JP2651539B2 - Original illumination device for copier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a document illuminating device for a copying machine, and more particularly, to a document illuminating device provided with a reduction function by a multi-stage variable magnification mechanism and a zoom mechanism, and An exposure adjusting plate is provided between the light source and the light source that irradiates light to the original on the document mounting table to make the light amount distribution on the photosensitive drum flat (uniform in the drum axis direction) by blocking part of the light from the light source. The present invention relates to a document illuminating device in a provided copying machine.

[Conventional technology]

Generally, as a light source for irradiating a document in a copying machine, co
In consideration of the lens characteristics such as the s ⁴ θ rule and the aperture efficiency, as shown in FIG. 6, a light distribution characteristic is used in which the amount of light at both ends is larger than that at the center.

However, there are variations in the sensitivity of the photosensitive drum and variations in light distribution characteristics due to manufacturing errors of the light source 27 itself.
It is practically difficult to flatten the light amount distribution on the photosensitive drum only by setting the light distribution characteristics described above, and good image quality cannot be expected.

In FIG. 6, L is the total length of the light source 27, and l is the maximum document width, which substantially coincides with the use area in the light source. The amount of light on both sides of the use area is sharply reduced.

Therefore, conventionally, as shown in FIG. 7, an exposure adjusting plate having a length extending over the entire length of the light source 27 is provided between the original placing table 2 and the light source 27 for irradiating the original a on the original placing table 2 with light. 30 is provided, and a part of the light of the light source 27 is blocked by the exposure adjusting plate 30, so that the light amount distribution on the photosensitive drum 12 is made flat. Incidentally, reference numeral 26 in the drawing denotes a slit for exposure.

Further, in the copying machine, a blank lamp 14 for erasing electric charges charged in a portion located outside the image forming width X of the photosensitive drum 12 is turned on, and a white portion located around the original a of the original presser 3 is turned on. The reflected light from 3a is also guided to the photosensitive drum 12, and the disappearance of the charge due to the reflected light and the disappearance of the charge due to the blank lamp 14 are used together to prevent black solid around the image. When a document a is reduced and copied on a copy paper larger than the size to be reduced, a gray stripe portion may be formed on the outside of the image depending on the reduction magnification, and the image quality may be degraded.

That is, since the blank lamp 14 is composed of a large number of static elimination lamps having a certain irradiation range, depending on the reduction magnification, the end portion of the original image (electrostatic latent image) formed on the photosensitive drum 12 is formed. (The end of the image width X) may be located in the middle of the irradiation range of one discharging lamp. In such a case, when the static elimination lamp 14a in which a part of the irradiation range overlaps with the end of the image forming width X is turned on, the charge disappears to the image area and a part of the image is lost. lamp
The lamps up to the static elimination lamp 14b outside the lamp 14a are turned on. In FIG. 7, the circles indicate the lit discharge lamps.
The mark “x” indicates a neutralization lamp that has been turned off.

Therefore, a portion Y located between the end of the original image of the photosensitive drum 12 (the end of the imaging width X) and the lit discharge lamp 14b.
In this case, only the reflected light from the white portion 3a located around the document a of the document presser 3 is irradiated, and the light quantity becomes insufficient. As a result, electric charges remain in the form of stripes on the photosensitive drum 12 outside the image width X, and when a copy paper having a size larger than the original image is used, gray stripes are formed on the outside of the copied image. Sometimes appeared. If the size of the copy paper is the same as that of the original image (imaging width X), no stripes appear on the copy paper. Therefore, the toner is wasted.

Conventionally, the following measures have been taken as a solution to such a problem.

(1) Extend the usable area by lengthening the light source.

(2) As shown in JP-A-57-178277, auxiliary light sources are provided at both ends of the light source, or
As can be seen in JP-A-133449, a pair of mirrors are provided at both ends of a light source to increase the amount of light illuminating the white portions of the document holder located on both sides of the maximum document width.

[Problems to be solved by the invention]

However, in the case of the former (1), since a long light source is used, the cost of the light source is high, which not only increases the cost but also increases the size of the copying machine.

Also in the case of the latter (2), cost increase was unavoidable due to the addition of components such as an auxiliary light source and a mirror.

In view of the above-mentioned conventional disadvantages, the present invention provides a method of reducing the size of a document having a maximum document width to a copy sheet larger than the size to be reduced, a gray stripe portion is formed on the outside of the image depending on the reduction magnification, and the image quality is reduced. Is to be solved with a very simple and economical configuration.

