Patent Publication Number: US-9897967-B2

Title: Cleaning unit and image forming apparatus

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a cleaning unit, to an image bearing unit including the cleaning unit, and to an image forming apparatus including the cleaning unit. 
     Description of the Related Art 
     An electro-photographic image forming apparatus is configured to form an image by transferring a toner image formed on an image bearing unit such as a photosensitive drum, intermediate transfer body etc., onto a recording medium such as a sheet of paper, plastic etc. 
     Conventionally, the image forming apparatus such as one disposed in Japanese Patent Application Laid-open No. 2006-139084 (see FIG. 8 thereof) for example is configured to remove unused toner left on the image bearing unit by a cleaning blade 525 and to recover the toner within a drum cartridge 600. The recovered toner is conveyed by a toner conveying member installed near the cleaning blade 525 to a waste toner container (recovered toner box) outside of the drum cartridge from an aspect of prolonging a life of the process cartridge. 
     As a toner conveyer member, there is a case of adopting a toner conveying screw formed into a cylindrical (spring) shape by spirally winding a metallic wire rod (for instance, a screw 622 in Japanese Patent Application Laid-open No. 2006-139084). This toner conveying screw is disposed within a cylindrical toner conveying path and is rotationally driven by a driving system, e.g., a screw gear 526 in the abovementioned disclosure. As for the rotational driving force of the toner conveying member of this sort, there is a case of transmitting a rotational driving force from a driving system rotationally driving a photosensitive drum within a drum cartridge through a drum gear, besides using an independent driving source. 
     Although there is also known a screw type toner conveying member in which a blade is molded spirally around a center shaft (metallic or resin-made), the screw formed into the cylindrical shape by the spring as described above has advantages over the conventional one in that it enables to downsize, lighten, simplify, and lower the cost of the toner conveyer unit. 
     In connecting the driving system (screw gear) with the cylindrical (spring) screw, i.e., the toner conveying member, to transmit the driving force to the toner conveying member, there is a case of using a support structure of axially supporting the toner conveying member by tensioning from both ends of the toner conveying member, similarly to the case of the screw having the center shaft. 
     However, conventionally, a structure of connecting the driving system (screw gear) rigidly and integrally with the toner conveying screw even if the toner conveying screw is formed of the cylindrical (spring) screw is often adopted. Then, if the cylindrical (spring) screw generates vibration in such conventional structure, the vibration is transmitted to the driving system (screw gear). 
     Here, a possible factor of the vibration of the toner conveying screw is a reaction force received by the screw when the screw conveys recovered toner within a drum cartridge. This reaction force can be decomposed into a force mainly in a toner conveying direction (expansion direction) and a force in a screw rotating direction (twist direction). 
     If the screw vibrates due to the reaction force and the vibration is transmitted to the image bearing unit, it is not preferable because the image bearing unit may vibrate. Accordingly, a configuration that can reduce vibration energy transmitted from the screw to the image bearing unit is required. 
     SUMMARY OF THE INVENTION 
     The present disclosure provides a cleaning unit configured to reduce vibration of the spring screw. One feature of the present invention is the cleaning unit configured to clean toner left on an image bearing unit including a cleaning member configured to remove the toner, a coil spring conveying the toner removed by the cleaning member in a longitudinal direction of the cleaning member, and a support member being rotatable and supporting one end of the coil spring to transmit a rotational driving force to the coil spring. The support member is provided with a long hole lengthy in the longitudinal direction of the coil spring such that one end of the coil spring engages with the long hole. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a section view schematically illustrating a structure of an electro-photographic image forming apparatus. 
         FIG. 2  is section view illustrating a main part of a drum cartridge employed in the image forming apparatus in  FIG. 1 . 
         FIG. 3  is a perspective view illustrating an appearance of the drum cartridge employed in the image forming apparatus in  FIG. 1 . 
         FIG. 4  is a perspective view illustrating a driving system of the drum cartridge illustrated in  FIGS. 2 and 3 . 
         FIG. 5  illustrates an exemplary structure of the cleaning unit. 
