IMAGE GENERATING DEVICE

Abstract: An image-generating device which is provided with a white-color reflection plate (32) at a specific position of a component part supporting light source (21) used for illuminating the original document in order to prevent charge from being generated at the position where separation belt (55) comes into contact with the photo­ receptor (51), while the device sufficiently cancels charge by effectively applying tapered tip part of the white-color reflection plate (32) without causing black streak to be generated.

Description: The present invention relates to an image generating device of the kind referred to in the preamble portion of patent claim 1. Such an image generating device is known from DE-A-3 015 835. Any conventional image generating device which generates toner image on a copying paper needs to securely peel the toner-image-received copying paper. To achieve this, one of prior art image generating devices provides means for peeling the toner-image-received copying paper by applying a separation charger, while another device according to the prior art provides means for peeling the toner-image-received copying paper from the photoreceptor by applying the separation belt. In particular, the latter art provides means for preventing a toner image from being generated at the position where the separation belt comes into contact with the photoreceptor by radiating light reflected from the white-color reflection plate onto the edge of the surface of the photoreceptor. When operating the system incorporating the constitutions mentioned above, since the portion of the original document being shut off from illuminating light by the white-color reflection plate is imaged on the surface of the photoreceptor, this portion eventually turns out to be black streaks. To solve this problem, one of the prior art devices provides means for allowing a part of illuminating light from the light source to be radiated onto the original document despite the presence of the reflection plate to cause majority of illuminating light to be reflected by the reflection plate. More particularly, the JP-A-10160/1982 proposes in its FIG. 9 a system having small holes in a specific position of the reflection plate for allowing illuminating light to pass through these holes. This prior art also proposes provision of a reflection plate composed of such material allowing a specific amount of illuminating light to pass through it. In addition, this prior art proposes a constitution for setting up specific angles related to the installation of the mirror-surface reflection plate and edge cutoff angle within the surface which is perpendicular to the original document, and in addition, it provides a pair of luminous bodies. Details of these are shown in FIGS. 11 through 14 of the JP-A-10160/1982. Of these image-generating devices having the constitution described above, the device allowing part of illuminating light to pass through the reflection plate prevents noticeable black streaks to be generated. On the other hand, if a negligible amount of light passes through the reflection plate, the device cannot effectively prevent black streaks from being generated. Conversely, if an excessive amount of light passes through the reflection plate, charge present in the portion where the separation belt comes into contact with the edge of the photoreceptor surface cannot sufficiently be cancelled. The latter image generating device which arranges the installation angle of the mirror-surface reflection plate and the cutoff angle of edge and installs a pair of luminous bodies needs to ensure high-precision in the installation and cutoff operations. If the needed precision degrades, the device cannot sufficiently prevent black streaks from being generated, and yet, it cannot thoroughly eliminate the charge from the photoreceptor. DE-A-30 15 835 discloses an image generating device for sequentially generating images in a copying machine by moving a light source on a supporting member in a scanning direction for scanning an original document held on a substantially planar contact glass with light from the light source and focusing light reflected from the document by a lens onto a photoreceptor to form on the photoreceptor a latent image of the content of the original document, developing the latent image into a toner image, transferring the toner image onto a copying paper to provide a toner-image-received copied paper, and separating the toner-image-received copied paper from the photoreceptor using a separation means, in which device a substantially planar reflection plate is disposed on the supporting member in a first plane substantially parallel to a second plane defined by the contact glass for movement in the scanning direction to cancel charge present on a predetermined portion of the photo receptor coming into contact with the separation means. The primary object of the present invention is to securely eliminate a charge from the portion of the photoreceptor with which the separation belt comes into contact, further to prevent black streaks from being generated in the border between the charge-eliminated and charge-remaining portions of the photoreceptor. A further object of the present invention is to dispense with the needs for providing extreme precision for the installation and the shape of the white-color reflection plate used for cancelling charge. This object is accomplished with an image generating device as claimed in claim 1. Dependent claim 2 is directed on a feature of a preferred embodiment of the invention. Desirably, the tapered tip end of the white reflection plate should have the cutout portion on the side of the light source unit. The image generating device having the constitution mentioned above first causes light reflected from the original document illuminated by the light source to be focused by lens means and then allows static latent image to be generated by generating an image on the photoreceptor. The image generating device then develops the static latent image into a toner