[Means for solving the problem]

In order to achieve the above object, a document illuminating device for a copier according to the present invention is configured such that a part of light of a light source is blocked between a document table and a light source that irradiates light on a document on the document table. Thus, in a document illuminating device of a copying machine provided with an exposure adjusting plate for flattening the light amount distribution on the photosensitive drum, the width of the exposure adjusting plate is set to be equal to or substantially equal to the maximum original width, and the maximum original An opening for irradiating the original holder with light from the light source is formed further on the side of the exposure adjusting plate set to have the same or substantially the same width as the original holder. The light source is also illuminated to a white portion to increase the amount of light reflected from the white portion of the original presser, and the reflected light is set to the same or substantially the same as the maximum original width. The opening formed further on the side of the plate Characterized in that to irradiate the al photosensitive drum.

[Action]

In the document illuminating device of the copying machine of the present invention configured as described above, when performing reduction copying, the reflected light from the white portion of the document holder whose light amount has been increased reflects the image on the photosensitive drum corresponding to the maximum document width. Irradiation is performed outside the region, and the charge on the photosensitive drum surface in this portion is reliably removed.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a so-called center-based copying type copying machine. In the figure, reference numeral 1 denotes a copying machine main body having a document table 2 and a document holder 3 made of transparent glass or the like which can be reciprocated upward, and an exposure device 5 is arranged in an upper space of the partition plate 4. . The exposure device 5 includes a document illumination device 6, reflection mirrors 7 to 1
0, a condenser lens 11 and the like. Condensing lens 11
The position of the lens can be changed steplessly in the direction of the optical path, and the magnification can be increased or reduced at an arbitrary magnification by a so-called zoom mechanism. Reference numeral 12 denotes a photosensitive drum, which includes a charging device 13, a blank lamp 14 capable of changing a charge removal area in accordance with selection of a magnification, a developing device 15, a transfer device 16, a copy paper separating device 17, and a cleaning device 18 for rotating the drum. They are arranged in this order along the direction. Reference numeral 19 denotes a loading portion of the cassette case 20, reference numeral 21 denotes a paper feeding and conveying device, reference numeral 22 denotes a paper discharging and conveying device, reference numeral 23 denotes a heat fixing device, and reference numeral 24 denotes a paper discharging tray.

The configuration of the document illuminating device 6 is as follows. That is, as shown in FIGS. 2 and 3, a slit 26 longer than the maximum document width 1 is formed in the fixed frame 25 located below the document table 2, and the light amount at both ends is larger than the central portion. Light source 27 and reflector 2 with light distribution characteristics that increase
8 and 29, and a light source 27 is provided between the document table 2 and the light source 27.
Exposure adjusting plate 30 that blocks a part of the light (mainly direct light that does not pass through the reflecting mirrors 28 and 29) to make the light amount distribution on the photosensitive drum 12 flat (uniform in the drum axis direction).
Is provided. The illustrated exposure adjustment plate 30 is composed of three plate portions 30a, 30b, 30c divided in the longitudinal direction of the light source 27, and each plate portion 30a, 30b, 30c is connected to the upper portion of the reflection mirror 28. Screws 32 are fixed to the attached mounting pieces 31. By loosening the screws 32, the central plate portion 30b can be moved in parallel, and the plate portions 30a and 30c on both sides are
It is configured to be able to swing around a screw 32 for fixing Ob.

In this embodiment, as shown in FIG. 2 and FIG. 4, in the original illuminating device 6 of the copying machine having the above-described configuration, portions indicated by broken lines of the plate portions 30a and 30c on both sides of the exposure adjusting plate 30. The width of the exposure adjustment plate 30 is set to be the same as or substantially the same as (slightly wider than) the maximum original width l, and the light from the light source 27 ( Openings S, S for irradiating the original press 3 with mainly direct light) are formed to increase the amount of light reflected by the white portion 3a outside the maximum original width l of the original press 3, and the reflected light is exposed. It is configured to irradiate the drum 12.

That is, the light emitted from the reflecting mirrors 28 and 29 illuminated toward the original presser 3 is added to the light illuminated on the original retainer 3 through the openings S 1 and S 2, so that the maximum original width l of the original retainer 3 is increased. The amount of light reflected by the white portion 3a to the outside is increased, and the reflected light is radiated to the outside of the image area of the photosensitive drum 12 corresponding to the maximum original width, thereby reliably removing the charge on the photosensitive drum surface in this portion. It is trying to make it.

Here, the exposure adjustment plate 30 having the configuration shown in FIG. 7 in which the openings S, S are not formed, that is, the exposure adjustment by the two-sided plate portions 30a, 30c whose ends are not cut and the central plate portion 30b. The amount of light applied to the document holder 3 when the plate 30 was provided was as shown by the dashed line in FIG.
The ends of 30a, 30c are cut to set the width of the exposure adjusting plate 30 to be the same as or substantially the same as the maximum original width l, and the both side plate portions 30a, 30c
When the light amount distribution on the photosensitive drum is adjusted so that the light amount distribution on the photosensitive drum 30c and the central plate portion 30b are flat, the amount of light irradiated on the original presser 3 is as shown by a solid line in FIG. It is clear that the amount of light increases from the broken line to the one-dot chain line outside the circle, and the amount of light reflected by the white portion 3a located outside the maximum original width l of the original presser 3 greatly increases.