         FIG. 6A  illustrates a state in which a toner conveying screw is located at a reference position in a driving-side support member supporting one end of the toner conveying screw of the cleaning unit in which the present disclosure is adopted. 
         FIG. 6B  illustrates a state in which the toner conveying screw is elongated in the driving-side support member supporting one end of the toner conveying screw of the cleaning unit in which the present disclosure is adopted. 
         FIG. 6C  illustrates a state in which a toner conveying screw is contracted in the driving-side support member supporting one end of the toner conveying screw of the cleaning unit in which the present disclosure is adopted. 
         FIG. 7  illustrates a driven-side support member supporting another end of the toner conveying screw in the cleaning unit in which the present disclosure is adopted. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     An embodiment for carrying out the present disclosure will be described below with reference to the appended drawings. It is noted that the embodiment described below is one exemplary embodiment of the present disclosure to the end, and a person skilled in the art may appropriately modify detailed configurations for example within a scope not departing from a gist of the present disclosure. Still further, numerical values adopted in the embodiment are referential numerical values and do not limit the present disclosure. It is also construed that sizes, materials, forms, relative dispositions of components described below are also appropriately modified depending on a configuration and on various conditions of an apparatus to which the present disclosure is applicable, and the scope of the present disclosure is not limited only to those configurations unless specifically described. 
     Embodiment 
     Overall Structure of Image Forming Apparatus 
       FIG. 1  illustrates one example of an entire configuration of an image forming apparatus  1  capable of carrying out the present disclosure. The image forming apparatus  1  in  FIG. 1  includes image bearing units (electro-photographic photosensitive bodies) forming respective color toner images of yellow, magenta, cyan and black and is configured to record a color image on a recording medium such as a sheet of paper and a film. The image forming apparatus  1  includes four photosensitive drums  12   a  (yellow),  12   b  (magenta),  12   c  (cyan) and  12   d  (black) disposed in parallel with each other. An intermediate transfer belt  16 , i.e., an intermediate transfer body, is disposed above the photosensitive drums  12   a  through  12   d  in a manner orthogonally crossing the respective photosensitive drums. 
     Disposed around each photosensitive drum ( 12   a  through  12   d ) driven by a motor (not illustrated) are a primary charger  13 , a developing device  14  and others. The photosensitive drum ( 12   a  through  12   d ) and the primary charger  13 , the developing device  14  and others can be unitized as a process cartridge ( 1   a ,  1   b ,  1   c , and  1   d ) attachable/detachable to/from the image forming apparatus  1 . An exposure unit  41  composed of polygonal mirrors and others is disposed under the photosensitive drums  12   a  through  12   d . It is noted that in  FIG. 1 , although reference numerals of the primary charger  13 , the developing device  14  and a transfer charging roller  19  described later are denoted only to those of the process cartridge  1   a  in order to avoid complications, those devices are provided in the same manner also in the process cartridges  1   b ,  1   c , and  1   d  (only their shapes are illustrated). 
     At first, a laser beam composed of an image signal of yellow component color is projected to the photosensitive drum  12   a  in a first image forming portion through the polygon mirror and others of the exposure unit  41  to form an electrostatic latent image on the photosensitive drum  12   a . Yellow toner is supplied to the electrostatic latent from the developing device  14  to visualize the electrostatic latent as a yellow toner image. 
     Along with a rotation of the photosensitive drum  12   a , the toner image arrives at a primary transfer position where the photosensitive drum  12   a  comes into contact with an intermediate transfer belt  16 . The yellow toner image on the photosensitive drum  12   a  is transferred onto the intermediate transfer belt  16  by a primary transfer bias applied to a transfer charging roller  19  at the primary transfer position (primary transfer step). 
     When a region of the intermediate transfer belt  16  carrying the yellow toner image moves to a next image forming portion, a magenta toner image which has been formed onto the photosensitive drum  12   b  by this time as described above. Then, the magenta toner image is superimposed and transferred by the transfer charging roller  19  onto the yellow toner image on the intermediate transfer belt  16  at a primary transfer position where the intermediate transfer belt  16  comes into contact with the photosensitive drum  12   b . Then, as the intermediate transfer belt  16  moves along, a cyan toner image and subsequently a black toner image are sequentially superimposed and transferred onto the yellow and magenta toner images at primary transfer positions of the respective image forming portions. 
