JPS5887566A - Image firming apparatus - Google Patents

Abstract

PURPOSE:To remove black frames accompanied by contraction magnification, by providing an array of LED's in parallel to the longitudinal direction of a photoreceptor drum. CONSTITUTION:The light emitting face of an LED array is arranged between the part 4 of the photoreceptor drum 1 of an electrostatic copying apparatus on which a latent image is formed by slit exposure, and a developing part 5 in parallel to the longitudinal direction of the drum 1 and facing the drum 1. X is the part on which a contracted image is formed, and Y is a part of 4 in addition to X. Since Y is not illuminated with light as a matter of cource, black frames are formed. To prevent them, the light emitting diodes of the array 17 are allowed to emit light by selectively controlling the emission in accordance with a microcomputer, and exposing the part y to light before a developing process. When the part X passes below the array 17, LED's are allowed to emit light only on the parts Y' and y', and after the part X has passed, all the length of them are allowed to emit light, permitting only Y to be exposed.

Description

Detailed Description of the Invention This invention relates to an image forming apparatus that performs variable-magnification copying by projecting the #4Fi original image of the present invention onto a photoreceptor surface via an optical system capable of continuous variable-magnification projection or multi-stage variable-magnification projection, * For details, see 1 of the Jin no Tane method.
The present invention relates to a means structure for uniformly exposing an unexposed area surface outside an exposed area by an optical system generated on a photoreceptor surface due to fine projection of an original image in an ILI image forming apparatus.

For the sake of convenience, a transfer type electronic copying machine capable of variable magnification copying will be described below as an example, as shown in FIG.

A drum-shaped electrophotographic photoreceptor is rotated in the direction of the arrow around an off-axis 2. The following processes are sequentially applied to the surface of the #photoreceptor to perform copying.

(1) Uniform Teiden (-Next Teiden) using charger 6.

(2) Simultaneously with the slit projection of the original image via the projection optical system, which will be described later, DC corona charging with the opposite polarity to the above-mentioned Teiden or AC corona static elimination is performed by the discharger 4. As a result, an electrostatic latent image corresponding to the projected image is formed on the surface of the photoreceptor.

(3) Toner development of the electrostatic latent image by the developing device 5.

(4) Transfer of the toner developed image onto the transfer material P surface by the transfer device 116. The transfer material P is fed between the photoreceptor 1 and the transfer section a16 from a paper feeding mechanism section (not shown) in synchronization with the rotation of the photoreceptor 1.

(5) Separation of the transfer material that has passed through the transfer section and is placed on the surface of the photoconductor & sequentially peeled off from the photoconductor surface by 7 (6) Rolling of the transfer material surface 4 Fixing device for toner image 8 established by. It passes through the fixing device and is ejected from the machine as a copy of Kyushu Transfer Material Co., Ltd.

(7) Cleaning of the surface of the photoreceptor from which the transfer material has been peeled off after passing through the transfer section using the cleaner 9. In step 4, residual toner, dust, etc. are removed, and the photoreceptor can be used repeatedly.

The original image projection optical system is a reciprocating original erasure stand 10 (hereinafter referred to as II).
(abbreviated as A manuscript table) and 1 capable of continuous or multi-stage variable magnification projection.
1i! In combination with the optical systems 14 to 16, the stacking table 10 is made of a transparent plate such as a glass plate, and normally stands by at the solid line water position in the figure as its home position, and moves forward to the left when a copying start signal is received. When it reaches the end point of the forward movement (double-point chain training), it is driven backward and returns to the initial home position. 11
is the manuscript frame.

Reference numeral 12 denotes a document pressure plate that is connected to the frame 11 with a hinge and can be freely opened/closed (raised/folded) on the top surface of the IJA horizontal stand 10.

The back side is the white side. The original 0 is placed on the upper surface of the original table 10 with the image side to be copied facing downward, and the original pressing plate 12 is placed over it.

Then, the document table 10 on which the document O is set is driven forward and
Then, the lower surface of the document table 10 passes through the slit illumination device 16 sequentially from the left side to the right side, and as a result, the downward facing document surface on the document table 10 extends the transparent wall thickness of the table 10 from the left side to the right side. The light is illuminated by slits. Then, the reflected light of the slit illumination light from the document surface is reflected by the fixed first reflecting mirror 14→
Variable magnification lens 15 → Fixed second reflection mirror 16 →
The light is guided along the inner path of the discharge 64 and projected onto the rotating photoreceptor directly below the discharge vessel 4 (slit II light).

