Abstract:
There is disclosed a cleaning apparatus which has a cleaning member for cleaning a surface of an image bearing member, a developer carrying member for carrying a developer cleaned by the cleaning member, a developer receiving member arranged below the cleaning member in a direction of gravity to receive the developer dropped from the cleaning member, and a developer carrying path for interconnecting the developer receiving member and the developer carrying member.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a cleaning apparatus for removing a developer on an image bearing member, a copying machine provided with this cleaning apparatus, and an image forming apparatus such as a printer. 
     2. Related Background Art 
     Conventionally, as an image forming apparatus of this type, there has generally been used an image forming apparatus for sticking toner to an electrostatic latent image electrostatically formed on a surface of a photosensitive member as an image bearing member to form a toner image, and electrostatically transferring this toner image to a transferring material (sheet, transparent film or the like). 
     In such an image forming apparatus, toner remaining (residual toner) on the photosensitive member without being transferred to the transferring material in transferring must be sufficiently removed each time in order to form a next image (image formation). As its cleaning means, means for pressing a cleaning blade made of an elastic material such as urethane rubber into contact with the surface of the photosensitive member to remove the residual toner has been put into wide practical use. 
     However, from the viewpoint of prolonging a life of a high-speed machine, in the image forming apparatus using an a-Si (amorphous silicon) photosensitive member, it is necessary to remove not only the residual toner but also various foreign objects such as deposited organic materials or corona products caused by presence of high-pressure members in the apparatus which may cause deterioration of image quality if stuck to the photosensitive member. These foreign objects cannot be removed completely only by the cleaning blade. 
     Therefore, in the case of the image forming apparatus using the a-Si photosensitive member and one component magnetic toner, integrally with the cleaning blade, a magnet roller may be arranged as removal assisting means in the vicinity thereof. That is, there has been used a method for removing various foreign objects in a slide-rubbing manner by using toner magnetism, collected toner and a magnetic brush formed on the magnet roller. The magnetic brush is uniformly formed by a toner coating amount regulating member. 
     Further, a constitution is employed where the toner coating amount regulating member and an end scraper are separately disposed and, through a gap between the two members, toner scratched off by the toner coating amount regulating member and the end scraper is smoothly sent to a waste toner carrying portion. 
     In addition to the foreign object removing operation, the aforementioned method has various advantages, such as prevention of so-called “blade tearing-off” which easily occurs when there is no toner at all on the surface of the photosensitive member by using the magnetic brush to supply toner little by little, and facilitation of toner removal by the blade by applying a mechanical force to the toner electrostatically stuck to the surface of photosensitive member to reduce a sticking force of the toner to the photosensitive member. The method has been effective to a certain extent in the image forming apparatus which uses only one component magnetic toner in order to obtain a black and white image. 
     Now, color toner in a multicolor image forming apparatus of two colors or more is usually prepared by mixing dyes or pigments in a transparent resin to make clear a color of a copy image, and it is often nonmagnetic toner. In the case of a constitution using only nonmagnetic toner including black toner, the residual toner is often removed by the aforementioned cleaning blade. 
     However, since control of toner concentration is not necessary for the one component magnetic toner, and a developing apparatus can be constituted to be simpler compared with two components, there have been seen examples of using it as black toner. In the case of such a constitution, if the cleaning apparatus having the magnet roller is applied, the color toner is not adsorbed by the magnet roller, which makes it impossible to prevent problems in a cleaning function. 
     A constitution which removes the magnet roller and depends only on the cleaning blade in order to coordinate the cleaning operation with the nonmagnetic toner is not advisable because of the aforementioned advantages of the magnet roller and a probably largest frequency of obtaining a black image. 
     That is, it is desired that cleaning of the nonmagnetic toner is carried out without losing the effects provided by the magnet roller in the cleaning of the magnetic toner. 
     Thus, when the nonmagnetic toner is actually collected in the cleaning apparatus comprising the magnet roller, first, the nonmagnetic toner is stuck to the magnetic toner on the magnet roller by the application of an electrostatic adsorbing force or van der Waals force to be removed. However, after supplying of the nonmagnetic toner to a certain extent, the toner is freed without being captured any more, and leaked to the outside. As a result, the toner may be scattered or stuck in a gap between the magnet roller to damage the cleaning function, or rubbed by the blade to be fused on the photosensitive member. 
     That is, while the magnetic brush formed around the magnet roller has a capturing function of nonmagnetic toner of a given amount or lower, further supplying of the nonmagnetic toner causes sudden deterioration of the capturing function. 