Therefore, as shown in FIG.
Is reduced to a copy paper larger than the size to be reduced, the end of the imaging width X of the photosensitive drum 12 corresponding to the maximum original width l does not match the arrangement pitch of the static elimination lamps in the blank lamp 14, Even in the middle portion of the irradiation range of a certain static elimination lamp 14a, the white portion of the original presser 3 is provided in a portion Y of the photosensitive drum 12 located between the end of the imaging width X and the lit static elimination lamp 14b. A large amount of light reflected from the portion 3a is irradiated. Therefore, the charge charged on the portion located outside the image width X (the portion Y) is reliably removed, and a gray stripe portion is not formed outside the image.

In the above-described embodiment, the present invention will be described with reference to a so-called center reference copying type copying machine in which copying is performed by making the width center of one side of the document table 2 in the feeding direction coincide with the width center of the document a. Although the present invention has been described, the present invention also applies to a so-called one-end reference copying type copying machine in which two sides of a document a are made to coincide with one side in the sheet feeding direction of the document table 2 and the side adjacent thereto. Can be implemented. That is, in this case, since one end of the photosensitive drum 12 corresponding to the document reference end of the image forming width X is always at a fixed position, the above-described problem does not occur on the reference end side. Is cut off at one end on the side opposite to the reference end, and the gap S is formed only on one side of the exposure adjusting plate 30.
Will be formed.

〔The invention's effect〕

As described above, in the document illuminating device of the copying machine according to the present invention, the width of the exposure adjustment plate is set to be the same or substantially the same as the maximum document width, and the width is set to be the same or substantially the same as the maximum document width. Further, on the side of the exposure adjusting plate, an opening is formed to irradiate the light from the light source to the document holder, and the light of the light source is also applied to the white portion of the document holder corresponding to the outer portion of the maximum document width. The amount of light reflected from the white portion of the original press is increased so that the reflected light is formed on the side of the exposure adjustment plate set to be equal to or substantially equal to the maximum original width. Since the photosensitive drum is irradiated from the opening, the following effects are obtained.

In other words, the original illuminating device of the copying machine according to the present invention adds the light emitted from the reflecting mirror toward the original holder to the original holder through the opening, so that the original is wider than the maximum original width. The amount of light reflected by the outer white portion is increased, and the reflected light is radiated to the outside of the image area of the photosensitive drum corresponding to the maximum original width, so that the charge on the photosensitive drum surface in this portion is reliably removed. Therefore, it is needless to say that, unlike the conventional structure, the problem that a gray stripe portion is formed on the outside of the image or the problem that the image quality is deteriorated can be solved well. As a specific means for solving the problem, since a means for setting the width of the exposure adjustment plate and forming an opening on the side is employed, the overall structure becomes extremely simple, which can contribute to miniaturization of the apparatus. above There is an advantage that can be achieved at a low cost.

[Brief description of the drawings]

1 to 6 show an embodiment of the present invention. FIG. 1 is a schematic sectional view of the entire copying machine, FIG. 2 is a plan view of a document illuminating device, and FIG. FIG. 4, FIG. 4 is a schematic diagram showing a state in which an image is formed on the surface of the photosensitive drum, FIG. 5 is an explanatory diagram showing a change in the amount of reflected light, FIG. 6 is a light distribution characteristic diagram of the light source, and FIG. FIG. 10 is a schematic diagram illustrating a state in which an image is formed on the surface of a photosensitive drum by a conventional document illumination device. Reference numeral 2 Document placement table 3 Document holder 12 Photosensitive drum 27 Light source 30 Exposure adjustment plate a Documents l
... Maximum document width, S ... Opening.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Toru Nakamaru 1-2-2, Tamazo, Higashi-ku, Osaka Mita Kogyo Co., Ltd. (56) References JP-A-60-252336 (JP, A) JP-A-61 -97665 (JP, A) JP-A-60-20963 (JP, A) JP-A-60-61772 (JP, A)

Claims (1)

(57) [Claims] 1. An exposure adjusting device for flattening a light amount distribution on a photosensitive drum by intercepting a part of light from a light source between a document table and a light source for irradiating the document on the document table. In a document illuminating device of a copying machine provided with a plate, the width of the exposure adjusting plate is set to be the same or substantially the same as the maximum document width, and the exposure adjusting plate is set to the same or substantially the same width as the maximum document width. An opening for irradiating light from the light source to the document holder is further formed on the side of the document holder, and the light of the light source is also applied to a white portion of the document holder corresponding to an outer portion of the maximum document width. The amount of light reflected from the white portion of the document holder is increased, and the reflected light is exposed through the opening formed on the side of the exposure adjustment plate set to be substantially the same as or substantially equal to the maximum document width. A copying machine characterized by irradiating a drum Manuscript irradiation apparatus.