Forward driving distance of the document table 10! In general, length and shortness are automatically controlled in accordance with the selected copying machine size.

For variable magnification copying, when a desired magnification rate is set using a magnification setter provided in the operation section, the imaging lens 15 is moved to nine positions corresponding to the set magnification by a control circuit such as a microcomputer, and the yA Kusunoki stand is 10 The forward speed or rotational speed of the photoconductor 1, the illuminance of the document illumination of the document slit illumination device 16, and the conditions of the voltage applied to the discharge device 6 and 40 are converted to appropriate conditions corresponding to the set magnification, and copying is executed. Ru.

Note that various types of projection systems are known, such as one in which the document table 10 is fixed and the optical system is moved, and one in which the document itself is conveyed and passed through an illumination section. Some use a belt type photoreceptor 1. As the electrophotographic process, conventionally known various principles and methods can be employed.

With such an image forming device capable of variable-magnification copying, it is impossible to perform both full-size copying and enlarged copying! In the case of one small copy, as shown in FIG. 2116, as the original image is reduced in size and projected onto one surface of the photoreceptor, the photoreceptor surface area Y outside the reduced projection area of the original image becomes an unexposed area that does not receive light irradiation. Become. To be more precise, the original reduced projection area X is the reduced projected image area of the original table 10 that includes the smaller projected area of the original 0. FIG. 2 shows an example of a new central part reference copy mode, and FIG. 6 shows an example of a one-sided reference copy mode. Two points @ Rensui's imaging lens 15 indicate the positions when photographing the same size bale.

Further, FIGS. 4 and 5 show examples of the development plane of the photoreceptor 1, the area state of the original 1-image reduction projection area .

In this way, the unexposed area Y generated on the surface of the photoreceptor due to the reduced projection X of the original image becomes wider as the reduced projection magnification of the original image increases. The unexposed area Y facing the photoconductor holds a strong dark potential to which the developed toner is attached. the result.

(2) In the developing section 5, as well as developing the area X which is the target area, the unnecessary unexposed area Y is imaged with # in solid black on the entire surface, so the developer is wasted and wasted.

(2) The burden on the cleaner 9 is increased in order to remove the highly charged developer' adhering to the unexposed area Y.

■When a transfer material larger in size than the image area X was selected and fed as the transfer material P, the solid black developer in the unexposed area Y was also transferred and the quality of the copied image deteriorated significantly. becomes.

This may cause other problems.

Even in the case of a direct method (electro7-attack method) using photosensitive paper as a photoreceptor, problems such as ① and ③ occur for the same reason when reduced copying is possible. In addition, even with photosensitive paper that erases the color of the exposed areas and forms a positive image when exposed to light, those that can be reduced in size may have problems in copying due to the occurrence of unexposed areas Y that are not erased. In order to eliminate the problem caused by the occurrence of unexposed areas on the photoconductor surface during reduction copying as described above, uniform cliff light is applied to the unexposed area Y, and the dark area potential of the area MY is concentrated. It is necessary to convert the surface to a sufficiently bright level in front of the image so that dust and toner do not adhere to it.

If the photosensitive paper uses light-erasable paper, it is necessary to perform the color erasing process by uniformly applying dust light to the unexposed area of the layer color-sensitive paper surface before the duplication and fixing process. be.

The present invention relates to the structure of a means for uniformly retouching the unexposed area Y of the enlarged photoreceptor surface, selectively and always uniformly only for the unexposed area Y of the photoreceptor surface, regardless of continuous reduction magnification, multi-stage magnification, or small magnification. The purpose of this device is to provide a light-emitting device capable of processing dust and light, and the exposure device uses a photoreceptor with 10 dimensions (in the case of a drum type, as many light-emitting diodes as the drum) are closely arranged in one unit. A one-dimensional array (17) is used, and the light-emitting part side faces the photoconductor surface, and the photoconductor surface is arranged horizontally, and the individual LEDs along the length of the LHAD array are connected to the original image. Light emission 71 is selectively performed according to the reduction ratio in order to uniformly eliminate the dark spots Y outside the exposure area that occur on the photoconductor surface due to the small width projection. IJ # The % image is what was done.

In the example of FIG. 1, the LED array 17 emits light 11I simultaneously with 4 units 4 and 1#! In the open position with respect to the device 5, the light emitting device 5111 is placed in close opposition to the surface of the drum 1 by repeatedly hitting the generatrix of the drum 1, which is a photoreceptor.