     Therefore, as one countermeasure, a method has been employed which prevents the deterioration of the cleaning function by supplying the magnetic toner to a cleaner at given intervals in accordance with a frequency of forming color images to reduce a ratio of the nonmagnetic toner. 
     However, according to the aforementioned conventional technology, the nonmagnetic toner is not completely bound by the magnet roller, and accumulated in a toner receiver below the magnet roller while a cleaning operation is repeated. As a result, a phenomenon called dripping occurs where the nonmagnetic toner is leaked from a toner container. 
     The toner scratched off by the toner coating amount regulating member is passed on the toner coating amount regulating member and guided to a waste toner carrying path, and then discharged to the outside of the machine by a waste toner carrying screw. However, while the magnetic brush of the magnet roller is rotated from the toner coating amount regulating member to a photosensitive drum, not a little nonmagnetic toner of a weak holding force is freed from the magnetic brush to be accumulated in the toner receiver. If the cleaning operation is repeated, the amount of accumulated toner only increases. 
     On the other hand, in the case of the magnetic toner, because of the application of a magnetic binding force, the amount of toner freed from the magnetic brush is small. Even if freed, the toner is recollected, and thus the toner accumulated in the toner receiver is never increased beyond a certain amount. 
     FIGS. 9,  10  and  11  show cases where toner coating amount regulating members are respectively a roller, a blade and a block. In these drawings, a reference numeral  5  denotes a magnet roller rotated in a direction of an arrow C. Similarly, a reference numeral  5   a  denotes a magnetic brush,  6  a waste toner carrying screw,  7  a cleaning blade,  8   a  a roller (toner coating amount regulating roller),  8   b  a blade (toner coating amount regulating blade),  8   c  a block (toner coating amount regulating block),  15  a photosensitive member (image bearing member, photosensitive drum) rotated in a direction of an arrow A,  25  a cleaning container,  28  a toner receiver,  29  a supporting member (also a wall member for separating the magnetic brush from a first waste toner carrying path),  32 ,  33  blades, and  35  the first waste toner carrying path. 
     In FIG. 9, if the toner coating amount regulating member is a roller  8   a , the roller  8   a  is supported on both side walls of the cleaning container  25 , and there are a blade  32  for scratching off toner scratched off by the roller  8   a , and a blade  33  for preventing reverse flowing of the toner from the first waste toner carrying path  35  to the toner receiver  28 . Besides, the supporting member  29  is present between the toner receiver  28  and the first waste toner carrying path  35  to support the blade  33 . Thus, the nonmagnetic toner accumulated in the toner receiver  28  is eventually leaked from a gap between the photosensitive member  15  and the cleaning container  25 , causing a phenomenon called dripping. 
     In the cases of FIGS. 10 and 11 where the toner amount regulating members are a blade  8   b  and a block  8   c , similarly, because of the presence of the supporting member  29  for supporting the blade  8   b  or a block  8   c  itself, dripping eventually occurs. 
     SUMMARY OF THE INVENTION 
     The present invention is a result of consideration given to the foregoing situation, and objects of the invention are to provide a cleaning apparatus capable of maintaining a stable cleaning function for a long time without any toner dripping, and an image forming apparatus. 
     According to a preferred embodiment for achieving the foregoing object, there is disclosed a cleaning apparatus which has cleaning means for cleaning a surface of an image bearing member, developer carrying means for carrying a developer cleaned by the cleaning means, a developer receiving member arranged below the cleaning means in a direction of gravity to receive the developer dropped from the cleaning means, and a developer carrying path for interconnecting the developer receiving member and the developer carrying means. 
     According to another preferred embodiment, there is provided an image forming apparatus which has image forming means for forming an image on an image bearing member by a developer, transferring means for transferring a developer image on the image bearing member to a transferring medium, cleaning means for cleaning a surface of the image bearing member after the transferring, developer carrying means for carrying a developer cleaned by the cleaning means, a developer receiving member arranged below the cleaning means in a direction of gravity to receive the developer dropped from the cleaning means, and a developer carrying path for interconnecting the developer receiving member and the developer carrying means. 
     According to these embodiments, the accumulation of developers dropped from the cleaning means to the developer receiver is prevented, and thus it is possible to limit dripping of the developers from the cleaning portion to a minimum. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a vertical sectional view schematically showing a constitution of an image forming apparatus of the present invention. 
     FIG. 2 is an enlarged vertical sectional view of a cleaning apparatus. 
     FIG. 3 is a perspective view seen from a toner reception side explaining a second waste toner carrying path. 
     FIG. 4 is a view showing a shape of a surface of a beam portion for forming the second waste toner carrying path, which is parallel to a toner receiver. 