     Meanwhile, a recording medium P is stored in a cassette  30 . The recording medium P is delivered one by one from the cassette  30  by a pick-up roller, is adjusted in its timing by a registration roller  40 , and then arrives at a secondary transfer position. The four-color toner image on the intermediate transfer belt  16  is transferred collectively onto the recording medium P by a secondary transfer bias applied to the secondary transfer roller pair  17 , i.e., a transfer portion, at the secondary transfer position (secondary transfer step). 
     The recording medium P onto which the four color toner image has been transferred is conveyed to a fixing roller pair  20 , i.e., a fixing device, disposed above the secondary transfer roller pair  17  by being guided by a conveyer guide. The four-color toner image on the recording medium P is fixed by receiving heat and pressure through the fixing roller pair  20 . Thus, the respective color toners melt, are blended, and are fixed as a full-color print image on the recording medium P. Then, by being guided by a conveyer guide, the recording medium P on which the toner image has been fixed is discharged onto a discharge tray  23  by discharge roller pairs  25   a  and  25   b , i.e., a discharge portion, provided downstream of the fixing roller pair  20 . 
     In a case of one-sided mode of forming an image only on one surface of the recording medium P, the recording medium P on which the image has been formed on one surface thereof is discharged onto the discharge tray  23  by the discharge roller pairs  25   a  and  25   b  as described above. Meanwhile, in a case of a duplex mode of forming images on both surfaces of the recording medium P, the recording medium P on which the image has been formed on one surface as described above is conveyed to a registration roller pair  22  in a state in which front and back surfaces thereof are reversed by passing through a duplex pass not illustrated. After that, an image is formed on the back surface of the recording medium P through a step similar to that of forming the image on the front surface. The recording medium P on which the images are formed on the front and back surfaces thereof is discharged onto the discharge tray  23  by the discharge roller pairs  25   a  and  25   b.    
     A life of a transfer belt unit  18  in which the process cartridges  1   a  through  1   d , the rollers  16   a  and  16   b  driving the intermediate transfer belt  16 , the transfer charging roller  19  and others are unitized is short, by its very nature, as compared to the entire image forming apparatus  1 . Therefore, the process cartridges  1   a  through  1   d  and the transfer belt unit  18  are configured to be replaceable during when the image forming apparatus  1  completes its entire life. It is possible to improve maintainability by unitizing the both process cartridges  1   a  through  1   d  and the transfer belt unit  18  and making them attachable/detachable. 
     Then, lately, there are electro-photographic image developing systems of single component toner and dual component toner developing systems. Along with the colorization, a dual component developer which is separated into toner and carrier is widely used from an aspect of a color developing nature. Meanwhile, in terms of a developing device of black color, the developing system is used separately depending on its use such that the single component developing system is used in a case where the device is required to be downsized and its space to be saved, while the dual component developing system is used in a case of a high-speed device. Still further, although a percentage between mono-chrome images and color images to be formed is gradually shifting to color images in the market, a number of mono-chrome images to be printed by an image forming apparatus are overwhelmingly greater than that of color images even though the image forming apparatus is configured to print mono-chrome and color images. Accordingly, durability of the black developer is desired to be longer than that of color developers. 
     On the other hand, a color image requires more faithful rendering performance, and an image forming apparatus forming images in a level of picture image quality is being developed. Accordingly, the size of toner particle to be used in such case is desirable to be as small as possible and a diameter thereof to be uniform. The market also demands to prolong a service life of periodic replacement components required to cut a running cost to suppress a maintenance cost. Lately, some developing device adopts an ACR (auto-carrier refreshing) system or downsizes a developing sleeve of the developing device to suppress deterioration and to prolong a life of the developer. Then, a color developing device capable of printing images equivalent to about a half million A4 size sheets is available in the market. 
     Drum Cartridge 
     In the present embodiment, the toner conveyer unit includes a toner conveying screw as a toner conveying member configured to discharge unused toner collected by cleaning toner remaining on the image bearing unit (photosensitive drum), to carry an electro-photographically formed toner image. 
