as shown in FIG. 3B, the light guide plate 15b has a plate thickness D of 3 mm, an incident surface width W1 of 15 mm, and a longitudinal length L of 323 mm. The transmittance is 80% or more, and the refractive index is 1.4 to 1.7. In addition, the light guide plate 15b is formed by an injection molding method or an extrusion method using acrylic resin, polycarbonate resin, polystyrene resin, vinyl chloride resin, or glass as a raw material in the present embodiment, but the light diffusion surface facing the emission surface 26 Since the surface other than 27 needs to be a smooth surface, a process such as polishing is performed after the molding as necessary. Alternatively, the entire surface of the light guide plate 15b may be a smooth surface and only the light diffusion surface 27 may be affixed with a double-sided tape that is clouded.
[0040]
Furthermore, the light guide plate 15b is provided with a light source at an end portion, for example, and a light emitting surface provided on a side surface portion along a longitudinal direction of a columnar light guide plate made of a translucent material, and a cutting process or a rough surface provided on the opposite surface. A structure having a light diffusing part by surface processing (Japanese Patent Laid-Open No. 8-43633) or light from an LED light source is incident from the end of a light guide formed of a bar-shaped transparent material, and the length of the bar-shaped body A saw-tooth for reflecting, diffusing, or reflecting / diffusing a light beam incident on the side surface portion facing the light emission surface, on the side surface portion extending in the direction, and emitting the light beam incident thereon It is also possible to apply a conventional technique such as a configuration having a shape area (Japanese Patent Laid-Open No. 10-133026).
[0041]
The LED lamp 15a is, for example, an LED chip bonded on a metal lead, and the portion is sealed in a lens shape with a transparent resin, and has a wavelength of 618 nm and an experimental resistance value of 200 Ω. Is used and is disposed close to the incident surface 25. Since the number of the LED lamps 15a is only one and light is introduced only from the front end side of the light guide plate 15b, the number of used lamps can be reduced and the cost can be reduced.
[0042]
FIG. 6A shows the relationship between the distance from the point light source 15a and the light intensity on the surface of the photosensitive drum 10. FIG. FIG. 6B shows the relationship between the distance from the point light source 15 a and the sensitivity deterioration on the surface of the photosensitive drum 10. Further, FIG. 6C shows the relationship between the distance from the point light source 15a and the amount of light applied to the surface of the photosensitive drum 10.
[0043]
When the light intensity in the static elimination process has a distribution as shown in FIG. 6A, the entire surface of the photosensitive drum 10 is stressed evenly in the charging / exposure process in repeated charging / exposure / static elimination. On the other hand, in the static elimination process, the light neutralization irradiation by the point light source 15a and the light guide 15b has a difference in the intensity of light irradiated on the photosensitive drum 10 depending on the distance from the point light source as shown in FIG. For this reason, the accumulation of stress due to repeated charging, exposure, and static elimination also becomes non-uniform in the main scanning direction.
[0044]
For this reason, as shown in FIG. 6B, the degree of light fatigue varies depending on the light intensity distribution by repeating the charging / exposure / static discharge processes on the surface of the photosensitive drum 10, and thus the sensitivity with deviation. It will cause deterioration.
[0045]
Therefore, as the light amount adjusting means of the present invention, as shown in FIG. 6 (c), by providing a deviation in the light intensity such as laser power in the exposure process according to the distance from the point photoelectric 15a, the charging and Since the deviation of the photosensitivity of the photosensitive drum caused by the repetition of the exposure / discharge process is corrected, the electrostatic latent image having high reproducibility can be obtained even when the deviation of the sensitivity deterioration due to light fatigue occurs on the photosensitive drum 10. An image can be formed.
[0046]
FIG. 7A shows the relationship between the black solid ratio and the surface potential using the life initial stage (shown as initial in the figure), the life end stage (shown as life in the figure), and the light amount adjusting means. It is shown in each of the end of life in the case (shown as corrected in the figure). Further, FIG. 7B shows the relationship between the number of repetitions and the sensitivity deterioration amount of the photosensitive drum 10 at each of the measurement position 0 mm (a position) and the measurement position 300 mm (b position) in FIG. FIG. 7C shows a relationship between the intensity (power) of light to be irradiated corresponding to the number of repetitions at the position a and the position b as an example of adjusting the intensity of light emitted by the light amount adjusting means. Yes. FIG. 7D shows the relationship between the exposure times corresponding to the number of repetitions at the positions a and b as an example of adjusting the exposure time in the light amount adjusting means.
[0047]
As shown in FIG. 7B, the degree of sensitivity deterioration in repetition varies depending on the distance (measurement position) from the point light source. For this reason, as shown in FIG. 7C, the laser power required to substantially correct the sensitivity deterioration of the photosensitive drum 10 during the image forming process is also obtained from the point light source. The rate of increase will vary depending on the distance.
[0048]
Therefore, in the control of the exposure amount such as the laser power, the table of the laser output required at the position a (measurement position 0 mm) in FIG. Tables indicating the tilt of the laser output required at each position in the scanning direction are provided, and the exposure amount is corrected substantially corresponding to the deviation of the sensitivity deterioration of the photosensitive drum 10 with reference to these tables. . This is because the exposure amount is usually expressed by the product of the intensity of light to be irradiated and the irradiation time (exposure time).
[0049]
As a result, as shown in FIG. 7A, stable sensitivity can be supplied from the beginning through the life regardless of the distance from the point light source.
[0050]
Further, an LED was used as a light source during the exposure process, and control as a light amount adjusting unit was performed in both the intensity of light irradiated on the photosensitive drum 10 and the exposure time. In this case, a table of exposure time required for each pixel in the main scanning direction on the photosensitive drum 10 as shown in FIG. 7D with respect to the number of repetitions is provided. With reference to the table, the exposure amount can be corrected substantially corresponding to the deviation of the sensitivity deterioration of the photosensitive drum 10.
[0051]
Accordingly, as shown in FIG. 7A, stable actual sensitivity can be obtained throughout the life from the beginning regardless of the distance from the point light source.
[0052]
As the exposure unit used in the present invention, both the laser scanner unit and the LED light array can be used. However, since the LED light array can perform digital exposure for each pixel as a minute exposure means, the exposure time is particularly good. This is effective when making adjustments.
[0053]
【The invention's effect】
As described above, according to the present invention, the following effects can be obtained.
[0054]
(1) The photosensitive member corresponding to the deviation of the sensitivity deterioration of the photosensitive member by adjusting the exposure amount of the photosensitive member in the image forming step according to the deviation of the sensitivity deterioration in the axial direction of the photosensitive member caused by the static elimination step. Since the exposure process can be performed with the adjusted light quantity taking into account variations in image density of the electrostatic latent image formed on the electrostatic latent image, the electrostatic latent image is not affected by deviations in the sensitivity degradation of the photoreceptor due to light fatigue. The image forming process with high reproducibility becomes possible.
[0055]
(2) During the image forming process, the intensity of light applied to the photoconductor is adjusted according to the deviation of the sensitivity deterioration in the axial direction of the photoconductor caused by the static elimination process. While keeping the exposure time constant for each pixel in the main scanning direction, exposure can be performed with the amount of light corresponding to the deviation in sensitivity deterioration of the photoconductor due to light fatigue, and the exposure amount can be adjusted easily and light fatigue It is possible to solve the problem in the image forming process caused by the deviation of the sensitivity deterioration of the photoconductor.
[0056]
(3) An exposure apparatus such as a laser scanner unit by adjusting the exposure time of light applied to the photoconductor during the image forming process according to the deviation of the sensitivity deterioration in the axial direction of the photoconductor generated by the static elimination process. In order to adjust the exposure time for each pixel in the main scanning direction of the photoconductor within a range that does not interfere with the exposure process while keeping the light quantity of the image constant, an image resulting from a deviation in sensitivity deterioration of the photoconductor due to light fatigue Problems with the forming process can be solved.
[0057]
(4) Light intensity or exposure by adjusting the intensity and exposure time of the light applied to the photoconductor during the image forming process according to the deviation of sensitivity deterioration in the axial direction of the photoconductor caused by the static elimination process. Compared with the case where the exposure amount is adjusted only in any one of the times, it is possible to perform adjustment over a wider range and with higher accuracy.
[0058]
Further, since the adjustable range is expanded, the allowable range of sensitivity deterioration due to light fatigue when using the photoconductor is expanded, so that the lifetime of the photoconductor can be extended.
[0059]
(5) During the image forming process, it is possible to easily adjust the light intensity in the light amount adjusting means by adjusting the exposure amount of the photosensitive member from the semiconductor laser or the light emitting diode. In particular, when a light emitting diode is used, the exposure time can be adjusted more easily.
[0060]
Therefore, it is possible to provide an image forming apparatus capable of forming a highly reproducible image without being affected by the sensitivity deterioration deviation of the photoreceptor due to light fatigue, and realizing a reduction in size and cost.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an example of a configuration of an optical static elimination device.
FIG. 2 is a diagram illustrating a configuration of an image forming apparatus according to the present invention.
FIG. 3 is a diagram illustrating a configuration of an image forming unit of the present invention.
FIG. 4 is a diagram illustrating a configuration of a static eliminator in the present embodiment.
FIG. 5 is a diagram illustrating a configuration in the vicinity of a photoconductor in the present exemplary embodiment.
FIG. 6 is a diagram illustrating a relationship between a distance from a light source and a light amount.
FIG. 7 is a view showing the principle of exposure amount adjusting means of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10- Photoconductor drum 15- Static elimination apparatus 30- Image forming apparatus 31- Image reading part 32- Image forming unit 34- Post-processing apparatus 46- Exposure unit 47- Image forming part 50- Paper feed part 100- LED array

Claims (5)

An image forming apparatus that performs an electrophotographic image forming process including a light static eliminating process and that performs the static eliminating process with a static eliminating apparatus having a point light source and a light guide,
For each position in the axial direction of the photoconductor, the longer the distance from the point light source, the smaller the rate of increase in exposure amount due to sensitivity deterioration due to light fatigue of the photoconductor in the image forming step. An image forming apparatus comprising a light amount adjusting means for correcting an exposure amount. The image forming apparatus according to claim 1, wherein the light amount adjusting unit adjusts an intensity of light applied to the photoconductor. The image forming apparatus according to claim 1, wherein the light amount adjusting unit adjusts an exposure time of light applied to the photoconductor. The image forming apparatus according to claim 1, wherein the light amount adjusting unit adjusts an intensity and an exposure time of light applied to the photoconductor. The image forming apparatus according to claim 1, wherein the light source for exposure is a semiconductor laser or a light emitting diode.

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