     FIG. 5 is a view showing another type of a toner coating amount regulating member. 
     FIG. 6 is a view showing a sheet material disposed at a tip of the toner receiver and brought into contact with a surface of a photosensitive drum. 
     FIG. 7 is a view showing a toner carrying screw and its rotational direction. 
     FIG. 8 is a view showing a toner carrying screw and its rotational direction in the case of another apparatus arrangement. 
     FIG. 9 is a vertical sectional view showing a constitution of a conventional cleaner where a toner coating amount regulating member is a roller-shaped member. 
     FIG. 10 is a vertical sectional view showing a constitution of a conventional cleaner where a toner coating amount regulating member is a blade-shaped member. 
     FIG. 11 is a vertical sectional view showing a constitution of a cleaner where a toner coating amount regulating member is a block-shaped member. 
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Next, the preferred embodiments of the present invention will be described with reference to the accompanying drawings. Portions denoted by similar reference numerals in the drawings denote similar components and functions, and repeated explanation thereof will be omitted as occasion demands. 
     Embodiment 1 
     An example of an image forming apparatus of the present invention will be described by referring to FIGS. 1 to  8 . However, it should be understood that the scope of the present invention is not limited to dimensions, materials, shapes, relative arrangements thereof and the like, unless specified otherwise. 
     The image forming apparatus shown in FIG. 1 is a color image forming apparatus of an electrophotographic system which can form full-color images of four colors, i.e., magenta (M), yellow (Y), cyan (C) and black (K). This image forming apparatus comprises a drum type electrophotographic photosensitive member (referred to as “photosensitive drum”, hereinafter)  15 . An electrostatic latent image is formed on the photosensitive drum  15 , toner is stuck to the electrostatic latent image to develop the image, and the developed toner image is transferred to a transferring material (e.g., sheet or transparent film), whereby a full-color image is formed. 
     An image reading portion  100  is installed in the upper part of an image forming apparatus main body. At the image reading portion  100 , an original S placed on an original glass base  30  is exposed and scanned by an exposure lamp. Accordingly, a reflected light image from the original S is converged on a full-color sensor  14  by mirrors  12   a ,  12   b  and  12   c  and a lens  13  to obtain a color separation image signal. 
     The color separation image signal is passed through an amplifier circuit (not shown), processed by a video processing unit (not shown), and sent out to an image forming portion  200 . At the image forming portion  200 , when a signal of an image forming state is entered, the photosensitive drum  15  which is an image bearing member is first rotary-driven in an direction of an arrow A by driving means (not shown). Around the photosensitive drum  15 , there are arranged a pre-exposure lamp  16 , a corona electrifier  17 , a laser exposure optical system  18  which is exposing means, a potential sensor  19 , a cleaning apparatus (cleaner)  24 , a fixed black developing device  21 K, three rotatable color developing devices  20 M,  20 Y and  20 C, and an intermediate transferring member (intermediate transferring belt)  9 . The developing devices  20 M,  20 Y and  20 C perform development in this order by toner of magenta, yellow and cyan. Incidentally, the color developing devices  20 M,  20 Y and  20 C use nonmagnetic toner, while the black developing device  21 K uses magnetic toner. 
     In the laser exposure optical system  18 , the image signal from the image reading portion  100  is converted into an optical signal at a laser output portion (not shown), the converted laser beam is reflected on a rotary polygon mirror  18   a , and projected through a lens  18   b  and a mirror  18   c  to the surface (outer peripheral surface) of the photosensitive drum  15 . In image formation, the photosensitive drum  15  is rotated in the direction of the arrow A, the photosensitive drum  15  discharged by the pre-exposure lamp  16 ′ is uniformly charged to a predetermined polarity/potential by the corona electrifier  17 , and the optical image is subjected to irradiation for each separation color, whereby an electrostatic latent image is formed. 
     Each of the color developing devices  20 M,  20 Y and  20 C is detachably held by a developing rotary  23  rotated around a rotary shaft  22 . In image formation, each developing device  20 M,  20 Y and  20 C is rotated and moved around the rotary shaft  22  in the state of being held by the developing rotary  23 , and the developing device  20 M,  20 Y and  20 C used for development is stopped in a developing position opposite the photosensitive drum  15 . Further, after a developing sleeve is positioned to face the photosensitive drum  15  by a very small gap, toner is stuck corresponding to the electrostatic latent image of the photosensitive drum  15  to develop a toner image. 
     In color image formation, the developing rotary  23  is rotated for each rotation of the intermediate transferring member  9  in a direction of an arrow B, and a developing process is carried out for the magenta developing device  20 M, the yellow developing device  20 Y, the cyan developing device  20 C and the black developing device  21 K in this order. 
     The toner image made visible by each developing device  20 M,  20 Y and  20 C on the photosensitive drum  15  is multi-transferred (primary transfer) four times (each image of four colors M, Y, C and K). Accordingly, the intermediate transferring member  9  is rotated in the direction of the arrow B in synchronization with an outer peripheral velocity of the photosensitive drum  15 . Incidentally, for the photosensitive drum  15  after the primary transfer of the toner image, toner remaining (residual toner) on the surface of the photosensitive drum  15  without being transferred to the intermediate transferring member  9  is removed by the cleaning apparatus  24  for each primary transfer of the toner image of each color, and the photosensitive drum  15  is thereby set ready for forming a toner image of a next color. 
     The intermediate transferring member  9  to which the toner image has been multi-transferred holds a transferring material  11  between itself and a transferring roller  10  (secondary transferring roller)  10 , and conveys it. Thus, the transferring material  11  receives simultaneous multi-transfer of the toner images of the respective colors on the intermediate transferring member  9 , and then it is conveyed toward a fixing apparatus  26  for carrying out fixing of a next process. 
     The transferring material  11  holding the toner image on the surface conveyed to the fixing apparatus  26  is conveyed by a fixing roller  27   a  and a pressure roller  27   b , heated and pressurized, whereby the toner image is fixed on the surface. After the toner image fixing, the transferring material  11  is discharged to the outside of the image forming apparatus main body. Thus, the image formation of the full-color images of the four colors is finished. 
     FIG. 2 is an enlarged explanatory view of the cleaning apparatus  24 . 
     The reference numeral  8   b  in the drawing is a blade-shaped toner coating amount regulating member made of a nonmagnetic material. For example, it is constituted of a nonmagnetic metal blade (stainless or the like). The reference numeral  6  denotes a waste toner carrying screw (waste toner carrying means). 
     A cleaning blade  7  which base end side (upper end side in FIG. 2) is fixed to a part (not shown) of a cleaning container  25  presses one edge  7   a  of its tip side (lower end side in FIG. 2) into contact with the surface of the photosensitive drum  15 , and scratches off residual toner left on the surface of the photosensitive drum  15  after transfer. The cleaning blade  7  is made of, for example a material having elasticity. For example, it may be made of urethane rubber or the like. A magnet roller  5  is arranged on the upstream side of the cleaning blade  7  seen from a moving direction (direction of the arrow A) of the surface of the photosensitive drum  15 . The magnet roller  5  is rotary-driven in a direction of an arrow C, and its surface is moved in the same direction as the moving direction (direction of the arrow A) of the surface of the photosensitive drum  15 . As the magnetic toner and the nonmagnetic toner are supplied by the developing devices  20 M,  20 Y,  20 C and  21 K, a part of the collected magnetic toner (referred to as collected toner hereinafter as occasion demands) forms a magnetic brush  5   a  which is a toner layer of a certain thickness decided by the toner coating amount regulating member  8   b  on the surface of the magnet roller  5 . 
     The toner coating amount regulating member  8   b  is arranged so that a thickness of the formed toner layer can be properly set larger than a minimum gap between the photosensitive drum  15  and the magnet roller  5 . The toner layer reaches a position opposite the photosensitive drum  15  following rotation of the magnet roller  5  to carry out sure slide-rubbing on the surface of the photosensitive drum  15 . The collected toner scratched off by the toner coating amount regulating member  8   b  is passed on the toner coating amount regulating member  8   b  and guided to a first waste toner carrying path  35 . It is then carried in an axial direction by rotation of the waste toner carrying screw  6 , and discharged to the outside. 
     The toner (mainly nonmagnetic toner) broken away while the magnetic brush  5   a  of the magnet roller  5  is rotated from the toner coating amount regulating member  8   b  to the photosensitive drum  15  drops onto a toner receiver  28  below the magnet roller  5 . The toner receiver  28  has an inclination descending from the magnet roller  5  toward the first waste toner carrying path  35 , and the nonmagnetic toner dropped to the toner receiver  28  is carried toward the first waste toner carrying path  35  by its own weight. Incidentally, toner carrying of the toner receiver  28  by its own weight can be effectively carried out by an inclination of about 20° from a horizontal direction as indicated by θ in FIG.  2 . 
     Between the toner receiver  28  and the first waste toner carrying path  35 , a supporting member  29  is disposed to project upward. This supporting member  29  supports the aforementioned toner coating amount regulating member  8   b  on its upper surface, and its lower part is supported by a plurality of toner reverse-flow preventing blades (beam portion)  34 . The supporting member  29  is also a wall member for separating the toner receiver  28  from the first waste toner carrying path  35 . 
     The plurality of toner reverse-flow preventing blades  34  form a ladder-shaped second waste toner carrying path  37  between the toner receiver  28  and the first waste toner carrying path  35 . As shown in FIG. 3, the toner reverse-flow preventing blades  34  are constituted of members having a wedge sectional shape (sectional shape parallel to the toner receiver  28 ) along a toner moving direction, and the plurality thereof are mounted in left and right directions (axial direction of the magnet roller  5 ). In the toner reverse-flow preventing blades  34 , as shown in FIG. 4, a sharp tip  34   a  is directed to the toner receiver side, and a wider base end  34   b  is directed to the first waste toner carrying path side. Further, the toner reverse-flow preventing blades  34  may be mounted by being inclined in a direction perpendicular to a moving direction (direction of an arrow K in FIG. 3) of toner carried in the first waste toner carrying path  35 . That is, when seen from the direction of the arrow K, the toner reverse-flow preventing blades  34  are inclined so that the base end  34   b  is positioned on the downstream side and the tip  34   a  is positioned on the upstream side. The second waste toner carrying path  37  is formed between the adjacent toner reverse-flow preventing blades  34 , and the nonmagnetic toner carried from the toner receiver  28  by its own weight is smoothly moved to the first waste toner carrying path  35  without being blocked by the toner reverse-flow preventing blades  34  because of the wedge shape of the toner-reverse flow preventing blades  34 . Further, for the nonmagnetic toner which has passed through the toner reverse-flow preventing blades  34  and entered the first waste toner carrying path  35 , since the toner reverse-flow preventing blades  34  are mounted by being inclined as described above, it is difficult to move from the first waste toner carrying path  35  to the toner receiver  28  side in the process of being carried in the direction of the arrow K by the waste toner carrying screw  6 . 
     Additionally, as shown in FIG. 5, if the toner coating amount regulating member  8   a  is a roller, by providing the inclination of the toner receiver  28  and the second waste toner carrying path  37 , even when the toner reversely flows from the first waste toner carrying path  35  toward the toner receiver  28 , the toner is carried again to the first waste toner carrying path  35 . Accordingly, the toner reverse-flow preventing blades  34  are not always necessary. However, preferably, the toner reverse-flow preventing blade  34  is disposed because such reverse-flowing toner has a direct effect on the magnetic brush  5   a.    
     Further, by loading a sheet material  36  such as a urethane sheet from the toner receiver  28  on the photosensitive drum  15 , it is possible to completely prevent dripping of toner from the cleaning container  25 . This sheet material  36  is constituted of, for example a resin sheet of polyethylene terephthalate (PET) or urethane. 
     Furthermore, when the waste toner is discharged to the outside of the machine by the waste toner carrying screw  6 , depending on a winding direction and a rotational direction of the waste toner carrying screw  6 , there are a case where the waste toner is carried by being pressed to the outlet side of the second waste toner carrying path  37  and a case where the waste toner is carried by being pressed to the wall of the cleaning container  25  of the opposite side. If the amount of waste toner is large, when the waste toner is carried by being pressed to the outlet side of the second waste toner carrying path  37 , there is a possibility of closing of the outlet by the waste toner or its reverse-flowing. 
     Thus, if the cleaning apparatus  24  is arranged to the left of the photosensitive drum  15  as in the embodiment shown in FIGS. 1 and 2, as shown in FIG. 7, the waste toner carrying screw  6  is wound counterclockwise, and its rotational direction is clockwise. On the other hand, if the cleaning apparatus  24  is arranged to the right of the photosensitive drum  15  (not shown), as shown in FIG. 8, the waste toner carrying screw  6  is wound clockwise, and its rotational direction is counterclockwise. According to this constitution, since the carried toner approaches a side opposite the outlet of the second waste toner carrying path  37  by the carrying operation of the screw, the waste toner can be discharged to the outside of the machine without closing the outlet of the second waste toner carrying path  37 , and without any reverse-flowing from the second waste toner carrying path. 
     The embodiment has been described by way of example where the toner coating amount regulating member is blade-shaped. However, while the foregoing basic constitution is maintained, a roller-shaped or block-shaped toner coating amount regulating member can be used. In this case, effects similar to the foregoing can be obtained. However, in the case of the block-shaped member  29 , the member itself is equivalent to the supporting member of the embodiment.