     This toner conveyer unit is disposed together with a cartridge, e.g., the process cartridges  1   a  through  1   d , containing the image bearing unit (photosensitive drum). Several different configurations are conceivable for the ‘cartridge’ as such an image bearing unit. For instance, there is known a configuration of a process cartridge storing the developing device  14  described above, the photosensitive drum  12 , the cleaning blade  320   a , a primary charger  13  and a waste toner container not illustrated within one cartridge. There is also known a separate type in which only the developing device part is separated as a separate unit and the photosensitive drum, the primary charger, the cleaning blade, the toner conveyer unit and others are unitized as a drum cartridge. 
     Regardless of such cartridge configurations, the toner conveyer unit of the present disclosure can be carried out as a unit conveying the recovered toner generated in cleaning the photosensitive drum. The following description will be made by exemplifying a configuration of using a separate type process cartridge especially on exemplary configurations of the toner conveyer unit disposed around the drum cartridge as the image bearing unit. 
     In the case of the configuration of the separate cartridge, a region of the photosensitive drum ( 12   a  through  12   d ) of the process cartridges  1   a  through  1   d  illustrated in  FIG. 1  can be unitized as a drum cartridge  10  as illustrated in  FIG. 2  for example. 
       FIG. 2  illustrates a sectional structure of a main part of the drum cartridge  10 . The drum cartridge  10  in  FIG. 2  includes the photosensitive drum  12  ( 12   a  through  12   d  in  FIG. 1 ) within a drum frame  301  (casing). A cleaning blade  320   a , the primary charger  13 , a scoop sheet  316  and others are disposed around the photosensitive drum  12  within the drum frame  301 . 
     While the photosensitive drum  12  around 30 mm in diameter is often used in general, the cleaning blade  320   a  made of a plate-like urethane material for example is urged so as to come into with the photosensitive drum  12  to scrape the residual toner on the surface of the photosensitive drum  12  in the drum cartridge  10 . In the configuration in  FIG. 2 , the cleaning blade  320   a  is attached to a frame  320  and is configured such that a tip of the cleaning blade  320   a  comes into contact with the photosensitive drum  12  by being urged by an urging device  340  such as a spring configured to urge the frame  320 . 
     The unused toner on the surface of the photosensitive drum  12  scraped by the cleaning blade  320   a  is conveyed to a waste toner container not illustrated by a toner conveying screw  414  disposed in parallel with the photosensitive drum  12  from an aspect of prolonging a life of the process cartridge. The toner conveying screw  414  is composed of a wire rod formed into a cylindrical spring as described later. The toner conveying screw  414  conveys the toner by being rotationally driven within a toner conveying path  414   e  through a driving system transmitting a driving force of the photosensitive drum  12  in the present embodiment. 
     It is noted that in the drum cartridge  10  in  FIG. 2 , the scoop sheet  316  is disposed in a vicinity of the cleaning blade  320   a  to prevent the toner from scattering within the apparatus. Further in the drum cartridge  10  in  FIG. 2 , the primary charger  13  is composed of a primary charging roller  317  and a cleaning roller  318 . 
     The structure of the drum cartridge  10  of the present embodiment will be described in detail below with reference to  FIGS. 3 through 6 .  FIG. 3  illustrates an appearance of the drum cartridge  10 . As illustrated in  FIG. 3 , the drum frame  301  is provided with through-holes at positions agreeing with a center shaft of the drum to dispose bearing portions  326  and  327  such as bearings and sintered bearings. A drum shaft  309  is inserted through the bearing portions  326  and  327 . This arrangement makes it possible to axially support and to rotationally driven the photosensitive drum  12  in high precision. Still further, the drum shaft  309  is in contact with an inner surface of the drum through a contact point not illustrated and provided within the photosensitive drum  12  to be electrically conductive and to be connected with the earth. 
     As illustrated in  FIG. 4 , disposed at an end of the photosensitive drum  12  is the driving system composed of a drum gear  401 , an idler gear  402 , and a screw gear  403  as a drive receiving portion transmitting the rotation of the photosensitive drum  12  (image bearing unit) to the toner conveying screw  414 . 
     The photosensitive drum  12  is coupled integrally with the drum gear  401  in  FIG. 4  by pressure-fitting, caulking and others. The rotational driving force transmitted from a driving source such as a motor disposed on the unit body side not illustrated to the drum shaft  309  is transmitted to the drum gear  401  and the photosensitive drum  12  through a parallel pin or the like not illustrated and provided integrally with the drum shaft  309 . Meanwhile, the screw gear  403  is coupled integrally with a driving-side support member  411  composing a support member of one end side of the toner conveying screw  414 . The driving-side support member  411  is supported by the drum frame  301  through a support member bearing  413 . Still further, another end side of the toner conveying screw  414  is supported by a driven-side support member  412  (other end support member in  FIG. 7 ), and a position of the other end of the toner conveying screw  414  having the cylindrical spring structure is restricted in a longitudinal direction (toner conveyance direction). 
     Along with an advance of an image forming process, the rotational driving force applied to the photosensitive drum  12  is transmitted to the driving-side support member  411  through the driving system composed of the drum gear  401 , the idler gear  402  and the screw gear  403 . Thus, the toner conveying screw  414  is rotationally driven. This arrangement makes it possible to advance the process of forming the image on the surface of the photosensitive drum  12  and to convey and recover the unused toner, scraped by the cleaning blade  320   a  (see  FIG. 2 ), by the toner conveying screw  414  in the same time. 
     Here, a configuration as illustrated in  FIGS. 5 and 6A through 6C  are conceivable as exemplary structures for supporting the toner conveying screw  414 . As illustrated in  FIG. 5 , a toner conveying screw  414  formed of a wire rod for a cylindrical spring includes a driving-side screw end  414   a , i.e., a spring free end. 
     A driving-side support member  411  on a side of a screw gear  403  includes a long hole  411   a  in a longitudinal direction of the toner conveying screw  414 . Conventionally, there is known a configuration of hooking the driving-side screw end  414   a , i.e., the spring end, of the toner conveying screw  414  to a long hole one end  411   b , in order to extend the toner conveying screw  414  to always apply a tension to the toner conveying screw  414  during an entire driving period. Thus, in this tensioned-spring configuration, the toner conveying screw  414  is connected rigidly and integrally with the screw gear  403  specifically in terms of the longitudinal direction (toner conveyed direction). 
     For instance, the conventional structure assumes a longitudinal dimensional tolerance of the driving-side screw end  414   a  of the toner conveying screw  414  of ±1.0 mm and a spring maximum expansion amount in conveying toner of around 0.2 mm. Then, an entire length of the toner conveying screw  414  to the driving-side screw end  414   a  is set to be shorter than the position of the long hole one end  411   b  by around 2 mm. This arrangement makes it possible to always apply the tension to the toner conveying screw  414  during the entire driving period especially in the longitudinal direction (toner conveying direction) even if the tolerance of the toner conveying screw  414  is minimum and to connect the toner conveying screw  414  almost rigidly and integrally with the screw gear  403 . 
     However, if the tension is always applied to the toner conveying screw  414  especially in the longitudinal direction (toner conveyer direction) and the toner conveying screw  414  is almost rigidly and integrally connected with the screw gear  403  as in the conventional structure, the abovementioned vibration problem would be raised. That is, there is a possibility that the vibration energy having the components in the expansion (or contraction) direction A and the twist direction B of the toner conveying screw  414  is transmitted to the screw gear  403 . Then, there is also a possibility that the vibration transmitted from the toner conveying screw  414  to the screw gear  403 , i.e., a drive transmitting portion, causes rotational fluctuation of the drum gear  401 , i.e., rotational fluctuation of the surface of the photosensitive drum  12 . This fluctuation may cause an image forming failure such as pitch irregularity as described above. Here, a reaction force containing the respective components in the toner conveying direction (expansion direction A) and in the screw rotating direction (twist direction B) may be cited as a factor of vibrating the toner conveying screw  414  of the toner conveyer unit. 
     Then, according to the present embodiment, the support member supporting one end of the toner conveying screw  414  is constructed so as to support the driving-side screw end  414   a , i.e., one end of the toner conveying screw  414 , movably in the longitudinal direction (toner conveying direction) as illustrated in  FIGS. 6A through 6C . This support member is also constructed to transmit the rotational driving force in a rotational driving direction of the driving system ( 401  through  403 ) to the driving-side screw end  414   a , i.e., one end of the toner conveying screw  414 . 
     Specifically, the support member of the toner conveying screw  414  is constructed as illustrated in  FIGS. 6A through 6C  for example. 
     As illustrated in  FIGS. 6A through 6C , the toner conveying screw  414  includes a center region where a winding pitch is relatively sparse and contributes to the conveyance of the toner and a positioning portion  414   d  where the winding pitch is relatively dense between the center region and the driving-side screw end  414   a , i.e., the spring free end of the toner conveying screw  414 . An inner diameter of the positioning portion  414   d  is larger than an outer diameter of the driving-side support member  411  with a slight margin, and the positioning portion  414   d  is slidable in the longitudinal direction (toner conveying direction) with respect to the driving-side support member  411 . Still further, the entire toner conveying screw  414  is positioned coaxially with the driving-side support member  411  by the engagement of the positioning portion  414   d  and the driving-side support member  411 . 
     A part continuing from the positioning portion  414   d  to the driving-side screw end  414   a , i.e., the screw free end, of the toner conveying screw  414  is entered to the center part of the driving-side support member  411  from a through-hole on a back surface side of  FIGS. 6A through 6C  for example, and a tip thereof is bent to construct as the driving-side screw end  414   a . Then, the driving-side screw end  414   a  is engaged within the long hole  411   a.    
     As illustrated in  FIG. 6A  for example, the long hole  411   a  provided through the driving-side support member  411  composes an engage portion engaging with one end of the toner conveying screw  414  formed into the coil spring. Then, the long hole  411   a  is defined with a dimension movably supporting the toner conveying screw  414  specifically in the longitudinal direction (toner conveying direction). In the present embodiment, the driving-side screw end  414   a , i.e., the spring free end, of the toner conveying screw  414  is engaged and supported between the one end  411   b  and the other end  411   c  of the long hole  411   a  during the entire driving period of the toner conveying screw  414 . 
     For example, a longitudinal dimensional tolerance of the toner conveying screw  414  within the long hole  411   a  of the driving-side support member  411  is assumed to be ±1.0 mm, and a spring maximum expansion and contraction amount during the entire driving period in conveying toner is assumed to be around 0.2 mm. In this case, an entire length of the long hole  411   a  is selected such that a gap in the longitudinal direction of the toner conveying screw  414  becomes around 1.5 mm respectively on both sides of the driving-side screw end  414   a . Accordingly, the entire length of the long hole  411   a  is preferable to be 3.0 mm or more. 
       FIG. 6A  illustrates a state in which the toner conveying screw  414  is in a free length condition. The driving-side screw end  414   a  is located at the center of the long hole  411   a  of the driving-side support member  411 , thus leaving gaps around 1.5 mm respectively to the both ends  411   b  and  411   c  of the long hole  411   a.    
     Still further,  FIGS. 6B and 6C  illustrate states in which the toner conveying screw  414  expands/contracts in the longitudinal direction (toner conveying direction) corresponding to a condition of the reaction force and others from the toner being conveyed.  FIG. 6B  illustrates the state in which the toner conveying screw  414  expands to its tolerance maximum length.  FIG. 6C  illustrates the state in which the toner conveying screw  414  contracts to its tolerance minimum length. 
     The driving-side screw end  414   a , i.e., the one end, of the toner conveying screw  414  will not always come into contact with the driving-side support member  411  especially in the longitudinal direction (toner conveying direction) by constructing the long hole  411   a  of the driving-side support member  411  with the abovementioned dimension and shape. That is, however the toner conveyance resistance varies, the tension-free state of the toner conveyer screw  414  is assured in the longitudinal direction (toner conveying direction) during the entire driving period of the toner conveying screw  414 . Still further, as illustrated in  FIG. 6C , if a toner conveyable area c of the toner conveying screw  414  is set so as to cover a wider range outside of an image forming area D of the photosensitive drum  12 , the whole image forming area D of the photosensitive drum  12  can be covered by the toner conveyable area C, thus, the toner conveying performance is not swayed at the peripheral area of the toner conveying screw  414 . 
     As described above, according to the present embodiment, one end support member  411  for the toner conveying screw  414  supports the driving-side screw end  414   a , i.e., the one end, of the toner conveying screw  414 , via the long hole  411   a , movably in the longitudinal direction (toner conveying direction). Still further, the toner conveying screw  414  accepts the driving force of the driving system ( 401  through  403 ) in the rotational driving direction transmitted via the engagement of the long hole  411   a  and the driving-side screw end  414   a , i.e., the one end. This configuration makes it possible to always free the tension between the toner conveying screw  414  and the screw gear  403  or the tension in the longitudinal direction of the toner conveying screw  414 , i.e., the tension in the toner conveying direction (in the direction in parallel with the toner conveying direction) in particular. Therefore, the vibration energy in the expansion (or contraction) direction A of the toner conveying screw  414  is consumed because the driving-side screw end  414   a  is movable in the longitudinal direction of the long hole  411   a . Even if vibrations having the respective components in the expansion direction A and the twist direction B is generated in the toner conveying screw  414 , the entire vibration energy transmitted to the screw gear  403  is considerably reduced. Thus, this arrangement makes it possible to suppress an irregular pitched image, which might be otherwise caused by the rotational fluctuation of the drum gear  401 . 
       FIG. 7  illustrates a support structure of a driven side (left side in  FIG. 3 ) of the other end of the toner conveying screw  414 . In  FIG. 7 , the driven-side support member  412  disposed on a side opposite to the drive transmitting portion in the longitudinal direction of the toner conveying screw  414  includes a coupling portion  412   a  integrally connectable with a driven-side screw end  414   b  of the toner conveying screw  414 . The driven-side support member  412  is approximately a cylindrical member and is rotatably supported by a support frame  412   b  of the driven-side support member  412 . The support frame  412   b  is secured at a predetermined position of the drum frame  301  through screwing or the like through an attachment portion  412   c . This arrangement makes it possible to position the other end (left side in  FIG. 3 ) of the toner conveying screw  414  in the longitudinal direction with respect to the drum frame  301 . 
     It is noted that the toner conveying direction of the toner conveying screw  414  is preferable to be in a direction E indicated in  FIG. 7 . Such arrangement makes it possible to urge the toner conveying screw  414  to the drum frame  301  through the driven-side support member  412  and to stably position the other end in the longitudinal direction when the toner conveying screw  414  receives the reaction force from the toner in carrying the toner. 
     As described above, the present embodiment adopts the configuration which frees the tension between the toner conveying screw  414  and the screw gear  403  or the tension in the longitudinal direction of the toner conveying screw  414 , i.e., the tension in the toner conveying direction in particular. Therefore, it is possible to considerably reduce the vibration energy generated by the toner conveying screw  414  formed into the cylindrical coil spring and transmitted to the driving system ( 401  through  403 ) caused by the vibration having the respective components in the expansion direction and the twist direction. Due to that, it is possible to reduce the rotational fluctuation on the photosensitive drum  12  coupled through the driving system ( 401  through  403 ) and to suppress the image forming failure such as the irregular pitch image from being generated. Still further, the present embodiment can be carried out simply at low cost just by defining the long hole  411   a  through the driving-side support member  411  in accordance to specification, dimension and others of the toner conveying screw  414  and requires no additional component, so that the present embodiment can improve the image forming function simply at low cost. 
     The configuration of the present disclosure can be broadly carried out in the toner conveyer unit including the toner conveying member being rotationally driven to convey toner like the toner conveying screw, in a drum (process) cartridge using the toner conveyer unit, or the like. It is noted that in the present embodiment, while the toner conveying member has been exemplified by the toner conveying screw formed by the wire rod for the cylindrical coil spring, the present disclosure may be broadly carried out in a device using a toner conveying member conveying toner by being rotationally driven. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2015-165594, filed Aug. 25, 2015, which is hereby incorporated by reference herein in its entirety.