JPH0570151B2 - - Google Patents

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.

(2) Prior Art and Problems to be Solved In the 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 the image, it has recently been possible to produce images of various sizes from the same original. Variable magnification type devices that can obtain copy images 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, causing the boundary between the image area and the non-image area to be crossed. There is a risk that the image in the vicinity of this portion may become unclear and the image quality may deteriorate.

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 which is not shown. Light from the original MS placed on the original stand forms an image on the charged photoreceptor D by the lens system LE to form 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 D becomes an image area, and the ranges in Y and Z become non-image areas unrelated to image formation. Therefore, in order to eliminate the charges in the non-image areas Y and Z, two LEDs 10 and 20 are arranged in the illustrated case, and these are turned on to eliminate the charges in the areas.

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. There is a possibility that a portion _L10 of the light beam projected from the shaped portion may enter the image area X and make the boundary thereof unclear.

In order to avoid these 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 in the vicinity to flow, thereby reducing the floating toner inside the copying machine. , dust, etc. adhere to the surface of the LED, and the amount of light reaching the surface of the photoreceptor gradually decreases, causing problems such as insufficient static removal.

In addition, if you change the luminous flux projection characteristics of the LED or paint the cylindrical part for light shielding, when multiple LEDs are installed in a row, the overlap of the irradiation ranges of adjacent LEDs may occur due to the arrangement error. This is undesirable because the illuminance decreases, resulting in insufficient static elimination, and blocking light with paint will cause more light to be 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, and is a method of illuminating an image carrier from an oblique direction using a light emitting element such as an LED. In particular, it is possible 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 quantity in the overlapping area of the illumination range caused by adjacent light emitting elements. The aim is to provide an illumination device which is possible without being brought close to the carrier surface.

(4) Explanation of Constituent Functions and Embodiments of the Invention In order to achieve the above-mentioned objects, the present invention is intended to solve the problem of a non-image area that occurs 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 the area, causing the image to disappear. , to avoid deterioration of image quality due to unclear boundaries of non-image areas, and to avoid unnecessarily increasing the amount of light in the main irradiation area of light emitting elements arranged in the lighting device. By deviating 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 the overlapping area of the irradiation areas of adjacent light emitting elements can be avoided. It is an object of the present invention to provide an illumination device that can apply as uniform an amount of static eliminating light as possible over the entire image area and prevent the occurrence of black streaks due to insufficient static eliminating.

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 elimination illumination device in the apparatus shown in FIG. 1, and its optical axis is assumed to be 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 the case of such arrangement of the light emitting elements, as mentioned above, when the image area exists on the left side in the figure, the light beam projected onto part a or its vicinity is
It will invade the image area and adversely affect the image.

FIG. 4B shows the a, b,
This schematically shows the light amount distribution shown along each part of c. The shaded area shown in the figure is the amount of harmful light that illuminates 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°. Figure 1A shows one of the light-emitting elements, and by arranging the light-emitting elements in this way, the luminous flux projected on each part a, b, and c in Figure 4A is shown in Figure 1A, respectively. As shown in f, d, and e, the portion corresponding to the light beam projected onto portion a 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 readily 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 to the opposite side of the area, and the amount of light in this area is large. Therefore, in addition to sharpening the boundary between the image area and the non-image area, it is necessary to maintain the amount of light necessary for static elimination while also providing sufficient amount of light to the overlapped areas with adjacent light emitting elements when multiple light emitting elements are arranged in a row. It becomes possible to apply the amount of static eliminating light as uniformly as possible over the entire length of the non-image area.
Further, the decrease in illuminance at the overlapping portion due to alignment errors 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. as
Of course, the present invention is not limited to LEDs, and can also be applied to lamps equipped with filaments.

(5) Effects of the Invention As explained above, the present invention is particularly effective in optically eliminating charges in non-image areas generated on the surface of an image carrier due to the reduction magnification in a variable magnification type image forming apparatus. Since the light-emitting element used for the image carrier 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 charge removal that enters the image area of the image carrier surface is largely cut off, and the peak light intensity is As the peak value of the area where the irradiation area is smaller, the number of areas reaching the opposite side of the image area increases. It reduces the lack of illuminance due to alignment errors, makes it possible to obtain as uniform illuminance as possible over the entire length of the non-image area, and achieves a homogeneous static elimination effect, sharpening both the image and non-image areas. This greatly contributes to obtaining high-quality 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.
Fig. 4A is the same as above, a side view showing the projection direction of the projected light flux of one light emitting element, Fig. 4B is a graph showing the light amount distribution of the same as above, 10, 12...Light emitting element (LED), D... Image carrier .

Claims (1)

[Scope of Claims] 1. A light-emitting element equipped with a lens portion on the light-emitting side of a transparent member, and a non-image area of the end of the photoreceptor in the axial direction of the photoreceptor is illuminated through the lens portion of the light-emitting element. An illumination device for extinguishing unnecessary charges by irradiating light, wherein the light emitting element is arranged at an angle so as to irradiate the photoreceptor with light obliquely in a direction from a non-image area to an image area.