image before transferring the toner image onto the copying paper, and peels the copied paper from the photoreceptor using the separation belt. According to the characterizing feature of the invention, the device causes the charge to be eliminated from a specific portion of the photoreceptor with which the separation belt comes into contact by radiating light reflected from the white-color reflection plate onto the edge portion of the photoreceptor, while installing the white-color reflection plate to the predetermined position of the component member supporting the light source unit. This effectively prevents the toner image from being generated on the belt-contacting position of the photoreceptor and also prevents the separation belt from being soiled by toner, and yet, the system allows the copied paper to be securely peeled from the photoreceptor. Since the original document illuminating position continuously varies, two status with and without occurrence of black streak are sequentially generated, and as a whole, a charge on the photoreceptor corresponding to the portion under these status almost disappears to eventually prevent a noticeable black streak from being generated. If the tip end of the white-color reflection plate is cut off on the side of the light source unit, light from the light source unit is also led to the upper edge portion of the white-color reflection plate, thus allowing the system to more securely prevent black streaks from being generated. The present invention will be better understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention in which: FIG. 1 is the schematic diagram explaining the charge cancelling operation to be done at the edge of the photoreceptive drum related to the present invention; FIG. 2 is the plan showing the essential parts of the optical system related to the present invention; FIG. 3 is the perspective view showing the constitution of the optical system related to the present invention; and FIG. 4 is the schematic diagram denoting the internal constitution of the electrophotographic copying machine incorporating the image generating device related to the present invention. FIG. 4 is the schematic diagram denoting the internal constitution of the electrophotographic copying machine incorporating the image generating device related to the present invention. The copying machine body 1 is provided with a contact glass 11 and an original-cover 12 on the top surface, while mounted a detachable paper-feeding cassette 13 at the predetermined position of a lateral surface and a paper-receiving tray 14 at the predetermined position of the opposite lateral surface. The copying machine body 1 incoporates an optical system 2, a copy treatment section 5, and a conveying section 6, respectively. The optical system 2 comprises a light source 21 illuminating the original document (not shown) placed on the contact glass 11, a slit 27 controlling the width of passing of the reflected light, mirrors 22 through 24 conducting light reflected from the original document, a lens 25, and another mirror 26. The optical system 2 moves the light source 21 and the mirror 22 at a specific speed and the mirrors 23 and 24 at one-half the movement speed of the light source 21 and the mirror 22 to sequentially expose the full surface of the original document to light before forming an image of the original document on the copy treatment section 5. The light source 21 and the mirrors 22 through 24 are named generally as optical unit 3 hereinbelow. FIG. 3 is the detailed perspective view of the optical unit 3, while FIG. 2 is the plan showing the essential parts of the optical unit 3. The light source 21 and the mirror 22 are installed to the predetermined positions of a first frame member 31. A white-color reflection plate 32 extending itself in parallel with the light source 21 is integrally formed with the light source 21 at the predetermined position away from the right above of the light source 21. The tip portion of the white-color reflection plate 32 adjacent to the light source 21 is cut off so that the tapered shape is formed. The mirrors 23 and 24 are respectively installed to the predetermined positions of a second frame member 33. A guide shaft 34 supports the first and second frame members 31 and 33 so that these can slide themselves as required. A guide rail 35 allows these frame members 31 and 33 to slide themselves. Both ends of a wire 36 transmitting drive force to the optical unit 3 are secured to the predetermined positions of the copying machine body 1. An end of wire 36 is wound an interim roller 42 which is secured to the second frame member 33 and then the wire 36 is secured to a stationary plate 37 being installed to the first frame member 31. The wire 36 is then wound onto a wire drum 39 via a guide pulley 38 and then wound onto a guide pulley 41 via a tension pulley 40, which is finally wound onto an interim roller 42. The copy treatment section 5 has the constitution in which a charger 52, a developer 53, a transfer charger 54, a separation belt 55, and a cleaner 56, are respectively installed in the periphery of a photoreceptor drum 51 constantly rotating itself in one direction in the order mentioned above. The static latent image generated on the surface of the photoreceptor drum 51 by radiation of light reflected from the original document is then developed into toner image by the developer 53. The transfer charger 54 then transfers toner image to a copying paper P, and then the toner-image-received copied paper is peeled from the photoreceptor drum 51 by the separation belt 55, and finally, the residual toner is collected from the surface of the photoreceptor drum 51 by the cleaner 56. The conveying section 6 is comprised of a paper-feeding roller 61 feeding copying paper P from the paper-feeding cassette 13, a resist roller 62, conveying rollers 63 and 64, a thermo-fixation device 65, and a paper-discharging roller 66. The resist roller 62 conveys a copying paper P to toner-transferring part synchronous with the static latent image, and then, the