Then, the desired silk booklet is set in a control circuit such as a microcomputer using a setting device, and the individual LEDs along the length of the LED play are set to the unexposed photoreceptor using a calculation signal from the control circuit corresponding to the set reduction ratio. Light is selectively emitted so that only area Y is illuminated. In other words, in the case of the center reference copying mode in the example of FIGS.
Only the LEDs included in both ends of the LED array corresponding to the area Y@Y are emitted so that they are exposed to the emitted light of the LEDs by passing through the area.

Immediately after the trailing edge of the exposure area
All LEDs of the ED array 17 are controlled to be in the form of light. In the example of Figure 3-5, in the case of the 4N photographic mode, the end light area Y existing on one side of the cliff base area
The trailing edge of area It is.

The unexposed area Y of the photoreceptor exposed to light by the selective light emission of the LED array 17 is converted from the dark area potential to the bright area potential where no dust imager adheres and reaches the area G# 5, so that the area Y is no longer exposed.
1 gE eliminates all of the problems mentioned above (■ to ■) without causing black development. 〇x In the case of the VL fold method and the light-erasable photosensitive paper method, the problems caused by the occurrence of unexposed areas are similarly resolved. be done.

LED array 17 corresponding to various reduction 4I magnification factors
Selective light emission control of individual LEDs can be easily and accurately automatically controlled by utilizing a microcomputer circuit, for example, regardless of the size change or multi-stage change.

Further, when the photosensitive layer of the photoreceptor 1 is, for example, a CdS-based photosensitive layer,
The spectral sensitivity of that photoreceptor! +! f-character generally indicates a custom order like the one shown in the graph in Figure 6 (circle ○). On the other hand, the spectral wave* characteristics of a halogen rung generally used as the document illumination device 16 is a curve (b), and the lens transmittance characteristics of a projection optical system are generally curved (c). As shown in the figure of the mass photoreceptor 1 (the spectral sensitivity characteristic is shown as a dashed line curve), the strong line is separated from the good sensitivity region (e) of the actual sensitivity curve (a).Therefore, the LED array 17
By using the emission wavelength spectrum of the liquid volume in the good sensitivity region (E) of the actual sensitivity curve of the photoreceptor 1, and applying the light directly to the photoreceptor (3), a strong dark potential in the unexposed area Y can be generated. The potential can be effectively converted to the bright area potential with a small amount of emitted energy.

LED array 170: Make the individual LEDs small and arrange them closely; add small lenses to the 9 individual LEDs; provide partition plates on the 9 individual LED thresholds; etc. to give directionality to the light emitted by the individual LEDs. This makes it possible to clearly separate the boundary line between the light area X, which is the th image area, and the unexposed area Y, and perform lightless processing only on the tilted castle Y.

In addition, the exposure unit IRFi by the LED array 17 is also used as a blank exposure means for a portion of the photoreceptor surface during full-size copying and enlarged copying.

[Brief explanation of drawings]

Figure 's1 is a schematic diagram of the configuration of an example of a transfer-type electrophotographic ridge-forming machine, and Figure 2 is a diagram showing the generation of light areas in the photosensitive area during reduction copying in the N5 group m copy mode at the center of the line. Figure 3 is a similar thigh view in single @4 quasi-ridge photography mode. Figure 4 shows the original area of the center base 111411 [the development plane of the photoreceptor in copying mode, the original image pongee small projection area, and the roughening filling area; Figure 5 shows the original area of the center base 111411 [in copy mode] Figure 6 shows the spectral sensitivity l1jL of the CdS photoreceptor.
Characteristic graph of each food such as characteristics. 1 is a photoreceptor, 10 is an original table, 17 is an LED array, X is an original volatile reduction projection area, and Y is an unexposed area. Patent applicant: Canon Co., Ltd. Figure 4, Figure 5

Claims (1)

[Claims] (1) In an image forming apparatus that performs variable-magnification copying by projecting an original image onto a photoreceptor surface via an optical system capable of continuous variable-magnification projection or multi-stage variable-magnification projection. The LED array is placed so that its light emitting part side faces the photoreceptor surface,
The IJD array is arranged across the photoreceptor surface, and the individual I and HD along the length of the IJD array are arranged in an unexposed area outside the original image exposure area created by the optical system on the photoreceptor surface as the original image is reduced and projected. In order to uniformly expose the surface, light emission is selectively controlled according to the slenderness ratio. An image forming apparatus characterized by: