JPS60237472A - Illuminating device - Google Patents

Abstract

PURPOSE:To enable distinct delineation of the boundary between an image area and a non-image area by disposing a light emitting element for destaticization of the non-image area so as to incline with respect to an image carrying body in the stage of forming the image by a reduction magnification. CONSTITUTION:The light emitting element 10 for destaticization of the non-image area in the stage of forming the image by the reduction magnification is provided. Said element is disposed to have 45 deg. angle of inclination with respect to the image carrying body. The luminous flux (f) on the outside irradiates the image region if the element 10 is disposed perpendicularly to the image carrying body but the luminous flux (f) does not arrive at the image region and is dissipated by scattering if the element is obliquely disposed as shown in the figure. Intrusion of part of the projected luminous flux into the image region and unnecessary destaticization are thus obviated and the boundary between the image region and the non-image region is distinctly delineated.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Field of the Invention The present invention relates to an illumination device suitable for use in an image forming apparatus using an electrostatic photographic process such as an electronic copying machine or a printer, particularly a variable magnification type image forming apparatus. It is related to the device.

[21 Prior Art and Problems to be Solved In a well-known image forming apparatus that transfers a transferable toner image formed on the surface of an image carrier onto a transfer material and fixes it, it has recently been possible to produce images of various sizes from the same original. Variable magnification type devices that allow copy images to be obtained are becoming widely used.

In this type of image forming apparatus, the size of the image carrier that forms the image of the original has a certain size that can receive the image at the maximum magnification, so it is natural that This results in a portion of the image carrier that is unnecessary for image formation.

Even in such a case, the unnecessary portions will normally be charged, so if the developing process is continued, the unnecessary charged portions will also be developed, and toner will be wasted. At the same time, toner also adheres to non-image areas.

For this reason, conventionally, an appropriate number of small light sources such as lamps or light emitting diodes (LEDs) are arranged near the surface of the image carrier, and these light sources are blinked as appropriate depending on the magnification to illuminate the surface of the image carrier. Measures are taken to eliminate charges in unnecessary parts.

Conventionally, LEDs have been mainly used as such static elimination light sources, but the light beam that illuminates the surface of the image carrier spreads and enters the image forming area on the surface, making the boundary between the image area and the non-image area unclear. This may cause the image in the vicinity of this area to become unclear, resulting in deterioration in image quality.

This will be briefly explained with reference to FIG. 3, which is a schematic diagram showing the main parts of a copying machine configured to form an electrostatic latent image on a rotating cylindrical photoreceptor, and in which an original (not shown) is shown. Light from the document MS placed on the stand forms an image on the photoreceptor charged by the lens system LE, forming an electrostatic latent image.

In the case of the illustrated magnification, only the range in the axial direction X of the surface of the photoreceptor is an image area, and the Y and Z ranges are non-image areas unrelated to image formation. Therefore, the non-image area Y,
In order to dissipate the charge on Z, two LEDs are used in the case shown.
I0.20 are arranged, and these light up to eliminate static electricity in the area.

In this case, the LED usually consists of a cylindrical transparent member and a convex lens-shaped part integrally formed at the tip in the light projection direction. Part of the luminous flux projected from the cylindrical part,
o may invade the image area X and make its boundary unclear.

In order to avoid such drawbacks, if the LED is placed close to the surface of the photoconductor, the rotation of the photoconductor and the resulting minute vibrations will cause the air around the area to flow, thereby removing floating toner, dust, etc. inside the copying machine. When it adheres to the surface of the LED, the amount of light reaching the surface of the photoreceptor gradually decreases, causing problems such as insufficient static removal.

Also, if you change the luminous flux projection characteristics of the LED or paint the cylindrical part with a light-shielding coating, when multiple LEDs are installed in a row, the adjacent LEDs may overlap due to alignment errors.
This is undesirable because the illuminance in the overlapping areas of the irradiation ranges decreases, resulting in insufficient static removal, and blocking light with trench coating will result in more light being absorbed, resulting in a loss of light quantity.

(3) Purpose of the Invention The present invention has been completed in view of the above-mentioned defects in image forming apparatuses. , to clearly demarcate the boundary between the image area and the non-image area on the surface of the image carrier, and to avoid insufficient light amount in areas where the illumination ranges of adjacent light emitting elements overlap.
In particular, it is an object of the present invention to provide an illumination device that allows these light-emitting elements to be placed close to the surface of an image carrier.

(4) Explanation of Constituent Functions and Embodiments of the Invention In order to achieve the above-mentioned objects, the present invention aims to solve the problem of non-image areas that occur on the surface of an image carrier when forming an image at a reduction magnification, especially in a variable magnification type image forming apparatus. By arranging the illumination device used to eliminate static electricity at an angle with respect to the surface of the image carrier, a portion of the projected light beam enters the image area and performs unnecessary static elimination in that area, causing the image and non-image to disappear. To avoid deteriorating the image quality by making the boundary between both image areas unclear, and to avoid unnecessarily increasing the amount of light in the main irradiation area of the light emitting element arranged in the lighting device. By shifting the excess light amount to the side opposite to the image area as much as possible, when using a plurality of light emitting elements, insufficient illuminance in nine overlapping areas of the irradiation areas of adjacent light emitting elements can be avoided, and a non-image area can be avoided. It is an object of the present invention to provide an illumination device that can prevent the occurrence of black streaks due to insufficient static elimination by applying a uniform amount of static elimination light as much as possible over the entire area.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 4A shows one light emitting element of the static eliminating illumination device in the apparatus shown in FIG. 1, and it is assumed that its optical axis is perpendicular to the image bearing surface. As shown in the figure, the projected light beam in this case is expanded into ranges indicated by symbols a, b, and c.

In such an arrangement of light emitting elements, as mentioned above,
If an image area exists on the left side in the figure, the light beam projected onto the 8th part or its vicinity will enter the image area and adversely affect the image.

FIG. 4B shows the above-mentioned a and b on the surface of the image carrier in the case of the light emitting element arrangement as shown in FIG. 4A.

C schematically shows the light amount distribution shown along each part. The shaded area shown in the figure is the amount of harmful light that irradiates the image area, and in this case, the main amount of light that reaches part b is the minimum amount of light necessary for static elimination, although it of course depends on the characteristics and arrangement of the light emitting element. A may be exceeded by a wide margin. If the amount of light is reduced in order to prevent this, when a plurality of light emitting elements are used (which is the case in most cases), there is a risk that the amount of light will be insufficient at the overlapping portion of the irradiation areas of adjacent elements.

In the present invention, in order to eliminate the drawbacks of the light emitting element arranged as described above, the light emitting element is arranged so that the optical axis of the light emitting element 10 is inclined with respect to the surface of the image carrier, as shown in FIG. be.

In the embodiment shown in the figure, the inclination angle is 45°. FIG. 1A shows one of the light emitting elements,
By arranging the light emitting elements in this way, the light beams projected onto portions a, b, and c in FIG. 4A become as shown by symbols f, d, and e in FIG. 1A, respectively, and are projected onto portion a. The portion corresponding to the light beam is scattered and lost without reaching the image area on the surface of the image carrier.

Figure 1B shows the light intensity distribution on the surface of the image carrier due to the above-mentioned light emitting element.As can be seen from this figure, the above-mentioned harmful light flux is largely cut off, the peak light intensity is small, and the image A large amount of light is projected on the opposite side of the area, and the amount of light in this area is large. Therefore, in addition to sharply demarcating the image area and non-image area, while maintaining the amount of light necessary for static elimination, when multiple light emitting elements are arranged in a row, the area where adjacent light emitting elements overlap can also have a sufficient amount of light. It becomes possible to apply the amount of static eliminating light as uniformly as possible over the entire length of the non-image area. However, the reduction in illuminance of 9 parts due to the alignment error between the light emitting elements is reduced.

In the above embodiments, the direction of the light emitting element is inclined at 45 degrees with respect to the image bearing surface, but it is possible to change this angle of inclination as appropriate depending on the characteristics of the light emitting element. It goes without saying that the invention is not limited to T and ED lamps, but can also be applied to lamps equipped with filaments.

(5) As described in detail, according to the present invention, when performing optical charge removal on a non-image area generated on the surface of an image carrier due to reduction magnification, especially in a variable magnification type image forming apparatus,
Since the light-emitting element used for this is arranged at an angle with respect to the surface of the image carrier, the portion of the light beam projected from the light-emitting element for static elimination that penetrates into the image area of the image carrier surface is cut wide, and the peak As the peak value of the area where the light intensity is obtained becomes smaller, the area that reaches the opposite side of the image area increases, so when using multiple light emitting elements as a lighting device, the arrangement in the overlapping area of the irradiation range of adjacent light emitting elements increases. By reducing the lack of illuminance due to errors, etc., and achieving as uniform illuminance as possible over the entire length of the non-image area, and achieving a homogeneous static elimination effect, it is possible to divide the image and non-image rain area into 7 yag areas. Dogs are helpful in obtaining accurate copies.

[Brief explanation of the drawing]

FIG. 1A is a side view showing the projection direction of the projected light beam of one light emitting element according to the present invention, FIG. 1B is a graph showing the light intensity distribution of the same, and FIG. 2 is a light emission in the illumination device of the image forming apparatus according to the present invention. FIG. 3 is a schematic end view showing the arrangement of elements, FIG. 3 is a schematic end view showing the arrangement of a static elimination light source in a known variable magnification type image forming apparatus, and FIG. 10.12 Light emitting element (LED), D... image carrier. Patent Applicant Canon Co., Ltd. Agent Patent Attorney Irie 1'-゛・・1 7/ Figure 1A Figure 2 Figure 31! I

Claims (1)

[Claims] An illumination device in which a light emitting element for irradiating light onto the surface of an image carrier of an image forming apparatus is arranged at an angle with respect to the surface of the image carrier.