toner-image-received copied paper P peeled from the photoreceptor drum 51 by the separation belt 55 is conveyed to the thermal fixation device 65 for thermally fixing toner image by the conveyor rollers 63 and 64, and finally, the paper-discharging roller 66 discharges the copy-completed paper P from the machine body 1 onto the paper-receiving tray 14. Referring now to FIG. 1, operations of the image-generating device having the above constitution related to the present invention are described in detail below. The copying machine incorporating the image-generating device related to the present invention first moves the optical unit 3 at a specific speed by transmitting drive force from the drive system (not shown) to the wire drum 39 so that the entire surface of the original document can sequentially be exposed to light. As the optical unit 3 moves, full-width area of the original document and the white-color reflection plate 32 are uniformly illuminated. The light reflected from these is then focused by the lens 25 via the slit 27 shown in FIG. 1 (A), and then, as shown in FIG. 1 (B), the static latent image corresponding to the image of the original document generated by causing image of the original document to be generated on the surface of the photoreceptor drum 51. More particularly, by effect of the light reflected from the white-color reflection plate 32, the charge at least in the portion R shown in FIG. 1 (B) in contact with the separation belt 55 can securely be cancelled. The static latent image corresponding to black streaks and the original document image is generated by the light reflected from such portions which are right above the light reflected from the original document and the edges of the white-color reflection plate 32. Note that, although no reflective light is actually present in such portions just mentioned above, the above description intentionally uses a term "reflective light" for explanatory convenience. However, since the black-streak-generating portions are sequentially variable relative to the movement of the optical unit 3, as a whole, static latent image close to white can be generated, and as a result, the image generating device related to the present invention securely prevents black streaks from being generated, thus eventually and significantly improving quality of the reproduced image. As is clear from the foregoing description, such portions of the photoreceptor drum 51 with which the separation belt 55 comes into contact generate satisfactory static latent image close to white without requiring significant improvement of precision related to the installation position and the edge shape of the white-color reflection plate 32. This allows the image generating device related to the present invention to securely prevent black streaks from being generated, and as a result, quality of the reproduced image can eventually and significantly be improved. As shown in FIG. 1 (C), since the preferred embodiment described above causes the light source 21 to obliquely radiate light against the position corresponding to the cutout portion of the white-color reflection plate 32, area allowing generating of black streaks is minimized, thus making it possible for the device related to the invention to generate satisfactory static latent image closer to white in those portions corresponding to edges of the white-color reflection plate 32. It should be understood that the present invention is not limitative of the preferred embodiment described above, but the present invention also allows the cutout portion of the white-color reflection plate 32 to be provided in a position remote from light source 21, and in addition, it also allows provision of cutout portions on both sides of the white-color reflection plate 32. Furthermore, it is also possible for the image generating device related to the invention to modify designs of the device in various ways without departing from the scope of the invention defined in the following claims.

Claims: Image generating device for sequentially generating images in a copying machine by moving a light source (21) on a supporting member (31) in a scanning direction for scanning an original document held on a substantially planar contact glass (11) with light from the light source (21) and focusing light reflected from the document by a lens (25) onto a photoreceptor (51) to form on the photoreceptor (51) a latent image of the content of the original document, developing the latent image into a toner image, transferring the toner image onto a copying paper (P) to provide a toner-image-received copied paper, and separating the toner-image-received copied paper from the photoreceptor (51) using a separation means (55), in which device a substantially planar reflection plate (32) is disposed on the supporting member (31) in a first plane substantially parallel to a second plane defined by the contact glass (11) for movement in the scanning direction to cancel charge present on a predetermined portion of the photoreceptor (51) coming into contact with the separation means (55), CHARACTERIZED IN THAT the reflection plate (32) terminates in an angled edge, said edge lying entirely in the first plane and being angled with respect to the scanning direction so as to intersect the scanning direction. Image generating device of Claim 1, in which said angled edge is straight shaped and is formed such that the leading end of the reflection plate (32) is positioned outwards of the trailing end. Image generating device of Claim 1, in which said angled edge is straight shaped and is formed such that the leading end of the reflection plate (32) is positioned inwards of the trailing end. Image generating device of Claim 1, in which said angled edge is turned at the midway point thereof such that said midway point is positioned inwards of the leading and trailing ends of the reflection plate (32).

Inventors: SHIBATA, KIYOSHI, TSUJI, KIKUNOSUKE
Applicants: MITA INDUSTRIAL CO., LTD.
Application year: 1987
Main classification: G03G15
IPC codes: G03G15, G03G21, B41J2